The U.S. Nuclear Regulatory Commission (NRC) on Feb. 17 proposed three rules to address safety-related issues following the disaster at the Fukushima Daiichi nuclear power plant in Japan.
The rules, the first since the NRC established its task force to recommend safety enhancements at all U.S. nuclear plants, were proposed to commissioners in a memo from R.W. Borchardt, NRC executive director for Operations.
“Each of the orders is focused on enhancing defense in depth at nuclear power plants through increased capabilities to minimize the potential for core damage following a beyond design basis external event,” the NRC said in the memo. “The staff considers that all nuclear power plants should be at the redefined level of adequate protection by Dec. 31, 2016, at the latest.”
Two orders from the NRC are proposed to be issued to all reactor licensees, including holders of active or deferred construction permits, and holders of combined licenses. These proposed orders say licensees must develop plans to address beyond design basis natural phenomena, such as earthquakes, floods and other natural disasters and reasonable protection of equipment identified under such plans.
The NRC also proposed that all plants improve instrumentation in pools used to store spent fuel.
The third order from the NRC pertains to licensees operating boiling water reactors with GE (NYSE: GE) Mark I and Mark II containments, similar to the design of the Fukushima Daiichi plant. This order would address containment vent structures at all plants with these containment systems. The memo said the events at Fukushima Daiichi highlight the possibility that beyond-design-basis external events could challenge the prevention, mitigation and emergency preparedness defense-in-depth layers. Borchardt wrote that at Fukushima, limitations in time and unpredictable conditions associated with the accident significantly challenged the attempts by the responders to preclude core damage and containment failure. The operators were unable to successfully operate the containment venting system.
“Had additional backup or alternate sources of power been available to operate the containment venting system remotely, or had certain valves been more accessible for manual operation, the operators at Fukushima might have been able to depressurize the containment earlier,” the report said. “This, in turn, could have allowed operators to implement strategies using low pressure water sources. Thus, the events at Fukushima demonstrate that reliable hardened vents at BWR facilities with Mark I and Mark II containment designs are important to maintain core and containment cooling.”
To implement these rules in a timely manner, NRC said each order has been made immediately effective. The licensing approach for operating power reactors in all three orders is similar. The staff plans to prepare guidance for implementing the requirements of the orders by August 2012. Licensees will then be required, by February 28, 2013, to submit to the NRC for review an overall integrated plan including a description of how compliance with the requirements of the order will be achieved.
Read the full report from NRC here
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