05000333/LER-2001-001
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition |
| 3332001001R00 - NRC Website | |
U.S. NUCLEAR REGULATORY COMMISSION 01 001 00 James A. FitzPatrick Nuclear Power Plant
EVENT DESCRIPTION
On February 21, 2001, with the reactor at approximately 100 percent power, it was discovered that conflicting design analyses existed for the configuration of an equipment hatchway, located in the northwest corner of the Reactor Building Secondary Containment [NH] between the ceiling of the 300 foot (ft.) elevation and the floor of the 326 ft. elevation. Specifically, the hatchway is credited as being open for the high energy line break (HELB) analysis. This analysis models a flow path from the 300 ft. elevation, through the open hatchway, and into the 326 ft. elevation. The Environmental Qualification (EQ) profiles for EQ equipment were established based on this analysis. The Fire Protection Program analysis assumes that a hatch cover is installed on the floor penetration (3 hour3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> designated 10 CFR 50 Appendix R barrier). The as-found configuration identified the hatch cover to be installed.
A review of EQ profiles and temperature margins of potentially effected area equipment was performed in support of equipment operability. This evaluation identified that, with the restricted flow path, during a postulated HELB, the 600 volt emergency switchgear [SWGR] located on the 300 ft. elevation in close proximity to the HELB break, could be susceptible to environmental conditions in excess of its existing EQs.
On February 21, 2001 at 1515 hours0.0175 days <br />0.421 hours <br />0.0025 weeks <br />5.764575e-4 months <br /> Operations entered Technical Specifications (T.S.) Limiting Conditions for Operation (LCO) 3.9.A.2.b. and 3.0.C. requiring the plant to be in Cold Shutdown within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> unless the 600 volt emergency switchgear was restored to an operable condition.
On February 21, 2001 at 1856 hours0.0215 days <br />0.516 hours <br />0.00307 weeks <br />7.06208e-4 months <br />, operators entered a Fire Protection Program required LCO for removal of the Reactor Building elevation 326 ft. hatchway cover. At 2138 hours0.0247 days <br />0.594 hours <br />0.00354 weeks <br />8.13509e-4 months <br />, following the removal of the hatchway cover, 600 volt emergency switchgear was returned to an operable condition.
The northwest equipment hatchway located between the ceiling of the Reactor Building 300 ft. elevation and the 326 ft. floor elevation was originally designed to have no cover. The only HELB postulated to occur for the 300 ft. elevation is in Reactor Water Cleanup (RWCU) System [CE] lines and therefore, this open hatchway was a significant consideration in developing EQ profiles for equipment in the adjacent 300 ft. elevation area as well as a less significant consideration for other Reactor Building breaks.
In 1984, Plant Modification F1-83-036 was completed which added a cover to the northwest equipment hatchway 326 ft. elevation in support of the Fire Protection Program upgrade.
FACILITY NAME 11) PAGE (3) DOCKET (2) LER NUMBER (6) 01 � 001 � 00
CAUSE OF EVENT
Given the age of this event, and based on the available information, it was concluded that the most probable cause for this event was inadequate work practices. [Cause Code B] The conclusions made following a review of the documentation associated with Plant Modification F1-83-036 were that the person(s) responsible for its development did not perform the level of detailed review necessary for implementation of the modification. Considerations were not given for the effects the proposed new hatchway cover would have on existing area HELB flow models. Consequently, the EQ profiles for both 71L15 and 71L16 were not revised.
ANALYSIS OF EVENT
This report is being submitted in accordance with 10 CFR 50.73(a)(2)(ii)(B), "Any event or condition that resulted in the nuclear power plant being in an unanalyzed condition that significantly degraded plant safety.
The safety function of the 600 volt emergency switchgear is to distribute safeguard loads from emergency onsite AC power sources, adequate for the safe shutdown of the reactor following abnormal operational transients and postulated accidents.
Switchgear 71L15 and 71L16 are electrical equipment providing power sources for the engineered safeguards and Emergency Core Cooling Systems in opposite redundant trains. If the equipment hatchway is assumed to be closed, it is conservatively assumed that a HELB would render both switchgear unavailable due to environmental effects.
An evaluation was conducted to determine the risk impact of leaving the equipment hatchway closed coincident with a postulated RWCU line rupture. The Conditional Core Damage Probability (CCDP) was quantified on the failure of both 600 volt switchgear 71L15 and 71L16 given an assumed intermediate break LOCA for the Reactor Water Cleanup system line rupture. Given the line break frequency, the Conditional Core Damage Frequency (CCDF) for this scenario was 7.47 x 10(-10). This resultant frequency does not significantly contribute to core damage risk for keeping the hatchway closed.
An Engineering evaluation is being prepared to evaluate the potential fire-related consequences of plant operation with the cover for the northwest Reactor Building equipment hatchway 326 ft. elevation removed.
EXTENT OF CONDITION
This condition was identified during an extent of condition evaluation recommended through corrective actions from a previously identified deficiency report. These reviews have been completed and no further similar conditions were identified.
James A. FitzPatrick Nuclear Power Plant
CORRECTIVE ACTIONS
1. An Engineering evaluation is being completed to determine whether the removal of the subject hatchway cover will/will not adversely affect the ability of the plant to achieve and maintain safe shutdown in the event of a fire. The evaluation will include an assessment of reasonably postulated fires which could challenge the barrier as well as the impact of the postulated fires on credited safe shutdown equipment.
(Scheduled Completion Date: June 15, 2001) 2. If the Engineering evaluation listed in Corrective Action No. 1 determines that the cover on the hatchway, located in northwest corner of the Reactor Building 326 ft. elevation, can be permanently removed, a Design Change Package will be developed to document the removal.
(Scheduled Completion Date: September 28, 2001) 3. Since the date of completion of the design package for Plant Modification F1-83-036, significant work control improvements have been made to the modification control process. Both Administrative and Design Control procedures now contain specific and detailed methodologies to aid engineers in the review, evaluation, and resolution of design change considerations.
4. A review of Plant Modification F1-83-036 will be completed to provide assurance that that there are no additional program/analysis interface issues which may not have been addressed.
(Scheduled Completion Date: July 31, 2001)
ADDITIONAL INFORMATION
A. N Previous Similar Events: N LER-94-006 reported an EQ concern affecting safety related switchgear caused by personnel error. However, the corrective actions taken would not have precluded this event from happening.
B. Failed Components: N None C. Applicability to NEI 99-02, Rev. 0, "Regulatory Assessment Performance Indicator Guideline".
This event is reportable as a Safety System Functional Failure in accordance with NEI guidance.