Tough new rules for Japanese nuclear power plants have been revealed in draft form. Among them are that power companies should be able to contain a severe accident situation for an entire week without outside help.
The draft proposals for accident prevention and mitigation came from Japan's newly established Nuclear Regulation Authority (NRA), which has enough independence to do its work free from governmental control and undue industrial influence. It published the proposals today, announcing a period of discussion with power companies before the end of January when it wants to begin formulating final versions for publication in July.
Meeting the demands of these rules will be essential for power companies wanting to restart nuclear reactors that have laid idle for many months. The NRA has previously said that utilities will be able to apply for inspections and approval prior to July, although it would not give its final opinion until after the final requirements had been passed into law.
Most of the draft requirements are directly inspired by the Fukushima accident and the troubles experienced by Tokyo Electric Power Company and government agencies in containing a loss of power brought on by tsunami flooding. Utilities will be required to provide alternative, possibly mobile, power supplies and multiple sources of cooling water. All reactors will also need filtered vents to allow potentially explosive hydrogen to escape safely in the event of serious core damage.
The most difficult and potentially expensive ideas are that power plants need a back-up control room and a method of injecting water to cool a molten core that has already left the reactor vessel but remains in containment. Power companies should also be capable of dealing with a severe accident situation for an entire week without outside help, which can be delayed in the case of a wider emergency such as a major natural disaster.
All but two of Japan's 50-reactor fleet remains shut down, pending regulatory change and approval from the NRA to restart. Ohi 3 and 4 are generating under special conditions to alleviate a power shortage in the congested and heavily industrialised Kansai region. Other reactors remain closed after reaching a mandatory shutdown for checks and being told plainly that approval for restart would not be given until safety requirements had been completely re-assessed.
Historically, power companies would ask the permission of local prefectural governments for approval to restart, and the outright lack of local support was one factor in the total shutdown. The last federal government said clearly that it wanted to move on from this informal condition, but it is not yet clear whether national or regional governments will have a role in granting future approvals or whether that power will lie solely with the NRA.
Researched and written
by World Nuclear News