Gov’t Doc.: Re-criticality a threat at Fukushima; Concern melted fuel to change it’s form — M.I.T. Q&A: Coolability of the molten corium is questionable (VIDEO)

Published: December 4th, 2013 at 8:40 pm ET
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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.

Watch the Q&A here (at 1:08:00 in)

Published: December 4th, 2013 at 8:40 pm ET
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132 comments

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