ML17341A533
| ML17341A533 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 08/31/1981 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17341A532 | List: |
| References | |
| NUDOCS 8109180201 | |
| Download: ML17341A533 (9) | |
Text
ENCLOSURE 3
SAFETY EYALUATION REPORT FOR CON A NM U
N N
MA A
TURKE AND 4 1.
INTRODUCTION' number of events have, occurred over the past several years which directly relate to the practice of containment purging. and venting 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 PHRs, 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'. design basis loss. of coolant: acci.dent (DBA-LOCA).,
The. NRC'osition'f-the November 1978 letter requested licen'sees to: cease-purging, (or venting) of: contai'nment'r 1'imit purging
('or-venting) to; an absolute, minimum; Licensees who, el'ected. to purge (or vent) the contain-ment. were requsted; to demonstrate. that. the: containment. purge. (or* vent) 8109180201 810831 PDR ADOCK 05000250 P
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that the containment purge (or vent) system design met the criteria out-lined in the NRC Standard Review Plan (SRP) 6.2.4, Revision 1 and the as-sociated Branch Technical Position (BTP)
CSB 6-4, Revision 1.
II.
DISCUSSION AND EYALUATION The purge/vent systems at Turkey Point, Units 3 and 4 consist of two 48-inch lines and two 54-inch lines, respectively, for purging the con-tainment atmosphere to allow personnel access and on'e 2-inch line in each unit to maintain the containment pressure during normal operation within a prescribed range.
The l.icensee responded to the NRC position letter of November 1978 by stat-ing that they planned to justify unlimited purging,. however;. they would continue their practice of mi'nimizing the number of purges and the dura-'ion of each purge during. power operation; Based on their reactor oper-ating experience, the licensee estimates that they need'00 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> of com-bined purges per year during power operation
(> 2L'ower) for the site (200 hours0.00231 days <br />0.0556 hours <br />3.306878e-4 weeks <br />7.61e-5 months <br /> total for both units).
We. have reviewed. the licensee's justification for the estimated annual usage of the purge system and find it to be ac-ceptable..
The licensee has; provided. the. results of an analysis of the mass of air and steam rel'eased; to the envi ronment prior to purge system isolation follow-ing a LOCA..
The effect"of the. containment. atmosphere being; rel'eased on:
contai'nment pressure has been bounded'y two: extreme: cases.(air al'one. and.
steam al'one)..
The;.total'ass, released is cal'culated; as; 11.,299 lbs.. air or, 8',588bs.
steam..
The. containment. pressure.
reduction resul'ting.fi om this:
loss; of-air, is. computed to. be 1'-84'si;. the, pressure reduction, associated'.
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with the loss of steam is 2.36 psi.
The licensees indicated that the effect of containment pressure upon the calculated. peak clad temperature is typi-cally 5'F psi tfrom results of the. FLECHT experiments).
Therefore, the ef-feet of purging on the ECCS performance is minimal fo'r the Turkey'oint plants.,
Me have reviewed the licensee's assumptions used in the above mass-release
- analysis, and conclude that the mass released through the purge sys-tern prior to the system isolation following, a LOCA has been conservatively calcul'ated.
The licensee has not provided sufficient information concerning the provi-sions made to ensure that isolation valve closure will not be prevented by debris which could potentially become entrained in the. escaping air and steam.
Me request that.additional assurance"of isolation valve closure such as debris screens should be provided fo':, the purge supply and exhaust ductwork.
.Any such assurance should be seismic Category I design.
vent system is periodically used. during normal plant, operation to main-tain the containment pressure within prescribed l,imits,.
The system util-izes, 2-inch valves, for containment isol'ation.
We have. reviewed the isol'a-.
tion provisi'ons for this system's containment'enetration and: conclude.
that they, comply with G'eneral'esi'gn Criteria '54 and 56.
Horeover;, the. con-cern over the, abili'ty. of.'he. valves; to cl'ose, during a, LOCA transient does'ot apply, to; these: small'alves-.
III. CONCLUSION We have reviewed the purge system against the guidelines of BTP CSB 6-4
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(Revision 1), "Containment Purging During Normal Plant Operation."
Me conclude that the Tui.key Point containment purge/vent system is acceptable, subject. to the licensee's installation of a debris'creen.
In addition, as a result of numerous reports on the unsatisfactory perform-ance of resilient seats in butterfly-type isolation valves due to seal de-terioration, periodic leakage integrity tests of the 48-and 54-inch but.-
terfly isolati'on valves in the purge system are necessary.
Therefore, the licensees, should also
- propose, a Technical Specification for testing the" valves in accordance with the following testing frequency:
"The-leakage integrity tests of the isolation valves in the contain-ment purge/vent lines shall be conducted at least once every three months."
The purpose of the. leakage integrity tests of the. isolation valves in the containment. purge 'lines is to identify excessive degradation of the resil-i ent: seats for these valves.
Therefore, they need not be, conducted with the precision required'or the. Type C isolation valve tests: in 10 CFR'art.
50,. Appendix J.
These tests would be performed. in. addition to the quantitative Type, C, tests. required by,. Appendix J and would not: relieve the:
l'icensee, of the responsibility to. conform to, the. requirements, of Appendix J'..
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C ENCLOSURE 4 RE UEST FOR ADDITIONAL INFORMATION Containment Purge and Vent Valve Operability Assurance Program Justification demonstrating operability of the Turkey Point purge and vent valves for long term in accordance with our "Guidelines for Demonstration of Operability of Purge and Vent Valves" is required (ref.. 1). This justi-fication should include, as a minimum, method of test or analysis, results of the, operability assurance
- program, and responses to inquiries transmit-ted in ref. 2.
Although. the letter of December 9, 1980 (L-80-398) indicated the operability
-program is complete, the analysis and responses to the clarifications to the September 27, 1979 letter have not.been submitted.
1)
Attachment to letter to utilities of September 27, 1979:
"Guidelines for Demonstration of Purge and Vent Valves."
2)
"Clar ification of September 27, 1979 L'etter. to Licensees Regarding Demonstration of Operability of Purge and Vent Valves."
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