ML17310A372
| ML17310A372 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 06/21/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17310A371 | List: |
| References | |
| NUDOCS 9306300073 | |
| Download: ML17310A372 (10) | |
Text
~A,YI REG(g(
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/p IV IA.*y0 UNITED STATES NUCLEAR REGULATORY COMIVllSSION WASHINGTON, D.C. 20555.0001 930 p
@DOCK 3062l OS000528 F'R SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO MENDMENT NO.
TO FACILITY OPERATING LICENSE NO.
NPF-41 MENDMENT NO.
TO FACILITY OPERATING LICENSE NO.
NPF-51 AND AMENDMENT NO.
TO FACILITY OPERATING LICENSE NO. NPF-74 ARIZONA PUBLIC SERVICE COMPANY ET AL.
PALO VERDE NUCLEAR GENERATING STATION UNIT NOS.
1 2
AND 3 DOCKET NOS.
STN 50-528 STN 50-529 AND STN 50-530
- 1. 0 INTRODUCTION By letter dated May 20, 1993, the Arizona Public Service Company (APS or the licensee) submitted a request for changes to the Teclmical Specifications (TS) for the Palo Verde Nuclear. Generating Station, Units 1, 2,
and 3 (Appendix A
to Facility Operating License Nos.
NPF-41, NPF-51, and NPF-74, respectively).
The Arizona Public Service Company submitted this request on behalf of itself, the Salt River Project Agricultural Improvement and Power District, Southern California Edison
- Company, El Paso Electric Company, Public Service Company of New Mexico, Los Angeles Department of Water and
- Power, and Southern California Public Power Authority.
The proposed changes would add a footnote to Surveillance Requirement 4.7.9 for each of the 3 units to state that the methodology used for selecting the test sample for snubber functional testing during the current outage for Unit 2 and the third outage for both Units 1 and 3 was not in accordance with the requirements of Surveillance Requirement 4.7 '
but adequately demonstrated the operability of the snubber populations 2.0 EVALUATION Snubbers are devices which allow movement of piping systems to accommodate thermal effects but which restrain movement during dynamic events.
The purpose of Technical Specification 3.7.9, "Snubbers," is to ensure that the structural integrity of the reactor coolant system and all other safety-related systems is maintained during and following a seismic or other event initiating dynamic loads.
In order to demonstrate the operability of the snubbers, Surveillance Requirement 4.7.9 requires that visual examination and functional tests be performed on the snubber.
Functional test requirements are established based on a statistical approach for demonstrating the operability of the entire snubber population by performing actual tests on a sample population.
Achieving acceptable results on the sample population demonstrate wi.th sufficient confidence that the entire population is operable.
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To provide assurance of snubber functional reliability, the licensee's TS require one of the following three functional testing methods to be used:
(1)
Functionally test IOX of a snubber type, with an additional IOX tested for each functional failure, or (2) functionally test a representative sample size and determine the sample acceptance or rejection in accordance with the statistically-generated TS Figure 4.7-1, "Sampling Plan for Snubber Functional Test," or (3) functionally test a representative sample size of 55 snubbers and determine sample acceptance or rejection using the equation N=55(1+C/2),
where "C" is the number of snubbers found which do not meet the functional test acceptance criteria.
In addition, the representative sample selected for the functional test sample plans shall:be randomly selected from the snubbers of each type and.reviewed before beginning the testing.
In correspondence with Region V, the licensee indicated that it had selected functional testing Sample Plan 2 for use at the Palo Verde Nuclear Generating Station (PVNGS).
However, for each
- outage, the licensee tested a
representative sample of mechanical snubbers (37) following Sample Plan 2 but tested one steam generator hydraulic snubber and one reactor coolant pump hydraulic snubber effectively following Sample Plan 1 for hydraulic snubbers.
While reviewing the snubber testing on Unit 2, it was discovered that the licensee had divided the snubbers into 5 groups.
These are:
(1) Pacific Scientific Arrester (PSA) 1/4 and 1/2 size Mechanical Snubbers (small),
(2)
PSA 1, 3, and 10 size Mechanical Snubbers (medium),
(3)
PSA 35 and 100 size Mechanical Snubbers (large),
(4) Steam Generator Hydraulic Snubbers, and (5)
Reactor Coolant Pump Hydraulic Snubbers.
The surveillance method that the licensee indicated it had selected states that a sample of 37 snubbers of each type is to be tested.
The TS definition of type requires that each of these five groups be considered as a snubber type.
Since each group was not treated as a type, the licensee tested far fewer snubbers than the words in.the TS would require.
Upon discovery, an evaluation of the snubber testing program was performed and concluded that the testing satisfactory demonstrated operability of the snubbers, however, it was determined that the program was not being conducted in full compliance with the Technical Specifications.
As
- such, on May 12,
- 1993, PVNGS Unit 1, 2,
and 3 entered the ACTION statement for Limiting Condition for Operation 3.7.9.
This ACTION statement allows 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to return snubbers to OPERABLE status.
At the end of this period, TS 3.0.3 would have had to be entered and plant shutdowns for both Units 1 and 3 would have had to commence.
Unit 2, which is currently in an outage, would have been prohibited from changing modes.
By letter dated May 14,
- 1993, as supplemented by a further letter of the same
- date, the licensee requested a Notice of Enforcement Discretion from TS 3.7.9 for Palo Verde Nuclear Generating Station, Units 1, 2, and 3, until an Emergency TS change could be processed and approved.
On May 14, 1993, the NRC verbally notified the licensee of its intention to exercise discretion not to enforce compliance with TS 3.7.9 until the licensee requested, and the staff completed its review o',
a change to the TS to address the nonconforming condition.
This verbal notification was confirmed in a letter dated May 18, 1993.
'I V
In a Hay 20, 1993, letter, the licensee requested an emergency change to the Technical Specification to state that the methodology used for selecting the test sample for snubber functional testing during the current outage for Unit 2 and the previous outage for both Units 1 and 3 was not in accordance with the requirements of Specification 4.7.9 but adequately demonstrated the operability of the snubber population.
The licensee stated that during the most recent test periods in Unit 1, 2, and 3 the number of hydraulic and mechanical snubbers tested would have met the sampling requirements of Sample Plan 1, with the exception of random sampling, for all types of snubbers except the "small" mechanical type in Unit 3.
- However, based on industry standards, an acceptable confidence level can be achieved utilizing a sample, plan which chooses an initial size of ten percent of each type of snubber and for each failure of a given type, the sample is expanded five percent for that type.
Therefore, the small mechanical snubbers would have met the sampling requirement for such a plan based on the number of snubbers in the initial snubber population.
Based on the above discussions, the NRC staff finds the change to the TS to allow for continued operation to be acceptable.
3.0 STATEMENT OF EMERGENCY CIRCUMSTANCES As part of the root cause of failure investigation of the failed snubbers, an evaluation of the snubber testing program was conducted.
It was determined
- that, although testing satisfactorily demonstrated operability of these
On Hay 12,
- 1993, PVNGS Unit 1, 2, and 3 entered the ACTION statement for Limiting Condition for Operation 3.7.9.
This ACTION statement allows 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to. return snubbers to OPERABLE status.
At the end of this period, TS 3.0.3. would have had to be entered and plant shutdowns for both Units 1 and 3
would have had to commence.
Unit 2, which is currently in an outage, would have been prohibited from changing modes.
The licensee requested a notice of enforcement discretion.
The NRC staff exercised discretion not to enforce compliance with TS 3.7.9.,
pending submission and review of an appropriate change to the TS.
The licensee requested the TS change on an emergency basis on Hay 20, 1993, stating that since the issue was just discovered and adequate time has not existed to process the amendment by normal exigent means.
Accordingly, pursuant to.10 CFR 50.91 (a)(5), the Commission has determined that there are emergency circumstances warranting prompt approval by the Commission.
4.0 FINAL DETERMINATION OF NO SIGNIFICANT HAZARDS CONSIDERATION The Commission's regulations in 10 CFR 50.92 state that the Commission may make a final determination that a license amendment involves no significant
a e
hazards consideration if operation of that facility in accordance with the amendment would not:
(1)
Involve a significant increase, in the probability or consequences of any accident previously evaluated; or (2)
Create the possibility of a new or different kind of accident from any accident previously evaluated; or (3)
Involve a significant reduction in a margin of safety.
The licensee stated that the amendment has been evaluated against the standards in 10 CFR 50.92, and the license amendment request involves no significant hazards considerations based on the following:
(1)
The proposed change-documents that the test samples used for snubber functional testing during the last surveillance for each unit were adequate to demonstrate operability of the entire snubber population.
Since the actual testing performed demonstrated the operability of the snubbers in the past, and the Technical Specification methodology for selecting test samples in the future is not changing, the proposed license amendment does not involves a significant increase in the probability or consequences of an accident.
(2)
The proposed change does not involve any physical modifications to the plant or changes to methods for operating the plant or equipment.
The proposed change involves documenting that past practices for selecting snubber functional test samples were adequate for demonstrating operability of the entire snubber population.
Since the actual testing performed demonstrated the operability of the snubbers in the past, and the Technical Specification methodology for selecting test samples in the future is not changing, the proposed change does not create the possibility of a new or different kind of accident from any accident previously evaluated.
(3)
The proposed change involves documenting that past practices for selecting snubber functional test samples were adequate for demonstrating operability of the entire snubber population.
Since the actual testing performed demonstrated the operability of the snubbers in the past, and the Technical Specification methodology for selecting test samples in the future is not changing, the proposed change does not involve a significant reduction in a margin of safety.
The NRC staff agrees that the above standards are satisfied and therefore hereby determines that the amendment request involves no significant hazards consideration.
5.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Arizona State official was notified of the proposed issuance of the amendment.
The State official had no comments.
- 6. 0 ENVIRONMENTAL CONSIDERATION The amendments'hange a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes surveillance requirements.
The NRC staff has determined that the amendments involve 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 made a final no significant hazards consideration finding regarding this amendment.
Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.
7.0 CONCLUSION
The Commission has concluded, based on the considerations discussed
- above, 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 compl.iance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
Linh Tran Date:
Dune 21, 1993
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