WASHINGTON (CN) – The U.S. Nuclear Regulatory Commission is asking for input on regulations covering blackouts at nuclear power plants following catastrophic events like the tsunami that inundated the Fukushima Dai-ichi nuclear power plant in Japan last year.
The NRC maintains general design criteria for all U.S. nuclear facilities and is considering amending the criteria governing natural phenomena and electrical system design.
U.S. nuclear plants are supposed to be designed to maintain power to critical safety systems even during the most extreme natural events, including earthquakes, tornadoes and tsunami.
However, there is currently no specific design requirement for onsite back-up electrical power generation capable of maintaining safety systems without recourse to offsite power.
The NRC is asking facility operators and the public if it should include new design criteria requiring redundant and overlapping onsite and offsite alternate power systems that have capacity to power critical safety functions assuming the failure of a single active component in each power system.
Redundancies the NRC is considering include two physically separated transmission lines into nuclear facilities with segregated circuits into the onsite electrical distribution system, designed and located to minimize the likelihood of simultaneous failure.
The NRC issued two safety orders the day after the one year anniversary of the Fukushima disaster, requiring all facilities to secure equipment to provide back-up onsite power for critical safety functions in the event of offsite failure.
The safety orders apply to all currently operating nuclear facilities while the revised design criteria will apply to any future plant construction or when currently operating facilities need to be relicensed.
The public has until May 4 to comment on the NRC’s proposed design criteria.
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