ML20203H248
| ML20203H248 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 07/23/1986 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20203H231 | List: |
| References | |
| NUDOCS 8608040343 | |
| Download: ML20203H248 (2) | |
Text
4 Engineering Branch Division of PWR Licensing-A Safety Evaluation Report for Callaway Plant, Unit 1 Docket No. 50-483 A.
Introduction By a letter dated July 17, 1984, Union Electric Company requested in part that the bases of Callaway Technical Specifications 4.6.1.2 and 3/4.6.1.2 be revised to allow local leak rate testing of certain containment isolation valves using water as test medium, in lieu of air as required by Appendix J to 10 CFR 50. The affected containment isolation valves and penetrations are associated with the essential service water system (ESWS) to and from containment air coolers.
The licensee's basis for the request is that the piping volume of the ESWS will form a passive seal water system.
The passive seal water system will then keep the concerned containment isolation valves water sealed following accidents so that there is little potential for contaminated air to leak out through these penetrations. A previous staff review indicated that although the proposed concept of a passive seal system had some merits, the water inventory of the proposed seal system could not be clearly defined and the amount of seal water available following certain accident scenarios could not be assured.
In responding to the staff review, the licensee submitted additional information in a letter dated October 3, 1984, on its prcposed passive seal water system.
The staff's evaluation of the additional information is provided below.
B.
Evaluation Section III.C.2 of Appendix J requires that containment isolation valves be Type C tested using air or nitrogen at a pressure of Pa with one exception. The exception is that tests for valves sealed with fluid from a seal system may be conducted with that fluid at a pressure not less than 1.1 Pa. The function of a seal system is to provide sufficient fluid to the affected penetrations and valves to prevent contaminated air from leaking out the containment.
0608040343 860723 PDR ADOCK 05000483 P
The licensee requests that the containment isolation valves EF-HV-33,-34. -45, and -46 be tested with water, in lieu of air, because a passive seal water system may be defined to provide sealing water to these valves. As indicated by the system design, the primary function of these containment isolation valves is to stay open following accidents and to provide cooling water to containment air coolers. These valves will only be called upon te perform their function of containment isolation, when the containment air coolers are required to be shut down due to failures or similar reasons. The valves will then be closed by operators via remote manual control.
Following the closure of these valves, the piping volume from the air coolers to the containment isolation valves may still be filled with water, which is counted on by the licensee to provide the sealing function for these affected valves.
In a previous review, the staff felt that the concept of a passive seal I
water system might be found acceptable if the amount of sealing water from the piping volume could be defined and assured. However, a close review of the events and scenarios of LOCAs indicates that one would not know for sure at what point these valves would be closed following the shut down or failure of the ESWS. Therefore, one would not know for sure how much water still remained in the piping volume after the valves were completely closed.
Even though we agree that the piping volume is large enough to hold the required amount of sealing water, the problem is that there is no way to verify and assure that an adequate amount of sealing water will remain in the piping volume following certain accidents. Since the water inventory of the proposed passive seal water system could not be assured and could not be monitored and replenished following accidents, we find that the proposed passive seal system could not perform the needed function of a seal system as called for by Appendix J.
C.
Conclusion Based on the above discussion, we find the proposed T.S. Change to allow water testing of certain containnent isolation valves unacceptable because these valves could not be assured to be water sealed as required l
by Appendix J.
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