Okay, the high volume highly radioactive leak has been halted and that is good news. Now here is the rest of the story.
Released today from the New York Times/Asia Pacific:
http://www.nytimes.com/...
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...
The article is long and technical--so I'll extract a few quotes, comment lightly, and leave it up to Kossacks to analyze and discuss further. The report refers to an assessment dated March 26th, which the Times reports is updated regularly, but remains fairly current and applicable.
Some solutions may create more problems, for example:
...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.”...
...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 assessment, as well as interviews with officials familiar with it, points to a new panoply of complex challenges that water creates for the safety of workers and the recovery and long-term stability of the reactors...
How long can water be pumped to cool the reactors?
...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...
More extensive damage to the radioactive pools than previously disclosed.
...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...
David A. Lochbaum, now director of the nuclear safety project at the Union of Concerned Scientists, comments:
...“I thought they were, not out of the woods, but at least at the edge of the woods,” said Mr. Lochbaum, who was not involved in preparing the document. “This paints a very different picture, and suggests that things are a lot worse. They could still have more damage in a big way if some of these things don’t work out for them.”...
Detailed assessments of each of the plant's six reactors are included in the document.
...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...
Other dangers:
...Nuclear experts say that radiation from the core of a reactor can split water molecules in two, releasing hydrogen. Mr. Wilmshurst said that since the March 26 document, engineers had calculated that the amount of hydrogen produced would be small. But Jay A. LaVerne, a physicist at Notre Dame, said that at least near the fuel rods, some hydrogen would in fact be produced, and could react with oxygen. “If so,” Mr. LaVerne said in an interview, “you have an explosive mixture being formed near the fuel rods.”...
Spent fuel pools, especially in reactor #4, remain a major concern:
...The N.R.C. report suggests that the fuel pool of the No. 4 reactor suffered a hydrogen explosion early in the Japanese crisis and could have shed much radioactive material into the environment, what it calls “a major source term release.”...
Enjoy spring everyone, and hope for the best. Let's also keep paying attention.