ML20210R013

Revised Tech Specs Bases Pages B 3.4.14-2 & B 3.4.14-6, RCS PIV Leakage

ML20210R013
Person / Time
Site:	Mcguire, McGuire
Issue date:	08/10/1999
From:	DUKE POWER CO.
To:
Shared Package
ML20210R006	List: ML20210R003 ML20210R013
References
NUDOCS 9908170012
Download: ML20210R013 (2)

Text

jp RCS PlV Leakage B 3.4.14

' BASES

' BACKGROUND (continued).

.The PlVs are listed in the UFSAR, Table 5-50 (Ref. 6). l Violation of this LCO could result in continued degradation of a PlV, which could lead to overpressurization of a low pressure system and the loss of the integrity of a fission product barrier.

APPLICABLE ' Reference 4 identified potential intersystem LOCAs as a significant SAFETY ANALYSES contributor to the risk of core melt. The dominant accident sequence in

, the intersystem LOCA category is the failure of the low pressure portion of the RHR System outside of containment. The accident is the result of a postulated failure of the PlVs, which are part of the RCPB, and the subsequent pressurization of the RHR System downstream of the PlVs from the RCS. Because the low pressure portion of the RHR System is designed for 600 psig, overpressurization failure of the RHR low pressure line would result in a LOCA outside containment and subsequent risk of core melt.

Reference 5 evaluated various PlV configurations, leakage testing of the valves, and operational changes to determine the effect on the probability of intersystem LOCAs. This study concluded that periodic leakage testing -

of the PlVs can substantially reduce the probability of an intersystem LOCA.

RCS PlV leakage satisfies Criterion 2 of 10 CFR 50.36 (Ref. 7).

i LCO RCS PlV leakage is unidentified LEAKAGE into closed systems j connected to the RCS. Isolation valve leakage is usually on the order of '

. drops per minute. Leakage that increases significantly suggests that j

something is operationally wrong and corrective action must be taken.

The LCO PlV leakage limit is 0.5 gpm per nominal inch of valve size with i a maximum limit of 5 gpm. The previous criterion of 1 gpm for all valve l l sizes imposed an unjustified penalty on the larger valves without  ;

providing information on potential valve degradation and resulted in j higher personnel radiation exposures. A study concluded a leakage rate limit based on valve size was superior to a single allowable value.

Reference 8 permits leakage testing at a lower pressure differential than between the specified maximum RCS pressure and the normal pressure of the connected system during RCS operation (the maximum pressure

' differential) in those types of valves in which the higher service pressure 9908170012 990810 PDR ADOCK 05000369 1 P PDR 1McGuire Units 1'and 2 B '3.4.14-2 Revision No. 5 F l

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A E ,- . 8 't - RCS PlV Leakage B 3.4.14 BASES REFERENCES

1. 10 CFR 50.2.

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2. 10 CFR 50.55a(c).

3. .10 CFR 50, Appendix A, Section V, GDC E5.

4. WASH-1400 (NUREG-75/014), Appendix V, October 1975.

5. NUREG-0677, May 1980.

6. UFSAR Table 5-50. l

7. 10 CFR 50.36, Technical Specifications, (c)(2)(ii).

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8. ASME, Boiler and Pressure Vessel Code,Section XI.

9. 10 CFR 50.55a(g).

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5 McGuire Units 1 and 2 - B 3.4.14-6 Revision No. 5 l

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