Fukushima Daiichi explosions as seen from the air on March 15, 2011.
Image: Flickr, daveeza
The top U.S. nuclear regulator, Gregory Jaczko, gave a dire assessment of Japan's nuclear crisis yesterday, saying that lethal radiation from uncovered spent fuel above one of the reactors could force emergency workers to abandon their fight to prevent meltdowns of damaged reactor cores at the Fukushima Daiichi plant.
Jaczko, chairman of the Nuclear Regulatory Commission, said his staff in Tokyo had been told by Japanese utility officials that cooling water that normally covers spent fuel was nearly or totally gone from an uncovered concrete pool above reactor Unit 4. Based upon that assessment, the U.S. Embassy in Tokyo advised Americans living within about 50 miles of the plant on Japan's northeast coast to evacuate farther away. Japan has called for an evacuation within about 12 miles of the plant.
His comments to a House committee were disputed but not explicitly denied by Japanese authorities, exposing an apparently major communications issue between the United States and Japan. If Jaczko's information was correct, the plant's owner, Tokyo Electric Power Co. (TEPCO) may have withheld information about the gravity of the crisis. If not, then a senior U.S. official may have wrongly inflamed fears in a country wracked by tragedy following last Friday's earthquake and tsunami.
"We can't get inside to check, but we've been carefully watching the building's environs, and there has not been any particular problem," Hajime Motojuku, a spokesman for Tokyo Electric, said Thursday morning in Japan, The New York Times reported.
Later Thursday, a spokesman for Japan's Nuclear and Industrial Safety Agency, Yoshitaka Nagayama, said, "Because we have been unable to go the scene, we cannot confirm whether there is water left or not in the spent fuel pool at Reactor No. 4."
Informed of Japanese reaction after his testimony yesterday, Jaczko told reporters, "I understand there is a conflict." He said the conclusions he and the NRC staff reached were based on the best information they had, and that they had chosen "to err on the side of caution." The possibility that fuel in the reactor pools could ignite led to the recommendation on evacuation, he said.
'Nobody knows'
"The problem is that nobody knows," said Thomas Neff, a reactor safety expert affiliated with the Massachusetts Institute of Technology. "If you don't know and you're TEPCO, you probably underplay it. If you're the regulator, you probably see it in a worse light."
"The odds are pretty good that no one has good information," said Peter Bradford, a NRC commissioner at the time of the Three Mile Island accident in 1979. "We sure didn't during the first five days" then.
Japan's Self-Defense Forces dumped water from a helicopter on reactor No. 3 and prepared to repeat the operation on unit No. 4, Japanese news services reported. Water cannons would also be used. Jaczko said the water cover in the spent fuel storage pool at No. 3 may soon be gone too, boiled away or evaporated by the heat from the spent-- but still radioactive-- fuel rods.
The condition of the spent fuel pools has been a source of rising anxiety and confusion since the crisis began. The earthquake and tsunami knocked out outside power to the reactor complex and the tidal wave also disabled backup diesel generators, whose fuel tanks were swept away. When auxiliary batteries were exhausted, the plant was without power to continue cooling reactor cores and spent fuel pools. Japanese crews have been trying to flood reactors with seawater and restore outside power to the plant.
"There is an enormous amount of radioactivity left in those pools," Edwin Lyman of the Union of Concerned Scientists said. "[I]t's unclear how long workers can stay in that environment without risking grave bodily injury. If they must be permanently evacuated, it's unclear how the extent of the damage that's now occurred can be contained."
See what we're tweeting about
11 Comments
Add CommentWhat would happen if we froze the fuel rods with liquid nitrogen. It has been a long time since Chemistry class, would this be possible or would it create a worse problem chemically speaking.
Reply | Report Abuse | Link to thisLou
I beleive the extreme heat of the spent fuel would quickly evaporate the liquid nitrogen as it has a much lower boiling point than seawater so it's not really an option. Plus, I doubt they could get a tank of liquid nitrogen to the plant with all the infrastructure damage.
Reply | Report Abuse | Link to thisinteresting thought but if you can get that large quantity of N2 then getting water back to the system would be much easier and more feasible.
Reply | Report Abuse | Link to thisMight have a heat transfer problem. Super cold liquid on very hot metal might cause fracturing, maybe explosively. How hot is containment vessels? Would hate to cause fracturing in those! Presence of seawater might mitigate this risk though. Still, would take a lot of N2 and there would be a significant increase in pressure....who knows....at this point might be worth the risks however. Good question.
Reply | Report Abuse | Link to thisMy complete guess is that liquid N2 would rapidly cool and embrittle the zircalloy casing. An uneven cooling would probably cause cracking either of the zircalloy or the cooling pool itself...
Reply | Report Abuse | Link to thispaddleman007: If you could get close enough to try to use liquid nitrogen, what would prevent you from just using something much easier to supply and transport, like sea water? I honestly have to ask what in the world you are thinking? Do you think they are leaving the rods sitting around heating up for a lack of an idea of what to put on them? Honestly, what?
Reply | Report Abuse | Link to thisCould they build up a large temporary wall around the plant and then flood it? With enough sandbags and portable temporary walls they maybe able to build the walls tall enough. I'm sure the military has ways of putting up walls rapidly for all sorts of purposes.
Reply | Report Abuse | Link to thisIn Fukushima the two back-up generators to replace power failure in the cooling system were swallowed by the tsunami.
Reply | Report Abuse | Link to thisThis was the source of the problem in the reactors.
But a startling fact has emerged in this nuclear accident in Japan The fact is that all nuclear plants in the world
contains a basic error in design, which is just using ONLY ONE hydraulic cooling circuit.
As in Fukushima. The most modern plants use the so-called external circuit of COOLING, which is an improvement over the old mills.
But this is only ONE external circuit, and in case of failure would cause the same phenomenon of Fukushima.
The principle is basic in engineering: if you have one, IN FACT you have none.
The aeronautical engineering widely used this principle, using two engines on airplanes, instead of just one.
In addition of two independent cooling hidraulic circuit, would be needed: two or more electric
stand-by generators to move them.
And two fuel tanks, diesel, independent to ensure supply.
All confined in a screened room and waterproof.
Recent expert analysis indicate that the generators for cooling can not be at the same level of the sea, to prevent flooding or invasion of the sea on the generators. Should be built on the highest level. Most nuclear power generators in the world has generators on the same level of the reactor, and are not shielded and not waterproof.
From NHK news, they said water is (probably) seen from reactor 4's roof, which looks like ripple reflections in the photo. So the priority is to cool reactor 3 first. The latest radiation level has come slightly down instead of going up.
Reply | Report Abuse | Link to thisThey intend to restore power to the cooling system now. Difficulties arise from the radiation which is preventing them to work effectively. Friday is the earliest date which they can restore the power.
From TV, it said they have 13 diesel power supplies as backup, several to each of the reactor. But 11 / 13 failed owing to the tsunami. The plant was designed to prepare for tsunami too but only to take water level of about 5m in height. (Need confirmation)
At this stage they should flood the sites with sea water. That permanently disables the plants some say? Well too f'ing bad. The Japanese government had no business leaving reactors online since the 1960's on the most unstable earthquake subduction zone on Earth.
Reply | Report Abuse | Link to thisNow, it comes out that TEPKO has been lying about safety for years!
Reply | Report Abuse | Link to thisDoes anyone know -- are TEPKO and BP connected?