3.3 Examine appropriate solutions able to avoid reactor concrete basemat melt-through by the molten core after RPV failure [...]
3.3.2 Injecting water on the top of the corium
Injecting water on the top of the corium subsequent to RPV failure could be performed using RCS make-up through the vessel breach or using a dedicated system.
EDF [French electrical utility Électricité de France] states that this strategy should be able to slow down or even prevent basemat melt-through. According to EDF, the conclusions of the dedicated OECD MCCI [Melt Coolability and Concrete Interaction] program  provide a tendency towards a good efficiency of this ex-vessel reflooding strategy. A complementary corium-concrete interaction test4 (test CCI-7) is planned in June 2012 to confirm the possible stabilisation of a corium pool by means of flooding from above.
IRSN has deemed that the tests performed in the frame of the MCCI program up to day were not conclusive as regards to get confidence to a complete corium cooling by injecting water on its surface (only 3 out of 8 tests exhibit cooling of the corium pool). [...]
Published: December 26th, 2013 at 8:55 am ET
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- AP: Melted Fukushima fuel is 12 inches from entering ground after eating through concrete, says simulation — Study: Molten core suspected of eroding through concrete foundation — Gov’t Expert: We just can’t be sure until actually seeing inside November 20, 2013
- Gov’t experts warn about mass of corium melting deeper than Japan, Tepco claim — Fukushima cores “could be eroded more extensively than announced” February 10, 2014
- French Nuclear Experts: Did corium pierce steel liners of Fukushima reactors? How deep did it erode concrete? (VIDEO) February 3, 2013
- Nuclear Professor: Centuries before attempting any work on Fukushima molten fuel? — Concern over “potential phase separations” in corium November 13, 2013