In TEPCO’s May Progress Status [PDF] report and in this attachment to the report, I see for the first time (for me) the plan to reuse the contaminated water leaking into the turbine building — which should address my concern that operators would be overwhelmed by the volume of contaminated water leaking from the primary containment of unit #1. On this temporary circulation strategy TEPCO writes:
Issue 1. Reactors: revision of prioritized countermeasures due to the coolant leakage
・ Entered into R/B in Unit1 after improving work environment. Confirmed status of R/B and calibrated instrumentations (reactor water level, etc.)
・ As a result, it turned out that the coolant leakage from PCV occurred in Unit 1 as well as in Unit 2. There will be the same risk in Unit 3.
・ Accordingly, as a major countermeasures to achieve “cold shutdown” in Step 2, revision was made to prioritize “establishment of circulating injection cooling (please refer to the figure in upper right)” over flooding operation (flooding the PCV up to the top of active fuel). In circulating injection cooling, contaminated water accumulated in buildings is reused to be injected into the PCV after being processed.
TEPCO has released a useful presentation containing many diagrams and photos of work in progress: Progress status of cooling (reactors)