TEPCO responds to NISA on reactor building, and more

Surprisingly, TEPCO has made a press release in the middle of the night (Tokyo time) to cover some of NISA's requests. It includes a rather complicated sixteen page handout which we'll summarize below.

-TEPCO is improving the conditions in the reactor building to allow for the performance, in the near term, of three jobs: First, installation of new water level measuring equipment for the pressure vessels; second, installation of the new external cooling facility; third, for the purpose of making new connections for the nitrogen feed to the containment vessel.

-TEPCO will recalibrate existing RPV and dry well level meters, and install new RPV measuring meters.

-Dry well flood level will be closely monitored so as not to flood the vent lines.

-TEPCO has finally revealed some details about the actual construction of the temporary cooling system it will install.. at least at Unit No. 1. Here is a clip from the handout:

As stated on the handout, existing systems will be combined with new connections and new systems to provide cooling. Notable features here are as follows:

*Use of an air blast cooling tower
*Use of heat exchanger internal to reactor building
*Supply of water in primary circuit both to pressure vessel and dry well

-Nitrogen injection will be disrupted by the new design, but TEPCO already has another location to inject the required nitrogen into the dry well and work to connect temporarily to this will be concurrent with that performed on the temporary cooling system.

-General dose rates in the expected work area are about 10 mSv/hr (in the US we'd rate this as 1000 mR/hr.) The reduction to the required <1mSv/hr (or less than 100 mR/hr) will be accomplished through reduction of airborne activity, removal of contaminated debris, and installation of shielding.

-Filtration of the reactor building atmosphere will also include a plan using further Alara Venti units to pressurize the air lock and reactor building, ensuring no leakage of contaminated air to the environment.

-There will be about one hour of open access through the unpressurized air lock to implement work; external release and exposure will be very closely monitored during this time.

-TEPCO's preliminary time line through the end of installation of the final components to achieve the temporary core cooling, and all prior required functions, is shown below.