ML20215N377

Safety Evaluation Re Util 860320 Response to Generic Ltr 84-09, Recombiner Capability Requirements of 10CFR50.44(c)(3)(ii). Licensee Should Remove All Potential Oxygen Sources from Containments

ML20215N377
Person / Time
Site:	Brunswick
Issue date:	10/30/1986
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20215N369	List: ML20215N367 ML20215N377
References
GL-84-09, GL-84-9, NUDOCS 8611050308
Download: ML20215N377 (2)

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATING TO RESPON'SES TO GENERIC LETTER 84-09 ON HYDR 0 GEN REC 0MBINER CAPABILITY BRUNSWICK STEAM ELECRTIC PLANT UNITS 1 AND 2 CAROLINA POWER & LIGHT COMPANY DOCKETS NOS. 50-324 AND 325

1.0 INTRODUCTION

The rule on-hydrogen recombiner capability (10 CFR 50.44(c)(3)) was issued on December'12,1981. On May 8, 1984, the staff completed an evaluation of the BWR Mark I Owner's Group report which responded to the i rule,= and issued Generic Letter 84-09, "Recombiner Capability Requirements of 10 CFR 50.44(c)(3)(ii)." This letter provided three criteria by which licensees could deterraine whether hydrogen recombiner capability was required.

By letters dated June 8,1984, June 27,1984, March 1,1985, July 18,1985 and March 20, 1986 Carolina Power & Light Company (the licensee) provided information-that attempted to demonstrate that' Brunswick Units 1 and 2 do not require > hydrogen recombiners to control combustible gases inside containment after an accident. Additional information was provided at meetings between the NRC staff and licensee staff on May 29 and November 8,}1985 and January 14, 1986. 9 2.0 EVALUATION In order to = justify that recombiners are unnecessary, the licensee provided an assessment indicating that the only post-accident oxygen generation would be due to radiolysis of reactor coolant, and that such radiolysis would not produce sufficient oxygen to provide a combustible mixture inside either containment. This assessment by the licensee assumed the probability of failures of the containment instrument air system concurrent with a LOCA is negligibly small.

' Based on the licensee's response to Generic Letter 84-09, it is our understanding that air is used as the working medium for the primary containment instrumentation during normal operation and potentially during post-accident operation. Also, for post-accident, the licensee has provided a redundant nitrogen containment atmosphere dilution system.

In attempting to justify not installing hydrogen recombiners, the licensee 8611050308 861030 4 DR ADOCK 0500 i

provided a probabilistic risk assessment (PRA) that was intended to show that the instrument air source of oxygen can be considered as effectively eliminated both during normal operating and accident conditions based on i

"m the low probability of a line rupture. The licensee's PRA analysis is

' insufficient to allow us to conclude that instrument air is not a potential oxygen source inside containment. The bases for our conclusion include the lack of application of the deterministic single failure criterion, the uncertainties associated with a PRA of the type provided, and the fact that Criterion 3 of Generic Letter 84-09 is not met.

Therefore, it is our position that the licensee should remove all potential oxygen sources (which includes the instrunent air system), or install recombiner capability consistent with Generic Letter 84-09 to demonstrate compliance with 10 CFR 50.44.

An acceptable approach to demonstrate compliance with the guidance to remove all potential oxygen sources is by committing to the following:

(1) Modify the non-essential instrument air system to provide automatic isolation upon receipt of the containment isolation signal assuming a concurrent single active failure.

(2) Verify that the essential nitrogen supply to the instrument system is a safety grade system and automatically supplies the instrument E L

system upon receipt of the containment isolation signal.

(3) Provide testing and surveillance Technical Specificatiens for the essential nitrogen supply system.

(4) Provide Technical Specifications for the essential nitrogen supply system that limit the condition for operation upon the loss of redundancy and the loss of the system.

(5) Verify that the plant operating procedures were reviewed for consis-tency with the above requirements, and that all differences were corrected in accordance with these changes. Furthermore, remove all procedures that advocate supplying air into the containment after re,ceipt of the containment isolation signal.

3.0- 40NCLUS10N Based on our review of the licensee's submittals, we conclude that the licensee should remove all potential oxygen sources from the Brunswick containments, or install recombiner capability, consistent with Generic Letter 84-09 to demonstrate compliance with 10 CFR 50.44 for post-accident combustible gas control.

Principal Contributor: P. Hearn Date: October 30, 1986

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