Fukushima update: get a grip part 2
March 19, 2011 - 8:06 pm
At this point, with the new air war in Libya to distract them, it’s possible the legacy media will calm down a bit. Until it does, be careful what you’re listening to — I’m still hearing news readers talking about “frantically pouring water on the exposed reactor core.”
Which they’re not.
For reasonably decent data, look at the IAEA Japan tsunami site, the Nuclear Energy Institute site, and the MIT Department of Nuclear Science and Engineering site.
Now, let’s get down to the status reports.
NEI: Radiation doses at the Fukushima Daiichi nuclear power plant continue to decrease. Radiation dose rates at the site boundary of the Fukushima Daiichi nuclear power plant ranged from 1 millirem to 3 millirem per hour on March 18. Eighteen locations were monitored in a 30-kilometer to 60-kilometer radius of the plant. The highest radiation dose rate at any of those locations was 14 millirem per hour.
This is a fairly substantial drop in the dose rate from just a few days ago — which is to be expected, because many of the radionuclides released have short half lives, minutes to hours. 1 millirem means 1000 hours to get 1 rem, 10,000 hours to get to 10 rem, the occupational dose limit in the US for one year — which you couldn’t get, because 10,000 hours is a little over 13 months.
Nature: Nature has also learned that initial CTBTO data suggest that a large meltdown at the Fukushima power plant has not yet occurred, although that assessment may change as more data flow in during the coming days. Lars-Erik De Geer, research director of the Swedish Defence Research Institute in Stockholm, which has access to the CTBTO data and uses it to provide the foreign ministry and other Swedish government departments with analyses, says that the data show high amounts of volatile radioactive isotopes, such as iodine and caesium, as well the noble gas xenon. But so far, the data show no high levels of the less volatile elements such as zirconium and barium that would signal that a large meltdown had taken place — elements that were released during the 1986 reactor explosion in Chernobyl in the Ukraine.
Rather, the data sit well, he says, with a scenario wherein the main release of radioactivity has come from the release of excess pressure in the containment vessels of affected reactors, and the subsequent explosion of the evacuated hydrogen-laden steam within the reactor buildings. The radioactive plume will spread around the hemisphere within weeks, he predicts, but the levels of radioactivity outside Japan will not be dangerous. The levels in Japan itself, outside the immediate vicinity of the Fukushima power plant, “wouldn’t scare me”, he adds.
[Emphasis mine.] Note two things here: the data are not consistent with a major meltdown or release of core material, which would make it more like Chernobyl. Secondly, the data don’t indicate any zirconium, which not only is evidence against a core meltdown, but also suggests there have been no “burning fuel rods”, no “fuel rod fire.”
IAEA (19 March, 1400Z): Radiation levels in major Japanese cities have not changed significantly since yesterday.
The IAEA radiation monitoring team took measurements at seven different locations in Tokyo and in the Kanagawa and Chiba Prefectures. Dose rates were well below those which are dangerous to human health.
The monitoring team are now on their way to Aizu Wakamatsu City, which is 97 km west of the Fukushima nuclear power plant. They have just provided initial measurements from three additional locations.
Measurements made by Japan in a number of locations have shown the presence of radionuclides – ie isotopes such as Iodine-131 and Caesium-137 – on the ground.
This has implications for food and agriculture in affected areas. The IAEA and the UN Food and Agriculture Organization (FAO) are consulting with the Japanese authorities on measures being taken in these areas related to food and agriculture.
The Japanese Ministry of Health, Labour and Welfare has announced that radiation levels that exceeded legal limits had been detected in milk produced in the Fukushima area and in certain vegetables in Ibaraki. They have requested the Bureau of Sanitation at the Fukishima Prefectural Office, after conducting an investigation of the relevant information, to take necessary measures, such as identifying the provider of these samples and places where the same lots were distributed and banning sales based on the Food Hygiene Law. (Note: The text originally read out at the briefing was: “The Japanese Ministry of Health, Labour and Welfare informed the Agency that radiation levels exceeding legal limits had been detected in milk produced in the Fukushima area and in certain vegetables in Ibaraki. The Ministry ordered protective measures including a ban on sales of these products.” An oral correction was made during the media briefing.)
We now have continuous online access to data from CTBTO radionuclide monitoring stations, which is being evaluated by Agency dosimetry specialists.
As far as the Fukushima Daini nuclear power plant is concerned, there is no record of any incidents or radiation releases at the site. Present elevated radiation levels at the Daini site are attributed by Japan to events at the Daiichi nuclear power plant.
[Emphasis again mine.] Presence of radioactive iodine would indicate some leakage of some sort from the reactors, as iodine is a major fission product from uranium. It’s also significant because one of the medium-scale health effects of Chernobyl was a spike in pediatric thyroid cancer, which the UN WHO associated with iodine release. But this should be taken with a grain of salt as well (iodized salt?) because the amounts are very small.
The major pathway for iodine to enter the body is from food; the biggest reason for the spike in thyroid cancer around Chernobyl was that contaminated milk continued to be sold and consumed.
Also note that they no longer believe the Fukushima Daini plant had any sort of radiation release — the two plants are close together, and they now believe any increases in radiation at Daini were caused by the Daiichi reactors.
It’s hard to imagine, but it’s now been eight days since the Honshu quake and tsunami, and evidence continues to accumulate that while it was certainly a bad industrial accident, the “doomsday” and “worst case” scenarios just haven’t happened. Every day longer makes those scenarios even less likely — the reactors are cooling, the Japanese are getting them supplied with power, and the fuel rods haven’t burned.