ML17341A077
| ML17341A077 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 02/23/1981 |
| From: | Chandrasekaran, Kohl K EBERLINE INSTRUMENT CORP. |
| To: | |
| Shared Package | |
| ML17341A078 | List: |
| References | |
| NUDOCS 8103060316 | |
| Download: ML17341A077 (10) | |
Text
1 ATTAChMENT 2 THIS REPORT SUPERSEDES ISSUE OF AUGUST 22, 1980 TECHNICAL EVALUATION REPORT PRIMARY COOLANT SYSTEM PRESSURE IS 0 LATI0 N VALVES FLORIDA POWER R LIGHT COt1PANY TURKEY POINT UNITS .3 AND 0 NRC DOCKET NO. 50-250, 50-251 NRC TAC NO. 12940 $ 12941 FRC PROJECT C5257 NRC CONTRACT NO. NRG43-79-118 FRC TASK 270 271 Prepared by Franklin Research Center Author: P. N. Noell The Parkway at Twentieth Street T. C. Stilwell
'Philadelphia, PA 19103 FRC Group Leader: P N~ N<<11 Prepared for Nuclear Regulatory Commission Washington, D.C. 20555 Lead NRC Engineer: P. J. Polk 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 party would not infringe privately owned rights.
l]9 Franklin Research Center A Division of The Franklin Institute The Senjamin Fran'kiln Par1n ay, Phila.. Pa. 19103 (215) 448-1000 p(O5O(
1.0 INTRODUCTION
The NRC has determined that certain isolation valve configurations in systems connecting the high-pressure Primary Coolant System (PCS) to lower-pzessure systems extending outside containment aze potentially significant contributors to an intersystem loss~f-coolant accident (LOCA) Such configu-
~
zations have been found to represent a significant factor in the zisk computed for core melt accidents.
The sequence of events leading to the core melt is initiated by the con-cuzzent failure of two in-series check valves to function as a pressure isola-tion barriez between the high-pressure PCS and a lowez-pressure system extend-ing beyond containment. This failure can cause an ovezpressurization and rup-ture of the low-pzessure system, resulting in a LOCA that bypasses contai.nment.
The NRC has determined that the probability of failure of these check valves as a pressure isolation barziez can be significantly reduced if the pzessure at each valve is continuously moni.tored, or if each valve is periodi-cally inspected by leakage testing, ultrasonic examination, or radiographic inspection. The 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 by DOR Generic Implementation Activity B&5.
In a generic letter'f 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 aze found to exist, licensees weze'urthez requested 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 known to lack integrity, and 3) whether plant procedures should be revised or plant modifications be made to i.ncrease reliability.
Franklin Research Centez (FRC) was zequested by the NRC to provide tech-nical assistance to NRC's B&5 activity by zeviewing each licensee's submittal
against criteria provided by the NRC and by verifying the 1'censee's reported findings from plant system drawings. This report documents FRC's technical revie~.
- 2. 0 CRITERIA 2 1 Identification Criteria For a piping system to have a valve configuration of concern, the follov-ing five i.tems must be fulfilled:
- 1) The high-pressure system must be connected to the primary Coolant System;
- 2) 'there must be a high-pressure/lo~-pressure interface p esent in the line;
- 3) this same pi.ping must eventually lead outside contai.ament;
- 4) the line must have one of the valve configurations showa in Figure 1 and
- 5) the pipe line'must have a diam'eter greater than 1 inch.
PCS ov IJQV ov Figure l. Valve Configurations Desi.gnated by the NRC To Be Included in This Technical Fvaluation
2.2 Periodic Testing Ciiteria For licensees whose plants have valve configurations of concern and choose to institute periodic valve leakage testing, the NRC has established criteria for frequency of testing, test conditions, and acceptable leakage rates.
These criteria may be summarized as follows:
2.2.1 Frequency of Testing
'Periodic hydrostatic leakage testing* 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 foz 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 Erom the Eully closed position (i.e., any time the diffezen- tial pressure across the valve is less than 100 psig), and prior to returning the valve to sezvice aftez maintenance, repair, or replacement wozk is performed.
2.2.2 Hydrostatic Pzessuze Criteria Leakage tests involving pressure differentials lower than function pres-sure differentials aze permitted in those types of valves in which sezvice, pressure will tend to diminish the overall leakage channel opening, as by piessing the disk into oz onto the seat with greater force. Gate valves, check valves, and globe-type valves, having function pressure differential applied over the seat, are examples of valve applications satisfying this requirement. When leakage tests are made in such cases using pressures lower than function maxmum pressure differential, the observed leakage shall be adjusted to function maximum pressure di fezent'al value. This adjustment shall be made by calculation appropriate to the test media and the ratio between test and function pressure differential, assuming leak-age to be directly proportional to the pressuze d'fferential to the one-half power.
2.2'3 Acceptable Leakage Rates:
~ Leakage rates less than or equal to 1.0 gpm are considered accept-able.
~ Leakage rates greater than 1.0 gpm but less than oz equal to 5.0 if
,
gpm aze considered acceptable the latest measured rate has not exceeded the rate detezmined by the previous test by an amount
-To satisfy ALARA requirements, leakage may be measured indirectly (as from the pe formance 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 measured leakage rate and the maximum permissible rate of 5.0 gpm by 50X or greater.
~ Leakage rates greater than 1.0 gpm but less than or equal to 5.0 gpm are considered unacceptable if the'atest 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 gpm by 50X or greater.
~ Leakage rates greater than 5.0 gpm are considered unacceptable.
- 3. 0 TECHNICAL EVALUATION 3.1 Licensee's Response to the Generic Letter In response to the NRC's generic letter [Ref. 1], the Florida Power &
Light Company (FPL) submitted [Ref. 21 two simplified flow diagrams showing the valve configurations of concern for Turkey Point Units 3 and 4.
The Licensee indicated in Reference 2 that specific surveillance tests to assess check valve status are not being performed on check valves in the various configurations of concern. Also, FPL's operating records covering the past 5 years have not indicated problems with these same check valves.
It is FRC's understanding that, with FPL'.s concurrence, the NRC will di-rect FPL to change its Plant Technical Specifications as necessary to ensure that periodic leakage testing (or equivalent testing) is conducted in accor-dance with the criteria of Section 2.2.
3.2 FRC Review of Licensee'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 the High-Head Safety Injection System and the Residual Heat Removal System (low-head system) piping lines.
In its review of the P&IDs [Ref. 3] for the Turkey Point Units 3 and 4, FRC found the following two piping systems to be of concern:
The High-Head Safety Injection System is connected to the hot-leg sides of two PCS loops (A and B) and also to the cold-leg side of all thzee PCS loops (A, B, and C). This system was examined foz valve configuzations of concern since the piping system is designed to an intermediate pressure level (1500 psig) which is lower than full reactor pressure. Each hot leg branch of the High-Head Safety Injection System has a single check valve and a motor-opezated valve in one of the series configurations of concern. Por the cold-leg branches of the High-Head Safety System, the two check valves and motor-operated valve in-sezies comprise the configura-tion of concern.
H The second system of concern is the Residual Heat Removal System.
This low-head injection system is connected to the cold legs of all three=primary coolant loops in a two check valve and a single motor-opezated valve configuration.
In both the High-Head Injection and the Residual Heat Removal sys-tems the high-pressure/low-pressure interface exists at the up-stream side of the motor-operated valves (MOVs). The valve config-urations of concern for both previously mentioned systems are list-ed below for Tuzkey Point Units 3 and 4:
High-Head Safety Injection System Loo A, hot le high-pres sure check valve, 874A high-pressuze MOV, 866A, normally closed (n.c.)
Loo B, hot leg high-pressure check valve, 874B high-pressuze MOV, 866B, n.c.
Loo A, cold le high-pressure check valve, 875A high-pzessure gate valve, 868A; normally open (n.o.)
high-pressure check valve, 873A high-pressure MOVs, 843A and B in parallel, n.c.
Loo B, cold le high-pressure check valve, 875B high-pressure gate valve, 868B, n.o.
high-pressure check valve, 873B high>>pressuze MOVs, 843A and B in parallel, n.c.
Loo C cold le high-pressure check valve, 875C high-pressure gate valve, 868C, n.o.
high-pressure check valve, 873C high-pressure MOVs, 843A, and B in parallel, n.c.
Residual Heat Removal System Turkey Point Unit 3 Loo A, cold le high-pressure check valve, 875A high-pressure check valve, 876A high-pressure MOV, 744A, n.c.
Loo B, cold le Branch l high-pressure check valve, 875B high-pressure check valve, 876B high-pressure MOV, 744B, n.c.
Branch 2 high-pressure check valve, 875B high-pressure check valve, 876D high-pressure MOV, 872, n.c.
Loo C, cold le
. high-pressure check valve, 875C high-pressure check'valve, 876C high-pressure MOV, 744B, n.c.
Turkey Point Unit 4 Loo A, cold le Branch 1 high-pressure check valve, 875A
high-pressure check valve, 876A high-pressure MOV, 744A, n.c.
Branch 2 high-pressure check valve, 875A high-pressure check valve, 876K high-pressure MOV, 872, n.c.
Loo B, cold le Branch l high-pressure check valve, 875B high>>pressure check valve, 876B high-pressure MOV, 744A, and B, n.c., in parallel Branch 2 high-pressure check valve, 875B high-pressure check valve, 876D high-pressure MOV, 872, n.c.
Loo C, cold le high-pressure check valve, 875C high-pressure check valve, 876C MOV, 744B, n.c. 'igh-pressure In accordance with the criteria of Section 2.0, PRC has found no other valve configurations of concern existing in this plant. These findings con-firm the licensee's response [Ref. 2].
FRC reviewed the effectiveness of instituting periodic leakage testing of the check valves in these lines as a means o f reducing the probability o f an intersystem LOCA occurring. PRC 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 plait probability of an intersystem LOCA in the Turkey Point Units 3 and 4.
- 4. 0 CONCLUSION Turkey Point Units 3 and 4 has been determined to have valves in two of the configurations of concern having (1) a two check valve and single MOV in-series configuration in the cold leg branches of the High-Head Injection and Residual Heat Removal Systems, and (2) a single check valve, MOV inseries configuration in the two hot leg branches of the High-Head Safety Injection System.
If FPL modifies the Plant Technical Specification for Turkey Point Units 3 and 4 to incorporate periodic testing (as delineated in Section 2.2) for the check valvesternitemized in Table 1.0, then FRC considers this an acceptable means of achieving plant compliance with the NRC staff objectives of Refer-ence l.
Table 1.0 Primary Coolant System Pressure Isolation Valves
~Ss Check Valve No. Allowable Leaka e*
High-Head Safety Injection Unit 3 Unit 4 Loop A, hot leg 3"874A 4-874A cold leg 3-875A 4-875A cold leg 3-873A 4-873A Loop B, hot leg 3-874B 4-874B cold leg 3-875B 4-875A cold leg 3-873B 4-873B Loop C, cold leg 3"875C 4-875C cold leg 3-873C 4-873C Residual Heat Removal Loop A, cold leg 3-876A 4-876A 4-876E
- To be provided by licensee at a future date in accordance with Section 2.2.3.
Loop B, *cold leg 3-876B 4-876B 3-876D 4-876D Loop C, cold leg 3-876C 4-876c
5.0 REFERENCES
[1]. Generic NRC letter, dated 2/23/80, from" Mr. D. G. Eisenhut, Department of Operating Reactors (DOR), to Mr. R. E; Uhrig, Florida Power & Light Company (FPL).
[2)'. Florida Power & Light Company's response to NRC's letter', dated 3/17/80, from Mr. R. E. Uhrig (FPL) to Mr. D. G. Eisenhut (DOR).
[31. List of examined P&IDs:
FSAR Drawings of .Turkey Point Units 3 and 4:
Fig. 4.2-1, (Rev. 30)
Fig. 6.2-1, (Rev. 33)
Fig. 9.2-1, (Rev. 33) sh. 1 Fig. 9 '-2, (Rev'. 30) sh. 2 Fig. 9.2-3, (Rev. 30) sh. 3 Fig. 9.3-la, (Rev. 33) sh. 1 Fig. 9.3-1b, (Rev. 33) sh. 2 Fig 9 3 2p (Rev. 33)
Fige 9 ' 3~ (Rev. 33)
Fig. 9.4-'1, (Rev. 33)