18 Feb (NucNet): Applicants planning to build new nuclear power plants in the US must assess the ability of their reactor designs to avoid or mitigate the effects of a large commercial aircraft impact, regulators said yesterday.

The Nuclear Regulatory Commission (NRC) issued a final rule requiring the assessment. NRC chairman Dale Klein said it was a �common sense approach� to address an issue raised by terror attacks in the US in September 2001.

The NRC pointed out that nuclear power plants are designed under very stringent requirements to assure they can safely shut down following �design-basis events� such as large fires, floods, earthquakes and hurricanes, as well as �improbable equipment malfunctions including pipe breaks�.

These requirements include having two redundant systems to accomplish each safety function. The rule treats large commercial aircraft crashes as �beyond-design-basis events�.

Under the rule, any design feature or functional capability adopted solely to comply with the rule will meet high quality standards but is exempt from NRC design-basis regulations, such as regulations for redundancy, the NRC said. �These design features and functional capabilities must address core cooling capability, containment integrity, spent fuel cooling capability, and spent fuel pool integrity following an aircaft impact.�

The NRC has already taken several steps to improve security at existing nuclear power plants and, in December 2008, voted to codify specified requirements in a separate rule for all existing and future nuclear power plants.

The NRC said yesterday: �The agency does not believe nuclear power plant operators should be required to prevent the impact of large commercial aircraft; that responsibility rests with the federal government. The NRC works closely with other federal agencies? to provide layered protection against such a threat. The agency expects these efforts would effectively preclude an aircraft attack from occurring.

�Should such an unlikely event take place at a new plant designed in accordance with the new rule, the NRC expects the plant would be better able to withstand such a crash than the same design without changes resulting from the rule.�

- by John Shepherd

>>Related reports in the NucNet database (available to subscribers)

US Aircraft Crash Study �Validates Confidence� in N-Plants (Insider No. 71, 23 December 2002)

NRC Approves Rule On New Security Requirements (World Nuclear Review No. 49, 19 December 2008)

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