Anti-nuclear group, the CNIC (Citizen’s Nuclear Information Center) held a press conference on March 13th, at the Foreign Correspondents Press Club (FCCJ) with Masashi Goto, a former Toshiba engineer who designed containment facilities for nuclear reactors. The following piece was contributed to JSRC by a journalist in attendance. The information is provided as background and her conclusions are based on her knowledge and years spent as a reporter in Japan. (In the last decade there have been several incidents of malfeasance and serious problems at nuclear reactors in Japan that were not earthquake related, though most of you already know this.)
“At present, there’s not an immediate danger of catastrophe. But if the cooling system stops, we could be facing one.”
So the question is, how long before we reach cold shut down?
“It’s hard to say for certain…We don’t know what is going on inside the plant. No one knows…We cannot know in detail what is happening inside the reactor core.
Asking him after the conference, he said the situation changes day by day, but we could know in a week or so, maybe longer, maybe shorter. Readers, please keep in mind this coming from one source. Granted, he’s a very knowledgeable engineer, but he’s one source…
Mr. Goto pointed out the main issue of concern is Fukushima Daiichi. There are two sites, with 10 nuclear generators, 7 of which have the risk of nuclear core meltdown. We move closer to that situation with each day, he says, and not enough has been done to prevent these potential risks.
There are two reactors that pose the highest risk right now, Daiichi unit 1 and unit 3. The control rods to stop the sustained fission reaction worked. But in normal circumstances, it takes days to let those isotopes decay and water needs to circulate as normal to cool the system gradually.
But due to the earthquake’s magnitude and the tsunami, the cooling systems for the reactors failed. So did the back-up diesel generators that would usually generate enough power to keep the cooling system running.
Faced with this emergency, the government employed an adhoc extreme measure of filling the entire containment vessel with sea water to keep the reactor cool. These containment vessels are already at 1.5x the pressure they are designed to withstand because of the temperature and steam. They can withstand 2x to 5x the amount of pressure they’re designed for (depending on the ground conditions on which they are built, etc.).
If the reactors can cool to cold shutdown by continuing this measure of circulating sea water, then we can avert meltdown. (A meltdown is the physical reaction that occurs when the rods get so hot that they melt and that radioactive material mixes with water inside the container causing a ‘steam explosion’ of radioactive particles.) He said that this is something akin to what happened at Chernobyl. Remember that the explosion we had the other day at Daiichi was a hydrogen explosion, not a steam explosion. Also, steam that is vented is a controlled method of releasing pressure from the container.
The problem we face now is that there has already been some melting of the rods, but they don’t know how much. We have already had radioactive material released into the air and more could be released if the cooling down doesn’t happen quickly enough (since more contaminated steam will have to be vented) or if other factors complicate the cooling.
I asked him afterward what would be a good time-frame for knowing whether the government’s cooling system (using sea water) is a success. Success, remember, is cold shutdown. He said it’s hard to tell, perhaps a week, maybe longer.>The situation changes day by day.
EDITOR’S NOTE (JAKE): There is another expert in the field who believes that Japan is in little danger, Dr. Josef Oehmen, a research scientist at MIT in Boston. What he says makes sense to me but on a purely gut level I tend to give Masashi Goto’s views on the situation a little more credence, simply because of his actual working experience in Japan.