ML20028A615
| ML20028A615 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 11/19/1982 |
| From: | Bordine T CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8211230063 | |
| Download: ML20028A615 (3) | |
Text
m Consurners Power Company General offices: 1945 West Parnall Road, Jackson, Mt 49201 * (517) 788-o550 November 19, 1982 Dennis M Crutchfield, Chief Operating Reactors Branch No 5 Nuclear Reactor Regulation US Nuclear Regulatory Commission Washington, DC 20555 DOCKET 50-155 - LICENSE DPR BIG ROCK POINT PLANT - RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION - CONTAINMENT PURGING / VENTING DURING NORMAL OPERATION NRC letter dated September 14, 1982 enclosed a Safety Evaluation Report (SER) for " Containment Purging and Venting During Normal Operation of the Big Rock Point Plant".
The letter specified that issuance of the SER resolves long-tenn review issues regarding conformance to Standard Review Plan Section 6.2.4 Revision 1 and Branch Technical Positions CSB 6-4' Revision 1.
Final resolu-tion however was subject to three conditions specified within the September 14, 1982 letter. The following is provided as our response to the three conditions:
Condition
" Provide an acceptable method of ensuring that the isolation valves in the purge supply and exhaust lines will not be prevented from closing or properly seating by debris. An acceptable method is the installation of debris screens in these lines."
Response to Condition Consumers Power Company will install debris screens in the containment ventilation supply and exhaust lines. This modification will be performed within one year of NRC's concurrence of the acceptability of this modifica-tion. NPC concurrence prior to starting this effort is necessary for the following reasons:
(1) because of ventilation system configuration, placement of screens within one pipe diameter of the inboard supply / exhaust valves does not appear practicable; (2) design and installation of the screens will be performed to provide assurance of integrity; however, scismic criteria will
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not be specifically addressed.
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D M Crutchfield, Chief 2
Big Rock Point Plant Containment Purging l Venting November 19, 1982 Condition "As a general philosophy, the NRC believes that the containment integrity should always be intact during power operation.
Operation of the purge system at Big Rock Point introduces a pathway for leakage which has to be closed by mechanical equipment in the event of an accident. Since a containment that operates with the purge valves closed requires no actions to achieve containment isolation, the staff recommends that licensees limit purging as much as possible. You should limit purging to the minimum time commensurate with identified safety needs. Therefore, commit to limit the use of the purge system to a specified annual time that is commensurate with identified safety needs."
Response to Condition Maintaining the ventilation supply and exhaust valves closed results in the following adverse conditions:
- 1) Airborne activity increase - The rate of increase in airborne activity depends primarily on Primary Coolant System (PCS) activity and PCS leak rate; under nominal conditions, it is estimated that respiratcry protection would be required in less than one week following ventilation valve closure.
Because of plant design, many activities cannot be performed remotely and require containment entry. Examples of such activities include operator rounds, surveillance tests, chemistry sampling, radiological surveys, corrective and prever.tive maintenance, and instrument calibration:. Specifically, operator rounds are performed inside containment every two hours, and a minimum v' 45 surveillance activities per week require containment entry. Therefor:
conclude that sealing containment would result in a significant inct on wholebody and internal radiation exposure.
- 2) Containment pressure increase - Increases in containment pre:sure would j
result from design leakoff from instruments (controllers) supplied by j
instrument air, other instrument air leaks, as well as normal use of service l
air.
In June, 1981, with containment ventilation valves closed, a pressure increase of 0.5 psi was observed over a 70 hour8.101852e-4 days <br />0.0194 hours <br />1.157407e-4 weeks <br />2.6635e-5 months <br /> period. Based on this previously observed pressure increase, we conclude the ventilation valves l
would need to be stroked approximately once per week to relieve pressure.
- 3) Containment temperature increase - Because the cooling units for contain-ment utilize service water from Lake Michigan (as opposed to chilled water) the ventilation system is used in maintaining cooler temperatures needed for normal equipment operation.
Based on the above considerations, closing containment ventilation valves during operation of the plant is not considered prudent; accordingly, Consumers Power Company cannot commit to restricting use of the contarament ventilation system.
oc1182-0082a142
I D M Crutchfield, Chief 3
Big Rock Point Plant Containment Purging / Venting November 19, 1982 Condition:
"You should propose a Technical Specification which requires that you perform leakage tests of the isolation valves in the containment purge lines at least once every three months. A model for this Technical Specification is included as part of Response to Condition Consumers Power Company concurs with the " increased frequency" logic presented as Enclosure 1 to the September 14, 1982 NRC letter. The position recommended by Enclosure I was apparently established "as a result of the numerous reports on unsatisfactory performance of the resilient seats" and the fact that containment purge / vent valve leakage tests are specified by Appendix J for an interval of 2 years. A 2 year test interva: is indeed an insufficient frequency to assure integrity of the resilient seats considering the enviran-mental conditions and use of the valves. Our review of the referenced "model Technical Specification" included as part of Enclosure 3 to the September 14, 1982 NRC letter and the Standard Technical Specification for Boiling Water Reactors (NUREG-0123) did not identify any requirement for an increased leak-age integrity test frequency over the 2 year Appendix J interval.
Big Rock Point may have, in fact, provided some of the data on unsatisfactory performance of resilient seats, (reference Enclosure 1 of NRC September 14, 1982 letter). After se.venteen years of operating history, the plant in 1979, changed the rubber sealing surfaces in the containment supply and exhaust valves in order to prov;.de more reliable scaling.
Coupled with an increased surveillance frequency c f six months, (reference our Technical Specification 3.7a) rather than the tw) year interval and a periodic seal replacement program, the Big Rock Point Plant has established a history of sustained good l
performance.
Consumers Power Company concludes that the 3 month leakage I
integrity test recommended by the Enclosure 1 appears unfounded and that our l
balanced program provides in appropriate plant specific basis.
l l
ote Thomas C Bordine Staff Licensing Engineer CC Administrator, Region III, USNRC NRC Resident Inspector-Big Rock Point c,c1182-0082a142