Today’s news from Fukushima: TEPCO and the government have produced a roadmap for the next 6-9 months, ending with all reactors in cold shutdown and all spent fuel pools under full control. Phase 1 (three months) consists of achieving a “steady reduction” of radiation. In Phase 2 (three-six months), the plan calls for first getting radiation releases under control and then substantially curbed. At the end of Phase 2, there is a decision point for the government. At that point (between November and January) evacuation orders will be reviewed. Evacuees will either be allowed to return to their homes to live or not. Today’s announcement is fundamentally a message to evacuees, signaling a timeframe of at least months. This will necessarily trigger a lot of decisions on the ground, as people realize they really need to move out of high school gymnasiums and other provisional arrangements.
One imagines that Phase 1 is about reducing the reactivity of the fuel assemblies in Units 1-4 by any means possible, both known and unknown. Phase 2 is presumably about constructing and bringing online new, closed cooling circuits, so that the direct spillage of highly radioactive cooling water can be ended. The difference between a roadmap and a blueprint is critical to today’s announcements. A blueprint describes a detailed plan. There is no blueprint at this time. A roadmap describes periods of action and key decision points. There is now a roadmap, but without details, it will necessarily be subject to continuous revision.
Meanwhile, there remains a serious tension between USG evacuation orders for Americans (80 km zone) and JG orders for Japanese (30 km zone). The much larger American evacuation zone includes Fukushima City (pop. 300,000 + evacuees). Why are the recommendations from the two governments so different? Because the two governments are responding to different political pressures (details in the next paragraphs). To the extent that hundreds of thousands of Japanese citizens are living in a state of great stress and uncertainty, it is critical that the evacuation orders be harmonized soon. Either there is a continuing and serious threat of further explosive releases or there is not.
The view from Tokyo: There is a good understanding by now of the radiation on the ground, both in terms of amount and kind. Iodine-131 that was released in mid-March in large amounts has largely decayed into ordinary iodine by this time, but cesium-137 will be present in some areas for decades. In some areas, there is enough cesium-137 on the ground to require long-term exclusion zones. These areas, by all published accounts, are not highly populated. Radiation releases (to the air) over the last two weeks have been steadily declining and are not large. It is likely that the Japanese government will begin to define some unpopulated, long-term exclusion zones in the coming days or weeks — a very, very difficult thing to do for any government. For Tokyo, the evacuation crisis is perceived to be primarily a political and public health question, not a reflection of continuing concern about new large releases. Tokyo needs to reestablish trust at home. Already, there are calls for the Prime Minister to resign, etc. The disaster grace period is over.
The view from K Street: The 80 km evacuation zone was recommended by the USG when the threat of catastrophic atmospheric releases was high. As long as the USG continues to recommend an 80 km evacuation zone, the implication is clearly that there is continuing American concern that there will be new onsite fireworks. Unless this is true (and it is not being communicated as true by the USG), why is the 80 km recommendation still there? Industry lobbyists in the US must be arguing for the relatively painless (for Americans) extension of the wider evacuation as a CYA contingency. I.e., it costs them nothing to recommend the wider zone and it insulates the industry from looking complacent should there be further explosive releases of the 800-ton onsite radioactive inventory.
Known risks While there will remain serious risks onsite for months, there is now a steady-state situation that is terrible but not catastrophic. Because the decay heat is now modest in all reactor cores and all spent fuel ponds but one (the SFP at Unit 4 is still problematic) the primary risks are associated with new external events, such as aftershocks, tsunami or typhoons, or with new facility failures (e.g., RPV, piping or valve failures). The cooling load in the Unit 4 spent fuel pond is around 2 MW steady-state. Access to the pool is limited and the integrity of the pool itself is questionable. An appropriate framework for thinking of the worst-case scenarios from now going forward is to realize that the situations in Units 1-4 are each characterized by fuel rod disintegration and melt (to various unknown degrees), which forces the operators to guard against unlikely but dangerous recriticality while always keeping the cooling water circulating to prevent further melting, even if that means environmental releases. Unit 4 is the only unit for which this problem must be solved while fully outside containment. In the other units, there are containment failures, instrumentation failures, salt build-up and corrosion, leaking water, etc — but the cores are at least still inside the main containment.
So, what comes next? We’ll see.