NYT on Recriticality: Japan nuclear prof. says chain reaction at Fukushima can’t be ruled out

[FourScore]

Japan May Declare Control of Reactors, Over Serious Doubts
By MARTIN FACKLER
Published: December 14, 2011

...Perhaps to give itself some wiggle room, the government is expected to use vague terminology, announcing that the three damaged reactors are in a “state of cold shutdown.” Experts say that in real terms, this will amount to a claim that the reactors’ temperatures can now be kept safely below the boiling point of water, and that their melted cores are no longer at risk of resuming the atomic chain reaction that could allow them to once again heat up uncontrollably...

SNIP

...“Claiming a cold shutdown does not have much meaning for damaged reactors like those at Fukushima Daiichi,” said Noboru Nakao, a nuclear engineering consultant at International Access Corporation...

SNIP

...Mr. Jennex said he believed the government’s claim that the reactors themselves were now stable, and particularly that the resumption of the heat-producing chain reaction called fission was no longer possible. While the discovery last month of the chemical xenon, a byproduct of fission, in one of Fukushima Daiichi’s reactors briefly raised alarms that a chain reaction had restarted, Mr. Jennex said enough of the radioactive fuel had decayed since the accident in March to make that unlikely.

Other experts disagreed. Kyushu University’s Mr. Kudo said that the restart of fission, a phenomenon known as recriticality, could not be ruled out until the reactors could be opened, allowing for an examination of the melted fuel. But he and other experts said their biggest fear was that another earthquake or tsunami could knock out Tepco’s makeshift cooling system. They noted that it was not built to earthquake safety standards, and relied on water purifiers and other vulnerable equipment connected to the reactors by more than a mile and a half of rubber hoses.

“All it would take is one more earthquake or tsunami to set Fukushima Daiichi back to square one,” Mr. Kudo said. “Can we really call this precarious situation a cold shutdown?”

http://www.nytimes.com/2011/12/15/world/asia/japan-set-to-declare-control-over-damaged-nuclear-reactors.html?_r=1

[izquierdista]

1. I can rule one thing out

Fukushima ever being "back to normal".