ML20247D036

Safety Evaluation Supporting Amend 119 to License DPR-69

ML20247D036
Person / Time
Site:	Calvert Cliffs
Issue date:	03/24/1989
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20247D029	List: ML20247D027 ML20247D032 ML20247D036
References
NUDOCS 8903300357
Download: ML20247D036 (4)

Text

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SAFETY EVAltfATION BY THE OFFICE OF NtfCLEAR REACTOR REGULATION RELATED TO AMENDNENT NO. 119 TO FACILITY OPERATING LICENSE N0. DPR-69 i

BALTIMORE GAS AND ELECTRIC COMPANY CALVERT CLIFFS NUCLEAR POWER PLANT. UNIT 2 DOCKET NO. 50-318 ONE-TIME SCHEDULAR EXTENSION FOR SNIIBBER FUNCTIONAL TESTS 1.0- INTRODUCTION By its letter dated October 14, 1988, the Baltimore Gas and Electric Company'(BG&E, the licensee) proposed changes to the Unit 2 Technical Specifications (TS). The proposed changes would 1) provide a one-time, temporary surveillance interval extension of up to 54 days for perfoming the snubber functional. tests required by TS 4.7.8.1.c, " Functional Tests,"

2) correct nomenclature errors in TS 3/4.7.8, " Snubbers," and 3) delete an obsolete note in TS 4.7.8.1 which states that "the steam generator snubbers 2-63-11 through 2-63-26 need not be functionally tested until the refueling outage following June 30, 1985."

The temporary, one-time snubber functional test surveillance interval extension shall expire at 11:59 p.m. on May 17, 1989 or upon reaching 199.9'F average reactor coolant system (RCSI temperature during initial RCS heatup following the Unit 2 Cycle 9 refueling outage.

2.0 BACKGROUND

Currently, TS 4.7.8.1.c requires the performance of snubber functional tests on a representative sample of 10% of each type of snubber in use at Unit 2 at least once per 18 months (550 days) while the unit is shut down.

TS 4.0.2.a allows a maximum surveillance interval extension of 25%.

During the previous refueling outage, Calvert Cliffs Unit 2 shifted from an 18-month to a 24-month operating cycle. The last snubber functional tests were completed on May 7, 1987. Even though Unit 2 shut down and commenced its refueling outage eight days early, due to a material failure, the per*omance of the snubber functional tests could not be rescheduled for a completion date early enough to prevent the mode 5 and 6 snubbers (seven on hig1 pressure safety injection and 10 on shutdown cooling) from being declared inoperable, and thus rendering their associated systems inoperable.

Furthermore, due to this material failure which necessitated immediate Unit 2 shutdown and cooldown to mode 5, the licensee was unable to conduct several 8903300357 890324 PDR ADOCK 05000318 P

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.e e required surveillance that must be conducted in modes 3 and 4 prior to refueling. Consequently, Unit 2 may now need to continue to operate in modes 3 or 4 for one to three days after March 25, 1989 (the 18 month plus 25% snubber functional test due date).

Therefore, the licensee has requested a snubber functional test extension to preclude the requirement to declare safety systems inoperable for modes j

3 through 6 due to the failure to perform this test at the required i

surveillance interval.

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3.0 EVALUATION Snubbers are required to be operable to ensure that the structural integrity of the RCS and of all other safety-related systems is maintained during and following seismic events, primarily, or also for other events initiating dynamic loads (e.g., a water hammer event).

Calvert Cliffs Unit 2 is located in a region that has experienced only infrequent and minor earthquake activity, with only 19 minor to moderate intensity earthquakes reported as occurring within 100 miles of the site over the last 250 years. Of these, none occurring within 50 miles of the site resulted in any structural damage to standing buildings.

Currently, BG&E utilizes 277 safety-related snubbers at Unit 2.

These snubbers are hydraulic snubbers manufactured by Grinnell which are typed according to their two basic designs as described in the BG&E application dated April 25, 1986 and the corresponding NRC Safety evaluation for Amendment No. 100 to Facility Operating License No. DPR-69. The small bore type snubbers, (261 total) constituting all plant safety-related snubbers with the exception of the steam generator snubbers, have bore sizes ranging from 1.5" to 1.6" and strokes from 3.75" to 10".

These small bore snubbers have the same design valve blocks with only one valve block per snubber. The large bore type snubbers, (16 total) which are located on the steam generators, have a 10" bore, a 5" stroke and two valve blocks per snubber.

In addition, the large bore snubber valve blocks are designed differently from those on the small bore snubbers. Unit I has a similar snubber configuration. Of these 277 snubbers at Unit 2, only 17 are required to be operable in modes 5 and 6 (10 for shutdown cooling and 7 for high pressure safety infection).

Since 1978, the licensee has functionally tested 413 snubbers on Unit I and 2 combined with only three test failures, all of which, however, were small bore snubbers on Unit 2.

Two failures occurred in November 1985 and one in May 1987. This corresponds to a failure rate of approximately 0.7% over a period of greater than 10 years.

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. In addition-the Unit 2 snubbers have 10-year service lives while the oldest snubbers have currently seen 7.5 years of use. Consequently, the end of snubber service life for any Unit P snubber should not be reached until the end of 1991.

Finally, of the 17 snubbers required for modes 5 or 6 operation, 5 (29%)

have individually undergone successful functional tests within the last two years.

The NRC staff has reviewed the snubber history at Calvert Cliffs and has determined that the probability of any further significant degradation of the 1) 261 snubbers receiving a surveillance interval extension of approximately three days and 2) the 17 snubbers requiring up to a 54-day extension, is-negligible.

Furthermore, based upon the Unit 2 snubber history and upon the recent testing of several of the modes 5 and 6 required snubbers, the NRC staff has determined that the Unit 2 snubbers should be capable of satisfactorily performing their function within those interval extensions.

An increase in the probability or the consequences of a snubber's failure to fulfill its function would occur only as the result of a sequential degradation of a snubber followed by.a seismic or dynamic load creating event. The probability of a seismic or dynamic loading event is not affected by this proposed one-time snubber functional test interval extension. Consequently, the NRC staff has determined that this schedular extension will not significantly increase the probability or magnitude of a loss of safety-related system structural integrity. The staff therefore concludes that the proposed temporary amendment to the TS Surveillance Requirement 4.7.8.1.c, providing a one-time schedular extension for snubber functional tests, is acceptable.

This extension shall expire at 11:59 p.m. on May 17, 1989 or upon reaching 199.9 F average RCS temperature during initial RCS heatup following the Unit 2 Cycle 9 refueling outage, whichever occurs earlier. At expiration, the currently required 18-month surveillance interval of TS 4.7.8.1.c shall be reinstated.

This evaluation is provided to support this one-time, temporary schedular extension only and is not applicable, nor can it be utilized, as justification for permanent schedular changes to snubber inspection and testing intervals beyond the currently allowed maximum interval of 18 months (550 days).

The proposed changes to correct nomenclature errors (TS 4.7.8.1.b and 4.7.8.1.d were noted as TS 4.7.8.b and 4.7.8.d in several places in TS 3/4.7.8.) and to delete the obsolete reference to the long-past starting

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l I date for steam generator snubber surveillance are administrative in nature. These changes have no impact on plant design, operation, testing, maintenance or any accident analyses or margins of safety. Thus, the NRC staff has determined that these administrative changes are acceptable.

4.0 INTENT The intent of the proposed change is to allow, for one-time only, a snubber function test surveillance interval of 18 months (550 days) plus the 25%

extension of TS 4.0.2 (138 days) plus an additional extension of up to 54 days. This temporary extension shall expire at 11:59 p.m. on May 17, 1989 or at the first time average RCS temperature reaches 199.9 F following the Unit 2 Cycle 9 core loading.

5.0 ENVIRONMENTAL CONSIDERATION

This amendment involves a change to a surveillance requirement. The staff has determined that this amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that this amendment involves no significant hazards consideration and there has been no public comment on such finding. Accordingly, forth in 10 CFR Sec 51.22(c)gibility criteria for categorical exclusion set this amendment meets the eli (9). Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the ' issuance of this amendment.

6.0 CONCLUSION

The Commission made a proposed determination that the amendment involves no significant hazards consideration, which was published in the Federal Register (54 FR 7309) on February 17, 1989. The Commission consulted with the State of Maryland. No public comments were received, and the State of Maryland did not have any comments.

Based on the considerations discussed above, the staff concludes that:

(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.

PRINCIPAL CONTRIBUTOR:

S. A. McNeil Dated: March 24, 1989 4