Mid -and -Long -Term Roadmap towards the Decommissioning of TEPCO’s Fukushima Daiichi Nuclear Power Station Units 1-4 (pg. 115), June 27, 2013: Development of technologies for controlling fuel debris criticality –> Purpose: In future, we will develop the technologies for monitoring and evaluation of sub-criticality in order to prevent re-criticality even in the case when the form of the fuel debris or the water volume changes in association with the fuel removal work etc. [...] Criticality evaluation [...] Conduct an analysis assuming the status of fuel debris and the plant after a severe accident, and review the scenario involving a criticality. [...] formulate measures to mitigate the influence of radiation exposure in the case of a criticality. [...] Liquid waste treatment and subcriticality control technology for cooling equipment [...] Considering the possibility that fuel debris may flow out, accumulate in the liquid waste treatment equipment as well as the cooling equipment and lead to criticality, monitoring of subcriticality is required. [...] Mid- to long-term cultivation of human resources [...] we will need more persons with expertise on basic nuclear core physics and criticality control, we will consider cooperative frameworks which will promote education and research in universities. Further, we will make efforts toward the development of the ability of young engineers, and secure the human resources required for ensured implementation and improvement of long-term debris criticality control.
Q&A with Lake Barrett, former U.S. Nuclear Regulatory Commission official and now an adviser to Tepco, March 30, 2011 (at 1:08:00 in): Mike [Podolsky?]: A few days ago I received an update from Japan talking about the measurements. The temperature outside the vessel was almost 300*C. The pressure inside the vessel was about 3 atmospheres. Which means that the temperature inside was much higher. The coolability of molten corium is questionable […] We should make a really organized effort to understand and look into long-term consequences, because it’s not clear that everything will go away in a smooth manner.
Published: December 4th, 2013 at 8:40 pm ET
- US Experts: Fukushima melted fuel “a concern for millennia”; Risk of criticality from corium moving, redistributing — Tepco Chief: Certainly a difficult path ahead… we’ll be able to move forward if we can find damaged fuel (VIDEO) June 4, 2014
- Nuclear Professor: Centuries before attempting any work on Fukushima molten fuel? — Concern over “potential phase separations” in corium November 13, 2013
- Nuclear Engineer: Every expert I talked to this week is very concerned about a criticality event during fuel removal at Unit 4 — “There’s good potential for a criticality” (AUDIO) November 21, 2013
- NPR: How can Fukushima’s molten fuel be contained so it stops contaminating the planet? Nuclear Expert: There’s no way to get at molten fuel… I’ve not seen a solution to this (AUDIO) September 17, 2013
- French nuclear specialists agree Fukushima “could still explode”, corium a threat — Reactors remain in meltdown says expert, molten lava could break through at any point March 11, 2012