At about 2:22 Eastern Daylight Time a journalist sent me a brief email to inform me that Dr. Jaczko had just told the House Energy and Commerce committee that the fuel pool at Fukushima Daiichi unit 4 was dry.
I had just read a status report that indicated that the temperature in that pool as of the morning of March 15, four days after the earthquake and tsunami struck, had been measured as 183 degrees F (about 84 degrees C). Since fuel pools are normally maintained at about 100 F, my “radcon math” brain immediately told me that the fuel pool would not even begin to boil for at least another day after that.
Even that was a very pessimistic number, because as the temperature in a container of water rises, the heat losses to the container and the surfaces increases. Of course, the elevated temperature was an operational concern – the higher the temperature, the greater the rate of evaporation and the greater the amount of fogging on the surface. (Think about what a hot tub surface looks like, especially at a ski resort where the air is pretty chilly. Now imagine that pool at about 60 – 70 F hotter. Lots of fog, not all that much water departing the pool.)
In the past several hours, with a break for a nap, I have done a lot of fact checking and communicating. One of the nice things about being an old ring knocker (I graduated from the Naval Academy almost 30 years ago) is that you can have a pretty useful set of highly placed friends. Some of them gave me enough information to confirm what I suspected. I cannot think of any way to say this gently – Dr. Jaczko was wrong. It is possible someone in his staff provided bad information, but it should not be all that difficult to see the problem with some simple, back of the envelop calculations.
I would think a guy with a PhD could do the math in his head – or at least enough of the math to ask for a verification of the analysis. I would expect someone who is in charge of a large, technically competent organization would double and triple check numbers and statements before going in front of C-Span cameras and a congressional committee and making statements and recommendations that distract the entire world from a real and growing food, water and shelter crisis. If I was in charge, I would not have asked anyone to evacuate any area that did not have a measured, significantly elevated radiation level. I would CERTAINLY not recommend an evacuation radius that was 3 times longer than the one recommended by a very technically competent host country.
In all of this, there are far too many people who are far too narrowly educated and far too polite to strongly question the statements of people who have been appointed to a position of authority – even if they know that the appointee has no professional background that would provide them with the ability to independently verify their statements.
In the interest of time, I am going to repurpose an email that I just shared with some colleagues and friends in response to a NY Times piece in which Dr. Jaczko is quoted as saying “We believe that radiation levels are extremely high, which could possibly impact the ability to take corrective measures.”
It is time to move from “extremely high” to real numbers. Kyodo News is reporting that the helicopter crews have measured levels above the cooling pool as follows:
At an altitude of 1,000 feet, the dose rate was 4.13 millisieverts (413 millirem)
At an altitude of 300 feet, the dose rate was 87.7 millisieverts (8.7 rem).
Those numbers do not exactly match the normal equations, but I assume that the helicopter crews were reporting their elevation above the ground, not their distance from the spent fuel pools. I have no way of knowing how high those are above the ground, but the distance between the helicopter and the top of the fuel rods is shorter by that elevation. Those dose rates require some attention and care, but they are not, by themselves, life threatening.
Based on those numbers, here is my analysis:
The spent (aka used) fuel pools are not generating much hydrogen. They are not boiling away. They are not empty. UO2 CANNOT burn, it is almost fully oxidized already. (That is what the O2 part of the compound equation is.) Between 90-95% of the material in a used fuel pool is UO2.
The water level in the pool at unit 4 is significantly lower than normal, which leads to higher radiation levels above the pools than normal.
The measured levels can be caused by a reduced amount of shielding above the still radioactive used fuel. Pools normally contain about 6M of water, the tenth thickness of water is .7 meters. You lose 70 cm of water, the dose rate above the water increases by a factor of 10.
As swimmers or hot tub lovers know, it is never surprising to see clouds of vapor rising from hot water on a cold day. However, even with an increased rate of evaporation, pools full of water take a long time to empty out.
The temperatures in the pool at unit 4 rose from about 40 C to 84 C during the first 4 days after the quake/tsunami. That should give you numerically inclined people the confidence to assert that boiling off of 6 meters of water could not have occurred during the 5th day. (Don’t forget about the latent heat of vaporization.)
All that said, adding even centimeters of water back to a pool is not something that a few helicopter loads can handle. They cannot carry all that much water; the stuff weighs a kilogram per liter.
It takes a 200,000 liters to raise the level of a pool that is 10 meters wide by 20 meters long by a meter. A CH-46 medium lift helicopter has a capacity of about 3,180 kg. It would require 63 trips to raise the water level one meter if my guess on fuel pool dimensions is reasonable.
See why they want to bring in fire cannons to top off the pool? This is not desperation, it is simple math and logistics.
Here is a great fact sheet from NEI about spent fuel pools.
Guardian UK (March 18, 2011) IAEA urges Japan to give more information on nuclear crisis.
This quote helps to illustrate why I am hard over on the terrible effects of evacuation orders that are completely unnecessary. They are not a “conservative” approach to a difficult situation, they add an extraordinary level of complexity and burden the people who still have a massive humanitarian crisis on their hands. It is bordering on immoral to add additional stress and anxiety that put real barriers on the ability to effectively take care of the higher priority tasks of providing food, water and shelter.
Officials have warned that the nuclear incident is hampering efforts to deliver aid to victims of last Friday’s earthquake and tsunami, with reports that drivers are reluctant to travel to areas even outside the exclusion zone.
If I was the President and I had someone on my staff who provided such lousy advice, I know what I would do. It might not even be a calm conversation and could involve a common send off for a poor performer, “don’t let the door hit you in the butt on your way out.”