Here are some of the latest measurements of radiation levels in the Fukushima region of Japan, these were made just last month.
There is something very striking about this image even at first glance. Notice that the no-entry zone has absolutely no correspondence whatsoever to radiation levels. It’s simply a circle drawn around the nuclear plant. Much of the area has quite low radiation levels and some of the area outside the exclusion zone has higher radiation levels than the area within it. Since there’s now no real danger of the reactors being further damaged or experiencing uncontrolled discharges, there’s absolutely no reason to enforce a no-entry zone based on such a blind method of drawing the map. If a no-entry zone is to exist at all (which it really, at this point, does not need to)
Actual Doses experienced:
Few areas exceed 20 uSv per hour by very much. The red area signifies areas with higher than this level, but most of this area is only slightly above 20 uSv/hr. Areas with 20 uSv/hr or more exist in a relatively narrow strip running northwest from the area of the nuclear plant.
A person lives in an area where the external radiation dose rate is 20 uSv/hr. Of course, this is really only outdoors and inside there will be less contamination, but for the sake of argument, lets assume the worst: They get 20 uSv/hr and they stay in that are all the time. There are 8760 hours in a year, so if they spend all their time outdoors in the 20 uSv/hr area, they receive 175,200 uSv per year or about 175 mSv per year.
This is still a bit unreasonable for what a person would actually be exposed to because it assumes they are always outdoors and standing over ground that has not been in any way cleaned of contamination. Indoors, the level will be a lot lower. If they travel outside the area of highest radiation, their dose is also reduced. As time goes on, both radioactive decay and natural weathering and erosion will reduce levels further. Therefore, after a year in such an area, it’s more reasonable to expect a total exposure of something like 100-150 mSv and maybe quite a bit less.
Most of the no-entry zone is far bellow this. The yellow areas would produce only about half the dose of the highest regions and the areas shaded green would result in an annual dose of only about 10-30 mSv her year. That’s hardly a lot of radiation.
How much radiation a person is exposed to in a year from background sources varies greatly depending on things like location, diet, travel and things like whether they happen to cook with natural gas, live in a granite structure or have radon seeping into their home’s foundation. About 3 mSv is a normal average for those living at sea level in much of the world. Of course, it’s quite common for it to be much higher than this. Areas with background radiation in excess of 10 mSv per year are quite common. A few areas have much higher. In the Guarpari region of Brazil, background levels can exceed 175 mSv per year due to local deposits of uranium and thorium. Residents of Kerala India experience doses of over 70 mSv per year. Ramsir Iran is famous for having some of the highest levels in the world at over 260 mSv per year. Locations across Africa and Australia may produce levels above 40 mSv per year.
Studies have been done of the populations of these areas and no ill effects have been documented as a result of the high radiation exposure. Of course, the expected radiation exposure from living in such an area for an extended period of time would be much higher than for those in the Fukushima area. Since the radioactivity in the Fukushima region is mostly limited to the surface and includes many relatively short-lived radioisotopes, it will diminish significantly in the years to come. Natural sources, on the other hand, are constantly replenished. So a person who lives in an area with increased radiation levels as a result of the Fukushima incident will not experience the same dose next year as they will this year. It will be less.
And no, there have been no calls that high background areas of the world be evacuated and declared off limits.
Living in the vast majority of the area around Fukushima would result in a radiation dose lower than living in many areas of the world and which could reasonably be considered acceptable. Visiting these areas, even for extended periods of time, in order to recover property, secure damaged structures and begin the cleanup would result in even lower levels of exposure. If a person were allowed to travel to the area and spent a cumulative few days in one of the highest areas of radiation, they would receive less exposure than from a dental x-ray. A person could spend a month in the regions of highest radiation and experience a total increase in annual dose that would be less than that millions of people around the world live with for their entire lives. Traveling through the area would result in even lower radiation exposure.
A More Reasonable Proposal:
I’d like to propose a more science-based and less restrictive zoning for the area around the Fukushima nuclear power plant. Under this proposal, the evacuation and no-entry order would be immediately lifted and the vast majority of the area would be available for immediate resettlement, property recovery and rebuilding.
Two zones would remain for the immediate future, the exclusion zone and the limited access zone.
The Exclusion Zone:
The area immediately around the plant boundary. This area would be accessible to plant workers, recovery teams and others involved in the cleanup, survey and general maintenance. The reason for keeping members of the public out is not only to reduce radiation exposure but also because this area is the primary area of remediation activity and is being used as a staging area for equipment and personnel. Those working in the area would need to follow standard procedure for dosimeter.
Limited, escorted visits by those who may live just outside the plant perimeter would be allowed for the purposes of recovering property, surveying damage and securing structures that may remain intact.
Limited Access Zone:
This area is defined not by simple distance from the plant but rather follows the approximate area of the highest radiation levels. Visitation to this area and travel through it would not be subject to major restrictions. The only restriction to access would be that the area would not be zoned for full time resettlement. While those living in that area would be allowed to visit their homes without supervision, they would continue to be offered shelter elsewhere and it would be requested that they not permanently settle into the area or remain there for several consecutive days, although such restrictions would be more of a request than a strongly enforced rule.
Recovery efforts, repair of infrastructure traversing the area and recovery efforts would begin immediately with little or no restriction. As the area would be considered to be free to visit but not designated for resettlement, schools, post offices and other facilities catering to residents would remain closed, but would be repaired and secured. Basic services like fire and ambulances would be restored as soon as possible.
Those wishing to resettle sooner in the area could begin remediation work, such as power washing surfaces and removing top soil and could have their property surveyed for safety and radiation levels. If a government-approved surveyor confirms that the total radiation levels for a structure and surrounding area are within certain standards and that the structure has been repaired to meet building codes, that property could be issued a certificate for residency.
The limited access zone would be the only area subject to government sponsored cleanup and radiation remediation measures. Areas outside this region would only receive such attention if an exceptionally high reading was found on a “hot spot.” Other than that, it’s just not worth the amount it would cost to reduce already low levels.
Eventually all resettlement limits would be lifted and the exclusion zone around the plant would also be eventually withdrawn, pending how the future of the recovery plays out.
This entry was posted on Sunday, March 18th, 2012 at 12:15 pm and is filed under Bad Science, Enviornment, Good Science, Nuclear, 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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