Japanese TV: Fukushima fuel cores have ‘molten-through’ containment vessels — Location of molten fuels is unknown — “Risk of re-criticallity” from filling vessels with water

Thursday, March 20, 2014
By Paul Martin

March 20th, 2014

On February 26, NHK released (Japanese only) a news on their overall view on un-dissolved nub parts of the Fukushima Daiichi nuclear accident. The identified issues are categorized in the following four topics;

De-fueling of “molten” core debris should start six years from now in the earliest — The core-meltdown has occurred in 1F1 through 1F3, resulting in penetration of the molten high temperature nuclear fuels through the RPV (Reactor Pressure Vessel) and leached at the bottom of the PCV (Primary Containment Vessel) in the Fukushima Daiichi accident. According to TEPCO’s schedule, the de-fueling should start in 2020 in the earliest. The overall decommissioning should be completed in a time span of 30-40 years.
Exact damage location of PCVs have not been identified — In attempting the above task, there is an urgent issue waiting for early solution. First of all, the exact damage locations of the PCVs where the fuel have molten-through has not been identified yet. TEPCO plans to fill the PCVs with water to shield against radiation […]
The molten fuels have not been characterized — Next issue is whereabout and characteristics of the molten fuels are not know. Without resolving these issues, it is not possible to establish the necessary approaches for de-fueling. In addition, there exists a risk of re-criticallity upon filling the PCV with water. The contaminated water is hindering human access for inspection with high radiation field and hazardous radioactive species. The Japanese Government and TEPCO are rushing for R&D of robots as well as theoretical predictions trying to grasp accurate status of nuclear fuels.
Searching for way out of contaminated water issues — Fundamental solutions are waited for the contaminated water issues which are generated through cooling of nuclear fuels. The contaminated water accumulated at the basements of buildings through leakage from PCVs. Its volume continue increasing, and a part of the water was found leaked unnoticed last year. […] leak path has not been identified […]

I believe NHK failed to identify two of the most important and serious issues among the consequences of Fukushima nuclear accident […] [one] issue is the root case of hydrogen explosion. NHK simply followed TEPCO’s scenario of zirconium-steam reaction. […]

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