ML20205T508

SER Re Util 820917,830701 & 0922 Applications for Amends to Licenses DPR-77 & DPR-79,changing Tech Specs to Permit Increase in Flow Rate of Air from Containment During Normal Operation.Changes Unacceptable

ML20205T508
Person / Time
Site:	Sequoyah
Issue date:	06/10/1986
From:	NRC
To:
Shared Package
ML20205T506	List: ML20205T502 ML20205T508
References
NUDOCS 8606130310
Download: ML20205T508 (2)

Text

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• SAFETY EVALUATION REPORT TECHNICAL SPECIFICATIONS FOR PURGE / VENT LINE OPENING LIMITATIONS SEQUOYAH NUCLEAR POWER PLANT, UNITS 1 AND 2 DOCKET NOS. 50-327/328 Introduction By letters dated September 17, 1982, July 1, 1983, and September 22, 1983, the licensee proposed certain changes to Technical Specification (TS) 3.6.1.9 concerning the number of containment purge / vent lines which may be open simultaneously during nonnal operation of the plant. The proposal would allow up to three pairs of purge / vent lines to be open, instead of the current limit of one pair. The purpose of the proposed change is to allow an increase in flow rate of air purged from the containment during normal operation, so as to better control containment pressure within Technical Specification limits, and reduce levels of airborne radioactivity. The licensee states that the current limita'-

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tion on purging / venting during nonnal operation, which is 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> per calendar year, as stated in TS 3.6.1.9, does not allow ALARA goals to be met when only one l pair of purge / vent lines may be open at a time.

l Evaluation The licensee provided an analysis to show that the offsite radiological consequences of a LOCA with three pairs of purge / vent lines open at the onset of the accident are within the guidelines of 10 CFR 100. Furthermore, the licensee performed a probabilistic risk assessment (PRA) study to quantify the effect on the containment isolation failure probability if more than one pair of purge /

vent lines are open during nonnal operation. The study concludes that the pro-bability of containment isolation failure at the onset of a LOCA is higher with three pairs of lines open than with one pair of lines open, but, in the licensee's judgement the differences in the probabilities of containment isolation failure are not significant enough to prohibit operation with three pairs of lines open.

8606130310 PDR 860610 P

ADOCK 05000327 PDR

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j- Nevertheless, the staff's position on this matter is clearly stated in Branch Technical Position (BTP) CSB 6-4, " Containment Purging During Normal Plant Operations," attached to SRP 6.2.4, " Containment Isolation System" (NUREG-0800). Section B.1.b. of the BTP states, in part, that the number of supply and exhaust lines that may be used should be limited to one supply line and one exhaust line, to improve the reliability of the isolation function as required by GDC 54.

The staff believes a more appropriate way for the licensee to meet their purging /

venting needs is to either justify an increase in the annual limit on purging /

venting on the basis of demonstrated need or replace the time limit altogether with the proviso that purging / venting be done only for safety-related reasons.

Safety-related reasons include the need to control containment pressure within p TS limits, or reduce airborne radioactivity and improve air quality (or environ-mental conditions) to facilitate personnel access for surveillance and mainten-ir.e activities.

Conclusion 1

Based on the above discussion, the staff finds the proposed changes to TS 3.6.1.9 unacceptable. However, as noted above the staff would consider an alternative proposal from the licensee for satisfying purging / venting needs.

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