ML20205M388
| ML20205M388 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 04/11/1986 |
| From: | Bloch P Atomic Safety and Licensing Board Panel |
| To: | |
| References | |
| CON-#286-760 79-430-06-OL, 79-430-6-OL, OL, NUDOCS 8604150210 | |
| Download: ML20205M388 (4) | |
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UNITEDSTATESOFAMKgJCA NUCLEAR REGULATORY C0 mig 0N Before Administrative Judges:
}( 40:28 Peter B. Bloch Cha Dr. Kenneth 6775cCollom Dr. Walter DecRpr$E2dcP A SERVED APR 141986 dants._
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Docket Nos. 50-445-OL In the Matter of
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50-446-OL
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TEXAS UTILITIES ELECTRIC COMPANY,
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et al.
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[ASLBP No. 79-430-06-OL]
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(Comanche Peak Steam Electric
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Station, Units 1 and 2)
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April 11, 1986
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MEMORANDUM (Analysis of Responses to Memorandum on Containment Paint)
In our memorandum of September 18, 1985 we expressed our concern regarding the exemption of Comanche Peak from the quality assurance requirements of Appendix B with regard to paint inside containment. We also asked for the basis of the Staff's conclusion that core blockage was highly unlikely in the event of a small break Loss of Coolant Accident (LOCA), even if the paint was unqualified. We have received two responses from the NRC Staff which included affidavits addressing our Concerns.
Y (a) NRC Staff Motion to Reconsider and Response to Board Memorandum of September 18, 1985. (October 9, 1985)
(b) NRC Staff Concluding Response to Licensing Board's September 18, 1985 Memorandum Concerning Containment Coatings.
(March 17, 1986) i L () '/
8604150210 860411 PDR ADOCK 05000445 O
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1 In the first response the Staff pointed out that there is no requirement that containment coatings be safety grade - that the Standard Review Plan Guidelines allow Applicants the option of 3
demonstrating that paint flaking will not adversely affect the perfomance of the safety grade core cooling system during accident conditions. This option has been chosen by a number of licensees and hence CPSES is not in a special category. The Staff also stated that the TUEC analysis of the effects of paint flakes on the ECCS was consistent with the guidance and methodology developed by the Str.ff for Unresolved Safety Issue (USI) A-43.
The second Staff response addresses their evaluation of'the model for estimating the risk that paint flakes will result in inadequate core cooling (ICC) following a small break LOCA. They point out that the assumption of having as much as 10 cu. ft. of paint fines ending up in the reactor plenum is highly conservative for a number of reasons.
First, the Applicant assumed that all of the paint would peel from the containment walls during a large break LOCA, a gross overestimate in view of the coating, testing and surveillance program (SER Supplement 9 atL-15). During a small break LOCA the environmental conditions are much less severe than those encountered during a large break LOCA, hence much less paint flaking would be expected. Yet the Applicants used the larger amount in their calculations. Also the transport velocity of the water in the containment would be much lower than the expected velocity
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6 during a large break LOCA, further reducing the amount of paint reaching the sump screens.
Following a small break LOCA, procedures require that the reactor coolant pump (RCPs) be stopped. Hence any fines sucked into the reactor vessel that might block the passages through the core, would settle out in the reactor plenum and hence would not reach the core.
In SSER-9 (at L-8) the Staff raised the possibility that the RCPs might be restarted, thereby resuspending the fines and transporting them to the core thereby essentially blocking the coolant flow. However "The Staff concluded that RCP restart following ECCS recirculation is unlikely at Comanche Peak." (Ibid at L-12). The basis for this conclusion is addressed in the affidavits of McCracken. MacKay and Mann. The Applicants revised emergency-response operating procedures prohibit restart of the RCPs except in the event of ICC.
Inadvertent restart due to operator error is highly unlikely because of the number of steps necessary to restart the pumps as well as verification procedures involving the joint re-t sponse of the Assistant Shift Supervisor and the Reactor Operator.
The Staff has persuaded us that the exemption of CPSES containment paint from the requirements of Appendix B is permitted by NRC regula-tions. Furthemore the Staff has adequately justified their conclusion that, in the event of a small break LOCA, the estimate of 10 cu. ft. of
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a paint fines deposited in the reactor plenum is conservative; that restart of the reactor coolant pumps is unlikely and hence core blockage should not occur as a result of water recirculation problems caused by failure of paint coatings inside the containment vessel.
FOR THE ATOMIC SAFETY AND L CENSING BOARD Pbter B. EIloch, Chairman ADMINISTRATIVE JUDGE Bethesda, Maryland l
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