Japan:Kan halted seawater injection/Operations stopped for 55 minutes over fears of 're-criticality'

Yomiuri Shimbun ^ | 05/22/11

[TigerLikesRooster]

Kan halted seawater injection / Operations stopped for 55 minutes over fears of 're-criticality'

The Yomiuri Shimbun

The injection of seawater into the No. 1 reactor at the Fukushima No. 1 nuclear power plant was stopped for nearly an hour soon after the Great East Japan Earthquake, at Prime Minister Naoto Kan's request, government sources have revealed.

The prime minister feared that injecting seawater might cause re-criticality to occur inside the reactor, the sources said.

Criticality refers to a self-sustaining chain reaction of nuclear fission in uranium atoms. Re-criticality is when a system achieves criticality despite mechanisms being in place to prevent it.

In the case of the Fukushima plant, control rods were inserted into the No. 1 reactor just after the March 11 temblor, with the aim of preventing criticality from occurring.

According to data released by Tokyo Electric Power Co. on May 16, injection of seawater into the No. 1 reactor began at 7:04 p.m. on March 12. TEPCO decided to use seawater because its freshwater supply was running short.

[TigerLikesRooster]

P!

[pnh102]

Kan?

[bgill]

It's highly likely that suspending the injection of seawater made the situation worse

Duh, even little ol' me realized that just reading the headline.

[ransomnote]

Ok so now Kan says a guy named Madarame told him about recriticality and Madarame is denying it (insert finger pointing here). I posted the link below as a separate FR thread but I wanted to excerpt a little of the finger pointing here:

#Fukushima Blame Game: “I Didn’t Say That,” Says Madarame about Recriticality

“His assessment that seawater might cause recriticality in the Reactor 1 was what supposedly prompted Prime Minister Kan to order TEPCO to halt the seawater injection on the night of March 12, as I reported in my post yesterday.”
http://ex-skf.blogspot.com/2011/05/fukushima-blame-game-i-didnt-say-that.html

[VanShuyten]

This just shows you how a simple statement from several weeks ago can be blown up enough to cause ridiculous policy decisions. Back then, there were concerns that very hot salt water would degrade the zirconium-clad control rods enough to seriously affect their ability to absorb neutrons, leading to “re-criticality”. That was just one of many questions posed about what to do. However, the idea that the reactors might start having uncontrollable nuclear reactions caught on with the press and others, and the popularity of that idea grew until it even affected Kan’s decisions. Pretty much anyone can see that cooling the cores with sea water is better than not cooling them at all.