ML20128G276

SER Accepting Continuation of 18-month Test Schedule for Drywell to Suppression Chamber Vacuum Breakers

ML20128G276
Person / Time
Site:	Hope Creek
Issue date:	09/26/1996
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20128G264	List: ML20128G259 ML20128G276
References
NUDOCS 9610080422
Download: ML20128G276 (3)

Text

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NUCLEAR REGULATORY COMMISSION WASHINoTON, D.C. 20665-4001

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION TEST SCHEDULE FOR THE DRYWELL TO SUPPRESSION CHAMBER VACUUM BREAKERS PUBLIC SERVICE ELECTRIC & GAS COMPANY ATLANTIC CITY ELECTRIC COMPANY HOPE CREEK GENERATING STATIQB DOCKET NO. 50-354

1.0 INTRODUCTION

By letter dated January 31, 1996, the Public Service Electric and Gas Company (PSE&G) requested approval for continuation of the 18-month test schedule for the Hope Creek Generating Station (HCGS) Drywell to Suppression Chamber (Torus) vacuum breakers. The submittal of PSE&G's January 31, 1996, request was required by HCGS Technical Specification 4.6.2.le., which requires Commission approval of the vacuum breaker test schedule in the event that the vacuum breakers fail to meet the specified leakage acceptance criteria. The failure of the vacuum breakers to meet the specified leakage acceptance criteria was reported in Licensee Event Report (LER) 95-031-00, submitted by letter dated December 11, 1995. The vacuum breakers were successfully retested on March 12, 1996. On August 9,1996, PSE&G submitted a' dditional information concerning the vacuum breakers.

2.0 DISCUSSION Section 6.2.1.1.4.1 of the HCGS Updated Final Safety Analysis (UFSAR) contains a description of the Drywell to Torus vacuum breakers. These vacuum breakers are provided to protect the Drywell from the effects of external to internal i differential pressure (Drywell vacuum), a design value of 3 psi, that could result from Drywell spray. There are eight 24-inch vacuum relief valves .

(vacuum breakers), each located on the lower end of a Drywell to Torus vent line. These vacuum breakers are of the self-actuating, check type, that can also be manually operated from the main control room. The location / '

orientation of the Drywell to Torus vacuum breakers is shown in HCGS UFSAR Figure 3.8-17.

By letter dated December 11, 1995, PSE&G submitted LER 95-031-00 which reported that HCGS was placed in Cold Shutdown, per Technical Specification (TS) 3.6.1.1, on November 11, 1995, after failure to maintain initial test conditions for the Drywell to Torus vacuum breakers. The LER noted that the "G" vacuum breaker seal was inadequate and the "F" vacuum breaker exhibited limit switch problems. By letter dated August 8, 1996, PSE&G identified that '

vacuum breakers "C", "F", and "H" did not have adequate sealing due to misalignment of the valve pallet to valve body as manifested by the seal not being centered on its body. This misalignment was corrected by replacing the 9610080422 960926 ENCLOSURE PDR ADOCK 05000354 P PDR

i seals, making valve pallet to pivot block adjustments to re-center the pallet,  ;

and drilling new pivot block holes to maintain the pallet centered in a stress i free condition. The "G" Vacuum Breaker, identified in the LER as having an inadequate seal, was subsequently.found to have an acceptable seal. The -

vacuum breakers were successfully retested prior to restart from Refueling Outage 6 on March 13, 1996.

i The PSE&G letters dated January 31, 1996 and August 9, 1996, also noted that l PSE&G had not conducted previous vacuum breaker testing in accordance with >

HCGS UFSAR Section 6.2.6.5, "Special Testing Requirements." The principal 1 difference in the testing methodology was that the requirements for " Type A" l testing were not met during vacuum breaker testing as described in the HCGS {

UFSAR. The licensee has changed the Hope Creek UFSAR to correctly reflect the test methodology and will comply with these requirements.

3.0 EVALUATION PSE&G has previously reported failures of the HCGS vacuum breakers to maintain an adequate test pressure. By letter dated July 2, 1992, the NRC staff approved a proposed test schedule in response to PSE&G's request dated June 2, 1992. The June 2, 1992, request was necessitated by LER 92-006 which reported that leakage had been detected in the "F", "G", and "H" Drywell to Torus vacuum breakers. While leakage of the "G" vacuum breaker was resolved by replacement of the seal, the "F" and "H" vacuum breakers were found to have misa.ligned valve pallets and broken alignment pins. Leakage is,the "F" and "H" vacuum br~eakers was eliminated by adjusting the bolting to achieve pallet alignment and replacement of the alignment pins. This corrective action did not appear to be effective in that valve pallet alignment problems reoccurred in the "F" and "H" vacuum breakers, as reported in LER 95-031-00. The current corrective action for the "F" and "H" vacuum breakers will relieve the residual stress from the original corrective bolting adjustments and can be expected to be effective.

The licensee's letter dated August 9, 1996, also notes that a leakage trending  !

program for the Drywell to Torus vacuum breakers has been instituted. The NRC -

staff believes that the leakage trending program will assist the licensee in ,

ascertaining adverse leakage trends and thus provide a basis for preventive maintenance. I Finally, with regard to the licensee's determination that they did not conduct  !

past vacuum breaker. testing in accordance with HCGS UFSAR Section 6.2.6.5, "Special Testing Requirements," the NRC notes that the acceptance criteria for  !

the test is contained in TS 4.6.2.le. Specifically, TS 4.6.2.le requires that an initial differential pressure of .80 psi be achieved and that the differential pressure not decrease more than .24 inches of water per minute for a period of 10 minutes. While the licensee may select the test ,

methodology to assure that the TS acceptance criteria are met, the NRC staff requests that the licensee make every possible effort to assure that the UFSAR accuratelv reflect current Hope Creek design and operating practices.

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4.0 CONCLUSION

The Hope Creek licensee has presented sufficient information to provide confidence that the failure mechanisms associated with subject Drywell to Torus vacuum breakers have been determined and that corrective measures will be effective. Moreover, the implementation of the Drywell to Torus vacuum breaker trending program will provide an improved basis for preventive maintenance. Accordingly, the NRC Staff concludes that continuation of the 18-month test schedule for the Drywell to Torus vacuum breakers is acceptable.

Principal Contributor: D. H. Jaffe Date: September 26, 1996

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