Accident precursors at 17-year low

8 January 1999

The number of incidents at US commercial nuclear power plants that theoretically could have escalated into a severe accident declined by half in 1997 to a 17-year low.

There were only five such events in 1997, according to the Nuclear Regulatory Commission’s Office for Analysis and Evaluation of Operational Data. This was half as many as in the previous two years and the lowest number since 1970.

None of the five “precursor” events had even a remote (1 in 10 000) probability of producing a severe core damage accident, the NRC said.

The five events included:

• A coolant system leak Oconee unit 2 (846 MWe PWR) in South Carolina on 21 April.

• The loss of offsite power at Three Mile Island unit 1 (870 MWe PWR) on 21 June.

• Problems with high pressure injection pumps at Oconee unit 3 (846 MWe PWR) in South Carolina on 3 May.

• The valve failure in the coolant system at the Maine Yankee plant on 22 January.

• The mechanical troubles at the St Lucie unit 1 (839 MWe PWR) in Florida on 22 November.

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