Today, Japan's prime minister is expected to announce that the severely damaged Fukushima Daiichi nuclear plant has achieved cold shutdown status.
That news and other recent developments at the plant blacked out by the March 11 earthquake and tsunami include:
TEPCO Kills Ocean Water Release Proposal
On Dec. 9, Tokyo Electric Power Co. announced it abandoned a plan to release decontaminated water from the plant into the ocean. TEPCO has estimated 400 metric tons of groundwater seep into basements of the four damaged units every day, adding to tons left over from the tsunami and emergency cooling measures. A decontamination and desalination system has been successful at recycling some of the water by treating and reinjecting it into damaged reactors. Still, the utility proposed releasing some treated water into the ocean, as storage facilities assembled at the site capable of handling 100,000 tons will reach capacity in March. That proposal met fierce opposition from commercial fishing groups, and TEPCO abandoned the idea, with Reuters reporting the utility will instead build more tanks and increase water recycling.
After 9 Months, Cold Shutdown
At a news conference today, Prime Minister Yoshihiko Noda is expected to announce the plant has met the requirements for what it describes as cold shutdown status. All three reactors facing core damage have achieved temperatures well below boiling for weeks. Meeting the Japanese government's and TEPCO's definition of cold shutdown, though, requires a determination that damaged units are not releasing radioactive material detectable at higher than 1 millisievert per year at the plant boundary, as well as temperature readings at the bottom of reactor pressure vessels below 100 C.
Cold shutdown, in that case, differs somewhat from the reactor status as defined by the U.S. Nuclear Regulatory Commission. The NRC considers a reactor in cold shutdown when its temperature drops below 200 F under atmospheric pressure following a reactor cooldown.
NRC Backs Staff Prioritization of Fukushima Recommendations
NRC commissioners gave the go-ahead to a plan by agency staff that prioritizes U.S. nuclear plant safety recommendations drafted following the Fukushima crisis. The NRC's Near-Term Task Force on the accident separated its recommendations into tiers, with the commission's support for action on the first two tiers announced in an NRC release Thursday. Tier 1 recommendations are those the agency believes can be implemented “without unnecessary delay.” Tier 2 recommendations will be implemented later because they require further technical assessment or other concerns.
Most of the issues fall under Tier 1 and include:
– Seismic and flood hazard reevaluations
– Seismic and flood walk downs
– Station blackout regulatory actions
– Equipment covered under Title 10 of the Code of Federal Regulations (10 CFR) 50.54(hh)(2)
– Reliable hardened vents for Mark I and Mark II containments
– SFP instrumentation
– Strengthening and integration of emergency operating procedures, severe accident management guidelines and extensive damage mitigation guidelines
– Emergency preparedness regulatory actions (staffing and communications)