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	NRC NEWS U. S. NUCLEAR REGULATORY COMMISSION
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No. 98-216

December 7, 1998

COMMERCIAL NUCLEAR POWER PLANTS HAVE LOWEST NUMBER
OF SEVERE ACCIDENT PRECURSORS SINCE 1970

The number of operational events at commercial nuclear power plants in 1997 that could have led to a severe accident causing damage to the reactor core was the lowest since 1970, a new analysis by the Nuclear Regulatory Commission shows. No serious accidents occurred.

Only five events - about half as many as in each of the previous two years - had conditions that could have remotely set the stage for a severe accident. These included the unavailability of equipment, loss of offsite power and a piping leak. All of the accident "precursors" in 1997 occurred at pressurized water reactors, which comprise about two-thirds of the 104 commercial nuclear reactors operating in the United States.

The report, prepared by the NRC's Office for Analysis and Evaluation of Operational Data, with the assistance of the Oak Ridge National Laboratory in Tennessee, also notes that 1997 was the first time since 1970 that there were no precursor events which had a probability of producing a severe core damage accident where the odds were greater than one in 10,000. The odds of the five precursors recorded in 1997 were between one in 10,000 and one in a million.

The declining trend in the number of accident precursors is consistent with other previously observed trends suggesting the safety of the nuclear power industry is improving along with its performance.

The text of the report, NUREG/CR-4674, "Precursors to Potential Severe Core Damage Accidents: 1997 A Status Report," will be available on the NRC home page.