ML19343D544

Primary Coolant Sys Pressure Isolation Valves,Hb Robinson Unit 2, Technical Evaluation Rept

ML19343D544
Person / Time
Site:	Robinson
Issue date:	10/24/1980
From:	Noell P, Stilwell T FRANKLIN INSTITUTE
To:	Polk J Office of Nuclear Reactor Regulation
Shared Package
ML19343D531	List: ML19343D530 ML19343D539 ML19343D544 ML19343D551
References
CON-NRC-03-79-118, CON-NRC-3-79-118 TER-C5257-265, NUDOCS 8105050195
Download: ML19343D544 (8)

Text

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ATTACHMENT 2 i

L TECHNICAL EVALUATION REPORT O

l i PRiiVi ARY COOLANT SYSTEM L

I

' PRESSURE ISOLATION VALVES L

L i CAROLIi1A POWER 8 LIGHT COMPANY jH.B.ROBINSONUNIT2 mass o c-r:n:susumumr NRC 00CKET NO.

50-261 l

NRC TAC NO.

12934 FRC PROJECT C5257 l NRC CONTRACT NO. NRC-03-79-118' FRC TASK 265 i

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. Noell I

Prepared for Nuclear Regulatory Commission Washington. D.C. 20555 Lead NRC Engineer: P. J. Polk October 24, 1980 i

This report was prepared as an account of work sponsored by an I

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 impiled, or assumes any legal i

liability or responsibility for any third party's use, or the results of*

such use, of any information, apparatus, product or procers disclosed in this report, or represents that its use by such third.

i party woulp not infringe privately owned rights.

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. Franklin Research Center A Division of The Franklin Institute i

$ / o f o S T) ( 9 $~~

n. s. nam.n Frankan Perweg, PMa Pa-19103(215)448-1000

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.o 1.0 IKIRODUCTION 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 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 j

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-t ture of the low pressure system, resulting in a LOCA that bypasses containment.

The NRC has determined that the probability of failure of these check l

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-l cally inspected by leakage testing, ultrasonic examination, or radiographic inspection. The NRC has established a program to provide increased assurance

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that such multiple isolation barriers are. in place in all operating Light l

Water Reactor plants designated by DOR Generic implementation 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

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plant systems communicating with the PCS: 1) two check valves in series or 2) j two check valves in series with a motor-operated valve (MOV).

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For plants in which valve configurations of concern are found to exist,

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licensees ware further requested to indicate: 1) whether, to ensure integrity of the various pressure isolation check valves, continuous surveillance or

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periodic testing was currently being conducted, 2) whether any check valver of

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concern were known to lack integrity, and 3) whether plant procedures should i

J be revised or plant modificatiocs be made to increase reliability.

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Franklin Research Center (FRC) was requested by the NRC to provide tech-f

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nical assistance to NRC's B-45 activity by reviewing each licensee's submittal j

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l assinet criteria provided by the NRC and by verifying the licensee's reported findings from plant system drawings. This report documents FRC's technical review.

1 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 interf ace 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.

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HP2 L LP Figure 1.

"21ve Configurations Designated by the NRC To Be Included in This Technical Evaluation

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2.2 Periodic Testing Criteria l

For licensees whose plants have valve configurations of concern and choose i

to institute periodic valve leakage testing, the FRC has established criteria I

for frequency of testing, test condit'ons, and acceptable leakage races.

These criteria may be summarized as foli us:

2.2.1 Frequency of Testing Periodic hydros tatic 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 /> if tes ting has not been accomplished in. the preceding 9 =enthe,

each time any check valve may have moved from the fully closed position (i.e., any time the dif feren-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.

2.2.2 Hydrostatic Pressure Criteria Leakage tests involving pressure differentials lower than function pres-sure dif ferentials are permitted in those types of valves in which service pressure will tend to diminish the overall leakage channel opening, as by l

pressing the disk into or 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 esses using pressures

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lower than function 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 test media and the ratio between test and function pressure differential, assuming leak-age to be directly proportional to the pressure differencial 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 or equal to 5.0

• gpm are considered acceptable if the latest measured rate has not exceeded the rate determined by the previous tes t by an amount

• 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 aupported by computations showing that the method is capable of derenstrating valve compliance with the leakage criteria.

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that reduces the margin between the measured leakage rate and the maximum permissible rate of 5.0 gpm by 50% or greater.

Leakage rates greater than 1.0 gpm 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 ths.t 1

I reduces the margin between measured leakage rate and the maximum permissible rate of 5.0 gpm by 50% or greater.

Leakage rates greater than 5.0 gpm are considered unacceptable.

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3.0 TECHNICAL EVALUATION

3.1 Licensee's Rens/ase to the Generic Letter In response to the NRC's generic letter (Re f.1], the Carolina Power &

Light Company (CPL) stated (Ref. 2} that, "The high-pressure to low-pressure system piping interfaces at H. B. Robinson Unit 2 have been reviewed and three Event V type interfaces (two check valves in series or two check valves in series with a motor-operated valve) have been identified."

The three interfaces identified were:

-High-Pressure Cold-Leg Injection Low-Pressure Injection / Residual Heat Removal

-Low-Pressure Injection / Accumulators The Licensee further stated, "The current surveillance requirements pro-vide for periodic leak testing of at least one check valve in each interface to ensure in'.egrity and functionality as a pressure and/or flow isolation barrier."

i of the three above-mentioned interface systems only the Low-Pressure l

Injection / Residual Heat Removal System has an Event V-type interface.

An i

additional system, the High-Pressure Hot-Leg Injection System, also contains a l

valve configuration of concern, as will be described in the following sections.

j It is FRC's understanding that, with CPL's concurrerce, the NRC will direct CPL to change its Plant Technical Specifications as necessary to ensure that periodic leakage testing (or equivalent testing) is conducted in accor-i dance with the criteria of Section 2.2.

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3.2 1RC Review of Licensee's Response licensee's response against the plant-specific Piping FRC has reviewed the and Instrumentation Diagrams (P& ids) [Ref. 3] that might have the valve con-figurations of concern.

FRC has also reviewed the ef ficacy 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 both the Low-Pressure Injection / Residual Heat Removal and High-Pressure Hot-Leg Injection Systems.

In its review of the P& ids (Ref. 3] for H. B. Robinson Unit 2, FP.C found i

the following two piping systems to be of concern:

The valve configuration of concern existing in the Low-Pressure Injection / Residual Heat Removal System consists in part of two in-series check valves in each of the cold-leg branches communicating with each of the three reactor coolant loops. Beyond these check valves the three cold-leg branches lead away from the PCS to two l

l motor-operated valves (HOVs) before the two piping trains, of this system penetrate the primary containment.

The high pressure / low-pressure interface exists on the upstream side of both HOVs.

In respect to the High-Pressure Hot-Leg Injection System, the valve configuration of concern consists of a single check valve in series with a HOV.

This configuration exists in both hot-leg branches leading to Reactor Coolant System Loops 2 and 3.

Again, the high-l The pressure / low-pressure interf ace exists upstream of each MOV.

appropriate valves for both systems are listed below:

Low-Pressure Injection / Residual Heat Removal Loop 1. cold leg high pressure check valve, 875A high pressure check valve, 876A high pressure MOV, 744A, normally closed (n.c.)

Loop 2 cold leg high pressure check valve, 875B high-pressure check valve, 876B high pressure MOV, 7448, n.c.

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e loop 3, cold lag I'

high-pressure check valve, 675C l'

high-pressure check valve, 876C high-pressure MOV, 74 4A, n.c.

High-Pressure Injection i

Loop 2, hot leg high-pressure check valve, 874B high-pressute MOV, 866B, n.c.

Loop 3, hot leg high-pressure check valve, 874A high-pressure MOV, 866A, n.c.

In accordance with the criteria of Section 2.0, FRC found no other valve 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 th'at introducing a program of check valve leakage testing in accordance with the criteria summarized in Section 2.0 will be an ef fective 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 f unctions.

It is also a step toward achieving a corresponding reduction in the plant probability of an intersystem LOCA in H. B.

Robinson Unit 2.

4.0 CONCLUSION

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It has been determined that the Low-Pressure Injection / Residual Heat Removal System in Robinson Unit 2 contains valving in one of the configurations f

(identified in Figure 1) designated by the NRC 'es a valve configuration of concern. Moreover, based on the previously docketed information and drawings made available for FRC review, FRC found that the hot-leg branches of the High-t l

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i Presrure Injection System also incorporate a valve configuration of concern.

Thus, if the licensee's review of the valving configuration contained in the hot-leg branches of the <igh-Pressure Injection System confirms FRC's findinc, 1

f then valve configurations of concern exist in two systems of Robinson Unit.'

and incorporate the valves listed in Table 1.0.

If CPL modifies the Plant Technical Specifications for H. B. Robinson t

Unit 2 to incorporate periodic testing (as delineated in Section 2.2) for the j

check valves itemized in Table 1.0, then FRC considers this an acceptable means

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of achieving plant compliance with the NRC staf f objectives of Referenec 1.

Table 1.0 Primary Coolant Syntam Pressure Isolation Valves System Check Valve No.

Allowable Leakage

• Low-Pressure Safety Injection /

Residual Heat Remr 'al Loop 1, cold leg 875A 876A Loop 2, cold leg 8758 8765 Loop 3, cold ;rg 875C 876C j

High-Pressure' Injection Loop 2, hot leg 8745 Loop 3, hot leg 874A 5.0 RE FERENCES 1.

Generic NRC letter, dated 2/23/80, from Mr. D. C. Eisenhut, Department

• of Operating Reactors (DOR), to Mr. E. E. Utley, Carolina Power & Light Company (CPL).

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• To be provided by licensee at a future date in accordance with Section 2.2.3.

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2.

Carolina Power & Light Company's response to NRC's 1cteer, dated 3/14/90, from Mr. E. E. Utley (CPL) to Mr. D. C. Eisenhut (DOR).

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List of examined F& ids:

t FSAR Drawings of H. 5. Robinson Unit 2:

l 541F055, (Rev. 6) 541F056, (Rev.-6)

I' 541F058, (Rev. 7) 694J731, (Rev. 9) 684J753, (Rav. 10) 484J879, (Rev. 10) 684J925, (Rev. 8) 685J433, (Rev. 4) e o

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