ML19331D994

Primary Coolant Sys Pressure Isolation Valves,Vt Yankee Unit 1, Technical Evaluation Rept

ML19331D994
Person / Time
Site:	Vermont Yankee File:NorthStar Vermont Yankee icon.png
Issue date:	07/21/1980
From:	Noell P, Stilwell T FRANKLIN INSTITUTE
To:	Polk P Office of Nuclear Reactor Regulation
Shared Package
ML19331D991	List: ML19331D994
References
CON-NRC-03-79-118, CON-NRC-3-79-118 TER-C5257-243, NUDOCS 8009040544
Download: ML19331D994 (5)

Text

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TECHNICAL EVALUATION REPORT PRIMARY COOLANT SYSTEM PRESSURE ISOLATION VALVES

. VERMONT YANKEE NUCLEAR POWER CORPORATION VERMONT YANKEE UNIT 1 NRC DOCKET NO. 50-271 N RC TAC NO. 12910 FRC PROJECT C5257 NRC CONTRACT NO NRC-03-79-118 FRC TASK 243

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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 Commission Washington, D.C. 20555 l

Lead NRC Engineer: P. J. Polk l

l July 21, 1980

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This report was prepared as an account o' work sponsore'd 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 third 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.

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A J Franklin Research Center A Division of The Franklin Institute 6009040 .

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The NRC staf f 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 beyond containment. This causes an overpressurization and rupture of the low 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 estdslished a program te provide increased assurance that such multiple isolation barriers are in place in all operating Light Water Reactor plants designated DOR Generic Implementation Activity 3-45.

In a generic letter of February 23, 1980, the NRC 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 cade to increase reliability.

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 drawings. This report documents FRC's technical l review.

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2.0 CRITERIA -

4 2.1 Iden*.ification 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.

IMid PCS7 I I A

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povl l HP:  : LP Figure 1. Valve Confii;urations Designated b:. NRC to be ncluded in This Technical Evaluation 3-

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3.0 TECHNICAL EVALUATION

FRC has rev, ved the response [Ref. 2] of the Vermont Yankee Nuclear Power Corporation (VaC) to NRC's generic letter [Ref.1] concerning the issue of PCS pres 9- isolation valve configurations for Vermont Yankee Plant.

The licensee s.tated that none of their piping systems have any of the valve configurations of concern, as d;. ;; bed 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 configurations of concern, thus verifying VYC's findings.

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4.0 CONCLUSION

S In VYC's Vermont Yankee Plant, all piping systems larger than 1-inch diameter that are intc? connected to the PCS are free of the valve configura-tions of concern. Therefore, no futher modifications to this plant's Techni-cal Specificati ns are necessary on this account.

5.0 REFERENCES

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[1]. Generic NRC letter, dated 2/23/80, from Mr. D. G. Eisenh.it, Department of Operating Reactors (DOR), to Mr. D. E. Vandenburgh, Vermont Yankee Nuclear Power Corporation (VYC).

[2]. Vermont Yankee Nuclear Power Corporation's response to the generic NRC j letter, dated 3/14/80, from Mr. D. E. Vanded>urgh (VvC) to Mr. D. G.

Eisenhut (DOR).

[3]. List of examined P& ids:

Ebasco Drawing:

G-191156 (Rev. 7)

• G-191159 (Rev. 3)

G-191167 (Rev. 17)

G-191168 (Rev. 13) v,

• e G-191169 (Rev. 17) Sh. 1 o f 2 G-191169 (Rev. 13) Sh. 2 of 2 G-191170 ( Rev. 10)

G-191171 (Rev. 9)

G-191172 (Rev. 16)

G-191173 (Rev. 9)

G-191174 (Rev. 12) Sh. 1 o f 2 G-191174 (Rev. 9) Sh. 2 of 2 G-191176 (Rev. 13)

G-191178 (Rev. 12) Sh. 1 of 2 O

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