ML17209B002
| ML17209B002 | |
| Person / Time | |
|---|---|
| Site: | Saint Lucie  |
| Issue date: | 10/24/1980 |
| From: | Noell P, Stilwell T FRANKLIN INSTITUTE |
| To: | Polk P Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML17209B000 | List: |
| References | |
| CON-NRC-03-79-118, CON-NRC-3-79-118 TER-C5257-221, NUDOCS 8104280648 | |
| Download: ML17209B002 (9) | |
Text
0 ATTACHNEHT 2 TECHNICAL EVALUATIONREPORT PRIIVIARYCOOLANT SYSTEM P RESSU RE ISOLATION VALVES FLORIDA PONER K LIGHT CONPANY ST, LUCIE UNIT 1 NRC OOCKET NO.
50-335 NRG TAc No.
12887 NRC CONTRACT NO. NRC43-79-11e FRC PROJECT C5257 FRG >ASK 221 Prepared by Franklin Research Center The Parkway at Twentieth Street Philadelphia, PA 19103 Author: P.
H. Hoell T.
C. Stilwell FRCGroup Leader:
P.
N. Noell Prepared for Nuclear Regulatory Commission Washington, D.C. 20555 Lead NRC Engineer:
P. J.
Polk Ocrober 24, 1980'his 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 liabilityor 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.
81 0488 0 t>>~+
JL> >J Franklin Research Center A Division of I ne Franklin Institute The Senjan>in Frani>lin Parkway. Phile., Pa. i ri 1 O3 js!5) ~8 10GO
1.0 INTRODUCT10H The HRC 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-o f-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 con-current failure of two in-series check valves to function as a pressure isola-tion barrier between the high-pressure PCS and a lower-pressure system extend-ing beyond containment.
This failure can cause an overpressurization and rup>>
cure of the low-pressure system, resulting in a LOCA that bypasses containment.
The NRC has determined that the probability of failure of these chec'k 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.
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-45.
ln a generic letter of February 23,
- 1980, the NRC requested all licensees to identify the 'ollowing 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 (HOV).
For plants in which valve configurations of concern are found to exist, licensees wer e furth er requested to indicate:
1 ) whether, to ensure integrity of the vaz ious pressure isolation check valves, continuous surveillance or periodic testing was currently being conducted,
- 2) whether any.check valves oz concern were known to lack integrity, and 3) whether plant procedures should be revised or plant modifications be made to increase reliability.
Franklin Research Center (FRC) was requested by the HRC to provide tech-nical assistance to NRC' B<5 activity by reviewing each licensee' submittal
against crite i.a provided by the HRC and by verifying the licensee's reported findings from plant system drawings
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Th's report documents PRC's technical review.
2 o 0 CRITERIA 2 1 Identifi.cation Criteria Por 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 inte.face 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 Pigure 1; and
- 5) the pipe line must have a diameter greater. than 1 inch.
~ov QOV
Pigure 1.
Valve Configu a" ons Designated by the NRC To Be Included in This Technical Evaluation
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0 2.2 Periodic Testing Criteria For li.censees whose plants have valve configurations of concern and choose to institute pe.iodic 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.'.2.1 Prequency 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 for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> i 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 rep acement work is pe.formed.
- 2. 2.2 Hydrostatic 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 g eater force.
Gate valves, check valves, and globe-type valves, having function pressure differential applied ove" the seat, are examples of valve applications satis "y ng this
'requirement.
When leakage tests are made 'n such cases using pressures lower than func 'on maximum pressure differential, the observed leakage shall be adjusted to function maximum pressure differential value.
This adjustment shall be made by calculation appropriate to the tes" med a and the ratio between test and function pressure different'al, assum'ng leak-age to be directly proportional to the pressure differential to the one-half power.
2.2.3 Acceptable Leakage Rates:
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Leakage rates less than or equal to 1.0 gpm are considered accept-able.
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Leakage rates g.eater than 1.0 gpm bu" less than or equal to 5.0 gpm are considered accepcable if the latest measured rate has not exceeded the rate determined by the previous test by an amount
- To satisfy ALARA requirements, leakage may be measured indirectly (as om the per ormance of pressure ind'cators) if accomplished in accordance with approved procedures and supported by computations showing that the me hod
's capable of demonstrat'ng valve compliance with the leakage cr'ter a.
that reduces the margin between the measured leakage rate and the maximum permissible rate of 5.0 gpm by 50Z or greater.
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Leakage rates greater than 1.0 gpm but less than or equal to 5.0 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 gpm by 50Z or greater.
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Leakage rates greater than 5.0 gpm are considered unacceptable.
3.0 TECHNICAL EVALUATION 3.1 Licensee's
Response
co the Generic Letter In response to the NRC's generic letter [Ref. 1], the Florida Power
'Light Company (FPL) supplied in Refezence 2 a simplified flow diagram showing the valve configuration of concern for St. Lucie Unit 1.
This flow diagram basically outlined the High-and Low-Pressure Safety Injection Systems con-nected to the Primary Coolant System (PCS) piping.
The licensee further stated that instrumentat'on is provided to monitor the pressure on the low-pressure side of the check valves closest to the Primary Coolant System (V3217, V3227, V3237,- and V3247).
Also, plant procedures will be revised, accozding to FPL, during the current refueling outage to provide periodic surveillance zesting for the remaining affected check valves:
a)
V3113 and V3114 b)
V3123 and V3124 c)
V3133 and V3134 d)
V3143 and V31'44 It is FRC's understanding that, with FPL's concur-ence, the NRC will direct FPL to change its Plant Technical Specificat ons as necessary to ensuze that periodic leakage testing (oz equivalent testing) is conducted in accor-dance with tne criteria oz Section 2.2.
3.2 FRC Review of Licensee's
Response
FRC has reviewed the licensee's zesponse against the plant-specific Piping and Instrumentaticn Diagrams (P&IDs) [Ref. 3] that might have the valve con-figurations oz concern.
PRC has also reviewed the efficacy of instituting periodic testing for the cneck valves involved in this particular application with respect to the re-duction of the probability of an intersystem LOCA in the the High-and Low-Pressure Safety Injection System pipe lines.
In its review of the P6IDs [Ref. 3] for St. Lucie Unit 1, PRC found the following two piping systems to be of concern':
The High-and Low-Pressure Safety Injection Systems are connected to the cold leg side of each of the four PCS loops by a single common piping line.
Due to the outward branching of these four cold leg piping lines, both the High-and Low"Pressure Safety Injection Systems contain the dual check valve and a single motor-operated valve (MOV) in-series valve configuration of concern.
~ The high-pressure/low-pressure interface is on the upstream side of the MOVs.
The valves wnich comprise these configurations of concern are listed below for both systems.
High-Pressure Safety Injection Loo lA1, cold le high-pressure check valve, V3227 high-pressure check valve, V3123 high-pressure MOV, HCV 3626, normally closed (n.c.)
Loon 1A2, cold le high-pressure check valve, V3217 high-pressure check valve, V3113 high-pressure MOV, HCV 3616, n.c.
Loo 1B1, cold le~
high-pressure check valve, V3237 high-pressure check valve, V3133 high-pressure MOV, HCV 3636, n.c.
Loo 1B2, cold le high-pressure check valve, V3247 high-pressure check valve, V3143 h.'gh-pressure MOV, HCV 3647, n.c.
Low-Pressure Safety Injection Loo 1Al, cold leg high-pressure che'ck valve, V3227 high-pressure check valve, V3124 high-pressure MOV, HCV 3625, n.c.
Loo 1A2, cold le high-pressure check valve, V3217 high-pressure check valve, V3114 high-pressure MOV, HCV 3615, n.c.
Loo 1B1, cold le high-pressure check valve, V3237 high-pressure check valve, V3134 high-pressure MQV, HCV 3635, n.c.
Loo 1B2, cold le high-pressure check valve, V3247 hi:gh-pressure check valve, V3144 high-pressure MOV, HCV 3645, n.c.
In accordance with the criteria of Section 2.0, FRC found no other valve configurations of concern existing in this plant.
These findings confirm 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 of reducing the probability of an intersystem LOCA occurring.
FRC found that introducing a program of check valve leakage testing in accordance with tne criteria summarized in Section 2.0 will be an effective measure in substan ially 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 tne plant probabi'ity of an intersystem LOCA in St. Lucie Unit 1.
4.0 CONCLUSION
St. Lucie Unit 1 has been determined to have valves in one of the configu-rations of concern in both the cold leg branches of the High-and Low-Pressure Safety Injection System.
If FPL modifies the Plant Technical Specifications for St. Lucie 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.
Table 1.0 Primary Coolant System Pressure Isolation Valves
~Ss tMl High-Pressure Safety Injection Check Valve No.
Allowable Leakage*
Loop 1A1, cold leg Loop lA2, cold leg Loop 1B1, cold leg Loop 1B2, cold leg V3227 V3123 V3217 V3113
.. V3237
" V3133 V3247 V3143 Low-Pressure Safety Inject ion Loop 1A1, cold leg Loop 1A2, cold leg Loop 1B1, cold leg Loop 1B2, cold leg V3124 V3114 V3134 V3144
- To be provided by the licensee at a future date in accordance with Section 2.2.3.
5.0 REFERENCES
1.
Generic NRC letter, dated 2/23/80, from ~Mr. D. G. Eisenhut, Department of Operat'ng Reactors (DOR), to Hr. R. E. Uhrig, Florida Power a Light Company (FPL).
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2.
Florida Power
& Light Company's response to NRC's letter, dated 3/17/80, from Nr. R. E. Uhrig (FPL) to Mr. D. G. Eisenhut (DQR).
3.
List of examined P&IDs:
FSAR Drawings of St. Lucie Unit 1:
(
Fig 5'-3 Fig. 6.3-1 Fig. 6;3-2 Fig. 9.3-2 Fig. 9.3-4 Fig. 9.3-5 Fig. 9.3-6