05000338/LER-2010-001
| Document Numbersequential Revmonth Day Year Year Month Day Year North Anna Unit 2 05000 339Number No | |
| Event date: | 1-3-2010 |
|---|---|
| Report date: | 07-12-2010 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition |
| 3382010001R00 - NRC Website | |
1.0 DESCRIPTION OF THE EVENT In July 2009, concerns were identified that were applicable to the North Anna Power Station (NAPS) as a result of NRC inspection activities at Surry Power Station (SPS) regarding Fire Protection. Documentation could not be found showing acceptable test results for usage of aluminum conduits that are present in various Appendix R fire barrier penetrations (EllS: PEN) throughout the station. The concern is that aluminum melts at approximately 1220°F whereas the Test Standard of record, ASTM E-119 requires a fire test temperature of approximately 1700°F. Steel conduits are not of concern because their melting temperature is over 2000°F. Aluminum conduits were part of the original plant design and construction. The effects of fire on aluminum conduit were not considered when the fire testing packages were compiled for NAPS. The packages addressed a steel conduit sleeve and an aluminum cable tray but not aluminum conduits in fire barriers.
A vendor was contracted to test the aluminum conduit in fire barriers in accordance with (lAW) IEEE 634-1978, Standard Cable Penetration Fire Stop Qualification Test. Although ASTM E-119, "Standard Test Methods for Fire Tests of Building Construction and Materials" is the test standard applicable in the licensing basis for NAPS, usage of the temperature criteria in ASTM E-119 is considered to be more conservative than required by other approved fire test methods because it is not specifically written for testing of conduit penetrations in fire rated barriers. IEEE 634-1978 is appropriate for testing aluminum conduit penetration seal configurations. On February 25, 2010, a discussion took place between Dominion Virginia Power and the NRC regarding the testing methodology. The NRC concurred with using IEEE 634-1978 as an acceptable test standard.
On May 13, 2010, evaluation of the test results from the vendor indicated three (3) of the seven (7) types of aluminum conduit representing existing configurations at NAPS failed the test criteria of IEEE 634-1978. The first type (Type 1) is described as providing at least ten inch depth of internal silicone foam seal in the aluminum conduit inside the plane of the fire barrier from one side. The second type (Type 2) is described as providing at least five inch depth of internal silicone foam seal in the aluminum conduit inside the plane of the fire barrier from one side. The third type (Type 3) is described as having aluminum conduit penetration without internal silicone foam seals or smoke seals in the fire barrier.
Additionally, multiple types of the aluminum conduit configurations when tested reached temperatures that could ignite cotton waste or NFPA Class A material. As such, administrative measures have been implemented to prevent contact of transient combustibles with the aluminum conduit configurations.
A walk down of accessible penetration areas and evaluation of drawings was performed and approximately 900 aluminum conduits in fire barriers for both North Anna Units 1 and 2 were identified for evaluation. These aluminum conduits were evaluated using the testing results to determine that approximately 300 conduits required modification to restore functionality.
� 2.0 SIGNIFICANT SAFETY CONSEQUENCES AND IMPLICATIONS Fire suppression, detection and plant response along with the compensatory measures implemented provided an adequate level of protection for redundant equipment. This situation has not resulted in any significant safety consequences or implications and the health and safety of the public were not affected at any time. A fire has not occurred in the affected fire areas that has challenged these penetrations.
Degraded fire barriers, such that the required degree of separation for redundant safe shutdown trains is lacking, is reportable as an unanalyzed condition that significantly degraded plant safety. Therefore, this report is being submitted pursuant to 10CFR50.73(a)(2)(ii)(B). At the time of discovery fire watches for the affected areas were already in place.
3.0 CAUSE The effects of fire on aluminum conduit were not originally considered when the fire testing packages were compiled for North Anna. The packages addressed steel conduit and aluminum cable trays but did not document aluminum conduits in fire barriers.
The NRC's original licensing requirements/guidelines for penetration seal qualifications are stated in Section D.3.d of Appendix A to BTP APCSB 9.5-1. This guideline incorporated, by reference, the specific test procedures outlined in ASTM E-119 (NFPA-251). The ASTM E-119 test was originally intended to determine the fire resisting capability of walls and floors assemblies. As such, it did not specifically address testing procedures for penetration seals. The NRC, however, determined that an adequate test procedure for penetrations seals could be adopted from the ASTM E-119 test.
As stated above, Branch Technical Position APCSB 9.5-1 requires cable penetration of fire barriers to be sealed to give protection at least equivalent to that in a 3-hr fire barrier. On April 1, 1977, NAPS submitted a "Fire Protection System Review" indicating compliance to this requirement and it included a report on a fire endurance test conducted at NAPS on December 15, 1976. This test report demonstrated the acceptability of a 6 inch metal sleeve with cables and an aluminum cable tray with cables penetrating a three hour rated fire barrier filled with Dow Corning Q3-6548 Silicone RTV Sealing Foam. The test was conducted IAW the preliminary draft of IEEE P634/D2, "Standard for Cable Penetration Fire Stop Test Procedure," dated October 5, 1976. On March 6, 1979, the NRC issued a Safety Evaluation Report on the Fire Protection Program for NAPS and concluded that the submittals identified the plant to be in compliance with Appendix A. This test along with one other test performed at NAPS in November 1975 was the basis for the acceptability of the conduit penetrations in fire barriers at NAPS throughout the 1980's.
In the early 1990's, Virginia Electric and Power Company contracted with Impell Corporation to generate documentation for the penetration seal configurations (PSCs) existing at SPS. This led to the issuance of several calculations used to justify the PSCs.
The test reports referenced by the calculations utilized acceptance criteria/testing methods from standards IEEE P634/D2, IEEE 383-1974, ASTM E-119-1976, ASTM E-814 and NEL- PIA/MAERP. The test reports were incorporated into technical reports TR EP-0011 and TR EP-0016. North Anna Power Station adopted the test reports by reference of their respective technical report into the NAPS Appendix R Report. During the 2009 NRC Triennial Fire Protection Inspection at SPS, the NRC reviewed the test reports and determined that sufficient documentation did not exist to qualify the use of aluminum conduits with silicone foam seals penetrating fire rated barriers as three hour fire rated.
4.0 IMMEDIATE CORRECTIVE ACTION(S) Upon identification of the potential fire barrier impairments, a station condition report was issued and compensatory measures were implemented in accordance with the North Anna Technical Requirements Manual.
5.0 ADDITIONAL CORRECTIVE ACTIONS A vendor was contracted and tested fire barrier penetrations containing aluminum conduit IAW IEEE 634-1978, Standard Cable Penetration Fire Stop Qualification Test.
A design change will be implemented to correct the fire barrier penetrations containing aluminum conduit as needed based on the testing results and site evaluations.
Procedures controlling the Fire Protection Program are being revised to address the test results. Fire barrier installation and test procedures are also being revised to ensure acceptable maintenance and installationof aluminum conduit configurations.
6.0 ACTIONS TO PREVENT RECURRENCE Actions completed and those in progress will ensure the program meets regulatory requirements and fire barrier penetratioris containing aluminum conduit are maintained in the required configurations.
7.0 SIMILAR EVENTS None 8.0 ADDITIONAL INFORMATION None �NRC FORM 366A (9-2007) PRINTED ON RECYCLED PAPER