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NRC NEWS

U.S. NUCLEAR REGULATORY COMMISSION

Office of Public Affairs Telephone: 301/415-8200

Washington, D.C. 20555-0001 E-mail: opa@nrc.gov

No.07-081 June 27, 2007

NRC IMPROVES METHOD FOR MEASURING

REACTOR PERFORMANCE DURING UNPLANNED SHUTDOWNS

The Nuclear Regulatory Commission has updated its Reactor Oversight Process (ROP) by

introducing the Unplanned Scrams with Complications (USWC) performance indicator, which tracks

events that can increase the risk associated with a reactors unplanned manual or automatic shutdowns,

which are called scrams.

The agency created the ROP seven years ago to improve its inspection and enforcement

programs for commercial nuclear power plants. NRC staff use performance indicators as part of the

ROP to evaluate several areas of plant activity. In 2000, the process included a performance indicator

that measured the ability of a reactors cooling systems to remove heat from its core after a scram. As

the NRC and industry evaluated that performance indicator, enough questions were raised to point out

the need for revisions. The agency and industry formed a task force in late 2004 to work on the issue,

and the groups work led to the USWC indicator.

This revision will keep better track of the small percentage of scrams that require extra work

from reactor operators, since those conditions could represent more risk than uncomplicated scrams,

said Jim Dyer, Director of the NRCs Office of Nuclear Reactor Regulation. If we see a plant having

too many complicated scrams in a short period of time, well know its time to increase our oversight.

The USWC indicator will monitor conditions that could complicate a plants scram recovery,

including:

- maintaining control over conditions needed for a chain reaction;

- providing electricity to emergency systems;

- activating emergency sources of cooling water;

- maintaining availability of normal cooling water sources, and;

- using emergency operating procedures to address complicated scrams.

Triggering any one of the criteria during an unplanned scram counts as an event, and two or more

events in a 12-month period will result in increased NRC oversight.

The development of the new indicator has included multiple public meetings and public

comments. More information on the USWC indicator is available on the NRC Web site at:

Notification to nuclear power plant licensees issued in a Regulatory Issue Summary (RIS 2007-12)

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