Will Davis at Atomic Power Review has two new posts outlining what I speculate will be an important change in TEPCO’s strategy toward reestablishing recirculation cooling of R1, R2, R3. We have been concerned about the complexity and labor-intensity of repairing the original plumbing to support circulatory cooling. Possibly TEPCO has similar concerns, if it is true that their new approach is evidently to construct new primary and secondary cooling, condensing circuits. Here’s Will on 16 April:
(…) The most interesting news of the day is the still developing story that TEPCO has ordered a large number of special heat exchangers, planned for a new external cooling system that it will construct for each reactor plant. This is a novel approach, and probably the best idea TEPCO has had yet. According to the Kyodo story, TEPCO will use several heat exchangers for each plant, and will connect them to the existing external emergency connections that it’s been using prior to this for core injection. Apparently TEPCO will use electric pumps, and two core connections to establish recirculating cooling flow and then use hoses to bring in and return seawater, if we understand the plan correctly. No timeline is given on this plan — but given the mounting complications of the water in the buildings and in the ground, I would have to say that this plan should be given top priority.
And an update today from Will on 17 April:
I’ve just read the first concrete piece of evidence about how the new systems TEPCO is planning to install will work. Apparently, the idea is to obtain the feed for the pumps from, according to the article, “the reactor containment buildings.” This still isn’t clear, but it does seem to indicate that TEPCO acknowledges the leakage and intends to recycle water in a sort of non-sealed, but closed loop fashion for the primary cooling… the heat from which will be transferred to sea water.
Right now, without any further information, it might be assumed that TEPCO will be taking the water directly from the dry wells or the suppression pools. Important to note is that the primary side of this system will become highly radioactively contaminated, so that the equipment will need to be shielded or else access controlled as the rad level around the equipment will be very high.
My speculation is they will try to flood and circulate the PCV including drywell and wetwell. Any thoughts, comments on this idea?
UPDATE: Kyodo News has a new bulletin that touches on Will’s perspective:
(…) Meanwhile, the utility is considering installing circulating water cooling systems for reactors and spent fuel storage pools outside the reactor buildings at the plant in a bid to bring it under control, sources familiar with the matter said.
The new systems would cool nuclear fuel inside the reactors and spent fuel pools in a stable manner. They would involve heat exchangers and circulation pumps to drain reactor coolant water from the containment buildings, cooling it with seawater and then sending it back to the reactors, the sources said.
TEPCO appears to have already placed orders for dozens of gasketed plate heat exchangers — each measuring 3 meters high, 1 meter wide and 2 meters long — for such systems, the sources said.
The existing circulating water cooling systems at the plant were crippled by the March 11 earthquake and ensuing tsunami.
(…) Radiation levels inside the containment buildings remain high. TEPCO plans to utilize the pipes that it has been using to pump water into the reactors in the new circulating water cooling loops, so it can minimize the need for work inside the dangerous buildings.
There are more details at Kyodo News. Evidently the TEPCO chairman will make an announcement today at 3PM. I will report back…