Hi all.
I am saddened by the nuclear reactor disasters occurring in Japan, compounding the misery from the earthquake and the tsunami that the people there have had to endure, and I hope and pray that they will be able to get control of the situation soon.
There are apparently many people concerned that radioiodine from the Japanese reactors could make it to California, and there is a run on potassium iodide supplements for protection from this possibility.
I just want to note that I think it would be virtually impossible for this to be a problem.
First, the iodine isotope of concern is I-131, which has a half-life of about 8 days. When the fission reaction is stopped, no further I-131 is produced, and what is there decays with an 8-day half-life, so that in a few multiples of 8 days, essentially none is left.
Even more important is that there is a great deal of water between Japan and California. The chemistry of iodine and water is well-known. Iodine will readily dissolve in water to form iodide and iodate ions, and the gaseous form, I2, will cease to exist. The huge volume of ocean water will dilute these ions, and their radioactivity will decay with the 8-day half-life.
The nuclear community was reminded of this years ago when the Three-Mile Island accident occurred. Part of the core melted, and some of the radioactive xenon and krypton (noble gases) was released, but there was no iodine release, because plenty of water remained within the containment dome, and the iodine dissolved in it and was converted to iodide and iodate. This was in contrast to what happened at the Chernobyl accident, in which the water was lost in the fire fueled by the burning graphite moderator. Graphite is not used in boiling water reactors or pressurized water reactors of the types built in Japan, the U.S. and elsewhere for power generation.
It's true that if there is a large thermal convection produced by heat release from the reactors, radionuclides can be carried up into the upper atmosphere, and can circle the globe without contact with ocean water. However, there is a big dilution factor in this case, and it will take some time for rainout of the soluble radionuclides to occur, limiting the dose rate again in two ways.
So the bottom line is that it would be virtually impossible for radioiodine to travel through the atmosphere across the ocean from Japan to the U.S.
This does not rule out travel of other radionuclides, and I would be surprised if the sensitive radiation detecting instruments worldwide would not be able to detect some.
However, considering the long distance between Japan and the U.S., and the associated dilution in the ocean and the atmosphere, the resulting dose rates will likely be very low.
I am not in any way minimizing the magnitude of this tragedy, especially for the Japanese people, but I think it is important for people in the U.S. to understand the limits on the possible direct consequences of radiation exposure from a source of release so far away.
Best regards,
Rich
I am saddened by the nuclear reactor disasters occurring in Japan, compounding the misery from the earthquake and the tsunami that the people there have had to endure, and I hope and pray that they will be able to get control of the situation soon.
There are apparently many people concerned that radioiodine from the Japanese reactors could make it to California, and there is a run on potassium iodide supplements for protection from this possibility.
I just want to note that I think it would be virtually impossible for this to be a problem.
First, the iodine isotope of concern is I-131, which has a half-life of about 8 days. When the fission reaction is stopped, no further I-131 is produced, and what is there decays with an 8-day half-life, so that in a few multiples of 8 days, essentially none is left.
Even more important is that there is a great deal of water between Japan and California. The chemistry of iodine and water is well-known. Iodine will readily dissolve in water to form iodide and iodate ions, and the gaseous form, I2, will cease to exist. The huge volume of ocean water will dilute these ions, and their radioactivity will decay with the 8-day half-life.
The nuclear community was reminded of this years ago when the Three-Mile Island accident occurred. Part of the core melted, and some of the radioactive xenon and krypton (noble gases) was released, but there was no iodine release, because plenty of water remained within the containment dome, and the iodine dissolved in it and was converted to iodide and iodate. This was in contrast to what happened at the Chernobyl accident, in which the water was lost in the fire fueled by the burning graphite moderator. Graphite is not used in boiling water reactors or pressurized water reactors of the types built in Japan, the U.S. and elsewhere for power generation.
It's true that if there is a large thermal convection produced by heat release from the reactors, radionuclides can be carried up into the upper atmosphere, and can circle the globe without contact with ocean water. However, there is a big dilution factor in this case, and it will take some time for rainout of the soluble radionuclides to occur, limiting the dose rate again in two ways.
So the bottom line is that it would be virtually impossible for radioiodine to travel through the atmosphere across the ocean from Japan to the U.S.
This does not rule out travel of other radionuclides, and I would be surprised if the sensitive radiation detecting instruments worldwide would not be able to detect some.
However, considering the long distance between Japan and the U.S., and the associated dilution in the ocean and the atmosphere, the resulting dose rates will likely be very low.
I am not in any way minimizing the magnitude of this tragedy, especially for the Japanese people, but I think it is important for people in the U.S. to understand the limits on the possible direct consequences of radiation exposure from a source of release so far away.
Best regards,
Rich