ML19343D235
| ML19343D235 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 10/24/1980 |
| From: | Noell P, Stilwell T FRANKLIN INSTITUTE |
| To: | Polk P Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19343D233 | List: |
| References | |
| CON-NRC-03-79-118, CON-NRC-3-79-118 TER-C5257-245, NUDOCS 8105040022 | |
| Download: ML19343D235 (10) | |
Text
Attachment 2 O
TECHNICAL E'/ALUATION REPORT PRIMARY COOLANT SYSTEM PRESSURE ISOLATION VALVES CONSUMERS POWER COMPANY PALISADES UNIT 1 NRC DOCKET NO. 50-255 NRC TAC NO.
12912 FRC PRCJECT C5257 N RC CONTRACT NO. NRC-03-79-118 FRCTASK 245 i
Prepared by Franklin Reserwii Center Author: P. N. Noell The Parkway at Twentieth Street T. C. Stilwell Philadelphia, PA 19103 FRC Group Leader:
P. N. Noell Prepared for Nuclear Regulatory Commission Washington, D.C. 20555 Lead NRC Engineer: P. J. Polk i
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October 24, 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 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 i
party would not infringe privately owned rights.
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. Franklin Research Center A Division of The Franklin institute The Beniarrwn Frankbn Parkway. Phda. Pa 19103 (215) us 1000
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1.0 INTRODUCTION
The NRC 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 eignificant contributors t'o an intersystem loss-of-coolant s,ccident (LOCA). Such configu-rations have been found to represent a significant factor in the risk computed for core melt accide'acs.
I The sequence of events leading to the core melt is initiated by the con-Jailure of two in-series check valves to function as a pressure isola-current tien barrier between the high-pressure PCS and a lower-pressure system extend-ing beyond containment. This failure can cause an overpressurization and rup-ture of the low-pressure system, resulting in a LOCA t'ist bypasses containment.
4 The NRC has determined that the probability of failure of these check valves as a pressure is,olation barrier can be significantly reduced if the pressure at each valve is continuously monitored, or if each valve is periodi-cally inspected by leakage tescing, ultrasonic examination., or radiographic inspection. The NRC has established a, program to provide increased assurance that such multiple isolation barriefs are in place in all operating Light Water Reactor plants designated by DOR Ceneric Implementatien Activity B-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 mo*or-operated valve (MOV).
For plants in which valve configurations of concern are found to exist, licensees were further regaested to indicate: 1) whether, to ensure integrity of the various pressure isolation check valves, continuous surveillance or periodic testing was currently being conducted, 2) whether any check valves of concern were keown to lack integrity, and 3) whether plant procedures should be revised or plant modifications be made to incr, ease 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
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against criteria provided by the NRC and by verifying the licensee's reported findings from plant system drawings. This report documents FRC's technical review.
2.0 CRITERIA 9.1 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 av c have a diameter greater than 1 inch.
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Figure 1.
Valve Configurations Designated by the NRC To Be Included in This Technical Evaluation
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2.2 Periodic Testing Criteria Tor licensees whose plants have valve configurations of concern and choose
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to institute periodic valve leakage testing, the NRC has established criteria '
1 for frequency of testing. test conditions, and acceptable leakage rates.
These criteria may be summarized as follows:
2.2.1 Frequency of Testing Periodic hydros tatic leakage tes ting
- on each check valve shall be accom-plished every time the plant is placed in the cold shutdown condition for refueling, each time the plant is placed in a cold shutdown condition for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> if testing has not been accomplished in. the preceding 9 months,
each time any check valve may have moved from the fully closed position (i.e., any time the differen-tial pressure across the valve is less than 100 psig), and prior to returning the valve to service after maintenance, repair, or replacement work is performed.
J 2.2.2 Rydrostatic Pressure Criteria Leakage tests involving pressure differentials lower than function pres-sure differentials are permitted in those types of valves in which service pressure will tend to diminish the overall leakage channel opening, as by pressing the disk into or onto,the seat with greater force. Gate valves, check valves, and globe-type valves, having function pressure dif ferential applied over the seat, are examples of valve applications satis fying this requirement. e When leakage tests are made in such cases using pressures a
lower than' function maximum pressure dif ferential, the observed leakage shall be adjusted to function maximum pressure differential value. This adjustment shall be made by calculation appropriate to the test media and the ratio between test and function pressure dif ferential, assuming leak-t age to be directly proportional to the pressure differential to the one-half power.
2.2.3 Acceptable Leakage Rates:
Leakage rates less than or equal to 1.0 gpm are considered accept-e able.
Leakage rates greater than 1.0 gpm but less than or equal to 5 0 e
gpm are considered acceptable if the lates t measured rate has not exceeded the rate determined by the previous test by an amount l
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- To satis fy ALARA requirements, leakage may be measured indirectly (as from the performance of pressure indicators) if accomplished in accordance with approved procedures and supported by computations showing that the method is capable of demonstrating valve compliance with the leakage criteria. -
that reduces the margin between the measured leakage rate and the maximum permissible rate of 5.0 spa by 50% or greater.
Leakage rates greater than 1.0 gpa but' less than or equal to 5.0 e
gpm are considered unacceptable if the latest measured rate ex-ceeded the rate determined by the previous test by an amount that reduces the margin between measured leakage rate and the maximum permissible rate of 5.0 spa by 50% or greater.
Leakage rates greater than 5.0 gym are considered unacceptable.
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3.0 TECHNICAL EVALUATION
3.1 Licensee's Response to the Ceneric Letter In response to the NRC's generic letter [Ref.1], the Con'sumers Power Company (CPC) stated [Ref. 2] that, "The Palisades Plant does not have an Event V isolation valve configuration as described in Figure 1 of the NRC letter dated February 23, 1980; however, the following valve configurations were reviewed.
Low-Pressure Safety Injection (LPSI)
Charging High-Pressure Safety Injectio'n ('HPSI) '
Other systems are connected to the PCS (Primary Coolant System] but are isolated by the containment isolation signal and were, therefore, excluded from this review.
Both the Charging and HPSI Systems consist of high-pressure piping between the pumps and the PCS and do not fall within the scope of the NRC February 23, 1980 letter."
The licensee further stated, " Surveillance is performed to verify the seating of check Valve ' A' (closest to PCS]. This surveillance is conducted l
during each plant start-up from cold shutdown by observation of the [ pressure indicator-controller] PIC. Use of the PIC allows for a continuous pressure monitoring on the low-pressure side of the subject chcek 'ralves.
The PCS isolation check valves have not caused any significant integrity problems."
It is FRC's understanding that, with CPC's concurrence, the NRC will direct CPC to change its Plant Technical Specifications as necessary to ensure
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that periodic leakage testing (or equivalent testing) is conducted in accor-dance with the criteria of Section 2.2.
3.2 FRC Review of Licdnsee's Response FRC has reviewed the licensee's response against the plant-specific Piping and Instrumentation Diagrams (P& ids) [Ref. 3] that might have the valve con-figurations of concern.
FRC has also reviewed the efficacy of instituting periodic testing for the check valves involved in this particular application with respect to the re-duction of the probability of an intersystem LOCA in High-and Low-Pressure Safety Injection pipe lines.
In its review of the P& ids [Ref. 3] for Palisades Unit 1, FRC found the following two piping systems to be of concern:
The High-and Low-Pressure Safety Injection Systems are connected to e
the PCS by a single, common piping line to each of the cold leg sides of the four PCS loops, lA, IB, 2A, and 2B.
Both the High-and Low-Pressu,re Safety Injection Systems have two e
check valves and a motor-operated valve (MOV) in one of the series configurations of concern.
In both systems the high-pressure / low pressure interface is on the up-stream side of the MOV.
The valves for each system are listed below:
High-Pressure Safety Injection Loop 1A, cold leg high-pressure check valve, 3101 high-pressure check valve, 3104 l
high-pressure MOV, 3007, normally closed (n.c.)
Loop 1B, cold leg high-pressure check valve, 3116 high pressure check valve, 3119 l
high-pressure MOV, 3009, n.c.
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Loop 2A, cold leg high-pressure check valve, 3131 high-pressure check valve, 3134 high-pressure MOV, 3011, n.c.
Loop 25, cold 1<eg high-pressure check valve, 3146 high-pressure check valve, 3149 high-pressure MOV, 3013, n.c.
Low-Pressure Safety Injection Loop 1A, cold leg high-pressure check valve, 3101 high-pressure check valve, 3103 high-pressure MOV, 3008, n.c.
Loop 1B, cold leg high-pressure check valve, 3116 9
high-pressure check valve, 3118 high-pressure MOV, 3010, n.c.
Loop 2A, cold leg high-pressure check valve, 3131 high-pressure check valve, 3133 high-pressure MOV, 3021, n.c.
Loop 2B, cold leg high-pressure check valve, 3146 high-pressure check valve, 3148 high-pressure MOV, 3014, n.c.
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In accordance with the criteria of Section 2.0, FRC found.no other valve,
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configurations of concern existing in this plant.
FRC reviewed the effectiveness of instituting periodic leakage testing of the check valves in these lines as a means of reducing the probability of an intersystem LOCA occurring. FRC found that introducing a program of check valve leakage, testing in accordance with the criteria summarized in Section 2.0 will be an effective measure in substantially reducing the probability of an intersystem LOCA occurring in these lines, and a means of increasing the probability that these lines will be able to perform their safety-related functions. It is also a step toward achieving a corresponding reduction in the plant probability of an intersystem LOCA in Palisades Unit 1.
4.0 CONCLUSION
Based on the previously docketed information and drawings made available for FRC review, FRC found that all four cold-leg branches common to both the High and Low-Pressure Safety Injection systems in Palisades Unit I centain a valve configuration of concern (identified in Figure 1).
Thus, if the licens-ee's review of the valving configuration contained in the cold-leg branches of both the High and Low-Pressure Safety Injection systems confirms FRC's finding, then the valve configurations ofi -cern existing in Palisades Unit 1 incorpo-rate the valves listed in Table 1.0.
If CPC modifies the Plant Technical Specifications for Palisades Unit 1 to incorporate periodic testing (as delineated in Section 2.2) for the check valves itemized in Table 1.0, then FRC considers this an acceptable means of achieving plant compliance with the NRC staff objectives of Reference 1. 1
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Table 1.0 Primary Coolant System Pressure Isolation Valves System Check Valve No.
Allowable Leakage
- High-Pressure Safety Injection Loop 1A, cold leg 3101 3104 Loop 1B, cold leg 3116 3119 Loop 2A, cold leg 3131 3134 Loop 2B, cold leg 3146 3149 Low-Pressure Safety Injection Loop 1A, cold leg 3103 Loop 1B, cold leg 3118 3133 Loop 2A, cold leg Loop 2B, cold leg 3148
- To be provided by the licensee at a future date in accordance with Section 2.2.3.
5.0 REFERENCES
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l '. Generic NRC letter, dated 2/23/80, from Mr. D. G. Eisenhut, Department of Operating Reactors (DOR), to Mr. D. P. Hof fman, Consumers Power Company (CPC).
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Consumers Power Company's response to NRC's letter, dated 3/18/80, from Mr. D. P. Hoffman (CPC) to Mr. D. G. Eisenhut (DOR).
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List of examined P& ids:
Bechtel drawings of Palisades Unit 1:
M-200 (Rev. 7)
M-201 (Rev. 13)
M-202 (Rev. 14)
M-203 (Rev. 12)
M-204 (Rev. 12)
M-205 (Rev. 13)
M-209 (Rev. 13)
M-219 (Rev. 8)
M-270 (Rev. 11) i s
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