ML19344E684
| ML19344E684 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 07/21/1980 |
| From: | Noell P, Stilwell T FRANKLIN INSTITUTE |
| To: | Polk P Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML17192A934 | List: |
| References | |
| CON-NRC-03-79-118, CON-NRC-3-79-118, TASK-06-04, TASK-6-4, TASK-RR TER-C5257-247, NUDOCS 8009020467 | |
| Download: ML19344E684 (5) | |
Text
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O TECHNICAL EVALUATION REPORT j
PRIMARY COOLANT SYSTEM PRESSURE ISOLATION VALVES COMMONWEALTH EDISON COMPANY DRESDEN UNIT 2 NRC DOCKET NO. 50-237 NRC TAC NO.
12914 FRC PROJECT C5257 NRC CONTR ACT NO. NRC-03-79-118 FRCTASK 247 Prepared by Franklin Research Center Author:
P. N. Noell/T. C. Stilwell The Parkway at Twentieth Street Philadelphia, PA 19103 FRC Group Leader:
P. N. Noell Prepared for Nuclear Regulatory Comrnission Washington, D.C. 20555 Lead NRC Engineer:
P. J. Polk July 21, 1980 This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the Uniteo 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 third party's use, or the results of such use, of any information, apparatus, product or pror disclosed in this report, or represents that its use by sue' tf, party would not infrnge privatel owned rights.
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1.0 INTRODUCTION
The NRC staff has determined that certain isolation valve configurations in systems connecting the high pressure Primary Coolant System (PCS) to lower-pressure systems extending outside containment are potentially significant contributors to an intersystem loss-of-coolant accident (LOCA).
Such configu-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 system extending be."'nd containment.
This causes an overpressurization and rupture of the lo pressure system, which results in a LOCA that bypasses con-tainment.
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 examination, 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 Reactor plants designated DOR Generic Implementation Activity B-45.
In a generic letter of February 23, 1940, the N1.C requested all licensees to identify the following valve configurations which may exist in any of their plant systems communicating with the PCS: 1) two check valves in series or 2) two check valves in series with a motor-operated valve (MOV). For plants in 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 integrity, and 3) whether plant proce-dures should be revised or plant modifications be made to increase relid>ility.
Franklin Research Center (FRC) was requested by the NRC to provide tech-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 drawinga.
This report documents FRC's technical review.
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a 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; 4
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.
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Valve Configurations Designated by NRC to be Included in This Technical Evaluation _
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3.0 TECHNICAL EVALUATION
FRC has reviewed the response [Ref. 2} of the Commonwealth Edison Company (CWE) to NRC's generic letter [Ref. l} concerning the issue of PCS pressure isolation valve configurations for Dresden Station 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 liagrams (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 configurations of concern, thus verifying CWE's findings.
4.0 CONCLUSION
S In CWE's Dresden Station 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-4 cal Specifications are necessary on this account.
5.0 REFERENCES
[1]. Generic NRC letter, dated 2/23/80, from Mr. D. C. Eisenhut, Department of Operating Reactors (DOR), to Mr. W. F. Naughton, Commonwealth Edison (CWE).
[2]. Commonwealth Edison's response to the generic NRC letter, dated 3/14/80, from Mr. W. F. Naughton (CWE) to Mr. D. G. Eisenhut (DOR).
[3}. List of examined P& ids:
Sargent & Lundy Drawing:
M-ll (Rev. C)
Sh. 2 M-26 (Rev. AA) Sh.1 of 2 M-26 (Rev. Y)
Sh. 2 of 2 M-27 (Rev. EE)
M-28 (Rev. V)
M-29 (Rev. MM)
M-30 (Rev. BB),
M-32 (Rev. V)
M-33 (Rev. W)
M-48 M-51 (Rev. FF)