05000298/LER-2005-003

LER-2005-003, Cooper Nuclear Station 05000298 1 of 4

Docket Number
Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
2982005003R00 - NRC Website

PLANT STATUS

Cooper Nuclear Station (CNS) was in Mode 1 at 100% power at the time of discovery on 6/21/2005.

BACKGROUND

The standby alternating current (AC) power system (EIIS:EK) consists of two independent on-site diesel generators (DG's) (EIIS:DG) adequate for maintaining the safe shutdown of the reactor following abnormal operational transients and postulated accidents in the event of failure of off-site power. Each DG unit has a fuel day tank (EIIS:DC). Both day tanks are supplied from either of two main fuel storage tanks (EIIS:DC). Both main fuel storage tanks combined are capable of providing sufficient fuel for seven days of operation of one DG unit under postulated accident conditions. Each fuel day tank will provide enough fuel to allow a minimum of five hours of full load operation of the DG unit.

Each of the two diesel fuel oil storage tanks is provided with its own transfer pump and piping connections to its respective fuel oil day tank. Cross-ties are provided such that either DG can be supplied from both fuel oil storage tanks.

CNS Technical Specification (TS) Limiting Condition for Operation (LCO) 3.8.1, AC Sources - Operating, requires two qualified circuits between the offsite transmission network and the onsite Class 1 E AC Electrical Power Distribution System; and two DG's to be OPERABLE in Modes 1 (Power Operation), 2 (Startup) and 3 (Hot Shutdown.) If two DG's are inoperable, the Action Statement requires the restoration of one DG to OPERABLE status in 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />.

LCO 3.8.2, AC Sources — Shutdown, requires one qualified circuit between the offsite transmission network and the onsite Class 1 E AC electrical power distribution subsystem(s) and one DG capable of supplying one division of the onsite Class 1 E AC electrical power distribution subsystem(s) in Modes 4 (Cold Shutdown) and 5 (Refueling). If the required DG is inoperable, the Action Statement requires that action be initiated to restore the required DG to OPERABLE status "Immediately.

CNS TS 1.3 says that when "Immediately" is used as a Completion Time, the Required Action should be pursued without delay and in a controlled manner.

EVENT DESCRIPTION

On 6/21/2005, during an NRC inspection, CNS determined that the DG Diesel Oil (DO) transfer pump in­ service test (1ST) flow test performed on 11/5/2004 while in Mode 4 resulted in a condition prohibited by TS.

On 5/14/2004, surveillance procedure for DG DO transfer pump 1ST flow test for Division 1 was revised to allow quarterly exercising of the two normally closed manual cross connect valves between DG Fuel Tanks 1 and 2. The new Revision 16 of the procedure allowed both DG fuel transfer pumps (from main storage tank to day tank) to be disabled from automatic start to permit validating cross-connect valve operation. The procedure instructed operators to record both tank level changes while opening these valves, thus validating that the valves have opened. Disabling the fuel transfer pumps was achieved by placing their switches to the OFF position. No steps were included in the procedure to declare both DG's inoperable. Performance of the surveillance takes approximately 30 minutes.

The surveillance was performed on 7/13/2004 and 10/7/2004 while the plant was in Mode 1, and on 11/5/2004 in Mode 4, without declaring both DG's inoperable. On 12/30/2004, as operators were preparing to execute the procedure for the fourth time, operators recognized that the steps to place the transfer pump switches to OFF would require declaring both DG's inoperable. The surveillance procedure was revised to avoid placing both transfer pump switches to OFF, and the surveillance was subsequently performed. A Condition Report (CR) was initiated and referred to the three earlier surveillances when both DG 1 & 2 were rendered inoperable.

During the CR initial reportability review, CNS determined that both DG's were simultaneously inoperable during the three events. In all 3 cases, there was no loss of safety function because DG day tanks will provide enough fuel to allow a minimum of five hours of full load operation of the DG. For July and October, the surveillances were completed within the 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> TS action limit for Mode 1 which satisfied the TS requirement. For November, the TS "immediate" action limit for Mode 4 was exceeded, but a condition prohibited by TS was judged to not exist due to the short time it took to execute the surveillance being within the completion time required by TS. CNS then categorized the CR as "Not-Reportable".

In June of 2005, NRC inspectors questioned the reportability determination for the 11/5/2004 event. On 6/21/2005, CNS reviewed the November 2004 event, and agreed that it was a condition prohibited by TS.

BASIS FOR REPORT

This event is being reported as a condition prohibited by plant TS per 10 CFR 50.73(a)(2)(i)(B),

SAFETY SIGNIFICANCE

No Safety System Functional Failure occurred. The inadequate evaluation of reportability is not an equipment or hardware related performance issue. In addition, the required DG was considered available during the surveillance since the restoration of the fuel oil transfer pump is procedurally directed and can be accomplished well within day tank depletion time. The condition did not challenge a reactor fuel, reactor coolant pressure, primary containment, or secondary containment boundary. The condition did not impact the plant's ability to safely shutdown or maintain the reactor in a safe shutdown condition.

As a consequence, the condition has no impact on the baseline Probabilistic Risk Assessment model and results in no change in core damage frequency.

CAUSE

The root cause was that Revision 16 of the surveillance procedure was inadequate in that it did not require or caution that performing procedure steps would render both DG's inoperable.

CORRECTIVE ACTION

Immediate action taken was to counsel individuals involved with the surveillance procedure Revision 16 on adherence to process requirements of changing procedures, attention to detail, and the need for rigor in reviewing and approving procedure changes.

The corrective action taken to prevent recurrence was to revise the surveillance procedure for DG DO transfer pump IST flow test for Division 1 to remove steps that allow both DG's to be simultaneously inoperable. This action was completed on 1/22/2005.

PREVIOUS EVENTS

On April 10,2000, during performance of the System Leakage Test surveillance procedure for refuel outage RE-19, the TS limit for Reactor Coolant System (RCS) heat-up rate was exceeded in Reactor Recirculation (RR) [EIIS:AD] loop B. The failure to meet TS Surveillance Requirement acceptance criteria was not recognized, and the required evaluation to determine if the RCS is acceptable for operation was not performed prior to start up from the RE-19 refuel outage. On March 20, 2003, with CNS in Mode 5 for refuel outage RE-21, a review of the surveillance procedure and past performance of the procedure was performed in support of a modification to replace temperature recorders. During this review the above condition was discovered. This event was the result of inadequate procedural guidance for equalizing RCS temperatures in preparation for starting an idle RR pump, and evaluating available RCS temperature data. This condition was reported to the NRC in LER 2003-03.