U. S. NUCLEAR REGULATORY COMMISSION
OFFICE OF PUBLIC AFFAIRS, REGION IV
611 Ryan Plaza Drive, Suite 400, Arlington TX 76011
|CONTACT:||Breck Henderson (817) 860-8128/e-mail: email@example.com|
RIV: 97-77 December 24, 1997
The Nuclear Regulatory Commission staff has proposed a $55,000 fine against Entergy Operations, Inc., the operator of River Bend Nuclear Station near St. Francisville, Louisiana, for two instances in which shutdown cooling system operation was not properly maintained during a refueling outage. The shutdown cooling system provides cooling for the reactor coolant system during outages.
The violations were documented during an NRC inspection conducted September 22 through October 17. They were discussed by Entergy and NRC officials on December 2 during a predecisional enforcement conference at the NRC Region IV office in Arlington, Texas.
The first violation, which took place on September 13 during testing of a newly-installed cooling system, occurred when reactor coolant temperature increased to greater than 200 degrees Fahrenheit and boiling ensued. NRC requirements do not permit reactor coolant temperature to be above 200 degrees in the absence of specific plant conditions, which were not in place at the time. The cause of this event was determined to be a deficiency with the test procedure. The procedure required the shutdown cooling system to be shut off, but it did not include adequate means to measure or predict reactor coolant temperature so that operators could restore shutdown cooling in time to prevent an excessive temperature rise. The procedure had been reviewed by River Bend organizations charged with ensuring such plans are adequate, but the error was not caught.
The second violation occurred on October 4 when the shutdown cooling system was inadvertently isolated during electrical testing. The system was off-line for about 17 minutes, and average reactor coolant temperature increased from 97 to 100 degrees.
The actual safety significance of these two events was low; nonetheless, the issues have regulatory significance. In the first event, River Bend operators did not recognize a fundamental factor that must considered in planning for shutdown maintenance activity referred to as "time-to-boil." Based on residual heat generated in the reactor core after shutdown, a prediction of the time before the water in the reactor vessel will boil can be routinely calculated. The lack of consideration of "time-to-boil" created the potential for safety consequences.
Consequences in this incident were minimized because the average coolant temperature exceeded 200 degrees Fahrenheit for less than 30 minutes, with a maximum average coolant temperature calculated to be about 205 F. Boiling would have had to continue for about seven hours to uncover the core such that damage could have begun. Although some steam was released, there was no significant airborne activity inside the plant and no radioactivity was released to the outside environment. There was no impact on public health and safety or on workers safety from either event.
However, Ellis W. Merschoff, Regional Administrator of NRC Region IV, said in a letter to Entergy Vice President John R. McGaha, ". . . based on the importance of plant staff being sensitive to the need to maintain and protect shutdown cooling, these violations are classified in the aggregate . . . as a Severity Level III problem." The agency's enforcement system uses four Severity Levels, with Level I being the most serious. The base civil penalty for a Severity Level III violation is $55,000.
Entergy has 30 days to respond to the NRC's citation, during which time it may pay the civil penalty or protest it. If the protest is denied, the utility may ask for a hearing.