Why You Can’t Build a Bomb From Spent Fuel

February 20th, 2010

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To build a nuclear weapon you need weapons grade fissile material. This could be plutonium or uranium. (It could theoretically also be something like neptunium or americium, but nobody has ever bothered with that, as it would be far more difficult.) In the case of uranium, it must be highly enriched uranium and in the case of plutonium, it must be “weapons grade” plutonium.

The process of extracting plutonium from spent fuel for reprocessing, use in fast reactors or MOX fuel usage is similar to that used to extract plutonium for use in nuclear weapons. For this reason, many nuclear energy opponents will scream “AH HA!” and say that a nuclear power reactor is clearly a “proliferation hazard” regardless of what type it is. Furthermore, they’ll tell you that reprocessing is the ultimate danger and that if we dare recycling fuel, then others will recycle their fuel too (many already do, by the way) and if they do that then certainly they’ll be building weapons.

Of course, there are plenty of countries that reprocess fuel to one degree or another and don’t have nuclear weapons. Germany, South Korea, Japan, Belgium and Italy either reprocess fuel or have done so in the past but never had a nuclear weapon. Countries like Russia, France and the UK reprocess civilian reactor fuel but have never used this fuel to build a nuclear weapon.

There’s a good reason for this. As it turns out, the spent fuel from a modern power reactor, such as a BWR or PWR reactor is completely unusable for a nuclear weapon.

Here is why:

You’ve probably heard of the two earliest combat-ready nuclear bombs, developed by the Manhattan Project: Little Boy and Fat Man. Little Boy was the codename for the uranium bomb which used a “gun triggered” design, firing a subcritical uranium slug into a subcritical uranium target to produce a supercritical mass. Fat Man was the code name for a plutonium-based bomb that used a spherical core with a semantically explosives to compress the plutonium, resulting in an “implosion” that would bring the core to critical mass.

Well, here is “Thin man” the third bomb design that was developed during the Manhattan project: the one which never made it past the early test phase.

To be more accurate, those are not nuclear bombs, but rather just the empty casings. No “thin man” type bomb was ever built, because a combination of laboratory experiments and calculations proved that the design would either not work at all, or work so poorly that it wouldn’t produce an explosion any larger than a nominal size conventional munition. The problem is plutonium, or rather, an isotope of plutonium, plutonium-240.

Plutonium is produced by neutron bombarding uranium-238 in a reactor. When uranium-238 absorbs a neutron, it becomes uranium-239. Uranium-239 has a half-life of only 34 minutes and decays to neptunium-239, which has a half-life of 2.3 days and decays to plutonium-239. Therefore, when uranium-238 is irradiated with neutrons, a few days later, some of that uranium will have become plutonium-239, which can be separated chemically. Plutonium-239 is fissile and it’s exactly what you want if you’re looking to build a nuclear weapon.

However, there’s a problem that comes with the irradiation process: During the irradiation period, some of that plutonium-239 will also absorb a neutron. If that happens, it will usually fission, but up to a third of the time it won’t – instead it will become Pu-240. Likewise, some of that neptunium-239 will absorb a neutron before it gets a chance to decay to plutonium-239, thus resulting in neptunium-240, which quickly decays to plutonium-240. Because of these reactions, any reactor-generated plutonium will have some plutonium-240 in it.

Plutonium-240 is what you do not want when you’re building a nuclear weapon. For one thing, it’s not fissile and for another, it’s highly radioactive (four times more so than Pu-239), but what really makes Pu-240 so problematic for weapons use is that it has a high rate of decay by spontaneous fission, which produces neutrons. The rate of spontaneous fission of Pu-240 is so high that even with a tiny bit in a sample of plutonium, it will have significant effects on critical mass. If plutonium were used in a gun-triggered weapon, the spontaneous fission rate would mean that the bomb would begin to fission before the two portions came fully together. This is per-initiation, and it results in the weapon blowing itself apart before it actually gets a chance to achieve a full blown nuclear reaction. It’s commonly known as a fizzle.

To avoid this, a much more efficient design would be needed, one which could slam the fuel together very quickly and start the reaction before per-initiation could destroy the weapon in a very small explosion. This is why the implosion triggered system was designed. It proved to be capable producing a reaction from plutonium. Although the designers were not as confident about the design, leading to the need for a test before deployment – something which was not done with the gun-triggered uranium bomb.

Yet even using the implosion design, the presence of Pu-240 was still a problem. Having some Pu-240 present in the plutonium turned out to be inevitable, but it was still necessary to keep it to a minimum. If the level of Pu-240 were too high, even the implosion design would fail.

In order to do this, a special plutonium breeding cycle needed to be developed. The key to producing plutonium that is high in Pu-239 and low in Pu-240 is to make sure that it only spends a short period of time being irradiated. Uranium targets, in the form of small “slugs” would be irradiated in a reactor for a period of only one to two months. This would allow a small amount of neptunium and thus plutonium to build up, but only a small number of the atoms would absorb a second neutron. The slug would then be processed to remove the plutonium and the uranium would then be irradiated again, once again for a couple of months.

In practice, this meant that the target had to be completely dissolved and reprocessed, since that’s the only way to extract the plutonium. The uranium that was left could be reused, but it had to be completely re-fabricated into a new target. It also required a “cool down” period to assure the neptunium had all decayed. This period of time also eliminated most of the short-lived fission byproducts, which made the material difficult to handle and complicated the separation process. Typically, the cool down period would last several weeks. Each target would only produce a tiny amount of plutonium, so the process had to be repeated thousands of times to accumulate significant amounts of plutonium.

If the targets had been left in the reactor longer, then they’d produce more plutonium, but more of the plutonium would be Pu-240, the type which needs to be avoided. All and all, the process of producing weapons grade plutonium yields only about half a pound of plutonium for every ton of uranium irradiated and processed.

To accomplish this, the United States built a truly massive complex at Hanford Washington. It took three reactors working full time from 1944 on to produce enough plutonium for the weapons used in 1945. A total of nine plutonium production reactors were built at Hanford and produced plutonium for US nuclear weapons until 1987. Hanford was joined by the Savannah River Site in 1953. Six reactors would be built at the Savannah River site for plutonium production. All of the plutonium in US nuclear weapons came from the reactors at Hanford and Savannah River. Not one ounce of weapons plutonium ever came from a commercial nuclear power plant.

Grades of plutonium:

In current terminology, “weapons grade” plutonium is considered to have roughly 93% Pu-2239 or more, while “fuel grade” or “mid grade” plutonium has at least 81% and “reactor grade” contains less than 81% Pu-239. Weapons grade plutonium is considered to be the type well suited for use in nuclear weapons, but this does not mean that lower grades can’t theoretically be used, at least to a point.

As the concentration of Pu-240 increases, the difficulties it presents become greater and greater, causing the weapon to become less reliable, yield is reduced and a failure becomes more and more likely. Advanced weapons designs employ features like neutron reflectors, super high velocity, highly precise implosion lenses and multi-point detonation mechanisms, boosted cores and pulse neutron generators. These technologies, possessed by only a handful of countries could theoretically be used to create a more efficient weapon that could potentially utilize lower grade plutonium – but only to a point. A highly advanced, super-efficient weapon could make use of plutonium with a content of 91% Pu-239 or possibly even 88%. However, much beyond this would be difficult to impossible for even the most advanced weapons.

This kind of technology would not be available to a country just starting a weapons program anyway. The designs used by the United States and Russia are the result of hundreds of tests and decades of intense research. They also require exotic materials like tritium. However, no country with the technology to make such weapons would ever bother using the lower quality plutonium – doing so would reduce the weapons yield and make fabrication more difficult. Both the US and Russia already have a surplus of old weapons grade plutonium. Regardless of whether you could use sub-weapons grade plutonium in an effective weapon, it still would never work with reactor grade plutonium.

The reason for this is simple: commercial power plants don’t produce the kind of high grade, low Pu-240 material that is required for weapons. The most common type of nuclear reactor used around the world for power generation is the pressurized water reactor. In addition to this, there are many boiling water reactors in use. There are also some heavy water reactors and a few gas cooled reactors in use. With a couple of exceptions (more on that later) these reactors are NOT designed to produce weapons grade material.

Power reactors are designed to burn their fuel until there isn’t much left in it to burn, or at least, until the fuel no longer efficiently sustains critical mass in the core. Utility companies would rather be cranking out gigawatts than shuffling around fuel rods, and for this reason, most PWR’s and BWR’s are only refueled every year or two. Typically only a portion of the fuel is replaced and each fuel rod is used for more than one refueling interval. Most fuel rods spend at least three years in a reactor before being replaced and some spend even longer.

Some reactor designs allow for online refueling. These reactors are often refueled every few months, with only one or two fuel assemblies changed each time and fuel rods spending two or more years in the reactor, depending on burnup and enrichment. The CANDU reactor is refueled in this manner, but its spent fuel still spends far more time being irradiated than a weapons plutonium target ever would.

Because of this the plutonium found in spent fuel from power reactors has a very high concentration of Pu-240, making it unsuitable for use in nuclear weapons. The high levels of Pu-240 are not as important when the plutonium is to be reused in reactor fuel. Fast reactors will burn Pu-240 without issue and in thermal reactors, while plutonium-240 usually requires two neutrons to fission, more than Pu-239, this does not preclude its use. The pre-initiation issues of a weapon do not exist in reactors.

The plutonium produced by power reactors has yet another issue: it contains the isotope plutonium-241, an isotope which is only present in negligible quantities in weapons grade plutonium. Pu-241 decays into Am-241 with a half-life of only fourteen years. Since most reactor spent fuel sits for years in storage, by the time it is processed, a significant quantity has decayed to Am-241. The combination of Pu-241 and Am-241 makes the material highly radioactive, causing potential problems with material irradiation, the self-irradiation of a weapons core can cause embrittlement and heating of the plutonium pit and potentially compromise the weapons integrity.

In higher burnup reactors significant quantities of Pu-242 also begin ton build up. Plutonium-238, a source of intense heat also can be found in the spent fuel of high burnup reactors and can present problems for weapons us even when present at quantities of less than 1%. In a pressurized water reactor’s spent fuel, only about 53% of the plutonium present is plutonium-239, the type needed for a weapon! Creating a weapon out of plutonium with such extremely low levels of the critical isotope is absolutely impossible.

In face, 93% pu-239 is considered the low end of what is generally acceptable for weapons use and would work rather poorly in most weapons designs. Countries like the US, Russia, France and other advanced nuclear weapons states usually use even purer plutonium with concentrations of unwanted isotopes as low as 3% or less.

The possibility of using power reactors to produce weapons grade plutonium:

Simply reprocessing the fuel from a power reactor would yield plutonium that is utterly useless for weapons use, but could the reactor’s fuel cycle be modified to produce higher grade plutonium? Perhaps, but it wouldn’t be easy. PWR and BWR reactors are complex to refuel and normally are only refueled on relatively rare occasions, every year or so at the most. Refueling requires shutting down the reactor, allowing it to cool and depressurize, opening the lid of the reactor, replacing the fuel and finally replacing the lid. It takes more than a week to do this, during which time the reactor is shut down.

Producing weapons grade plutonium would mean irradiation cycles as short as a month. This would mean the reactor would be shut down almost as much as it was running, dramatically compromising its power producing capabilities. The cumbersome procedure would be made even worse because of the fact that the fuel assemblies use long, cladding rods, not the easily processed slugs that weapons reactors use. A power reactor of this type might be able to handle a fuel system more favorable to such frequent reprocessing and re-fabrication, but only with very extensive modification.

CANDU reactors can be refueled online, but the spent fuel they produce is very low in plutonium. A CANDU reactor could theoretically be used to produce weapons grade plutonium, but again, it would require extensive modification of the fuel cycle. Fuel would have to be ejected more frequently and doing so would reduce the power output of the reactor. Additionally, since the breed ratio of a CANDU under normal operation would not produce enough plutonium to make it a viable weapons reactor, there would need to be some modification of the fuel, likely using some level of enrichment combined with natural or depleted uranium target rods. It could be done, but like the PWR, it wouldn’t be especially easy and it would be pretty obvious to the world what you were doing.

There are two types of power reactors which are designed in a manner that allows them to produce weapons grade plutonium. The RBMK and Magnox reactors were both conceived as dual-purpose reactors and as such have the features necessary to produce weapons grade plutonium. The spent fuel from both of these reactors is useless for weapons production when they are run in a manner that maximizes their efficiency as power reactors, but the fuel cycle can be modified in order to produce nuclear weapons. However, both of these reactors are considered obsolete designs. The last Magnox reactor was built in 1971 and will be decommissioned this year. Most of the RBMK’s built have been decommissioned, but a handful are still in operation in Russia – a country which has no reason to produce more plutonium for weapons, given the enormous unused stockpile they already have.

A country wishing to produce plutonium-based nuclear weapons would be better off building a dedicated reactor or reactors for plutonium breeding. That is what every nuclear armed nation has done. The difficulties in making a power reactor produce weapons grade material are likely to be greater than simply building a purpose-built reactor, and in both cases the intentions would be fairly obvious. The fuel that comes out of a power reactor is useless for weapons production and therefore could never be spirited away to reprocessing to yield weapons grade material.

The great deception:

In 1977, President Jimmy Carter ended the reprocessing of nuclear fuel in the United States, thus making the US the only major nuclear nation with no reprocessing of spent fuel at all. In doing so, he created the nuclear “waste” problem, which prior to the end of reprocessing had been non-existent. At the time, he ordered some very selective information declassified to support this decision.

As anyone who understands nuclear weapons design would immediately realize that reprocessing of spent fuel absolutely does not yield weapons grade material, Carter asserted that, in fact, weapons grade material was not required to build a nuclear weapon. To support this claim he announced that the US had conducted a test in 1962 of a device containing “Reactor Grade Plutonium.” The problem was that Carter lied, if only by omission.

As is mentioned above, there’s not a single hard line at the 7% concentration. Plutonium containing 8% or 9% Pu-240 could certainly be used in a reasonably sophisticated weapon, although with reduced yield. When the 1962 test was conducted, there were only two terms for plutonium grades: “weapons grade” and “reactor grade.” In the contemporary terminology, “reactor grade” plutonium was anything with less than 93% plutonium-239, so a sample with 92.5% would qualify as reactor grade.

Additional information on the test was released in 1997. The biggest revelation was the source of the plutonium: it was not American but was imported from the UK. If the US wanted to test how lower grade plutonium would preform in a weapon, why not just use plutonium recovered from one of the power reactors in the US? After all, by 1962, the US had a number of PWR’s, including Shippingport, Yankee Rowe, Vallecitos Nuclear Center as well as a number of prototype naval reactors in operation at the Idaho National Laboratory.

The reason is simple: researchers were aware that the plutonium produced by these kind of reactors was so low in Pu-239 that it just plain would not work in a weapon. The test was likely intended to assess the effect of using lower grade plutonium in a weapon and confirm theoretical calculations, but to do this they needed plutonium that was lower than weapons grade, but not by too much, or the test would fail completely.

The DOE has never released the details of exactly what the composition of the plutonium was, nor have they released information about what the weapons yield was or whether the weapon incorporated advanced design features. The fact that it came from a Magnox reactor, however, is very telling.

Note in the graph seen above that of all the power reactor designs, the Magnox produces the least Pu-240 in its spent fuel and thus the most Pu-239. This is not by accident, as the Magnox reactor was originally designed as a weapons material reactor. Magnox reactors that continued to run in recent years produced plutonium with about 18% Pu-240, but this is only because they were operated at a high burnup level to produce power efficiently. When Magox reactors first came online, they were run at a much shorter fueling interval, more similar to the reactors at Savannah River and Hanford. Their primary purpose was to produce weapons grade plutonium. Electricity was also generated from the reactor’s heat, but this was seen as a byproduct, not the primary function of the reactor.

The first Magnox reactors became operational in 1956 at Calder Hall at the Stellafield nuclear site. The facility operated in a low-burnup mode intended for weapons production until 1964. After 1964 the reactors continued to produce weapons grade plutonium intermittently until 1995. The Chapelcross nuclear power station opened in 1959 and was considered the “sister plant” to the Calder Hall reactors. Chapelcross was also intended primarily to produce nuclear weapons material. In its early years, it ran on natural uranium at a low burnup that produced weapons grade plutonium. Berkely station opened in July of 1962. Berkeley was the first nuclear power plant in the UK that was owned by a civilian agency, the “Central Electricity Generating Board.”

Thus, there were only three nuclear reactors in the UK that potentially could have provided plutonium in 1962. Calder Hall can be ruled out because it was known to be operating at full capacity in weapons production mode at the time. Thus, the material it produced would be considered “weapons grade.” Reports indicate that in its early years, Berkeley was also used for producing weapons grade material. To this day the British government remains secretive about its historical plutonium breeding capabilities, and the level to which Berkely was used to produce nuclear weapons material is not entirely clear.

Had the material come from Chapplecross, it would have represented an abnormally long period of irradiation, since Chapplecross was primarily producing weapons material. Had it come from Berkeley, it would also have had to be low burnup, if only because of timing. Considering that it takes a good two to three months to cool, reprocess and fabricate fresh uranium rods into a weapons pit, that would have left only about three months for irradiation at Berkeley, even if the test took place in late December of 1962. Since the plant came online in July, there wouldn’t be enough time to heavily irradiate fuel rods. Also, at the time Magnox reactors ran exclusively on very low enrichment or unenriched fuel, limiting burnup, and because burnup directly effects fuel element integrity, early experiments with Magox reactors at higher burnup progressed conservatively, with usage extended in small intervals.

Therefore, the source of the plutonium can be determined to be either the very first round of spent fuel discharged from Berkeley, after having been irradiated for only a period of about three months max or possibly was from an extended irradiation period at Chapplecross. The fuel was not comparable to modern spent fuel, because, at the time, no British reactor was capable of producing such material. The fuel would have been lower than the US standard for weapons grade material – but only slightly.

The nature of the test can be inferred by a combination of its timing and the vague statement released in 1997: “This test was conducted to obtain nuclear design information concerning the feasibility of using reactor-grade plutonium as the nuclear explosive material. “

The test was probably done to establish a lower threshold for what would constitute acceptable plutonium for use in a weapon. This had already been established by calculations and sub-critical experiments, but this test would confirm how lower quality plutonium worked in a weapon. For example: Would the fuel cycle of the new Berkley nuclear plant produce material with weapons potential? Theory predicts that the use of plutonium of a quality slightly lower than the weapons grade standard would still produce a reasonable tactical yield in an advanced weapon design, but would diminish the total yield significantly. This is probably what happened in 1962.

One must remember that the material was only slightly lower grade than weapons grade plutonium – this is beyond question because of the source of the material being the low-burnup Magox reactors. Had it been from a modern power reactor or the power reactors that were being built outside the UK, it simply would not have worked at all.

And finally, on a “fizzle bomb”:

Some have said that this would be a deadly weapon as a “super dirty bomb” – the reality is that it would be a very big, bulky weapon that wouldn’t be much more powerful than its own weight in dynamite. It might spread around some plutonium, but the radio-toxicity of plutonium is not all that high and the spread of such material would be fairly local. Given that it’s primarily an alpha emitter, it would have to be inhaled or ingested to cause harm. If one went off, a couple blocks would need to be shut down while some guys in Tyvex suits washed everything down. We’ve actually experienced some weapons accidents that spread plutonium in a local area before. They weren’t the end of the world.

As a strategic weapon, it’s useless, as a tactical weapon, it’s pointless and as a weapon of terror, it’s only as terrifying as you let it be.

THEREFORE: NO MATTER WHAT ANYONE SAYS, SPENT FUEL FROM NUCLEAR POWER REACTORS AND ITS REPROCESSING IS ABSOLUTELY NOT A PROLIFERATION HAZARD. IT DOES NOT BECOME ONE IF THEY SAY IT IS ENOUGH TIMES. IT’S NOT. NOT PROCESSING NUCLEAR FUEL ON THE GROUNDS THAT IT PROMOTES NUCLEAR WEAPONS PROLIFERATION IS JUST PLAIN WRONG AND ALSO AN IDIOTIC ARGUMENT.

Understand?


This entry was posted on Saturday, February 20th, 2010 at 6:58 pm and is filed under Bad Science, Enviornment, Good Science, History, Nuclear, Obfuscation, Politics. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
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253 Responses to “Why You Can’t Build a Bomb From Spent Fuel”

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  1. 151
    DV82XL Says:

            Concerned Citizen said:

    The author of this lie is well known for being a vocal endorser of depleted uranium, especially against civilians and innocent targets..

    Depleted uranium has become an unfashionable cause for antinuclear activists. It is old news. I guess you didn’t get the memo. Organizations like your Campaign Against Depleted Uranium are in decline, and you are now forced to troll on sites like this in the hope of gathering any interest in you nonsence.

    The fantastic claims of well-known activists have grown progressively more extreme since 1999. Without any credible health or environmental studies in post-war Iraq on DU, activists have claimed the effects are comparable to those of the Chernobyl nuclear reactor explosion. Some prominent activists have claimed that not only has the use of DU already caused genocidal effects in Iraq, but that the US uses DU munitions to intentionally inflict genocide on populations. In some cases, one lie leads to another, such as when one activist asserted – without supporting data – that U.S. missiles and bombs contain large quantities of DU, and then a publicity-seeking, fund-raising organization calling itself the Uranium Medical Research Centre used this claim to advance its own unsupported assertion that the U.S. had spread uranium contamination across Afghanistan, resulting in severe health effects. The prize for the most outlandish claim about DU to date goes to activist Leuren Moret. Moret, who works closely with Doug Rokke and other anti-DU extremists, has uttered some of the most bizarre and uninformed statements about DU, including the following statement made in February 2004:

    “Anyone within 1,000 miles of Iraq; anyone within 1,000 miles of Afghanistan is potentially contaminated now. It’s not just the people [living] in the country Anyone going to Iraq or Afghanistan now will become contaminated. There’s no way to escape it.”

    Such certainty is the hallmark of the DU extremists. However, Moret’s most distinctive and substantial contribution to the decline of rational discourse about the effects of DU is her claim that the use of DU munitions has resulted in atmospheric pollution by radioactive dust equal to the detonation of 400,000 Nagasaki bombs. Of course, there are differences of opinion even among the most irrational and uninformed extremists another activist says the use of DU is equal to only 250,000 Nagasaki bombs.

    When moderate activists raised concerns about the accuracy of the increasingly alarmist claims about DU, they became the target of character assassination campaigns. In fact, the debate over DU has declined to the point where the simple act of questioning a claim made by Doug Rokke, Asaf Durakovic, or other prominent activists is labeled a heresy by a small jury of vocal extremists thus rational discourse about the use and effects of DU munitions has become increasingly difficult and rare.

    You idiots have driven off much of the support you had from the other groups opposing nuclear technologies because you were becoming an embarrassment to them, and in many ways have done them more harm than good. So rant on, because every time DU nuts come raving accusations and foaming at the mouth, more people realize just how stupid antinuclear beliefs are.


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  2. 152
    Finrod Says:

            Concerned Citizen said:

    The only “Great Deception” is that by Mr. Packard and his cronies, who are tied to the military industrial complex and stand to make a lot of money by putting profit and plutonium over people and the welfare of the world.

    Yes, it’s so much easier to throw wild accusations around than to engage in sensible debate. Especially when reason is not on your side, eh?


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  3. 153
    drbuzz0 Says:

    *sigh*

    This begins again.

            Concerned Citizen said:

    The only “Great Deception” is that by Mr. Packard and his cronies, who are tied to the military industrial complex and stand to make a lot of money by putting profit and plutonium over people and the welfare of the world. Plutonium is a deadly substance that kills everything it touches and produces the most horrendous weapons in imagination. Plutonium has no other use and reprocessing is simply a way of masking it and spreading it to more weapons and more nation states.

    You don’t even understand how any of this works, do you? How on earth could other countries being armed with nuclear weapons make *me* rich? It’s not like they would be buying them from me – not that I manufacture them to begin with, but nuclear weapons programs are generally developed indigenously with only basic components imported, and if they were imported, it’s not likely to be from the US anyway.

    Nobody gets rich off of reprocessing either. Reprocessed fuel is, at best, on par with once-through fuel in terms of expense and can actually cost a bit more. The biggest draw to reprocessing is it dramatically reduces waste and basically eliminates spent fuel as a waste product. Reprocessing concentrates the fission byproducts and turns most of the bulk of the spent fuel into fairly innocuous stuff.

    If I were part of the “military industrial complex,” which I’m not I’d make no money off of this either. The US never has used reactor grade plutonium in weapons and even if they started building weapons again, we would have no need to breed plutonium for many years. There’s a huge backlog of surplus plutonium pits at the Y-12 complex and Pantex. Therefore, if weapons building resumed, it would be years to exhaust the plutonium in the inventory.

    Even after that, would I make any money? No. Not many make money off of nuclear weapons. The Sandia corporation, perhaps, the contractors who run Pantex and Savanah River maybe. It’s not a big cash buisiness though. A lot of it is done in house by the government.

            Concerned Citizen said:

    The author of this lie is well known for being a vocal endorser of depleted uranium, especially against civilians and innocent targets.

    This again. No, I absolutely do not condone the use of depleted uranium against innocent civilians any more than I do the use of tungsten, lead or steel. However, I am offended by the use of the plight of those in waring regions as an excuse to try to go after nuclear energy or just push bad science by claiming that depleted uranium has anything to do with it.

    If anything, the move to kinetic energy based anti-armor weapons is an improvement because they don’t cause much collateral damage if they miss and they don’t leave unexploded ordinance.

    But that’s besides the point. War is hell and death and destruction come with it. A military action which is done to protect national and world security or to oppose direct aggression is justified and a military action which is directly aggressive and not justified by greater needs that can’t be met diplomatically or which is aimed at causing harm to innocent targets is not justified and is wrong.

    Whether or not depleted uranium is used in a conflict has no bearing on whether it’s a justified action. If it is justifiable to fire at a target with an explosive or tungsten round, it is equally justifiable to do so with DU. If it is not, then it is no more wrong or right to use depleted uranium.


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  4. 154
    Chris Brown Says:

    Concerned Citizens comments clearly show that he he is simply demonizing those witha different opinion. If you have a differant view then him you ust somehow be evil or corupt. This has become a far too common feature of American life – we no longer can have honest disagreements. The debate on health care is an exsample – both sides view the other as evil instead of people with an honest disagreement about policy.

    It is a sad state of affairs and does not bode well for democracy……


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  5. 155
    DV82XL Says:

            Chris Brown said:

    Concerned Citizens comments clearly show that he he is simply demonizing those witha different opinion.

    Na, he’s just trying to drive some traffic to his web page. As I wrote above, the anti DU crowd has even soured-off other anitnukes with their over the top accusations. They are a spent force, and no longer part of the conversation.


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  6. 156
    Finrod Says:

    Back in the days when I was basking in ignorance of nuclear matters, before I made it my business to bring myself up to speed on them, I had vaguely heard of some depleted uranium controversy. I had imagined that DU must be some spent fuel byproduct, particularly foolhardy to fire around the place. When I seriously started to investigate just what DU was, I was astonished to learn that my default assumptions were so far off base.

    I think that phenomenon is what Concerned Citizen and his/her fellow-travellers are counting on. Trying to sound just scientific enough that a non-scientist who isn’t thinking too hard on the matter will be decieved by their propaganda.


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  7. 157
    Ryan Says:

    A load of disgusting lies and missrepresentation of things, because it’s known that u can build a nuke out of any plutonium as it is stated clearly many times and ignored by this writer, who says it would be hard and the nuke not so powerful, but does it matter if u r killed by it? It’s still enough to blow up most of a city. What about a DIRTY BOMB? HUH?? HUH??

    If spent fuel were not the most dnagerous thing on earth we would not be struggling to figure out what to do with it to save future generations from its dangers. It is toxic basically forever and is the most dangerous thing we have. Falling into the hands of terorists is pretty much the nightmare u worry about a nuclear 911

    Nuclear power is not any good anyway. Its worse than any other for polution and makes plenty of carbon, because yea u have to dig everything up, and also the fact that wind + solar r pretty much cheaper than anything else. Why wind + solar r not used to power everything is simply big corporations. If u put a solar panel on ur car then guess what no gas ever again, and the corporations won’t like that one bit u know.

    Why is it every peace and enviornment group ever says nukeler is the worst kind of power? r they all lying or are u?

    This econemy is another thing. How about jobs for everyone? Look at those who are winning. look at spain. They r all about solar and they have a lot better jobs bc of it.

    Why anyone would write this kind of idiot crap is money and whoever wrote it probably government employed or corporate scum who is scared ****less of the solar power coming and tries to stop it to make $$$ off of us all. capitalism is worse than the nazis and that’s what u can see here. but how much money do u need to make when you get blown up? u want to make money on nuckler war? I got bad news 4 u bc when the bombs fall they dont care if u got the money, they blow u up just the same. Scumbags!


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  8. 158
    Chris Brown Says:

    Crazy is as crazy does…….

            Ryan said:

    A load of disgusting lies and missrepresentation of things, because it’s known that u can build a nuke out of any plutonium as it is stated clearly many times and ignored by this writer, who says it would be hard and the nuke not so powerful, but does it matter if u r killed by it? It’s still enough to blow up most of a city. What about a DIRTY BOMB?

    HUH?? HUH??

    If spent fuel were not the most dnagerous thing on earth we would not be struggling to figure out what to do with it to save future generations from its dangers. It is toxic basically forever and is the most dangerous thing we have. Falling into the hands of terorists is pretty much the nightmare u worry about a nuclear 911

    Nuclear power is not any good anyway. Its worse than any other for polution and makes plenty of carbon, because yea u have to dig everything up, and also the fact that wind + solar r pretty much cheaper than anything else. Why wind + solar r not used to power everything is simply big corporations. If u put a solar panel on ur car then guess what no gas ever again, and the corporations won’t like that one bit u know.

    Why is it every peace and enviornment group ever says nukeler is the worst kind of power? r they all lying or are u?

    This econemy is another thing. How about jobs for everyone? Look at those who are winning. look at spain. They r all about solar and they have a lot better jobs bc of it.

    Why anyone would write this kind of idiot crap is money and whoever wrote it probably government employed or corporate scum who is scared ****less of the solar power coming and tries to stop it to make $$$ off of us all. capitalism is worse than the nazis and that’s what u can see here. but how much money do u need to make when you get blown up?

    u want to make money on nuckler war? I got bad news 4 u bc when the bombs fall they dont care if u got the money, they blow u up just the same. Scumbags!


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  9. 159
    DV82XL Says:

            Ryan said:

    What about a DIRTY BOMB?

    HUH?? HUH??

    Dirty bombs have been on the radar for decades, the idea goes that terrorists unable to secure a nuclear weapon would instead strap an explosive device to a container filled with radioactive material, which would likely be stolen from a medical or industrial facility. The fear is that such bombs could cause injury or death by spreading radioactive material over potentially large areas. This fear is largely unfounded.

    Basically, the principal type of dirty bomb, or Radiological Dispersal Device (RDD), combines a conventional explosive, such as dynamite, with radioactive material. In most instances, the conventional explosive itself would have more immediate lethality than the radioactive material. At the levels created by most probable sources, not enough radiation would be present in a dirty bomb to kill people or cause severe illness. For example, most radioactive material employed in hospitals for diagnosis or treatment of cancer is sufficiently benign that about 100,000 patients a day are released with these materials in their bodies.

    To better gauge the threat, Sandia National Laboratory in Albuquerque, New Mexico, in partnership with Defence Research and Development Canada, (DRDC) in 2006, conducted a series of blasts to determine how certain materials behave during an explosion. In one set of tests, Canadian defence scientists exploded various devices thought to be similar to terrorist bombs a few meters off the ground. Those tests suggested the kinds of fragments that could lead to acute radiological sickness tend to travel less far than feared. Other tests, simulating urban ground environments such as sand, dirt, and concrete, suggested that dirt or grit from the area tended to create larger fragments during the blast, lowering their distance. That’s good news for first responders, such as police and fire fighters. They shouldn’t need to wear full radioactive suits or air tanks, because the size and type of fragments that would be produced by likely weapons wouldn’t warrant that kind of protection, ending up mostly on the ground rather than in the air.

    Given the level of security now mandated for radioactive material, and the small amount of damage that can be done with such a device the likelihood of this sort of attack is very small. A potential terrorist wants a lot of bang for the risks he is taking, and this system just won’t give it.


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  10. 160
    Michael Karnerfors Says:

            Ryan said:

    What about a DIRTY BOMB?

    HUH?? HUH??

    u want to make money on nuckler war? I got bad news 4 u bc when the bombs fall they dont care if u got the money, they blow u up just the same. Scumbags!

    Someone needs to go on de-caff…

    Either we’re dealing with a full time-troll here… or someone that is not quite in touch with the facts of the matter.

    To be honest, I’ll be more relieved if it really is a troll.

    /Michael


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  11. 161
    DV82XL Says:

            Michael Karnerfors said:

    Someone needs to go on de-caff…

    Either we’re dealing with a full time-troll here… or someone that is not quite in touch with the facts of the matter.

    To be honest, I’ll be more relieved if it really is a troll.

    /Michael

    Mike, I don’t think he’s in touch with any part of reality, never mind anything as trivial as the facts about anything.


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  12. 162
    Shafe Says:

            Ryan said:

    If u put a solar panel on ur car then guess what no gas ever again, and the corporations won’t like that one bit u know.

    Oh, but Ryan, it’s even better than that. When you’re driving and put your hand out the window, what do you feel? Wind! Since there’s always wind when you’re driving, just put lots of little turbines all over your car and get even more free energy, even at night.

    And guess what, your alternator’s spin is dictated by engine speed, not electric demand. So there are a lot of times when your alternator is just spinning with the engine and wasting the electricity that’s not being used. You could use that wasted energy to electrolyze water to generate hydrogen to fuel your car.

    It’s all out there along with the 100mpg engines that the oil companies won’t release the patents for. Don’t let that stop you. I wanna see a go-getter like you driving around with solar panels and wind turbines on your car. Go get ‘em, Tiger!


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  13. 163
    drbuzz0 Says:

            DV82XL said:

    Dirty bombs have been on the radar for decades, the idea goes that terrorists unable to secure a nuclear weapon would instead strap an explosive device to a container filled with radioactive material, which would likely be stolen from a medical or industrial facility. The fear is that such bombs could cause injury or death by spreading radioactive material over potentially large areas. This fear is largely unfounded.

    Given the choice between being exposed to an explosive device that disperses a radioisotope of fairly strong emissions versus being exposed to something like sarin nerve gas, mustard gas or even something relatively low-tech like hydrogen cyanide, chlorine or hydrogen sulfide. The later usually need a descent concentration to kill, but compounds like sarin are capable of killing at concentrations less than 1% the lethal level of cyanide.

    In 1995 a cult used sarin nerve agent to attack the Tokyo subway system. There were five attackers, each of whom had only a 900 ml bottle of sarin. The attack only killed five, but that was mostly because it was done improperly. They left punctured bottles of liquid sarin on trains, but sarin in liquid form does not radilly form a vapor at ambient pressure. It evaporates slower than water. “Proper” dispersal requires it to be aerosoled or vaporized. Had it been, it could have killed many hundreds or thousands.

    Even relatively low tech chemical weapons could kill many if they were released in somewhere like a subway station, a crowded airport terminal or a big public event. Mustard gas might kill some but it would also cause horrendous burns that would be tailor made for dramatic news coverage.

    Not only that, but of all the terrorist weapons that could be smuggled somewhere, a “dirty bomb” is the one that has the best chance of being detected since you don’t actually need to open it and sample the contents or even see the device to know its there. Radiation detectors are simpler and smaller than any chemical detector, and they don’t require the device to be leaking or have residue on it.

    All and all, I’d be worried about an attack with a device laced with something else besides radioisotopes.


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  14. 164
    drbuzz0 Says:

    Oh, one other thing: I don’t know about everyone else, but I find the use of the letter u for the word “you,” the word r for “are,” ur for “you’re” or “your” and “ppl” for people to be annoying to the extreme. It’s so stupid and makes someone sound like a complete and utter idiot.

    The one place it’s acceptable to me is in text messages, because of the message length limits and the whole issue of typing it out on a tiny keypad or even a number pad. In those cases, it’s something of a necessity to keep the message as short as possible while keeping it understandable.

    For anything else, it’s idiotic.


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  15. 165
    Lantzelot Says:

    In this particular case I agree fully that it seems stupid, and if it is a troll we’re dealing with then that is probably the purpose as well.

    But from another viewpoint, it seems to happen in every language as an effect of the introduction of a new technology (cell phone text messages). You can find a similar parallel about 200 years ago in several languages when a new technology (newspapers) became available to many people, some pronounciations changed because people started to speak as things were written, believing that it was the educated or “upper class” way of speaking.

    In China there is an emerging “problem” with young people who use the wrong chinese characters because they have the same pronounciation as the intended ones. Older people are of course outraged about this uneducated way of using the language.

    So it is a global “problem” and it has been around for a long time. A language is not a static thing and you may see this as part of the evolution of it, accept it and go with the flow (it doesn’t mean that you have to write like that yourself).
    Or you can try to fight it by calling for better (stricter?) language education, and pointing it out every time that you encounter the phenomena. But it will be a battle that you will lose. So if you decide to join the Dodo and the T-Rex, at least try to do it with a smile, and be amused about the new ways that your cherished language is changing.

    Sorry for elaborating off topic. :-)


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  16. 166
    drbuzz0 Says:

    Yeah, I know, and the language actually went through a couple of other times when there were abbreviations added and some of them jumped to regular language. This happened because of telegrams, which charged by the word and post cards. One of the common ones that may date to telegrams and other short communications is “ASAP” sometimes spoken as “ay-sap” meaning “as soon as possible”

    Usually with these kind of things they are frowned upon as improper for a long period of time before ever being accepted as correct. Right now, we’re in the very early part of the use of these abbreviations, certainly in most context. Hence, I’ll say they’re improper. Come back in 50 years and we’ll see if they’ve wormed their way into the proper usage of language.

    Of course, some phrases never seem to make it to the point of being acceptable. The word “ain’t” has been around a very long time as a general purpose contraction for almost any other negative contraction. Anyone with class and education will generally use it only in an ironic context. Using it in any kind of official or formal setting shows beyond doubt that someone is an uneducated lower-class type. This is all the more true when combined with a double-negative, which I maintain, will never be proper because it’s a logical error as well as a grammatical error. (actually it’s not, double invention is not logically incorrect, they cancel each other out)

    While flipping stations if I came across some trial court coverage. The witness said “So when he ain’t there I knew there ain’t no way nobody got in there cause he ain’t the type to go out and leave the door open”

    (Or something to that effect)

    I didn’t even need to glance at the screen to guess that the witness didn’t have many teeth. Probably was caught by dragging I dollar bill through a trailer park, I’d imagine.

    That kind of statement would have been indicative of someone like that in 1990, 1950 or 1890.


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  17. 167
    Shafe Says:

            Lantzelot said:

    So it is a global “problem” and it has been around for a long time. A language is not a static thing and you may see this as part of the evolution of it, accept it and go with the flow (it doesn’t mean that you have to write like that yourself).
    Or you can try to fight it by calling for better (stricter?) language education, and pointing it out every time that you encounter the phenomena. But it will be a battle that you will lose. So if you decide to join the Dodo and the T-Rex, at least try to do it with a smile, and be amused about the new ways that your cherished language is changing.

    I can’t seem to express my disagreement with your comment without writing a thesis, so let me just say, “I disagree.”

    There’s no need to accept laziness and ignorance, and I will always reject:

    -Improper construction, e.g. irregardless, ironical

    -Homophone confusion, e.g. there, their, they’re; two, to, too. (sorry Steve)

    -Saying “in lieu of” when you mean “in light of”

    -Going slow when the sign says “stop”

    -Amputating my right hand when the problem is in my left.

    Wrong is wrong, and popularity does not make any of these right.


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  18. 168
    drbuzz0 Says:

    Note: some comments from this were removed, because they were not relevant to the topic and were not comments I wanted to really discuss.


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  19. 169
    Silverthorn Says:

    I’m coming late to this party, but I’ll go ahead and post a comment anyway.

    An associate sent me a link to this blog after I had e-mailed a comment on US energy policy. I had said basically that any state that seriously wanted to develop nuclear weapons these days had the capability to do so, with or without a domestic nuclear power industry; that power reactors weren’t necessary or even helpful to the process, and that an effective anti-proliferation policy must focus on removing the motivation that states have for building nuclear weapons.

    The biggest motivation for a state to acquire nuclear weapons is fear for its own security. Particularly fear of war arising from competition for limited supplies of oil in the absence of realistic alternatives. From that perspective, encouraging the deployment of nuclear power is sound anti-proliferation policy, because it can reduce anxiety about what will happen when oil production starts to seriously lag demand.

    That’s about the only point I’d want to add to what yor wrote, Dr. Buzz0. Kudos! The article well researched, well referenced, yet very accessible. It will be an important piece of material in the case for a sane energy policy. And the comments following it, though a bit hard to wade through, have been a gold mine of additional information. You have some very knowledgable readers.

    It’s frustrating that there are such seemingly contradictory statements from what should be authorative sources on the feasibility of using spent power reactor fuel. I’ve been trying to chase that down as much as I can. It’s beside the point, in that whether or not it’s *possible*, it’s clearly much more difficult and gives a much less practical device than starting from weapons-grade material. And any state that has the industrial and technical sophistication to build a workable device from such difficult and inferior starting material certainly has the technical sophistication to produce weapons-grade material.

    Still, since “all reactor waste is potential bomb material” has become such a cornerstone of the anti-nuclear forces, it would be nice if the matter could be firmly laid to rest. I doesn’t look like that will be easy, however.

    I note that Carey Sublette, author and maintainer of the NWFAQ at The Nuclear Weapon Archive, appears to be aligning with the “all is potential bomb material” side. In his section 6 on materials, there are some pretty agressive statements about the yields that can be expected even from devices that are certain to pre-initiate. Also statements suggesting that isotopic refinement of reactor wastes is perhaps more feasible than usually supposed. He states that plutonium hexafluoride has similar properties to uranium hexafluoride and can be used for refinement in the same types of gas centrifuges used to enrich uranium. The Wikipedia entry on “plutonium hexafluoride” seems to confirm the “similar properties” statement. Interestingly, though, it mentions PuF6 as being of interest for laser-based refinement, not for processing in a gas centrifuge.

    It seems possible that there is classified knowledge of an efficient way to reprocess reactor wastes to extract relatively pure Pu239. If so, fear that that knowledge may leak out (or be independently rediscovered) might explain some of the conflicting information we’re seeing.

    BTW, it’s not too hard to show that a device with plutonium chemically refined from reactor waste *will* pre-initiate. That doesn’t seem to be disputed. The controversy seems to be over how much yield can be achieved despite pre-initiation.

    The certainty of pre-initiation is because rate of spontaneous neutron emission is high enough than in any pit that’s close to critical mass, there will always be active neutrons flying around. Each spontaneous neutron triggers some number of induced fissions; so long as the mass remains sub-critical, the expected number of induced fissions is finite, but it climbs rapidly as criticality is approached. It’s also easy to show that the rate of fissions doesn’t grow all that rapidly if the mass is only a little above criticality. I suppose it’s possible that the implosion shock wave can keep compression going for a few tens or even hundreds of microseconds after the population explosion of fission neutrons begins. By then, the pit may be sufficiently super-critical that inertia will keep it that way long enough for a substantial fission yield. It’s something that should be amenable to calculation.


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  20. 170
    DV82XL Says:

            Silverthorn said:

    It seems possible that there is classified knowledge of an efficient way to reprocess reactor wastes to extract relatively pure Pu239. If so, fear that that knowledge may leak out (or be independently rediscovered) might explain some of the conflicting information we’re seeing.

    BTW, it’s not too hard to show that a device with plutonium chemically refined from reactor waste *will* pre-initiate. That doesn’t seem to be disputed. The controversy seems to be over how much yield can be achieved despite pre-initiation.

    It bears repeating – all new nuclear weapon states have followed ‘traditional’ (if you will) routes to acquire weapons. This is because it is the simplest, cheapest, and most reliable path. Also, posturing to the contrary aside, the international non-proliferation apparatus/bureaucracy, really cannot stop any nation from doing what it pleases inside its own borders. Consequently there is no good reason to follow some untried idea, should some country come to the desision to mount a nuclear weapons program.

    Furthermore, at best these alternate designs are harder than the standard ones, so they are no risk from non-state actors, who would already have an insurmountable task, building a simpler HEU based device.

    As for other technology coming to fore, it is hubris of the worst kind to believe this can be stopped or controlled. History is at the very least, is clear on that.


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  21. 171
    drbuzz0 Says:

            Silverthorn said:

    Still, since “all reactor waste is potential bomb material” has become such a cornerstone of the anti-nuclear forces, it would be nice if the matter could be firmly laid to rest. I doesn’t look like that will be easy, however.

    I note that Carey Sublette, author and maintainer of the NWFAQ at The Nuclear Weapon Archive, appears to be aligning with the “all is potential bomb material” side. In his section 6 on materials, there are some pretty agressive statements about the yields that can be expected even from devices that are certain to pre-initiate. Also statements suggesting that isotopic refinement of reactor wastes is perhaps more feasible than usually supposed. He states that plutonium hexafluoride has similar properties to uranium hexafluoride and can be used for refinement in the same types of gas centrifuges used to enrich uranium. The Wikipedia entry on “plutonium hexafluoride” seems to confirm the “similar properties” statement. Interestingly, though, it mentions PuF6 as being of interest for laser-based refinement, not for processing in a gas centrifuge.

    It seems possible that there is classified knowledge of an efficient way to reprocess reactor wastes to extract relatively pure Pu239. If so, fear that that knowledge may leak out (or be independently rediscovered) might explain some of the conflicting information we’re seeing.

    Yes, the two are similar physically and chemically, but they’re not identical. Isotopic separation is not a simple task. It requires some very very precise equipment and very precise management of the material state.

    In a gas centrifuge the uranium hexafluoride is run through at a high pressure so and enters the centrifuge at supersonic speeds through a nozzle. The centrifuge itself spins at near supersonic speed and has a temperature gradient applied to it. Keeping the temperature within tight bounds is critical as the gas is run at a range that is very close to the point of sublimation.

    The gas is also corrosive and therefore special materials need to be employed in the construction of the gas centrifuge.

    In theory the process should work with plutonium hexafluoride. However, it would not be as simple as feeding a uranium centrifuge plutonium hexafluoride. The physical differences, though small, are enough to mean that the system would need to be redesigned to operate at slightly different pressures, temperatures and differing velocities.

    Yes, it could work, but there would be a fair amount of R&D invested in the conversion of uranium hexafluoride systems to run on plutonium hexafluoride.

    The fact that plutonium is more radioactive would tend to complicate the task. Not only could radiation make handling it more difficult, but it could cause degradation of some of the components and introduce heat into the system which might not be desirable.

    These centrifuges are actually amazing pieces of technology. The gas is pushed to the ends with so much force that it begins to liquefy as it is collected.

    This is also reason why even a tiny problem with design could be catastrophic. If you were to have a tiny piece of a nozzle break off and enter the gas centrifuge or if there were a spot on the outside where some of the material started to sublimate and crystallize it could unbalance the rotor. An unbalanced centrifuge can fly apart and send shrapnel flying in all directions like a bomb.

    Then on top of this, compared to uranium, you’re going to need to process the plutonium more times.

    Every time uranium enters a centrifuge, it can come out with a bit more U-235 and a bit less U-238. With plutonium, you’re talking about a mass difference of one AMU, not three. So you’ll need to cascade it through the centrifuges more times.

    If that’s not bad enough you’ve got undesirable isotopes on both sides of Pu-239. Concentrating Pu-239 from Pu-240 and Pu-241 also increases Pu-238, which causes enormous heat problems.

    So in short, if you have the technology to separate isotopes of uranium, you’d be better off doing that then going through the extreme and unproven steps of converting to plutonium enrichment.

    As for lasers – that might be a better solution. However, laser enrichment is still not a small task. It’s within the capabilities of a nation state, perhaps, but its still a major industrial operation. On top of that, laser enrichment will still be less efficient in plutonium because of the lower mass difference and does not eliminate the problem of having to separate our isotopes that are both lighter and heavier.


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  22. 172
    Ray1952 Says:

    Plutonium hexaflouride is pretty close to uranium hexaflouride, but “pretty close” is not good enough when dealing with the insane tolerances that enrichment equipment needs to be built and operated to.

            Silverthorn said:

    It seems possible that there is classified knowledge of an efficient way to reprocess reactor wastes to extract relatively pure Pu239. If so, fear that that knowledge may leak out (or be independently rediscovered) might explain some of the conflicting information we’re seeing.

    Possible if the fuel cycle were modified. Otherwise, perhaps slightly better plutonium could be obtained by processing portions of the fuel bundles that were less irradiated, but then you would get much less quantity and need much more reprocessing to get it.

    There’s no way of processing out better Pu-239 from the waste in general. Isotopes are, for all intents and purposes, chemically identical, at least at these heavy elements. There have been attempts to enrich uranium using chemical methods. All have generally failed except for a process the French demonstrated, which was somewhat workable but much worse than other enrichment methods. It was based on ion exchange and the slightly lower rate of U-238 in chemical reactions of this type.

    It would make no sense to enrich plutonium. Better to enrich uranium. It is so much easier and uranium gives you a more reliable and easier to develop weapon.

    The presumed goal of building a weapon out of plutonium that is from reprocessing would be to do so in a clandestine manner or avoid the need for enormous enrichment facilities. This would completely defeat that purpose.


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  23. 173
    Silverthorn Says:

    I’ve been doing a little research on laser isotope separation (LIS).

    There’s no way of processing out better Pu-239 from the waste in general. Isotopes are, for all intents and purposes, chemically identical, at least at these heavy elements.

    LIS is not your everyday chemical process. Different isotopes of an element have very slightly different energy levels in their electron shells and chemical bonds. In UF6, in particular, the U-F bonds have vibrational resonances whose precise value depends on the relative mass of the fluorine and uranium nuclei.

    A precisely tuned laser can excite the U-F bonds for U^235-F6 molecules, while leaving those for U^238 either unaffected or much more weakly excited. The excited bonds are then in a higher energy state, from which a second laser pulse at a shorter frequency can break them altogether. A UF6 molecule that loses one of its fluorine atoms in this manner becomes a UF5 molecule; UF5 precipitates out of the gas mix as a white powder.

    Or so says my reference on the subject, which is an appendix to a report on the history of Iran’s research efforts on LIS. That report is online here.

    The generic process goes by the acronym MLIS, for “molecular laser isotope separation” (as distinct from AVLIS, for “atomic vapor laser isotope separation”, which is mentioned in the NWFAQ but is apparently no longer being researched.) A specific formulation of MLIS for uranium enrichment is the SILEX process, developed by a pair of Australian scientists over the period from 1996 to 2002, with support from a private US corporation. GE has licensed the process, and reportedly wants to begin operating a SILEX enrichment facility in the US in 2012 or 2013.

    GE’s application to the NRC for permission to build the plant has stirred opposition. A news article that was published by the Australian ABC news network following the recent nuclear summit in Washington quotes a physicist from Georgetown University as saying that the process is “too dangerous to be allowed”. Not dangerous for the usual reasons you might expect to hear from anti-nuke activists, mind you, but dangerous because it is too damned good to be allowed loose in the world. It’s a 3rd generation enrichment process, reportedly as superior to enrichment by gas centrifuge as gas centrifuge enrichment is to gaseous diffusion. For a given SWU capacity (SWU = “Separative Work Units”, the standard measure of uranium enrichment capacity) the SILEX plant would apparently use about one tenth the energy of a gas centrifuge plant, and would be smaller and harder to detect. The good doctor was afraid that if a plant were allowed to operate, knowledge of the process would inevitably leak, and presumbably find its way into the hands of terrorists.

    The ABC story is here. There’s also good coverage of the SILEX story at NextBigFuture.

    None of the articles / postings I’ve found mention plutonium. However, given the nature of the process and the fact that PuF6 has similar properties to UF6, I can see no reason whatsoever why the SILEX process couldn’t be adapted for enruchment of plutonium from reactor wastes. Details would be different; the precise laser frequencies would be slightly different, and there would likely be different handling issues. But I think we will have to assume that in the near future, LWR reactor wastes will be “mine-able” for weapons-grade plutonium.

    Does that mean that the anti’s are right, and that we should allow the proliferation spectre to keep us from building new power reactors? Or, more to the point, to vigorously oppose the programs that are already underway in many different contries?

    No, not at all. It just reinforces what I’ve already said: that the genie of nuclear weapons capability has escaped its bottle and is at large in the world. We can’t expect to make it impossible, or even significantly more difficult, for states to acquire nuclear weapons if they really want them. So we need to focus instead on building a world where they won’t feel the need to acquire them. Where they won’t feel they need them as a deterrent against invasion or domination by hostile powers. Or need them for negotiating leverage in competition for increasingly precious water, mineral, and food resources. We can’t allow the world to become starved for energy.

    Even if we allowed the anti’s to dissuade us from building new nuclear power in the US — where there is no proliferation issue at all — it wouldn’t make a dime’s worth of difference in the larger world that we profess to be concerned about. China is pressing full-speed ahead on its own nuclear power program, and expects to become a major supplier to the rest of the world. South Korea is well into that race as well. New nuclear power plants are being rapidly built, and the US cannot stop it. All we can do is “cut off our nose to spite our face”. We can take what some see as the moral high ground by refusing to embrace morally reprehensible nuclear power, and set an example for the rest of the world as we level the Appalachians for coal, pour CO2 into the atmosphere, and sink slowly into 3rd world status while Asia flourishes.

    Or we could take the lead in developing and supplying next-generation reactors that burn up essentially all their fuel and are happy to consume current waste stockpiles.

    Now that’s a really hard choice, isn’t it?


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  24. 174
    ABison Says:

    There is a topical discussion under this article http://atomicinsights.blogspot.com/2010/07/curious-meeting-to-take-place-in.html
    Peter Bradford seems to need some persuasion with facts and logic. Would anyone knowledgeable care to comment?


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  25. 175
    DV82XL Says:

    I have commented myself blue in the face on this subject and have come to the conclusion that people that want to believe this will continue to, no matter how high you pile the facts, and no matter how implausible this idea of bombs-from-waste is shown to be.

    I also believe that this nonsense is a red herring that is dragged through this whole debate because the protagonists have realized that they can get a rise of of the pronuclear nerds at will, by bringing it up. I have written elsewhere that the best defence to deal with this and similar topics is to ignore it.

    Why people like Rod Adams, and other pronuclear bloggers feel the need to give these agents provocateurs a platform is beyond me. This is one of the reasons I am no longer commenting on nuclear forums and blogs, these people will not be convinced, because they are not open to be convinced, but they can show up and shred a discussion with one or two posts of this nature at will.


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  26. 176
    ABison Says:

    Some of us certainly do miss your comments.


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  27. 177
    katana0182 Says:

            ABison said:

    Some of us certainly do miss your comments.

    I second that emotion.


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  28. 178
    George Carty Says:

            Finrod said:

    I think that phenomenon is what Concerned Citizen and his/her fellow-travellers are counting on. Trying to sound just scientific enough that a non-scientist who isn’t thinking too hard on the matter will be decieved by their propaganda.

    Sounds similar to what a lot of cosmetic ads do…


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  29. 179
    DV82XL Says:

            ABison said:

    Some of us certainly do miss your comments.

    Thank-you, I’m touched.


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  30. 180
    drbuzz0 Says:

    There is something that I can say about my claim that effective nuclear weapons can’t be built out of reactor spent fuel or that even if they could, the technical challenges and diminished reliability, longevity and performance would be so extreme it would render the while issue a totally non-credible threat.

    I’m a skeptic and I hate being told “Just trust me” or when the media relies on unconfirmed, vague, anonymous sources on something.

    Unfortunately, I have to do that in this circumstance. I know these assertions are correct because I have confirmation that they are. This has been verified, generally off the record. I have had some communications with people who know things. Some hypothetical questions were asked and some slightly weaselly but very clear answers were given, off the record.

    Really I wish I could provide all the verifiable data to back this up beyond any dispute, but you just have to take my word for it, I guess. Either that or do your own homework and try to find someone who might know a thing or two.


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  31. 181
    DV82XL Says:

    Wait – are you saying it is possible…?


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  32. 182
    Robert Hargraves Says:

    Maybe the South Korea situation will shake something out. South Korea is protected by the US “nuclear umbrella” that says we will treat attacks on it as attacks on us. Obama has slightly weakened the nuclear umbrella by limiting when nuclear weapons would be used. Suddenly the South Koreans want to reprocess spent fuel but claim they have no intention of making weapons. This thread indicates (and I believe it) that normal burnup spent fuel would make a very poor weapon. Maybe more information will have to be released to permit the US to say something like “We know South Korea isn’t making weapons from spent fuel because…”. We let India slide around the NPT; something like that could happen with South Korea.


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  33. 183
    DV82XL Says:

            Robert Hargraves said:

    We let India slide around the NPT; something like that could happen with South Korea.

    Bob, the Indians never signed the NPT in the first place arguing that the NPT created a club of “nuclear haves” and a larger group of “nuclear have-nots” by restricting the legal possession of nuclear weapons to those states that tested them before 1967, but the treaty never explains on what ethical grounds such a distinction is valid.

    Furthermore they were ‘punished’ by getting cut off from fuel and technology for the temerity of exercising their sovereign rights in this matter, so it was hardly a case of letting them get away with it.


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  34. 184
    drbuzz0 Says:

            DV82XL said:

    Wait – are you saying it is possible…?

    That would depend on how you define “reactor grade.”

    Low burnup spent fuel may be possible, although extremely difficult. I’m not sure where you would pin the line as “absolutely impossible” because it’s a spectrum, not a black and white issue.

    <7% will be usable in an explosive, but with difficulties and reduced yield/reliability/longevity and greater fabrication problems. As the quality is reduced, these issues become more and more pronounced to the point where it eventually gets insurmountable.

    What I can say is that the level of plutonium that comes from todays pressurized water or boiling water reactors is not going to do.


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  35. 185
    DV82XL Says:

            drbuzz0 said:

    What I can say is that the level of plutonium that comes from today’s pressurized water or boiling water reactors is not going to do.

    OK. Agreed, it was how you stated it in 180, that made me think it was otherwise.


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  36. 186
    Rod Adams Says:

    I have just posted my version of why it is not possible to produce a weapon using plutonium recycled from used commercial nuclear fuel. For those who know me, you will not be surprised to learn that one of the things I tried to make clear was WHY the non-proliferation establishment has worked so hard to slow the development of a plutonium economy.

    I know my efforts to engage in discussion with antis can frustrate some people, but I want to say again that I know I cannot convince the people on the other side. My hope is that there are interested but not yet convinced observers who can read both sides and make their own decisions. I try to carefully proof read my work and ensure its technical and ethical accuracy and hope that helps to sway the uncommitted to the pro-nuclear position.

    The facts are on our side; so is the benefit to humanity. The people who work so hard to scare people away from the only proven competition for fossil fuels are either inadvertently helping their sworn enemy, or they are working for the fossil fuel industry and know what they are doing.

    Comments would be welcome on my attempt to knock down the assertion that a 1962 test using plutonium sourced from the UK proves that plutonium from used commercial nuclear fuel is too dangerous to recycle.

    http://atomicinsights.blogspot.com/2010/07/proving-negative-why-modern-used.html


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  37. 187
    DV82XL Says:

            Rod Adams said:

    I know my efforts to engage in discussion with antis can frustrate some people, but I want to say again that I know I cannot convince the people on the other side. My hope is that there are interested but not yet convinced observers who can read both sides and make their own decisions. I try to carefully proof read my work and ensure its technical and ethical accuracy and hope that helps to sway the uncommitted to the pro-nuclear position.

    It’s not the antinuclear side that needs to be convinced. They are ether doctrinaire, and thus impervious to reason, or as you rightly assume, crypto-fossil-fuel agents masquerading as antinuclear supporters. This needs to be taken outside to the people, and this is where we are failing badly.

    Our opponents have the popular media’s ear, and as long as they do, they can feed them lies like this one, confident that the truth will not get out into the light. As much as I love blogs like Atomic Insights, none of them has the reach into the minds of the masses that is needed to make a significant impact in areas like this. In fact I suspect that this thread has been read by more folks from outside the nuclear circle than all of the others on any of the pure nuclear sites combined.

    The lack of effort in outreach, with a few notable exceptions, coupled with my own geographic and financial limitations, has been a source of great frustration to me. I am afraid I do not see a significant future for nuclear energy in the West unless our enemies are denied exclusive access to the high ground of public opinion.


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  38. 188
    Shafe Says:

            DV82XL said:

    …This needs to be taken outside to the people, and this is where we are failing badly.

    Our opponents have the popular media’s ear, and as long as they do, they can feed them lies like this one, confident that the truth will not get out into the light. As much as I love blogs like Atomic Insights, none of them has the reach into the minds of the masses that is needed to make a significant impact in areas like this. In fact I suspect that this thread has been read by more folks from outside the nuclear circle than all of the others on any of the pure nuclear sites combined.

    Speaking purely anecdotally of my own experience, I only stumbled across Depleted Cranium because of its broad subject matter. I had finished reading a blog entry from the Houston Chronicle’s science writer about the scheme of using wind power to pressurize idle pipelines with nitrogen as a means of storing and transporting energy. I googled the idea and found Buzzo’s entry on the same topic. I must admit it was his unapologetic and thorough shellacking of the idea that roped me in.

    I began reading his archived blog entries to see what he had to say on other topics and got hooked. I had never read so much on the topic, not just of nuclear power, but quackery, renewable energy, conspiracies, and the like. The nuclear entries really opened my eyes to the importance of the issue. Prior to that point I generally held that nuclear power was an over-vilified issue and the best chance of reducing fossil fuel use, though I was more indifferent to the issue of CO2 as I have never fully bought into the doom-saying of Al Gore and the IPCC. I had never heard of mountain-top-removal mining or really the scale at which coal production is growing. I figured nuke plants were the way to go, but was not impassioned on the issue and didn’t think they had much of a chance anyway because of the anti-nuke culture.

    Once I found that there were lucid voices speaking in reasoned but urgent tones of the need for expanded nuclear power and the terribly political and underhanded means of squelching pro nuclear voices, I set out to learn more, and am continually more convinced of the importance of reviving nuclear growth and countering antinuclear sentiment when I find it.

    You can partially thank chain emails for my traffic. Bogus claims in my inbox lead me to sites like Snopes.com and taught me to be immediately skeptical of what I read. So when I read claims like the nitrogen pipeline scheme I start googling. That may be why Depleted Cranium is so useful to the issue of nuclear power, as it brings in a large cross-section of skeptical readers and, like me, exposes them to the issue.

    I guess my point is that you can have all the sites you want serving as echo chambers within the pro-nuke community or battling with the anti-nukes, but until there is more of a nuclear presence in general interest sites, net traffic will continue to pass the issue by. Buzzo has managed to cast a net that is bringing outsiders like me in, but more nets need to be cast in more seas.


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  39. 189
    drbuzz0 Says:

            DV82XL said:

    I am afraid I do not see a significant future for nuclear energy in the West unless our enemies are denied exclusive access to the high ground of public opinion.

    I’m a bit more optimistic. The public opinion of nuclear energy in the US and many other Western nations is quite good and is rising. There is a vocal and politically active minority, but I don’t think they can keep things from moving forward forever. The advantages are there and all the smoke and mirrors in the world can’t hide it. It’s clear that it works and works well for those societies that have embraced it and that’s getting hard to hide.

    It’s going to take a while, that I’ll fully admit. Some may have to be dragged kicking and screaming, but it will happen sooner or later.

    Things will begin to shift, slowly at first. In some ways they already are. There will be steps forward and occasionally backward, but eventually it will all come crashing down.


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  40. 190
    Shafe Says:

    By the way, I’ll be visiting home (Houston) in a few weeks. Anyone got a list of good books I might be able to find on the topic of nuclear power at a used book store while home? Here in Bishkek, I’m pretty much limited to perusing websites. The bookstores here might have some interesting reading, but my Russian sucks.


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  41. 191
    DV82XL Says:

            drbuzz0 said:

    I’m a bit more optimistic. The public opinion of nuclear energy in the US and many other Western nations is quite good and is rising.

    Unfortunately positive public opinion, and public support are not the same thing.

    One of the major revelations for me on this issue is that real public opinion on nuclear matters is nowhere near what both the antinuclear side, the media, and the governments claim it is. The fact is that very few polls have been done, and even fewer that have be done with the sort of rigour that one would expect for such an important subject. Those that have been done like the Eurobarometer survey carried out for the European Commission’s directorate-general for energy and transport on the subject have yielded surprising results, yet policy in most of the EU on nuclear energy has remained little changed, with politicians claiming that there is no public support.

    Much the same in happening in Canada with projects being squashed in the planning stages, even in the face of positive public opinion. Look at the current efforts to build a merchant NPP in New Brunswick, or the attempt by Bruce Power to begin a study on replacing Nanticoke with a nuclear power station, or the stymied plans to build a NPP at the Whiteshell.

    In the US its beginning to look as if the best that can be accoplished is that new builds will keep up with old plant retirements, which have been eroding the total percentage of nuclear supplied power for some time now. Nuclear will be lucky if it grows to 25% in the next thirty years, if things continue as they are.

    In terms of what has to be done to achieve significant reductions in burning carbon-base fuels, next to nothing is being accomplished and growth in nuclear energy such as it is is little more than token efforts, accompanied by much hand wringing over the collection of false issues (like proliferation, and waste management) that have been carefully cultivated by the opposition to be trotted out whenever there is danger of real progress.

    All of the so-called problems are simple creations of propaganda. The proliferation issue has been done to death, as has the radiation issue and the LNT nonsense it’s based on. All of them are false dilemmas, designed to create the illusion of problems where none exist. First and foremost it seems that few understand that the debate is not really centred on technical issues, nor is it centred on public fears as delineated by antinuclear forces. As a consequence there is no “designing around” these perceived issues, in fact attempting to do so only allows the other side to claim these efforts validate these problems.

    The waste issue is a case in point. The uncontrolled and persistent wastes from combustion driven energy is by many orders of magnitude a greater problem than nuclear wastes could ever be. Rather than go on the offensive and push this fact at the public, nuclear has tried to fix this non-existent problem by planning, and in some cases, creating ridiculously over complicated disposal sites. The upshot of this tactic however is that first it corroborates the belief that these are necessary, and second, as illustrated neatly by the farce surrounding The Yucca Mountain Repository is the United States, a convenient target for the opposition. Similar efforts are facing organized protests in other countries as well.

    How often does it have to be repeated that the reasons given by antinuclear forces objecting to nuclear power are contrived, and they will not accept any ‘solution’ – they are not interested in one, and nether is the general public, because in fact they don’t care. Consider this: how often do you see protests at dry-cask storage sites left over from decommissioned nuclear plants? The reason you don’t is that as far as the public is concerned they ARE a solution, and the protesters know that getting people worked up would be a hard sell.

    (Even the subject of this thread is contrived to the point of being ludicrous: Even if a nation with a nuclear weapons complex the size and calibre of the ones in Nuclear weapon States could, theoretically build a device with RGP that might, under idea conditions, and a lot of luck, go supercritical, this still wouldn’t be a weapon. An explosive device isn’t a weapon until it is deliverable, reliable, and deployable in militarily significant numbers. The whole argument becomes sterile if this factor taken into account.)

    As well, there is not a nuclear industry per se; almost every company involved in nuclear, also have energy interests in other sectors. They will act in their shareholders best interests, and if that means they can make more money building windmills than reactors, that is what they will do. Thus is is a waste of time to attempt to curry the favour of these players. No help whatsoever can be expected from this quarter.

    Furthermore, too much hope is being put in the new entries into the reactor market. Even those that are legitimately looking to introduce new designs, face an almost unscalable wall of regulation, and the hostility of those firms that have obtained type-approval for their products, and will not likely stand still if the bar is lowered for newcomers. And like it or not, there are players in the small reactor sector that are more about attracting investment, than they are about bringing a product to market.

    In a similar vein, debate about what GenIV design is superior is at best premature, but is certainly becoming divisive. the product cycle for GenIII and GenIII+ designs is not done, and will be twenty years before GenIV technology will be launched. During that time several new reactor types will be tested and it is likely that in the end a mix of designs will be the outcome, rather than one type taking all. At the moment getting new NPP built with existing technology should be the major thrust of everyone’s effort. There is no point drawing knives on each other now over this; it is a very sterile issue.

    The deployment of nuclear energy cannot be accomplished by cultivating political support, and looking for a legislative solution. The enemies of nuclear energy simply have pockets too deep and have ingratiated themselves too firmly into government to allow a small group of elected officials to overcome the influence these interests can apply. The only hope is create a groundswell of public support and very few in the pronuclear movement seem to want to do anything more than pay lip-service to this, hoping it seems, that there is some short-cut that will see some ‘Manhattan Project’ launched from the top down to bring about a nuclear revolution.

    This is not just the case in the States, but all over the West. If a real Nuclear Renaissance is what we want, it is going to have to be a popular movement – it is just that simple, and anyone thinking there is a short cut is deluding themselves.


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  42. 192
    ABison Says:

    @Shafe: This book is a great read and gives some perspective of the depth of nuclear phobia:

    Spencer R. Weart, Nuclear fear: a history of images
    http://books.google.com/books?id=NuFubjYl1poC

    Most of the content is online. One can buy a used paperback for couple bucks:
    http://www.amazon.com/gp/search?index=books&linkCode=qs&keywords=0674628365


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  43. 193
    Brian Weeks Says:

    In current terminology, “weapons grade” plutonium is considered to have roughly 93% Pu-2239 or more, while “fuel grade” or “mid grade” plutonium has at least 81% and “reactor grade” contains less than 81% Pu-239.

    Typo here – please correct. Pu-2239?


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  44. 194
    George Carty Says:

            DV82XL said:

    The deployment of nuclear energy cannot be accomplished by cultivating political support, and looking for a legislative solution. The enemies of nuclear energy simply have pockets too deep and have ingratiated themselves too firmly into government to allow a small group of elected officials to overcome the influence these interests can apply. The only hope is create a groundswell of public support and very few in the pronuclear movement seem to want to do anything more than pay lip-service to this, hoping it seems, that there is some short-cut that will see some ‘Manhattan Project’ launched from the top down to bring about a nuclear revolution.

    If the pockets of the anti-nukes are THAT deep, couldn’t they shut out pro-nuclear public support by buying all the main political parties so that all the election candidates are anti-nuclear? That’s my big worry — that nuclear energy will be suppressed by undemocratic means…


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  45. 195
    DV82XL Says:

            George Carty said:

    If the pockets of the anti-nukes are THAT deep, couldn’t they shut out pro-nuclear public support by buying all the main political parties so that all the election candidates are anti-nuclear? That’s my big worry — that nuclear energy will be suppressed by undemocratic means…

    Well to a certain extent they HAVE bought the leadership of most major parties. However despite the fact that the lower echelon elected members (what we call back-benchers in the Commonwealth system) normally have little influence, they still need to be elected, and have in the past forced change because of public opinion. The fact is no amount of lobbying or slush funding is going to outweigh the threat of a significant number of them losing their seats.

    Look at the history of most hot-button issues, and you will see politicians voting to save their asses, regardless of party position.


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  46. 196
    R.J. Moore II Says:

    An extremely fascinating piece, I knew the basics of how fission weapons and reactors worked but you really added a lot of detail to the matter. Keep up the awesome posts, nuclear physics and engineering are great reading.


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  47. 197
    George Carty Says:

    Why do space probes use (hugely expensive) plutonium-238 in their RTGs, rather than (much cheaper as found in spent fuel) strontium-90?

    Sure Sr-90 is a beta emitter while Pu-238 is an alpha emitter, but Sr-90 doesn’t emit appreciable quantities of gamma rays, and wouldn’t cladding it with about a centimetre thickness of non-radioactive metal should prevent the betas doing damage to the rest of the spacecraft?

    Or is Sr-90′s half-life (28.8 years, rather than Pu-238′s 87 years) too short for space probes?


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  48. 198
    drbuzz0 Says:

            George Carty said:

    Why do space probes use (hugely expensive) plutonium-238 in their RTGs, rather than (much cheaper as found in spent fuel) strontium-90?

    Sure Sr-90 is a beta emitter while Pu-238 is an alpha emitter, but Sr-90 doesn’t emit appreciable quantities of gamma rays, and wouldn’t cladding it with about a centimetre thickness of non-radioactive metal should prevent the betas doing damage to the rest of the spacecraft?

    Or is Sr-90′s half-life (28.8 years, rather than Pu-238′s 87 years) too short for space probes?

    A couple of reasons:

    1. You would need more of it, because it has a lower power density. Mass is the enemy in space flight.
    2. It would require more shielding. Sr-90 is a beta emitter, but it produces secondary x-rays as a result and this would require quite a bit of shielding ionizing radiation is an issue for space probes because it could interfere with sensitive instruments.
    3. Half-life could potentially be an issue, depending on the mission. If it’s something like Voyager, which is still functioning decades after launch then the halflife could definately be an issue. Probably would not be an issue for something like the Mars Science Laboratory though.


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  49. 199
    Anon Says:

    ⁹⁰Sr also has a lower energy density than ²³⁸Pu so you’d need more of it (and every kilogram costs thousands with a space probe, a centimetre of cladding would also add more mass).

    The shorter half life of ⁹⁰Sr also means that the probe would need even more to last the same amount of time before they don’t have enough power to operate (though it’d probably work pretty well).

    When it comes down to it they also tend to launch those space probes on their most powerful rockets and so saving a couple of hundred kilograms on the RTG can allow them to carry an extra couple of hundred kilograms of scientific instruments (which is what the probe is built to carry anyway).

    When launch costs come down enough ⁹⁰Sr could make sense for more space missions and might even end up dominating over ²³⁸Pu but probably not right now (though ²⁴¹Am (longer half life but lower power density), ²¹⁰Po (short high power use only, make sure you cool it well because it has enough heat to vaporise itself) as well as ²⁴²Cm and ²⁴⁴Cm (need lots of shielding) could also be used in RTGs).


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  50. 200
    George Carty Says:

            Anon said:

    ⁹⁰Sr also has a lower energy density than ²³⁸Pu so you’d need more of it (and every kilogram costs thousands with a space probe, a centimetre of cladding would also add more mass).

    Thanks, I checked the info on the two isotopes again — each one of ²³⁸Pu’s alpha particles carries ten times the punch of a ⁹⁰Sr beta particle, so I guess that explains the difference in power densities.


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