ML19332A751

Primary Coolant Sys Pressure Isolation Valves,Millstone Unit 2, Technical Evaluation Rept

ML19332A751
Person / Time
Site:	Millstone
Issue date:	07/21/1980
From:	Noell P, Stilwell T FRANKLIN INSTITUTE
To:	Polk P Office of Nuclear Reactor Regulation
Shared Package
ML19332A749	List: ML19332A751
References
CON-NRC-03-79-118, CON-NRC-3-79-118 TER-C5257-216, NUDOCS 8009180219
Download: ML19332A751 (4)

Text

. ,

v s

TECHNICAE EVALUATION REPORT PRIMARY COOLANT SYSTEM

PRESSURE ISOLATION VALVES 1

L NORTHEAST NUCLEAR ENERGY COMPANY MILLSTONE UNIT 2 NRC DOCKET NO.30-336 NRC TAC NO. 12882 FRC PROJECT C5257 NRC CONTR ACT NO. N RC-03-79118 FRC TASK 216 Prepared by Franklin Research Center Author: P. N. Noell/T. C. Stilwel The Parkway at Twentie*h Street Philadelphia, PA 19103 FRC Group Leader: P. N. Noell v

Prepared for Nuclear Regulatory Commission Washington, D.C. 20555 Lead NRC Engineer:  ?. J. Polk t

July 21,1980 This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, or any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for any inird party's use, or the results of such use, of any information, apparatus, product or process disclosed in this report, or represents that its use by such third party would not infringe privately owned rights.

hLlJ Franklin Research Center A Division of The Franklin Inst;tute e m ne e Paan, a . Pa 19:C3 (2:S; 43100C 8009180219

I l '

)

1.0 INTRODUCTION

?

l I The NRC staf f has determined that certain isolation valve configurations k

[ in systems connecting the high pressure Primary Coolant System (PCS) to lower-s pressure systems extending outside containment are potentially significant contributors to an intersystem loss-of-coolant accident (LOCA). Such configu-i I

rations have been found to represent a significant factor in the risk computed for core melt accidents. The sequence of events leading to the core melt is initiated by the failure of two in-series check valves to function as a pres-sure isolation barrier between the high pressure PCS and a lower pressure I

t system extending beyond containment. This causes an overpressurization and l rupture of the low pressure system, which results in a LOCA that bypasses con-

! tainment.

?

l The NRC has determined that the probability of failure of these check valves as a pressure isolation barrier can be significantly reduced, if the pressure at each valve is continuously monitored, or if each valve is periodi-cally inspected by leakage testing, ultrasonic excmination, or radiographic

[

inspection. NRC has established a program to provide increased assurance that such multiple isolation barriers are in place in all operating Light Water p Reactor plants designated DOR Generic Implementation Activity B-45.

l In a generic letter of February 23., 1980, the NRC requested all licensees I

to identify the following valve configurations which may exist in any of their j .

plant systems communicating with the PCS: 1) two c, heck valves in series or 2) h two check valves in series with a motor-operated valve (MOV). For plants in s

s 5

which valve configurations of concern were found to exist, licensees were further requested to indicate: 1) whether, to ensure integrity, continuous surveillance or periodic testing was currently being conducted, 2) whether any valves of concern were known to lack int egrity, and 3) whether plant proce-dures should be revised or plant modifications be made to increase reliability.

Franklin Research Center (FRC) was requested by the NRC to provide tech-f e

nical assistance to NRC's B-45 activity by reviewing each licensee's submittal against criteria provided by the NRC and verifying the licensee's reported findings from plant system drawings. This report documents FRC's technical review.

l i

h m .

i Y

~

2.0 CRITERIA 2.1 Identification Criteria For a piping system to have a valve configuration of concern, the follow-

! ing five items must be fulfilled:

1) The high pressure system must be connected to the Primary Coolant System;

2) there must be a high pressure / low pressure interface present in the line;

3) this same piping must eventually lead outside containment;

4) the line must have one of the valve configurations shown in Figure 1; and

5) the pipe line must have a diameter greater than 1-inch.

1 lt!.d PCS<

gov

)( l

= '

s 1A I

. - W ,

/

f i

=

1l' Iwovi Wovl l HP  ; LP Figure 1. Valve Configurations Designated by NRC to be Included in Tnis Technical Evaluation

1 W

3.0 TECHNICAL EVALUATION

~

l FRC has reviewed the response [Ref. 2] of the Northeast Nuclear Energy Company (NNE) to NRC's generic letter [Ref.1] concerning the issue of PCS pressure isolation valve configurations for Millstone Plant Unit 2.

The licensee stated that none of their piping systems have any of the valve configurations of concern, as described by the identification criteria.

FRC independently checked the plant Piping and Instrumentation Diagrams (P& ids) [Ref. 3] for piping systems that might have these valve configura-tions. In this review of the licensee's response against the P& ids and the identification criteria, FRC found no valve confisurations of concern, thus verifying NNE's findings.

4.0 CONCLUSION

S In NNE's Millstone Plant Unit 2, all' piping systems larger than 1-inch diameter that are interconnected to the PCS are free of the valve configura-

[ tions of concern. Therefore, no futher modifications to this plant's Techni-cal Specifications are necessary on this account.

5.0 REFERENCES

{l]. Generic NRC letter, dated 2/23/80, from Mr. D. G. Eisenhut, Department of Operating Reactors (DOR), to Mr. W. G. Counsil, Northeast Nuclear Energy Company (NNE).

' [2]. Northeast Nuclear Energy Company's response to the generic NRC letter, dated 3/18/80, from Mr. W. G. Counsil (NNE) to Mr. D. G. Eisenhut (DOR).

[3]. List of examined P& ids:

Bechtel Drawing:

25203-26014 (Rev. 1) 25203-26015 (Rev. 1) 25203-26017 (Rev. 3) 25203-26025 Sh. 1 of 3 (Rev. 1) 25203-26025 Sh 2 of 3 (Rev. 1) 25203-26025 SF. 3 of 3 (Rev. 1)

I

- , , s. r, . , ., _ u...-,, m.. - ,. -._-m+.-<rr- - - -