05000482/LER-2005-006
| Docket Numbersequential Revmonth Day Year Year Month Day Yearnumber No. 05000 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition |
| 4822005006R00 - NRC Website | |
Background:
The reactor coolant pump (RCP) [EIIS Code: AB] seal assembly [EIIS Code: SEAL] provides for controlled leakage of Reactor Coolant System water. A fire has the potential to cause a loss of cooling to the RCP seals. Failure to restore the RCP cooling in an appropriate time could result in damage to the RCP seals. Failure of the RCP seals could result in an inability to maintain pressurizer level during plant shutdown, thus not satisfying the 10CFR50 Appendix R, Section 1111.2.b requirement.
Plant Conditions Prior to the Event:
MODE —1 Power —100 percent Normal Operating Temperature and Pressure
Event Description:
Wolf Creek Generating Station (WCGS) orginally committed to restoring seal injection to the RCP seals within 30 minutes, after evacuating the control room, to protect the RCP seals.
In 1986, WCAP 10541, documented that the lower RCP internals water volume would provide limited cooling to the seals for approximately 13 minutes following loss of all seal cooling. Previous timing of procedure OFN RP-017, Control Room Evacuation, had shown that RCP seal injection could be restored within 13 minutes so no additional actions were taken by WCGS.
A Westinghouse Direct Work Request, DW-94-011, made a recommendation that seal cooling never be restored if the RCP Vendor Manual limits cannot be met. However, it did not prohibit restoration of seal cooling if circumstances require and allow. Based on timing performed during training, WCGS had always met the RCP Vendor Manual limits.
In January of 2005, Westinghouse issued WCAP-16396-NP, "Reactor Coolant Pump Seal Performance for Appendix R Assessments". In this document, Westinghouse stated that the maximum RCP seal leakage would be limited to 21 gpm if RCP seal cooling were not restored and a natural circulation cool down were completed.
In June 2005, Information Notice IN 2005-14, Fire Protection Findings on Loss of Seal cooling to Westinghouse Reactor Coolant Pumps, was issued and discussed the finding of WCAP-16396-NP. With the receipt of IN 2005-14, WCGS decided to implement the methodology of not restoring RCP seal cooling following a complete loss of seal cooling. However, the procedure revision has not yet been issued.
During the November 2005 NRC triennial inspection, the actions of procedure OFN RP-017 were timed using a more conservative approach than previously used at WCGS. Using this conservative approach, RCP seal cooling would not be restored until 20 minutes after evacuation from the control room. At that point, an eight hour non-emergency report to the NRC Operations Center was made in accordance with 10CFR50.72(b)(3)(ii)(B).
Basis for Reportability:
Failure to restore the RCP cooling, after a postulated fire, in an appropriate time could result in damage to the RCP seals. Failure of the RCP seals could result in an inability to maintain pressurizer level during plant shutdown, thus not satisfying the 10CFR50 Appendix R, Section 1111.2.b requirement. Based on this information, WCNOC made an eight hour Emergency Notification System call in accordance with 10 CFR 50.72(b)(3)(ii)(B).
This condition is also reportable pursuant to 10 CFR 50.73(a)(2)(ii)(B) for any event or condition that resulted in the nuclear power plant being in an unanalyzed condition that significantly degraded plant safety.
Root Cause:
Wolf Creek's license basis committed to account for only one spurious signal and does not require the scenario of additional spurious signals.
Corrective Actions:
Procedure OFN RP-017 will be revised to remove steps for restoration of RCP seal cooling.
Safety Significance:
A fire in the control room could adversely affect safety systems to perform their intended function. There is a potential for core damage if RCP seal integrity is not maintained or restored. The loss of coolant through the RCP seals could exhaust fluid level in the reactor system and potentially cause core damage.
A fire, causing the evacuation of the control room, did not occur. This condition resulted in no significant safety consequences and the health and safety of the public were not affected at any time.
Operating Experience/Previous Events:
None