Tuesday, April 5, 2011

New York Times Article on #Fukushima I Nuclear Reactor Hints at Fresh Troubles

The New York Times article is based on the leaked confidential assessment by the US Nuclear Regulatory Commission.

In the assessment, according to the article, the NRC thinks:

  1. There may be no water in the Reactor Pressure Vessel of the Reactor 1;
  2. Spent fuel rods may have blown up and spread to 1 miles from the reactors;
  3. Too much water in Containment Vessels could rupture the Vessels in a strong aftershock.

The 1st explains why the temperature of the RPV of the Reactor 1 has not come down below 200 degrees Celsius, despite cooling with sea water and now with fresh water.

(TEPCO is injecting nitrogen gas in the Containment Vessel of the Reactor 1. I sure hope they won't end up blowing it up instead...)

OK, people who want to scream at NY Times for fear-mongering, come out and scream!

NY Times says the NRC assessment seems to have been based mostly on the information shared with them by the Japanese government and TEPCO.

From New York Times (emphasis added; 4/5/2011):

United States government engineers sent to help with the crisis in Japan are warning that the troubled nuclear plant there is facing a wide array of fresh threats that could persist indefinitely, and that in some cases are expected to increase as a result of the very measures being taken to keep the plant stable, according to a confidential assessment prepared by the Nuclear Regulatory Commission.

Among the new threats that were cited in the assessment, dated March 26, are the mounting stresses placed on the containment structures as they fill with radioactive cooling water, making them more vulnerable to rupture in one of the aftershocks rattling the site after the earthquake and tsunami of March 11. The document also cites the possibility of explosions inside the containment structures due to the release of hydrogen and oxygen from seawater pumped into the reactors, and offers new details on how semimolten fuel rods and salt buildup are impeding the flow of fresh water meant to cool the nuclear cores.

......

The document, which was obtained by The New York Times, provides a more detailed technical assessment than Japanese officials have provided of the conundrum facing the Japanese as they struggle to prevent more fuel from melting at the Fukushima Daiichi plant. But it appears to rely largely on data shared with American experts by the Japanese.

Among other problems, the document raises new questions about whether pouring water on nuclear fuel in the absence of functioning cooling systems can be sustained indefinitely. Experts have said the Japanese need to continue to keep the fuel cool for many months until the plant can be stabilized, but there is growing awareness that the risks of pumping water on the fuel present a whole new category of challenges that the nuclear industry is only beginning to comprehend.

The document also suggests that fragments or particles of nuclear fuel from spent fuel pools above the reactors were blown “up to one mile from the units,” and that pieces of highly radioactive material fell between two units and had to be “bulldozed over,” presumably to protect workers at the site. The ejection of nuclear material, which may have occurred during one of the earlier hydrogen explosions, may indicate more extensive damage to the extremely radioactive pools than previously disclosed.

......

The assessment provides graphic new detail on the conditions of the damaged cores in reactors 1, 2 and 3. Because slumping fuel and salt from seawater that had been used as a coolant is probably blocking circulation pathways, the water flow in No. 1 “is severely restricted and likely blocked.” Inside the core itself, “there is likely no water level,” the assessment says, adding that as a result, “it is difficult to determine how much cooling is getting to the fuel.” Similar problems exist in No. 2 and No. 3, although the blockage is probably less severe, the assessment says.

.......

A rise in the water level of the containment structures has often been depicted as a possible way to immerse and cool the fuel. The assessment, however, warns that “when flooding containment, consider the implications of water weight on seismic capability of containment.”

Experts in nuclear plant design say that this warning refers to the enormous stress put on the containment structures by the rising water. The more water in the structures, the more easily a large aftershock could rupture one of them.

1 comments:

Robbie 001 said...

I had thought about the water weight due to uncontrolled emergency flooding inside the facilities but I was only thinking about the weight driving leaks this is very disturbing. Another thing that came to mind was water doesn't like being compressed. I remember when I was a teen we used to play with powerful fireworks known as M-80's (the real ones, an 1/8 stick of dynamite) We would collect some 5 gallon plastic buckets from a local work site dumpster and drill a 1" hole in the lids. When you dropped an M-80 in the hole 5 secs later the explosion would crack the side of the bucket open and blow the lid about 50' in the air. Then we filled one with water (real M-80's are waterproof) the force of the explosion peeled open the bucket flat to the ground and sent the lid into orbit. The increase in destructive force was incredible! I wonder if hydrodynamic shock was a factor in some of the various ruptures during the unmonitored pressure runaways and explosions in the suppression pools?

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