ML20039F887
| ML20039F887 | |
| Person / Time | |
|---|---|
| Site: | Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png |
| Issue date: | 12/18/1981 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20039F886 | List: |
| References | |
| NUDOCS 8201140015 | |
| Download: ML20039F887 (4) | |
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SAFETY EVALUATION REPORT FOR CONTdINMENT PU_RG_ING/ VENTING DURING NOPFAL OPERATION HADDAM NECK PLANT DOCKET NO. 50-213 I.
INTRODUCTION A number of events have occurred over the past several years which directly I
relate to the practice of containment purging and ventihg during normal plant operation.
These events have raised concerns relative to potential failures affecting the purge penetrations which could lead to degradation in containment integrity, and, for PWR's, a degradation in ECCS performance.
By letter, dated November 28, 1978, the Commission (NRC) requested all li-censees of operating reactors to respond to certain generic concerns about containment purging or venting during normal plant operation. The generic concerns were twofold:
(1)
Events had occurred where licensees overrode or bypassed the safety actuation isolation signals to the containment isolation valves.
These events were determined to be abnormal occurrences and were so characterized in our report to Congress in January 1979.
(2)
Recent licensing reviews have required tests or analyses to show that containment purge or vent valves would shut without degrading containment integrity during the dynamic loads of a design basis loss of coolant accident (DBA-LOCA).
The NRC position of the November 1978 letter requested licensees to cease purging (or venting) of containment or limit purging (or venting) to an absolute minimum.
Licensees who elected to purge (or vent) the containment 8201140015 011218 PDR ADOCK 05000213 ENCLOSURE P
o v.
2-were requested to demonstrate that the containment purge (or vent) system design met the criteria outlined. in the NRC Standard Review Plant (SRP) 6.2.4, Revision l and the associated Branch Technical Position (BTP)
CSB 6-4.
II.
DISCUSSION AND EVALUATION The purge system, consisting of two 42-inc.h lines,.was designed to purge the containment atmosphere to improve working conditions for personnel.
In addition, an iodine filtration system, located inside the containment, aids in removing airborne radioactivity that may be released from the reactor coolant system during nonnal operation. The licensee stated, in a letter dated January 3,1979, that.the 42-inch purge valves in the Haddam Neck Plant are manually operated valves, and that purging through them is prohib-ited during plant operation in Modes 1 through 4 by Technical Specifications.
The licensee further stated, in a letter dated December 10, 1979, that vent-ing needs during plant operation are satisfied by the 1-inch diameter, con-tainment air particulate monitoring lines. The air monitoring lines do not fall within the scope of review for containment purge / vent operations.
Ho-ever, we have reviewed the isolation provisions for these 1-inch lines and conclude that their isolation provisions comply with General Design Criteria 54 and 56. ~ Moreover, the concern over ability of the valves in these lines to close during a LOCA transient does not apply to these small valves.
III. CONCLUSION We agree with the licensee that maintaining the 42-inch purge valves closed during plant operation in Modes 1 through.4 will preclude the release of radioactivity to the environs via the containment purge system should a
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loss-of-coolant accident occur.
We, therefore, conclude that the purge system design and use for the Haddam Neck Plant tre acceptable. However, as a result of the numerous reports on unsatisfactory performance of the re-silient seats for butterfly-type isolation valves in containment purge and vent lines, periodic leakage integrity tests of the above 42-inch butter'f.ly isolation valves have been found necessary. We, therefore, request that the licensee propose a technical specification for testing these valves in accordance with the following recommended testing frequency:
"The leakage integrity tests of the isolation valves in the containment purge lines shall be conducted at least once every six months."
The purpose of the leakage integrity tests of the isolation valves in the containment purge lines is to identify excessive degradation of the resilient i
seats for these valves. Therefore, they need not be conducted with the pre-cision required for the Type C isolation valve tests in 10 CFR Part 50, Ap-pendix J.
These tests would be perfonned in addition to the quantitative Type C tests required by Appendix J and would not relieve the licensee of the responsibility to conform to the requirements of Appendix J.
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I Epciosur.e3 CONTAINMENT. SYSTEMS SURVEILLANCE REQUIREMENTS (Continued)
The containment purge and vent isolation valves shall be demonstated 4.6.3.4 months. Valve OPERABILITY shall be 0PERABLE at intervals not to exceed determined by verifying that when th'e measur.ed leakage rate is added to the leakage
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rates determined pursuant to Specification 4.6.1.2.d for all.other Type B and C penetration, the combined leakage rate is less than 6P equal to 0.60La.
However, the leakage rate for the containment purge and vent isolation valves shall be compared to the previously measured leakage rate to detect excessive i
valve degradation.
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