ML20135C422
| ML20135C422 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 12/02/1996 |
| From: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | |
| Shared Package | |
| ML20007D650 | List: |
| References | |
| NUDOCS 9612060303 | |
| Download: ML20135C422 (4) | |
Text
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j NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20566-0001
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION BELATED TO THE INSERVICE TESTING PROGRAM NORTHEAST NUCLEAR ENERGY COMPANY MILLSTONE NUCLEAR POWER STATION. UNIT 3 DOCKET NUMBER 50-423
1.0 INTRODUCTION
i Title 10 of the Code of federal Regulations (10 CFR) Section 50.55a, requires that inservice testing (IST) of certain ASME Code Class 1, 2, and 3 pumps and valves be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel Code and applicable addenda, except where relief has been requested and granted or proposed alternatives have been authorized by the Commission pursuant to 10 CFR 50.55a(f)(6)(i), (a)(3)(1), or (a)(3)(ii).
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order to obtain authorization or relief, the licensee must demonstrate that:
(1) conformance is impractical for its facility; (2) the proposed alternative provides an acceptable level of quality and safety; or (3) compliance would result in a hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Section 50.55a(f)(4)(iv) provides that inservice tests of pumps and valves may meet the requirements set forth.in subsequent editions and addenda that are incorporated by reference in 10 CFR 50.55a(b), subject to the limitations and modifications listed, and subject to Commission approval. NRC guidance contained in Generic Letter (GL) 89-04, " Guidance on Developing Acceptable Inservice Testing Programs,"
provided alternatives to the Code requirements determined to be acceptable to the staff and authorized the use of the alternatives in Positions 1, 2, 6, 7, 9, and 10, provided the licensee follows the guidance delineated in the applicable position.
When an alternative is proposed, which is in accordance with GL 89-04 guidance and is documented in the IST program, no further evaluation is required; however, implementation of the alternative is subject to NRC inspection.
Section 50.55a authorizes the Commission to grant relief from ASME Code requirements or to approve proposed alternatives upon making the necessary findings. The NRC staff's findings with respect to granting or not granting the relief requested or authorizing the proposed alternative as part of the licensee's IST program are contained in this Safety Evaluation (SE).
By letter dated April 24, 1996, the Northeast Nuclear Energy Company (licensee) submitted Relief Request R-1 for Millstone Unit 3, second 10-year interval program for inservice testing of valves. The Millstone Unit 3 IST program will be updated to the requirements of the 1989 Edition of ASME Section XI for the second 10-year interval that is scheduled to begin on October 23, 1996.
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9612060303 961202 PDR ADOCK 05000423 P
l 2.0 RELIEF REQUEST R-1 1
Relief is requested from OM-10, Paragraph 4.3.1, which states that safety and relief valves shall meet the IST requirements of OM-1,1987 Edition. The subject of this request is Paragraphs 8.1.1.8, 8.1.2.8, and 8.1.3.7 of OH-1, which requires safety and relief valves to be tested with a 10-minute hold time between successive openings. This relief request pertains to all Code Class 1, 2, and 3 safety and relief valves, 2.1 Licensee's Basis for Reauestina Relief The licensee provided the following basis for the relief request:
Relief request R-1 generically applies to all safety and relief valves.
The current test method for set pressure testing of safety / relief valves requires a minimum of two consecutive actuations with ten minutes between actuations.
This generic relief will require a [5-] minute hold time between successive actuations for all safety [and] relief valves.
This IST Program change is a slightly different test method than specified by the Code, but provides a similar level of performance monitoring. This relief request will allow utilizing a [5-] minute hold time when performing set pressure testing of safety [and] relief valves, and will reduce test time and potentially radiation exposure. The increased hold time between tests is not necessary to ensure repeatable results nor does it increase the accuracy of the set pressure test.
1 The ASME OM Committee conducted an evaluation comparing [5-] minute versus [10-] minute hold time between successive valve actuations with regard to set pressure when using saturated steam. The comparison is based on actual valve test data compiled over several years and includes both main steam safety and pressurizer safety relief valves. Valves similar to those identified by the ASME OM committee are currently installed at Millstone Unit No. 3.
The data presented for each valve type is an averaged value of the standard deviation for each valve in that particular group. These averaged values are compared to the same valve group with both a [5-] and [10-] minute hold period between openings. Normal range for main steam relief valves is approximately 1200 psig and for pressurizer safety relief valves is 2500 psig. The average deviations found are within normal gauge increments and accuracies.
The required hold time between tests is not necessary to ensure repeatable results.
The increased hold time between tests does not increase the accuracy of the set pressure test. Temperature stabilization is important for high temperature valves. A [10-] minute hold time creates an excessively long test period based on the number of tests being conducted and the total time duration of the test.
Temperature stabilization is not a concern for valves tested at ambient conditions.
o Sr- =ry of the Averaaed Values of the Standard Deviation for Each Valve Tvoe and Hold Period Interval VALVE TYPE AVERAGE DEVIATION fosia)
Crosby main steam safety valves:
10 minutes between openings 2.463 5 minutes between openings 2.358 Crosby pressurizer safety relief valves:
10 minutes between openings 5.273 5 minutes between openings 5.075 Dresser main steam safety valves:
10 minutes between openings 1.823 5 minutes between openings 2.973*
- Note: This data came from a full flow test program rather than a limited lift.
Dresser main steam safety valves:
10 minutes between openings 3.476 5 minutes between openings 5.200 (Data compiled by Wyle Laboratories' Engineering Staff.)
Dresser main steam safety valves:
10 minutes between openings 3.696 5 minutes between openings 3.365 Target Rock main steam safety relief valves:
10 minutes between openings 3.250 5 minutes between openings 3.069 (Data compiled by Westinghouse Safety Valve Test Facility Staff.)
2.2 Alternate Testina The licensee proposed the following:
Safety and relief valves will be tested with a five minute hold time between tests.
3.0 EVALUATIDN The Code requires safety and relief valves to be tested with a 10-minute hold time between successive openings and requires the number of valve openings at set pressure shall be sufficient to demonstrate satisfactory repeatability with a minimum of two consecutive openings within Code tolerance. This relief request proposes a 5-minute hold time, which would reduce test time and possible radiation exposure to personnel conducting the test. Temperature
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stabilization during hold time prior to valve opening is an important consideration when performing set pressure testing under high temperature i
conditions. A comparison of average standard deviations determined for the set pressure tests under saturated steam conditions is provided in i
Section 2.1, above, for 5 and 10-minute hold times between openings. The results indicate that, in the majority of cases, average standard deviations actually decreased for the 5-minute hold time, indicating an improvement in i
the repeatability of test conditions. Based on the study conducted by the ASME OM Committee, it appears overall that, for the subject valves at Millstone Unit 3, using a 10-minute hold time in lieu of a 5-minute hold time i
between successive openings would provide an acceptable level of quality and 4
safety.
The ASME OM Committee is currently moving toward revising OH-1 to incorporate the 5-minute hold time requirement. The NRC has reviewed the study conducted by the ASME OM Committee and believes that the proposed alterative to use a 5-minute hold time between successive openings of safety and relief valves would i
i provide an acceptable level of quality and safety.
The present testing of safety and relief valves provides an acceptable level of quality and safety.
The present testing is an accordance with the OH-1, 1987 Edition, which requires a 10-minute hold time between successive openings. Based on the study conducted by the ASME OM Committee comparing the average deviation resulting from 5-minute hold times with the average j
deviation resulting from 10-minute hold times, testing of the valves at Millstone 3 using a 5-minute hold time also provides an acceptable level of quality and safety.
4.0 CONCLUSION
Based on the determination that the proposal to test the relief and safety valves with a 5-minute hold time between successive openings provides an acceptable level of quality and safety, the proposed alternative is authorized i
pursuant to 10 CFR 50.55a(a)(3)(1).
Principal Contributor: K. Dempsey Date: Decenber 2, 1996 e
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