ML18139B576
| ML18139B576 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 10/08/1981 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML18139B575 | List: |
| References | |
| REF-GTECI-B-24, REF-GTECI-IS NUDOCS 8110280639 | |
| Download: ML18139B576 (5) | |
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I.
INTRODUCTION SAFETY EVALUATION REPORT FOR CONTAINMENT PURGING/VENTING DORING NORMAL OPERATION SURRY POWER STATION, UNITS l AND 2 DOCKET NOS. 50-280/281 ENCLOSURE 2 A number of events have occurred over the past several years which di-rectly 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/vent penetrations which could lead
'to a degradation of containment integrity, and, for PWRs, a degradation of ECCS performance.
By letter, dated November 28, 1978, the Commission (NRC) requested all licensees 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 1 i censees 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).
In our letter of November 1978, we requested that licensees cease purg-ing (or venting) of containment or limit purging (or venting) to an ab-solute minimum.
Licensees who elected to purge (or vent) the contain-ment were requested to demonstrate that the containment purge (or vent)
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.**-i e system design met the criteria outlined in the NRC Standard Review Plan (SRP) 6.2.4, Revision 1 and the associated Branch Technical Position (BTP)
CSB 6-4.
The purge/vent systems in each unit at Surry consist of two 42-inch penetra-tions for purging the containment atmosphere to facilitate personnel access.
In addition, each unit has a containment vacuum system which consists of an 8-inch penetration and two 2-inch penetrations for evacuating the contain-ment to the prescribed.subatmospheric condition.
II. DISCUSSION AND EVALUATION Each unit at Surry utilizes a subatmospheric containment design. Also, an iodine filtration system, located inside the containment, aids in removing*
airborne* *radi oacti vi ty that may be *re 1 eased from. the reactor cool ant system during normal operation. Therefore, containment purging or venting through the 42-inch and 8-inch penetrations is not necessary whenever the reactor coolant temperature exceeds 200°F, except for the short term operation of the above systems to break the vacuum in the containment or establish the vacuum during startup.
By letter dated February 21, 1980, the licensee com-mitted to not perform containment purging ope_rations unless the plant is in*
the cold shutdown or refuel.i ng mode, and not purge whenever the reactor coolant temperature is above 200°F until an evaluation of purge valve oper-ability under LOCA conditions is complete and justification for purging has been provided to the satisfaction of the staff. The licensee further indi-cated that it wou*ld be several weeks before the evaluation would be complete~
To date, the licensee has not provided the evaluation and has made no firm
.decision regarding purge system operation.
e We have reviewed the licensee's submittals related to the containment purge/
vent issue and have concluded that further delay of the resolution of this issue is not warranted. Maintaining.the 42-inch purge valves and the 8-inch valves on the steam jet air ejector lines closed during plant operating Modes 1 through 4 will preclude the release of radioactivity to the environs via the containment purge system and the steam jet air ejector system should a loss-of-coolant accident occur. Therefore, the licensee should propose a change to the Technical Specifications reflecting their prior commitment to maintain the above named 42-inch and 8-inch valves in a closed position.
A_mechanical vacuum pump system is periodically used during normal plant op-eration to maintain the containment at the prescribed subatmospheric pressure.
This system utilizes 2-inch gate valves for containment isolation. The me-chanical vacuum pump system does not fall within the scope of review for con-tainment purge/vent operations.
Howeve*r, we have reviewed the isolation pro-visions for the penetrations of this system and conclude that their isolation provisions comply with General Design Criteria 54 and 56. Moreover, the con-cern over ability of the valves to close during a LOCA transient does not apply to these small valves.
I II. CONCLUSION We find acceptable the licensee's prior co1T111itment to maintain the 42-inch purge system valves and the 8-inch steam jet air ejector system valves closed during Modes 1 through 4, and the licensee should propose a change to the Technical Specifications which reflects this conmitment~
Also, as a result of the numerous reports on unsatisfactory performance of the res.ili ent seats.
- for butterfly-type isolation valves in containment purge and vent lines, periodic leakage integrity tests of the above 42-inch and 8-inch butterfly isolation valves have been found necessary.
We, therefore, request that the
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- 1 icensee propose a technical specification* for testing these valves in ac-cordance with the following reconmended testing frequency:
"The leakage integrity tests of the isolation valves in the contain.;.*
ment purge lines and the steam jet air ejector system 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 and the steam jet air ejector system lines is to identify excessive degradation of the resilient seats for these valves.
Therefore, they need not be conducted with the precision required for the Type C isolation valve tests in 10 CFR Part 50, Appendix J. These* tests would be performed in addi ti.on to the quantitative Type C tests required by Appendix J and would not relieve the 1 i censee of the responsibility to con.form to the requirements* of* Appendix.* J. *.
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. 1.0 Introduction Safety Evaluation Report Minimum Containment Pressure Setpo1nt (Item II.E.4.2(5) of NUREG-0737)
Surry Nuclear Power Plant, Units 1 and 2 Docket Nos:
50-280, 281 ENCLOSURE 3 As a consequence of the accident at TMI-2, implementation of I number of new requirements has been recorrrnended for operating reactors. These new require-ments are described in NUREG-0660, *NRC Action Plan ~veioped as I Result of the TMI-2 Accident,* Hay 1980, 1nd NUREG-0737, *clar1ffcation of TMI Action
- Plan Requirements,* November 1980. The NRC staff has also requested 11cen-sees to submit fnfonnation sufficient to pennit.1n independent evaluation of their response to these new requirements. This report pl"'Ovides an evaluation of the response to Action Plan Item II.E.,.2, position 5, by the designated license~.
2.0 Evaluation Our consultant, the EG&G Energy Measurements Group (a subcontractor to Lawrence Lfvennore National Laboratory. which has the TMI Action Plan contract) has reviewed the licensee's sullnittals and prepared the attached technical evaluation report of the lfce~see's contafrvnent pressure setpofnt used to 1so1ate nonessential containment penetrations *. We have reviewed this evaluation and concur in its basis and findings.
J.O Conclusions The infonn~t1on submitted by the 11censee provided sufffcfent details of the lfcensee's contafnment iso1ation pressure for the staff to conclude that the req,u{rements of Item II.E.4.2(5) of NUREG-0737, with the 1ddftiona1 guidelines developed by the staff, have been met.