Anon said:

I think we all know the chances of that.

Maybe a US satellite malfunctioned (with a real test you’d expect other instruments to have confirmed it).

No, it has not been confirmed. There are some other things that seem to have been recorded by instruments, however, including a magnetic pulse detected by ionospheric observatories and scattered reports of possible fission byproduct detection.

One of the stories that has circulated, coming from some Russian officials is that it was a test of a very small fusion-boosted fission weapon conducted by Israel with possible assistance from South Africa. The intent was to hide the test (which tends to be very hard to do) by making it very small, conducting it in a very remote area and doing it at sea, rather than underground, which would produce detectable seismic disturbances. Also, conducting it under as heavy as possible cloud cover and during daylight would help hide the flash. However, enough cloud cover cleared and a satellite was close enough to detect it.

I can’t say for sure that this is true, but I think it very likely is. The number one thing that makes me think this is that so much is classified. We know the United States flew many missions in the area looking for fallout, and we’re told that they didn’t find anything unusual. But if not, why is the actual data from the sampling flights classified? Routine sampling mission data is usually not classified. Why is the communication between NATO countries, Australia and others still tightly guarded? If there was nothing to it, I would not expect so much would still be unobtainable.

This is what I think might have happened (and this is only a guess, and I can’t say for sure it is true.):

There was an Israeli test, which they had hoped would be undetected, but once it became public that the US had detected it and that the Israelis were forced to go to the US and basically say “Okay, we’ll tell you what happened, but you have to keep this all secret.”

That would have been agreed to for a number of reasons. Whether or not the US was happy about another country entering “the club,” which it probably wasn’t, it still would have good reason to keep the information secret. First, Israel is generally regarded as a friendly nation and an ally, and it was not a good idea to cross your allies during the Cold War. Secondly, it’s very obvious that if it became public that Israel had conducted a nuclear test, it would have been very inflammatory to the Middleeast, and nobody wanted that. Third, politically, relations with Israel are always a hot-button issue in the US. There is a huge pro-Israel lobby and because of this, most US politicians feel very uneasy about saying anything negative about Israel’s actions or policies, and a nuclear test would have really been a political problem.

Even to this day, any countries which might be directly aware of an Israeli test would probably think it’s better not to let that out. One can easily see how the existence of such a test would be seized upon by Iran as reason to justify their own nuclear ambitions.

But again, that’s just my own speculation.

        Anon said:

Maybe a US satellite malfunctioned (with a real test you’d expect other instruments to have confirmed it).

No its not ever been confirmed, but the potential involvement of Israel, who were rather tight with S.A. at the time (there were suggestions it was a joint test) might have kept some data from coming to light.

        Jim Baerg said:

If some people is concerned about cheap enrichment making fission bombs too easy, perhaps they should be promoting reactors that don’t need enrichment. Eg: CANDU IFR LFTR.

Of course this assumes that bomb proliferation is their real concern & not some ideological or financial investment in the anti-nuclear power position.

I think we all know the chances of that.

Maybe a US satellite malfunctioned (with a real test you’d expect other instruments to have confirmed it).

        Ray1952 said:

South Africa publicly admitted development starting in the 1960’s. Never tested a weapon, but came close.

Maybe they didn’t – then again maybe they did

Of course this assumes that bomb proliferation is their real concern & not some ideological or financial investment in the anti-nuclear power position.

A country that is simply trying to produce a nuclear weapon of minimal capabilities might decided that the gun-trigger design (which necessitates HEU and not Pu) is the easiest way to do it because it avoids some engineering challenges and is almost certain to work if the material is obtained.

Any “mature” nuclear power will use implosion triggering (of varying types and sophistication) for all weapons. They may be uranium or plutonium. Actually, a fully matured and fully capable nuclear power will want both the capability to enrich uranium AND produce plutonium.

The advantages being:

plutonium – used for the pits of modern nuclear weapons. Smaller size. Smaller critical mass. More neutrons (for use in irridiating fusion secondary). Therefore plutonium weapons can be smaller and give more “bang for your buck.”

uranium – HEU and uranium of various enrichment levels is used in the secondary to initiate the reaction to create fusion. Also may be used in the tamper to boost the yeild further. A warhead might have a primary with plutonium and a spherical secondary with a HEU ’spark plug’ in the center and then surrounded by a shell of uranium, which could be HEU to further boost the yeild in the small package, since it has a greater fission cross section than LEU or DU (both of which can also be used, as they will fission adequately in the super high flux of hard neutrons)

Enriched uranium is also desirable for the reactor used to make plutonium. A plutonium production reactor can be made with only natural uranium, by just piling it up with graphite or heavy water, but natural uranium is never going to give the kind of neutron flux you’d get with enriched uranium and a reactor using enriched uranium can be much smaller.

A quick aside: No country has ever really “shocked” the world with a nuclear detonation, at least not since 1945. The Soviet Union was a little surprising because it detonated one sooner than expected, but it was known they were working on it.

North Korea’s tests came after a nuclear program that everyone knew existed for decades before.

It was well known that the UK, France and China were all engaged in nuclear weapon development before their first tests occurred.

India tested a weapon in 1974, two years after it became public that it was preparing for a weapons test and having had a development program since the 1940’s.

Also well published that Pakistan was working on nuclear weapons since the 1970’s and their completion of most facilities needed for weapons was known by the 1990’s.

South Africa publicly admitted development starting in the 1960’s. Never tested a weapon, but came close. Was well known they were preparing.

There has never been a circumstance of a country detonating a nuclear weapon and the response of the world being “We had not the slightest idea that they had been developing nuclear weapons or had any intent to test a nuclear weapon any time around now.”

        drbuzz0 said:

I don’t know if India or Pakistan did any work on gun triggered weapons.

Both these countries went straight to Pu implosion-type weapons from the start, however Pakistan also manufactured a miniaturized weapon design that could be delivered by fighter aircraft outside the scope of their main program, (that is by another agency) and these may have been HEU fueled gun-type devices. Little has been heard of these after the late 80’s and it is unknown if these weapons are still part of that country’s arsenal.

        Matte said:

I was not sarcastic, not one bit…

If you want a usable weapon as a final product you need the implosion type. I know that in the Swedish nuclear weapons program there was never any discussions about weoponising anything but an implosion type Pu-device. I do realise that it does require “good” Pu to make it work, but as a chemist I can say that that is the easy part…

Also if I can put together an effective RSV-device (if I wanted to), I am sure an explosives expert can knock up the geometry required for an effective implosion device…the rest is just machining!

If you just want a big bang with a lot of enrichment hassle, sure, go for the gun and slugg type.

The issue of implosion versus gun-triggered devices is one that has been discussed in many areas before and many nations have chosen to start off with the gun-triggered uranium type. One thing about that kind of weapon is that it’s so simple and reliable (compared to implosion type) that if it’s correctly made and has suitably enriched uranium it is basically guaranteed to work. It is considered reliable enough that a simple one could be fielded without testing. In that case, you might be off a little on the yeild, but unless you completely bungle the design, it will work.

Implosion is much more efficient, of course. It’s the preferred method for both plutonium and uranium devices and plutonium devices require implosion.

Both routes require some advanced technologies.

Uranium alone requires complex chemical conversion and fluoridation along with enrichment and de-fluoridation and smelting. Uranium is a tough material to work with, requiring vacuum furnaces and machining under inert gas etc.

Plutonium weapons can be done without enrichment, although uranium enrichment still can help, because enriched uranium can give you a reactor with better neutron economy, which means you can irradiate the fuel more effectively and make more plutonium faster. Plutonium requires a suitable reactor. Power reactors don’t work well for this. It should be purpose-designed to have material easily cycled through it relatively quickly.

Then the plutonium must be separated. The chemistry of doing this is straightforward, but any operation doing so must be large, because the yield of weapons grade plutonium from a single cycle of irritation is very low. Hence, large amounts of material need to be processed to get enough plutonium for weapons use.

The radioactivity of plutonium complicates things. The fluids used for extraction need to be cooled from decay heat of plutonium and leftover fission byproducts. Hotcells are required for assembly etc.

Plutonium is notoriously difficult to work with as a metal. It’s much worse than uranium. Plutonium metal can spontaneously combust and it’s very brittle and reactive. Actually, the properties of plutonium make it problematic for weapons use on its own. It needs to be alloyed with a few percent of other metals to make it usable. The exact formulas are secret, but are known to contain mostly gallium.

If you look at what it took the US to create both uranium and plutonium for weapons, neither was a simple task. Uranium enrichment took up much of the Y-12 complex, using electromagnetic separation and gas diffusion.

Plutonium production was done at Hanford Washington. It required a very large reactor and reprocessing complex be built. Uranium slugs were fabricated, irradiated, cooled and then placed in containers to be transported by rail a few miles away to the reprocessing and materials recovery complex. After plutonium concentrate was obtained, it was shipped elsewhere to be converted to metal, alloyed and fabricated.

It’s not especially easy either way. Doable, by state-level standards, but not easy.

BTW: Gun triggered weapons are generally regarded as obsolete by modern nuclear states. The United States used the gun-triggered design for the first uranium bomb, but after that most weapons were implosion-triggered. A few weapons designs in the late 1940’s and early 1950’s were gun triggered (such as the mark 8 and mark 11) Gun triggered devices were used in a few low-yeild and special weapon designs of the 1950’s, such as artillery rounds.

The Soviet Union never really went very far with the gun triggered design either. They may have used it for some low-yeild or special purpose designs, but, like the US, by the time ‘advanced’ designs were being made, in the 1950’s.

I don’t know about the French, Chinese and British (they may have early on, but certainly would be considered obsolete by now)

The South African nuclear weapon program went the route of gun-triggered uranium weapons. It’s rumored that that is how the Israel program produced its first generation of weapons as well (But probably not in use anymore) I don’t know if India or Pakistan did any work on gun triggered weapons.

I’ve been to Urenco and know some of the basic design points. Sure I won’t be designing a full height, articulated carbon rotor design like they use. But a simple straight maraging steel rotor is fairly simple. The lower bearing is a “needle floating in oil-film” affair, which is fairly standard for high speed applications like this. (And probably an off the shelf part by now from any of a dozen suppliers).

While silex might be cheaper in the long run, gas centrifuge technology is out there now, much simpler and much easier to build covertly. Ordering a laser with the right wavelength is suspicious. Ordering a oil film bearing for 15.000 RPM applications is not (anymore).

        Anon said:

That might be part of the reason North Korea is interested in enrichment (using A. Q. Khan technology).

BTW: You might want to include <sarcasm> tags when saying that implosion type bombs are easier.

I was not sarcastic, not one bit…

If you want a usable weapon as a final product you need the implosion type. I know that in the Swedish nuclear weapons program there was never any discussions about weoponising anything but an implosion type Pu-device. I do realise that it does require “good” Pu to make it work, but as a chemist I can say that that is the easy part…

Also if I can put together an effective RSV-device (if I wanted to), I am sure an explosives expert can knock up the geometry required for an effective implosion device…the rest is just machining!

If you just want a big bang with a lot of enrichment hassle, sure, go for the gun and slugg type.