ML20040A593
| ML20040A593 | |
| Person / Time | |
|---|---|
| Site: | La Crosse File:Dairyland Power Cooperative icon.png |
| Issue date: | 01/31/1982 |
| From: | Laudenbach D EG&G, INC. |
| To: | |
| Shared Package | |
| ML20040A589 | List: |
| References | |
| NUDOCS 8201210272 | |
| Download: ML20040A593 (4) | |
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DRAFT TECHNICAL EVALUATION REPORT 6
i FOR CONTAINMENT PURGING AND VENTING 00 RING l
NORMAL OPERATION OF THE LA CROSSE BOILING WATER REACTOR, UNIT 1 1
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Revision 1
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(Docket Number 50-409) 1 i
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- D. H. Laudenbach January 1982 i
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820 121 oS7'A l
- EG&G, Inc., Energy Measurements Group, San Ramon Operations 3
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I DRAFT TECHNICAL EVALUATION. REPORT FOR CONTAINMENT PURGING AND VENTING DURING NORMAL OPERATION OF THE LA CROSSE BOILING WATER REACTOR, UNIT 1 Revision 1 (Docket No. 50-409) 4 I.
INTRODUCTION A 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.
Inese events have raised concerns relative to potential failures affecting the purge penetrations which could lead to degradation in containment integrity, and, for PWRs, a degradation in ECCS performance.
By letter, dated November 28, 1978, the Comission (NRC) requested all licensees of operating reactors to respond to certain generic concerns about containment purging or venting during normal plant opera-tion. The generic concerns were twofold:
(1)
Events had occurred where licensees overrode or by-passed the safety actuation. isolation signals to the 6
containment isolation valves.
Inese 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 anal-yses 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 wno elected to purge (or vent) the con-tainment were requested to demonstrate that the containment purge (or vent) system design met the criteria outlined in the NRC Standard Review Plan (SRP) 6.2.4, Revision 1, and tne associated Branch Technical Position (BTP)
CSB 6-4, Revision 1.
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DISCUSSION AND EVALUATION The la Crosse Boiling Water Reactor (LACBWR) containment ventila-tion provisions consist of a 20-inch supply line, a 20-inch discharge line, and a 4-inch vent header. Each 20-inch line is equipped with two normally-open butterfly-type valve isolation dampers located inside containment.
The 4-inch vent header is equipped with two isolation globe valves, one on each side of the containment wall.
A single normally-closed 20-inch !
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butterfly-type valve isolation damper is located inside containment in the recirculation duct.
This damper automatically opens when tne other dampers are closed to permit air recirculation in the containment building.
The licensee responded to the NRC position letter of November 1978, by indicating it was their intention to justify continued unlimited ventilation because of the significant problems created by containment ventilation cessation.
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i The licensee indicated that the LACBWR containment building, which is designed for continuous ventilation, contains the reactor vessel and most of the associated reactor plant equipment.
Inis equipment is normally operated and maintained during plant operation, thus requiring routine entry by Operations and Maintenance personnel.
Additionally, Technical Specification surveillance requirements necessitate frequent entry into the containment building by Operations personnel.
A normal resident period for Operations personnel in the containment building is approximately 2.5 man hours daily.
Cessation of Containment venting would result in excessive radiation exposure to LACBWR personnel.
Any future restriction on personnel access to the containment building could have a l
deleterious effect on plant operations and safety.
Cessation of contain-ment venting would also nave a detrimental affect on primary system leak rate determination.
The lower reactor cavity is purged and slightly pressurized with clean outside air to prevent entry of af rborne activity from other containment building areas which could ca.m false leakage indications or mask an actual primary system leak.
The lower cavity pressurization would have to be stopped to prevent excessive containment pressure buildup.
Additionally, the buildup of activity witnout ventila-tion would cause the fixed filter monitors to reach levels that would render them useless for primary system leak detection.
l The licensee has not provided sufficient information concerning the provisions made to ensure that isolation valve closure will not be prevented by debris which could potentially become entrained in the escap-ing air and steam.
We recommend that debris screens be provided for the purge supply and exhaust systems.
The debris screens should be Seismic Category I design and installed about one-pipe-diameter away from the inner side of each inboard isolation valve.
The piping between the debris screen and the isolation valve should also be Seismic Category I design.
l The licensee has not provided the results of an analysis which includes the amount of the mass of air and steam released to the environ-ment prior to purge system isolation following a LOCA, nor have they provided an analysis which demonstrates the acceptability of tne provisions made to protect structures and safety-related equipment located beyond the purge system isolation valves.
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CONCLUSIONS We have reviewed tne La Crosse Boiling Water Reactor (LACBWR),
Unit 1, purge system against the guidelines of BTP CSB 6-4, Revision 1,
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" Containment, Purging During Normal Plant Operations."
We are unable to complete our review of tne LACBWR purge / ventilation system because the licensee has not provided:
(1)
Sufficient information concerning provisions made to ensure that isolation valve closure will not be prevented by debris wnicn could potentially become entrained in the escaping air and steam.
(2)
An analysis of airborne radiation released as a result of a LOCA, which includes the amount of air / steam which will be released tc the environ-ment prior to purge system isolation following a LOCA.
(3)
An analysis of the provisions to protect struc-tures and safety-related equipment located down-stream of the purge isolation valves against a loss of function from the environment created by the escaping air and steam.
Although the licensee has provided information to justify un-limited purging / venting during power operations, our view is that system use should be limited.
The plant is inherently safer with closed purge /
vent isolation valves than with open lines which require valve action to provide containment integrity.
We, therefore, recomend that tne licensee be requested to commit to limiting the use of the purge / vent system to a specified annual time that is comensurate with identified plant operation-al needs.
In addition, as a result of numerous reports on the unsatisfac-tory performance of resilient seats in butterfly-type isolation valves due to seal deterioration, periodic leakage integrity tests of the 20-inch butterfly isolation valves in the purge system are necessary.
Therefore, the licensee should 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 containment purge / vent lines shall be conducted at least once every three months."
The purpose of the leakage integrity tests of tha isolation valves in the i
containment purge lines is to identify excessive degradation of the resil-l ient seats for these valves.
Therefore, they leed not be conducted with l
the precision required for the Type C isolation valve tests in 10 CFR part 50, Appendix J.
These tests would be performed in addition to the quanti-tative Type C tests required by Appendix J, and would not relieve the licensee of the responsibility to conform to the requirements of Appendix i
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