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NUREG /CR-4692

ORNL/ NOAC-233

OAK RIDGE

NATIONAL

LABORATORY

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APIEI)p . a r 

'Ju

Operating Experience Review

of Failures of Power Operated

Relief Valves and Block Valves

in Nuclear Power Plants

G. A. Murphy

J. W. Cletcher 11

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Prepared for the

U.S. Nuclear Regulatory Commission

Division of Engineering Technology

under Interagency Agreement DOE 40-544-75

OPERATED BY

MARTIN MARIETTA ENERGY SYSTEMS, INC.

FOR THE UNITED STATES

DEPARTMENT OF ENERGY
.1

NOTICE

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.

Available from

Superintendent of Documents

U.S. Government Printing Office

Post Office Box 37082

Washington, D.C. 20013-7982

and

National Technical Information Service

Springfield, VA 22161
NUREG/CR-4692

ORNL/NOAC-233

Dist. Category AN, R1

Engineering Technology Division

Nuclear Operations Analysis Center

OPERATING EXPERIENCE REVIEW OF FAILURES OF

POWER OPERATED RELIEF VALVES AND BLOCK

VALVES IN NUCLEAR POWER PLANTS

G. A. Murphy

J. W. Cletcher II*

*Professional Analysis, Incorporated

Manuscript Completed - September 9, 1987

Date of Issue - October 1987

Prepared for the

U.S. Nuclear Regulatory Commission

Division of Engineering Technology

under Interagency Agreement DOE 40-544-75

NRC FIN No. B0828

Prepared by the

OAK RIDGE NATIONAL LABORATORY

Oak Ridge, Tennessee 37831

operated by

MARTIN MARIETTA ENERGY SYSTEMS, INC.

for the

U.S. DEPARTMENT OF ENERGY

under Contract No. DE-AC05-840R21400
CONTENTS

Page

LIST OF ACRONYMS ................. ***e....... vii

1I INTRODUCTION ................ i1.................................. 

2. PURPOSE ..................... 3 

3. SCOPE .... *....*...*.... ... .................... ... .. .. 4

4. STYLES OF PORVs ..... .......................................... 6

5. FAILURE RATES FOR PORVs AND BLOCK VALVES ........... ....... 13

6. RESPONSE TO SPECIFIC QUESTIONS ................................ 17

7. SUMMARY .................................. 26

8. CONCLUSIONS .................. ................. 27

9. REFERENCES ............. ..... *...... * .*.*. .... e* .. *....... 28

APPENDIX A: DATA BASE SEARCH PARAMETERS * ......................... 29

APPENDIX B: EVENT TABLES ........ .... .. ........... .......... ...... 31

APPENDIX C: HUMAN ERROR EVENTS ......... . . . .* .. . . . . . . . . .. . . . . . . .. . 55

APPENDIX D: PORV MANUFACTURERS INTERVIEW SUMMARY ................. 59

APPENDIX E: SUMMARY OF EPRI-RECOMMENDED TESTING, DIAGNOSTIC,

AND MAINTENANCE PRACTICES FOR PORVs AND BVs .......... 73
v

FOREWORD

The Nuclear Operations Analysis Center (NOAC) has supported the Oak

Ridge National Laboratory Nuclear Plant Aging Research Program (NPAR)

for the past 4 years. The first major report of that program, Survey of

Operating Experience From LERs to Identify Aging Trends (NUREG/CR-3543)

was prepared by NOAC in 1983 and formally published in January 1984.

Since that time, NOAC has contributed to several other documents for the

NPAR Program, including reports on motor-operated valves, check valves,

auxiliary feedwater pumps, and other nuclear plant components.

The present document reports the results of a survey of operating

experience with power-operated relief valves (PORVs). It includes an

analysis of reported events of PORV failures, interview responses of

four PORV manufacturers, and conclusions concerning PORVs designated as

safety-related components.

NOAC has designed and developed a number of major data bases that

it operates and maintains for the Nuclear Regulatory Commission. These

data bases collect diverse types of information on nuclear power plants

from the construction phase through routine and off-normal operation.

These data bases make extensive use of plant-operator-submitted reports,

such as the Licensee Event Reports.

NOAC also publishes staff studies and bibliographies, disseminates

monthly nuclear power plant operating event reports, and prepares the

Technical Progress Review Journal NucZear Safety.

Joel R. Buchanan, Director

Nuclear Operations Analysis Center

Oak Ridge National Laboratory

P.O. Box Y

Oak Ridge, TN 37831

615-574-0377 (FTS: 624-0377)
vii

LIST OF ACRONYMS

B&W

BV

BWR

CE

DET/RES

DOE

EPRI

INPO

IPRDS

LER

LTOP

MOV

NOAC

NPAR

NPE

NPRDS

NSSS

POP

POPS

PORV

PSV

PWR

RCS

RECON

SCSS

TMI

W

10 CFR 21

I&C

Babcock & Wilcox

block valve

boiling water reactor

Combustion Engineering

Division of Engineering Technology/Office of Research

Department of Energy

Electric Power Research Institute

Institute for Nuclear Power Operations

In-Plant Reliability Data System

Licensee Event Report

Low-temperature overpressure protection

motor-operated valve

Nuclear Operations Analysis Center

Nuclear Plant Aging Research (Program)

Nuclear Power Experience

Nuclear Plant Reliability Data System

Nuclear Steam Supply System

primary overpressure protection

primary overpressure protection system

power-operated relief valve

pressurizer safety valve

pressurized water reactor

reactor coolant system

REmote CONsole

Sequence Coding and Search System

Three Mile Island

Westinghouse

Title 10 Code of Federal ReguZations Part 21

Instrumentation and Control
OPERATING EXPERIENCE REVIEW OF FAILURES OF

POWER-OPERATED RELIEF VALVES AND BLOCK -

VALVES IN NUCLEAR POWER PLANTS

G. A. Murphy J. W. Cletcher II*

ABSTRACT

This report contains a review of nuclear power plant

operating events involving failures of power-operated relief

valves (PORVs) and associated block valves (BVs). ' Of the

230 events identified, 101 involved PORV mechanical failure,

91 were attributable to PORV control failure, 6 events

involved design or fabrication of the PORVs, and 32 events

involved BV failures. The report contains a compilation of

the PORV and BV failure events, including failure cause and

severity. The events are identified as to plant and valve

manufacturer. An assessment of the need to upgrade PORVs

and BVs to safety-grade status concludes that such action

would improve PORV and BV reliability. The greatest improvement in reliability would result from using newer, more

reliable PORV designs and improving testing, diagnostics,

and maintenance applied to PORVs and BVs, particularly the

BV motor operator. A summary of interviews conducted with

four PORV manufacturers is also included in the report.

1. INTRODUCTION

This report was prepared by the Nuclear Operations Analysis Center

(NOAC) in response to a request from the Nuclear Regulatory Commission

(NRC) Division of Engineering Technology (DET)1 for a survey of poweroperated relief valve (PORV) and block valve (BV) operating experience.. The information is provided under the Nuclear Plant Aging

Research (NPAR) Program to support the resolution of Generic Issue 70

(GI-70) "PORV and Block Valve Reliability."

PORVs are valves that require an external power supply (normally

air and/or electric) for actuation and are typically controlled by an

electrical signal resulting from high system pressure or by manual

actuation from the control room.

This report contains a compilation and review of operating events

involving PORVs and their associated BVs in pressurized-water reactor

(PWR) nuclear power plants. Most of the event descriptions were

obtained from Licensee Events Reports (LERs) contained in the NOAC file

on the Department of Energy (DOE) RECON data base (pre-1981) and the

*Professional Analysis, Incorporated.
2

Sequence Coding and Search System SCSS) data base (post-1981).. Additional information on selected events was obtained from the Institute

for Nuclear Power Operations (INPO) Nuclear Plant Reliability Data

System (NPRDS), the NRC Foreign Event File at NOAC, Nuclear Power

Experience (NPE) reports, and other relevant reports.

Four PORV manufacturers were interviewed to obtain their response

regarding selected questions of interest to the NRC. A summary of the

manufacturers' responses is contained in Appendix D.

3
3

2. PURPOSE

' The purpose of this study was to survey nuclear plant operating

experience for PORV and BV failure events in support of the resolution

of GI-70.r' Neither-PORVs nor BVs havebeen shown by 'safety-analysis to

be needed for safe shutdown of the pl'ant or to initigate'the-consequences

of an accident.. However,' NRC has recently determined-that PORVs are, in

'fact;- relied upon to mitigate certiin':design-basis' accidents.' The

acceptability of relying on non-safeti-grade PORVs to-mitigate a designbasis accident is presently the subject of'NRC'Generic Issue 70: "PORV

and Block Valve Reliability." -
4

3. SCOPE

This report reviewed events reported from 1971 to mid-1986. The

earliest PORV failure event found in the search occurred in 1971. However, because LER reporting requirements were upgraded in 1976, more

complete information is available for later events, especially those

coded into the LER SCSS data base (1980 to present).

Note that because PORVs are-not classified as safety related, their

failures were. not always reported, especially in earlier years (before

1979) (see Fig. 1). Consequently, PORV failures may have been more

prevalent than indicated. However, after the Three Mile Island Unit 2

(THI-2) accident, increased sensitivity to PORV (and BV) operability

problems probably led to increased reporting of such events. Nonetheless, a revised LER reporting rule, which went into effect Jan. 1, 1984,

did not specifically require reporting of all PORV or BV failures;

hence, the number of LER-reported failures of these components has

decreased sharply from post-THI levels. In both cases, the actual

number of PORV and BV failures may actually be higher than shown on

Fig. 1. One purpose of the new LER rule was to shift reporting of

single failures to the INPO NPRDS system. In time, NPRDS should have

better PORV failure data, provided that the utilities accurately and

consistently report such failures.

ORNL-DWG 87-4168 ETD

. 8

50

40

Iz

w 30

U0

us

m

E 20

z

10

0

1971 1972 1973 1974 1975 1976 1977 1978 1979

YEARS

Fig. 1. Reported PORV failure events 1971-1986 'i
5

Computer searching of the NOAC/RECON and SCSS LER data bases

yielded 548 event descriptions; the NPE data base provided 202 event

descriptions; and the INPO NPRDS provided 78 event descriptions. In

addition, several' reports that' addressed-PORV failures were reviewed to

gather information leading to identification of other PORV failure

events - both reported and unreported (formally). Appendix A contains

a list of the computer data bases that were searched and a description

of the search strategy applied to each one. In many cases, an event

reported in an LER was -also contained, in NPE, NPRDS, or other reports.

In addition, NPE and NPRDS were searched independently for PORV and BV

failures. Those found were also added to the data base for this report

(and correlated with an LER if one-was filed).

All the events collected were reviewed and screened for cases that

involved actual failures of PORVs, BVs, or the associated control systems. A total of 230 events were identified; some events are duplicated

because they involved a failure of both the PORV and its control system. These events are contained in Tables 1-8 in Appendix B. Events

that included successful actuation and reseating of PORVs or BVs in the

course of a plant transient or test evolution are not included in this

report.
6

4. STYLES OF PORVs

Two styles of PORVs are in general use in domestic PWRs - the

pilot-operated relief valve and the air-operated (spring-closure)

valve.

4.1 Pilot-Operated Relief Valves)

Manufacturers: Crosby Valve and Gage Company

Dresser Industries

Garrett Corporation

Target Rock Corporation

- The pilot-operated relief valve consists of a main valve with

piston- or diaphragm-operated disk and a pilot (Figs. 2-5). Under

normal operating conditions, the pilot allows system pressure into the

piston chamber. Because the piston area is greater than the disk seat

area, the disk is held closed. When the set pressure is reached, the

pilot is actuated to vent the piston chamber, which allows the disk to

open. Some valve designs also shut off system fluid to the piston

chamber.

The Target Rock PORVs are normally installed with system pressure

over the disk. The system fluid fills a cavity above the main disk and

in the bonnet tube. When the solenoid coil is energized, the resulting

electromagnetic force lifts the movable core together with the stem and

pilot disk, uncovering a pilot port and exhausting the fluid into the

outlet nozzle. This creates a low-pressure area above the main disk

that is sustained as long as the pilot valve remains open. The higher

inlet pressure acts on the unbalanced area of the main disk to provide

the opening force.

Target Rock PORVs have been provided to Tennessee Valley Authority

(TVA) for replacement of present PORVs at Bellefonte, Sequoyah, and

Watts Bar Nuclear Plants.

4.2 Air-Operated (Spring-Closure) Relief Valves

Manufacturers: Control Components, Inc.

Copes Vulcan

Fisher Controls Company

Masoneilan

MUESCO Controls, Inc.

The air-operated (spring-closure) style of PORV (Figs. 6 and 7)

utilizes a large compression spring to provide seating force to the

*The Garrett PORV product line was acquired by Crosby in 1984.
7

, , ORNL-DWG 87-3688 ETC

_ , .. - ,., ; , :. . I . , . ... ,= . I';

Fig. 2. Pilot-operated relief valve (Courtesy -of Dresser Industries)
8

ORNL-DWG 87-3944 ETD

BODY

BONNET

CAGE

GUIDE

PISTON RING

PISTON RING

PLUG

ROD MAGNET

SEAL

SEAT

SPRING

SPRING GUIDE AND

ROD RETAINER

SOLENOID VALVE ASSEMBLY

SWITCH ASSEMBLY

SWITCH COVER

.

Fig. 3. Pilot-operated relief valve (Courtesy of Crosby Valve and

Gage Company).-
9 I

ORNL-DWG 87-3943 ETD

1 ARMATURE ASSEMBLY

2 BALL

3 BALL GUIDE

4 BODY ( 5 CANOPY

6 ELECTROMAGNET ASSEMBLY

7 LOWER SEAT

B MAGNET ROD ASSEMBLY ( 9 MAGNETIC SHUNT

10 OVERRIDE ASSEMBLY

11 PRESSURE VESSEL

12 RETURN STEM

13 SCREW

14 SEAT RETAINER

15 SPRING

16 SPRING RETAINER

17 STOP ASSEMBLY

18 SWITCH ASSEMBLY

19 SWITCH COVER

20 UPPER SEAT

Fig. 4. Solenoid valve assembly for Crosby PORV - part

Fig. 3 (Courtesy of Crosby Valve and Gage Company)

No. 13 on
10

ORNL-DWG 87-3691 ETD

I BODY 1

2 BONNET ASSEMBLY 

3 COVER

4 ELECTRICAL ASSEMBLY

5 FIXED CORE.

6 INDICATOR TUBE

7 MAGNET ASSEMBLY

B MAGNETIC SLEEVE 19

9 MAIN DISK

10 MOVEABLE CORE

11 PILOT DISC

12 PILOT SEAT

13 PISTON RING

14 PLUG

15 PLUNGER

16 REED SWITCH ASSEMBLY

17 RING

18 ROD

19 ROD, DISC

20 ROD PLOT DISC

21 SLEEVE.

22 SOLENOID ASSEMBLY

23 SPRING

24 SPRING RETAINER

.1 . !

Fig. 5. Solenoid pilot-operated relief valve (Courtesy of Target

Rock Corporation)

2
11:

ORNL-DWG87-3690 ETD

1 BONNET

2 CAGE WITH SEAT

3 CAGE SPACER

4 GLAND FOLLOWER

5 GUIDE BUSHING

6 LEAKOFF CONNECTION

7 OPERATOR ASSEMBLY

8 PACKING

9 PACKING GLAND

10 PLUG

11 STEM

12 VALVE BODY

. Fig. 6. Air-operated. (spring-loaded) relief..valve (Courtesy of

Copes-Vulcan)
12

ORNL-DWG 87-3689 ETD

2

3

4

5

6

7

8

9

10

11

12

Fig. 7. Operator assembly for air-operated (spring-loaded) relief

valve - part No. 7 on Fig. 6 (Courtesy of Copes-Vulcan)

valve stem and plug with an air-loaded reverse-acting operator attached.

To open the valve, air pressure'loads the diaphragm chamber to overcome

the spring force, thus lifting the valve plug off the seat. Positive

closure is provided by the spring return upon venting the air pressure

from the diaphragm chamber.- The' Control'Components,' Inc.', PORV'differs

in that air pressure provides both the valve opening and closing forces

with a compression spring providing a backup closing force.

Detailed descriptions of each manufacturer's valve may be found in

Ref. 2.
13

5. FAILURE RATES OF PORVS AND BLOCK VALVES

'Because of the historically inconsistent reporting of PORV and BV

failures, no meaningful failure rates 'for these devices could be calculated from the data collected for this report.' However," two reports

that contain an analysis of PORV and BV reliability were reviewed. A

summary of the findings from each report follows.

5.1 "Estimating Failure-to-Close Probabilities for

Pressurizer Valves," W. W. Weaver, Babcock & Wilcox,

-- Nuclear Power-Generation Division (Ref . 3) -

Three categories of valves were considered in this .study for failure to close: (1) motor-operated valves (MOVs), 2 to 4 in. in diameter;

(2) PORVs; and (3) pressurizer safety valves (PSVs). For each category

a Bayesian approach was employed to estimate failure-to-close-probabilities incorporating -previously- unreported data. The resultant values

differ from -other -published sources: of data, such as WASH-1400 and

NPRDS. For PORVs of the type in use-atB'Babcock & Wilcox (B&W) and Combustion Engineering (CE) plants, Weaver calculated a mean value of

9.8 x 10-3 (total number of failures/total number of demands).'- The

report also mentions 'an unnamed'different type of PORV* that was being

considered for use in the larger 1205 fuel assembly' (FA)] 'B&W' units.

This new valve'has accumulated 25',000'cycles without failure as a pressurizer spray valve, which is a different environment from a PORV application. Pressurizer spray is actually more stressful to the valve

internals -than a PORV application; however, the intermittent operation

of a PORV would appear to induce a higher chance of ailure than the

regular demand (e.g., typically eight' per day) --of the spray valve application. For the new - valve, a failure' distribution with a mean of

4 x 10-4 per demand was calculated.

*The unnamed valve alluded to is a Target Rock-supplied solenoidoperated pressurizer spray valve. These _valves were supplied to Oconee

1, 2, and 3 and have been in operation since 1976. Prior to installation, a 100,000-cycle test was conducted by the Nuclear Steam System

(NSS) supplier (B&W) at-225'F ambient temperature, 2200 psi, with fluid

temperature at 600'F. - At -Oconee,---it was -reported -that the valves have

not required a single incidence ofrmaintenance.:- ' l

Weaver's report states that the pressurizer spray valve duty cycle

is "actually more stress'ful to the valve internals than a PORV application." This is true in the case of an air- or motor-operated valve with

stem packing, but' not for the Target Rock solenoid valve. This valve

has no packing and as such does not require''a stem to be driven through

pressure-loaded packing, which can quickly start leaking under this service. Target Rock states that because the P in a pressurizer spray

application is relatively -low, -their -solenoid valve has a slow, gentle

action, taking about -3.5' s' to -open and 4 s to -ciose. For the valve

tested by B&W, Target Rock-states that the gentle burnishing action of

disc to seat contact resulted in valve leakage improving to 1/10 of the

initial value after 100,000 cycles.
14

The MOV data is based on NUREG/CR-1363 (Ref. 4) and RADCAS

(Ref. 5). A value of 8.1 x 10-4 for failure to close per demand was

calculated from the tables in Ref. 4, which was used in a Bayesian analysis of RADCAS data of 34'failures in 1433 demands.

The table below summarizes the values obtained for the MOV failure

to reclose:

Prior Posterior

Evidence 5th - 9ct Mean ag. t 9t Mean factor percentile Menpercentile

8.1 x 10~ 3 34/1433 1.33 x 10-2 1. 8 x 10-2 2.46 x 10-2

8.1 x 1-4 10 34/1433 1.63 x 10-2 2.22 x 10-2 2.98 x 10-2

5.2- ThecIn-Plant Reliability Data Base'(IPRDS)'for

Nuclear Plant Components: Interim Report - The

Valve Component (Ref. 6)

The IPRDS is a data base developed primarily from in-plant records

of maintenance actions. These records were obtained directly from

selected nuclear.plant maintenance, files. Data were collected from two

PWRs, which included'PORVs and pressurizer MOVs. A preliminary compila-'

tion of'reliability for 26 PWR safety system MOVs yielded, for 10 failures, a mean failure rate to operate on demand of 6.4 x 10-.

A summary of',the valve failures for PORVs and MOVs for Plants I and'

2 is shown in Table 5.1,below.,

Failure andrepair descriptions for PORVs and pressurizer OVs from

Plant 1 and Plant 2 are shown in Tables 5.2 and 5.3.

a

Table 5.1 Summary of valve failure

Plant I ~Plant 2

PORV HOV PORV MOV

Valve seat leakagea

Limitb switch,

Air/regulator leak

Operator failure

Failed to reset

Lifted prematurely

Solenoid failure

Other

- TOTAL'

10 2 3 3

3 0 0 0

4 0 0 . 0

2 0 0, 0

O 0 1 .0

0 1 0

O 0 1 0

1 0 '0 4

7- 2 T 7

aThe amount of valve seat leakage was

not given in-the maintenance records.

bPosition indication.,
'15

Table 5.2. IPRDS Plant 1

Valve ' - Failure' description

PORV-1 Valve leaks'

PORV-1 Excessive leakage

PORV-1 Leaking

PORV-1 'During test, cycled once but

not twice -

PORV-1 Regulators leak

PORV-. .Limita switches need adjustme

PORV-1 Valve leaks through.,

PORV-1 Leaks through

PORV-1 Air leak in inlet to PORV

nipple' '

PORV-1 (No documentation)

PORV-2 Leaks slightly

PORV-2 Leaks by

PORV-2 High-temperature alarm inindicating seat-leakage

PORV-2 Limita switches require setting

PORV-2 Regulator leaks

PORV-2 Stem plug and.cage assembly

removed during shutdown

PORV-2 Limita switches out of adjust

ment

PORV-2 Valve leaks through

PORV-2 Diaphragm on operator leaking

PORV-2 Air regulator for PORV

MOV-1 'Small body to bonnet leak

-MOV-2 Small body to-bonnet-leak

Repair description

Replaced gasket and lapped

seat

.,Beveled and lapped seat -

replaced gasket

Polished both seats and re-

'placed-gasket

- Installed'gaskets and one

screen

Renew gaskets and gages

ent Adjusted limita switches

.,Adjusted spring tension

Loosened lock and adjusted

valve

Installed solenoid, tested

Changed diaphragm

No leaks at normal pressure

Machined seat, straightened

Replaced stem and flex gasket

Adjusted limita switches

Renewed gaskets and gages

Machined stem plug face and

cage seat; lapped plug and

seat

t- Adjusted upper limita switch

Inspected and repaired valve

Repair.as instructed

Replaced regulator

Retorq'ued and seal welded

.-.Retorqued and-seal welded....

aposition indication.
16

Table 5.3. IPRDS Plant 2

Valve Failure description . Repair description

PORV-1 Valve opened for preoperation

test crew, and it did not

reset; incorrect preload

tension on valve spring

(failure occurred prior to

commercial operation date)

PORV-1 PORV-1, -2, 3 lift'prematurely

(failure occurred, prior to

commercial operation date)

PORV-1 Valve leaks through; seat

and plug wire drawn

PORV-2 Valve is leaking by (failure

prior to commercial operation

date).

PORV-2 Valve leaking by at normal

pressure because disk is

ruined

PORV-3 Valve failed to open

MOV-1 (Not documented)

MOV-1 Packing leak

MOV-1 (Not documented)

MOV-1 Packing leak

MOV-2 (Not documented)

MOV-3 Valve wedge jammed in seat;

overtorqued byomotor operator and by hand to effect

isolation for another job

MOV-3 Will not-open electrically;

broken terminal on switch

Adjusted preload tension on

valve spring and functionally

checked

Found bad solenoid valve on

PORV-3; replaced solenoid

and calibrated

Installed new seat and lapped

plug; new gaskets, repacked,

functionally' checked

Valve not seated; seated

valve and stroked to ensure

properly seated

Deterioration from service;.

installed new stem and disc;

replaced seat ring gasket and

bonnet gasket; replaced packing .,

Solenoid valve no good; replaced solenoid valve

Retorqued packing gland per

procedure

Natural end of packing life;

repacked valve

Valve was jammed shut at

clearance point

Natural end of packing life;

repacked valve

Valve was jammed shut at

clearance point

Pulled bonnet and freed wedge;

stem reassembled and repacked

Broken terminal on benchboard

switch repaired
17

6. RESPONSE TO SPECIFIC QUESTIONS

Task 7'of the NRC NPAR Program Brief FIN NO. B0828 for FY 1985-1986

contained nine questions concerning PORV and BV'operating experience.

This section of the report addresses those questions.

6.1 How Many PORV/BV Failures Have Occurred?

Because PORV and BV failures were not reportable events, it is not

possible to state exactly how many failures have occurred. However,

this report surveyed five nuclear plant operating experience data bases,

plus' several industry reports to compil a list of reported events involving PORV and BV failures.. For, the period 1971 to July 1986, 192

PORV failure events, 32 BV failure events, and 6 reported design "failure" events were identified. -A compilation of these 230 events is contained in Tables 1-8 of Appendix B of this report.

6.2 What Were the Causes of Valve Failures and Type of Plant

Where Failures Occurred?

The root cause(s) of PORV or BV failures could not be determined

from the information found 'in the'various event' reports. ' However,

details from LER and other- event descriptions were'

provide information on the proximate cause for most c

Tables -8 of Appendix B contain descriptions 

ure events listed by PWR NSSS vendor.

Table 1 B&W PORV events - mechanical failure

Table 2 B&W PORV events - control failure

Table 3 W* PORV events - mechanical failure

Table 4 W PORV events - control failure

Table 5 CE PORV events - mechanical failure

Table 6 CE PORV'events - control failure

Table 7 PORV BV events

pieced 'together to

of the failures.

f PORV and BV fail-

(32 events)

(10 events)

(53 events)

(68 events)

(16 events)

(13 events)

(32 events)

Table 8 PORV events - design/fabrication failures (6 events)

There were -ten -events for r which no plant identification was available

from the source data- base.''One event is a Westinghouse (W) PORV control

failure," and nine events -involve PORV mechanical failures - four -at W,

four at CE, and one at a B&W plant.

The PORV events for each NSSS vendor are broken down into two general categories:

Mechanical failures - failures of. the PORV or its pilot valve/

solenoid, if the pilotjis an.,integral part of the' PORV. Failures

of remotely located pilot solenoid valves were classified as

*W - Westinghouse
I

18

control failures (below). Mechanical failures of BVs include the

motor operator or valve, but not associated controls or indicators.

Control failures - those* cases where remote switches, solenoid

valves, wiring, relays, accumulators, etc., failed or caused degraded operation or immediate failure of the PORV or BV function.

6.2.1 Failures at-B&W-plants

About half of the reported mechanical failures of PORVs at B&W

plants (Dresser and older Crosby designs) appeared'to occur in the main

portion of' the'valve and involved seat leakage, while the rest of the

failures originated in the-pilot valve portion. The Dresser and Crosby

valve designs' use steam pressure to open or close the valve via the

pilot valve. The pilot 'valve internals are, therefore continuously

subjected to reactor-coolant system (RCS) heat' and pressure, plus the

dynamic effects of steam during actuation. 'The close tolerances and

greater number of moving parts exposed to steam in these designs can

make them more susceptible to failure than the air-operated (springclosure) designs. Four out of seven PORV failure-to-close events

occurred at B&W plants that used the Dresser or Crosby pilot-operated

design:

ANO-1 September 1974 (Dresser)

Davis-Besse September 1977 and June 1985 (Crosby)

TMI-2 March 1979 (Dresser)

In these cases, the PORV was stuck open. Such occurrences can represent

a challenge to plant safety if the PORV BV cannot be closed to isolate

the stuck-open PORV.

6.2.2 Failures at plants

The majority of the reported mechanical failures for air-operated

(spring-closure) PORVs involved seat leakage. W units used mostly

Copes-Vulcan or Masoneilan designs. The seat/plug/cage interface is the

only portion of these designs that is subject to steam temperature and

pressure. The external appurtenances such as actuator diaphragm, limit

switches, and pilot solenoid valve are normally only exposed to containment atmosphere, which is relatively benign under normal operating conditions.

6.2.3 Failures at CE plants

Seat' leakage was also predominant in the reported failures for

PORVs in CE plants. Since most CE units have blocked off their PORVs

(or do- not have any),-there are only' a few PV mechanical'failures reported for these plants. One interesting event at St. Lucie 2 (Table 5,

Appendix B) involved loss of magnetism on the position indication

magnets due to high temperature. I
19

6.2.4 Control failures

Reported control failures for PORVs involved loss of power, circuit

design errors, controller malfunctions,. and degradation or; loss of the

air/nitrogen actuating pressure., NorthAnna Units -l and 2 accounted for

a substantial number of.,reported PORV. control'problems. Both units were

plagued by design problems: in- the PORV nitrogen supply system. The

event descriptions indicate that a design change was to be implemented

at a future outage.

6.2.5 PORV BV failures

Table 7 in Appendix B contains a' compilation of PORV BV events.

Twelve events involved failure of the valve motor operator, mostly

torque or limit switch problems. Four events described problems with

the valve (mostly packing leaks). Five events involved failures in the

controls to the.BV operator* PORV BV failures do not appear to occur

any more frequently than failures of ;other MOVs subjected to similar

conditions. The valves and motor operators used in PORV BV. service are

similar to those used for other purposes in the plant.' 'An assessment of

MOV service wear and aging is contained in Ref. 7.

6.2.6 Design/fabrication -failures

Table 8 in Appendix B contains six events that describe problems

that originated- in the designphase-of valve procurement. These type

failures were, until recently, not reportable. - Hence, not many events

of this type were found. New reporting requirements for deficiencies

found during plant construction are now included under 10 CFR Part 21

and f10 CFR Part 50.55(e), the-Construction- Deficiency Report system.

This new system, in use- since April 1984, should -provide more data on

this type event. Reference 8 provides.more information on-the reporting

requirements and describes the Construction- Deficiency Report event

data base. . --

6.3 -What was the Failure Severity - Degraded or Failed?

Each PORV and BV event' collected for the report was' judged'as to

the severity of the failure. The terms chosen for this report are'defined as follows:

Degraded: - D) The- component operates at less than -its specified

(but performance level.

-operable) - l ,'

Failed: (F) The -component -is completely unable to perform its

function. -

* , - ,i -*
20

Seventy-six percent of the PORV events attributable to mechanical

failure were judged as degraded, that is, the valve was operable but

leaking through or the packing leaked. The amount or severity of'leakage was not'found in the reports. About-two-thirds of the-PORV control

events (67%) were failures - that is, immediate loss of -control.

Slightly over half the BV 'events (53%) were degraded, with the

balance (47%) being failures. Five BV 'failures involved the valve controls. Fifteen- BV -events: were attributable 'to some failure of the'

valve, while 12 events involved the motor operator.

A compilation of PORV and BV events as to failure severity is shown

below:

Failure severity - PORV and BV events

Degraded Failures Total

PORV mechanical 77 24 101

''- ' PORV control 30 61 91

PORV design 6 0 6

BV events 17 15 32

Total 130 100 230

6.4 To What Extent Did Operator or.Maintenance

Actions Contribute to Valve Failures?

The 230 events compiled for this report were'-reviewed to determine

to what extent operat'or-or maintenance actions could have contributed to'

the failure. Appendix C contains a summary list-of 38 events that were

judged to involve some'human'error. ' - - -

'Ten events-specifically identified operator error as a cause, mostly from administrative errors. Twenty-eight events involved maintenance

or Instrumentation and Control (I&C) errors. Six of these could be

attributed to procedure or drawing error; the remaining 22 appeared to

be simply mechanical or' electrical' miscues -'such as shorted leads or

misassembled components. Nine events could be attributed to errors in

original design, errors in design changes, or other administrative problems.

6.5 Are Certain Designs More Prone to Failure than Others?

A review of the events collected for this report indicates that the

Dresser and Crosby pilot-valve designs accounted for about 40% of the

PORV mechanicalfailures.- These designs were involved in:failures that

occurred at all nine B&W plants and four CE plants. (Most.CE units have

blocked off their PORVs or do not employ them in the design.)
21

The pilot-operated relief valve- has 'been a contributing factor in

all the major B&W transient events, most notably the TMI-2 accident and

two events at Davis-Besse (9/77 and 6/85). The close tolerances and

greater number of moving parts exposed to steam in these designs can

make them more susceptible to failure. -'Careful selection of materials

and proper design for" the: expected service conditions are necessary.

However, a newer design of 'the Crosby (formerly Garrett) pilot-valve

type appears to have better reliability than the original version.

Target Rock Corporation has' developed a solenoid pilot-operated relief

valve (SPORV) that has been extensively tested 'and is apparently reliable, but no long-term nuclear operating experience has been accumulated

on this design.

The pilot-operated relief valve does' have several' -advantages. As

the system pressure increases, the force holding the disk in the closed

position increases. This allows the system operating pressure to be increased to values within 5 of set pressure without danger of increased

seat leakage in the- main valve. Pilots can be designed with a separate

control for set pressure and blowdown. The valves can be set to open

fully at the set pressure and close with very short blowdown.

Another advantage of pilot-operated valves is cost. The large

spring and associated space envelope of air-operated (spring-closure)

valves can be replaced by a small pilot, thus-reducing the mass and cost

of the valve. Additionally, the -lower profile- of the pilot-operated

relief valve provides greater resistance to seismic forces.

A disadvantage of '- the pilot-oper-ated' relief 'valve is in the increased complexity of the pilot with multiple parts (versus a single

spring) and the associated reduction in reliability. A particular concern is -the susceptibility to foreign matter of the small control passages in the pilot. -

In contrast, the air-operated '(spring-closure) relief valve design

appears less susceptible-to catastrophic (stuck-open) failure than the

pilot-operated relief valve design... But the spring-loaded design requires a system of solenoid valves,' accumulators, and associated piping

to-operate. Upgrading this additionalequipment to safety-grade quality

to provide needed reliability under normal and worst case'- (LOCA) lossof-coolant accident conditions introduces additional cost and complexity

to the PORV controls.- "Such design requirements present a' trade-off

versus the relatively compact "pilot-operated design, which 'needs only

electrical- connections for operation. - '

Table 6.1 presents-'a compilation of-PORV mechanical failures'listed

by 'PORV manufacturer. Note that the Dresser and Copes-Vulcan designs

have been used for a numberof years,-hence the relatively high total

number of-events. -

; - .. - . - a 
22

Table 6.1.. PORV.mechanical

failures (excludes

'design events)

' , Failure severitya

Manufacturer

- F D Total

'Crosby (p)b 2 5 7

Dresser'_ (p) 8 25 33

Garrett (p) 5 5

Copes-Vulcan (a)C 3 25 28

Masoneilan (a) 3 7 10

Control' 2 - 2

components-(a)

Unknown 8 8 16

Total 24 77 101

aF -failed

D'-' degraded

b( ) pilot-operated

(a) air-operated (spring close)

6.6. To What Extent Would Upgrading of!Valves, Operators, and

Control Systems to Safety-Related CriteriaHave Prevented the Failures?

Based o a review of the failure events, it appears that if the

valves, operators, and' contriol components involvedin. the failures. had

been installed, tested, and maintained in accordance with requirements

applied. to- safety-grade components, some .of the failures most likely

would, have. been prevented. Upgrading the components to safety-grade

standardswould provide a documented history of each activity applied to

the component and' provide redundant. control circuitry constructed, to

Institute of-. Electrical and Electionic'Engineers (IEEE) requirements.

However, the basic,.design of the components would be, unchanged, other.

than having 'to. meet .the environmental qualification. criteria required

for safety-grade equipment. Fo'r example, there are few differences

between motor operators used for PORV BVs and the same make and model

used in safety-related applications. Similarly, the physical design of

PWR pressurizer PORVs in wide use would not be appreciably different if

they were constructed to safety-grade standards.,

Because the performance of certain PORV designs appears to degrade

with use, consideration should be given to choosing or specifying PORV

designs that can be periodically tested to meet the inservice inspection

and testing requirements of 10 CFR 50.55a(g).
23

-The causes of component failure-in the, events -collected for this

report do not appear to- have any. relationship to -the quality level that

would have been applied to the components had they- been safety-grade.

Safety-grade components of similar design suffer similar failures -

especially in the- case. of MOVs. The -air-operated (spring-closure)

relief valve designs -appear to mechanically fail mostly through seat

leakage, while the pilot-operated designs ;appear more likely to stick

open (and challenge the BV). (See events at Davis-Besse and TMI-2 in

Appendix B, Table B.1.)

A severe challenge to-safety could occur in a PWR if the PORV

sticks open-and the BV fails to close, that'is,-a small-break LOCA. On

the other hand, PORV or BV seat leakagei'(occurring after closure) is a

tolerable condition that can be mitigated through normal shutdown procedures. -Based on a review of the failure' events collected for this

study, it is concluded that the greatest safety benefit could be

achieved by using PORV designs which are resistant 'to 'sticking open,

coupled with- 'improved -diagnostics, maintenance, and testing of PORVs,

BVs, and BV motor operators. Appendix E contains a summary from the

Electric Power Research Institute (EPRI) of recommended testing,

diagnostic,' and maintenance practices for-PORVs and BVs; '

As for BV motor operators, considerable NRC 'and industry-effort is'

presently being applied to improving valve motor-operator reliability in

nuclear power plants. Based on a review of the BV failures in this report, it appears that the application of advanced diagnostic techniques

and improved maintenance and testing of BV operators could provide more

reliable' operation of this key 'component.' Reference 7 contains a detailed analysis of valve motor operator aging and service wear effects.

- 6.7 To What Extent Was Valve QA/QC Inadequate?

The sources of information for the PORV and BV failure events collected for this report do not contain information about the level of

quality assurance (QA)/quality control (QC) applied to the component(s)

in question. Each of the valve manufacturers contacted for this project

indicated that they -have QA program in place and -that it -conforms to the

requirements of Appendix B of 10 CFR 50. -Their nuclear grade PORVs are

constructed to ASME Sect. III under 10 CFR 50 Appendix B when so specified by the utility or architect/engineer (A/E). A judgment -as to

whether the -QA/QC applied to the PORVs involved in the reported events

was adequate was not possible. - -'

6.8 To What Extent Have Other Human Factor-Considerations

Affected the Valve Failures That Have Occurred

(i.e., Procedures, Maintenance Practices,

Control Room Configuration?)

Section 4.4 of this report summarizes the operator and maintenance

actions that may have contributed to the failures. The human factors
24

that may have contributed to these- events are complex and interrelated. Such-detaifwas not available in the sources of operating experience. data searched- for this report. 'Th4 PORV manufacturers con- *

tacted for this-project 'stated that there was-'little feedback from utilities regarding; the 'effect' of procedures or' maintenance practices on

PORV reliability.' All PORV manufacturers provide-maintenance procedures

for their valves and-felt that-most utilities followed them.

6.9 What Are the Most Common Failure Mechanisms for

PORVs and BVs?

A review 'of the PORV mechanical failure events indicates that most

problems occurred due to sure steam/water cuttin the seat/plug

interface, eventually leading to leakage. En only one event was boric

acid a problem. In this case, boric acid cr buildup on the

(Dresser) valve, lever (exterior to the valve) was given as one of several reasons for the PORV sticking open. No events reviewed listed

boron incompatibility:with,PORV materials as a possible failure cause.

Other problems,-for PORVs included acking leka e (probably due to

agin heg parts.

For block valves, motor-operator torqueand limit switch problems

and valve packing leakage,were involved in most of the failures. An assessment of. MOV servicewear and aging,is contained in Ref. 6.

--Inte-ina leakage was the predominant PORV mechanical failure mode

apparent from the study (61%). This is leakage through the valve seat

into the valve outlet tailpipe. Only 12% of the PORV mechanical failure

events involved a failure to open.

For PORV-controls,-52 out of 91 events (57Z) involved a degradation

of the air or electrical actuation controls' that 'would have prevented

operation of the PORV if it had been required. Eleven events where the

FORV unintentionally opened resulted mostly from inadvertent or accidental actuation by human'error.

For BVs, about one-third of the events 'involved external leakage,

and about 'one-third'involved'failure of the BV to close on demand.' Such

'failure'can''pose a threat to safety if it occurs in coincidence with a

i stuck-open PORV. For" this reason, ability to close is the most important function for PORV BVs.'-

There are a- number of apparent PORV internal leakage events, and

many plants operate 'iith the BV closed when the unit is at power'.

Therefore, it is also important that the BV be able to open reliably as

well as close.

A summary of the identified failure modes for PORVa and BV is

shown in Tables 6.2 through 6.4.

I
25 <I.

Table 6.2. Failure modes - PORV mechanical

B&W W CE Total

Leakage - internal' 19- 33 10 62

Leakage - external - 3 - 3

Fail to open 3 8 1 12

Fail to close 4 3 - 7

Other 6 6 5 17

Total 32- 53 16 101

Table 6.3. Failure modes PORV controls

~B&W W CE Total

Fail to open 3 '2 1 6

Fail to close 1 '1 -2

-Spurious opening 1' 4 6 11

Control'degraded 1 49a 2 52

Other 4'. '12 4 20

Total 10 68 13 91

a~enty-.five events involved recurring'prob-

' les with-'nitrogen control systems at North Anna 

and 2.,

I I

Table.6.4.. Failure modes - BVs

Leakage - external, 12

Fail to open , 2

- . Fail .. -to-close.- 12

Spurious opening 3

- .Other O , 3

Total 32

I ,
26

7. SUMMARY

PORVs and their BVs were not designed as safety-related components. They are used to relieve reactor coolant pressure at a level

below the setpoint of the spring-loaded- pressurizer code safety

valves. This prevents the lifting of the code safety-valves and the

resultant increased maintenance frequency that is usually required to

tightly reseat them (necessitating cold shutdown). The pressure-relieving capacity of the PORVs is normally not considered in plant safety

analyses. The PORV block valves are installed because of expected leakage through the PORVs. The pressure-retaining elements of PORVs and BVs

are within the reactor coolant pressure boundary and are constructed to

the same codes and standards as those required for safety-related components within the reactor coolant pressure boundary.

Neither PORVs nor BVs have been shown by safety analysis to be

needed for safe shutdown of the plant or mitigating the consequences of

accidents. However, NRC has 'recently determined that PORVs are, in

fact, relied upon to mitigate certain design-basis accidents. The

acceptability of relying on nonsafety-grade PORVs to mitigate a designbasis accident is presently the subject of NRC Generic Issue 70: "PORV

and Block Valve Reliability."

In support of the resolution of GI-70, the purpose of this study

was to survey nuclear plant operating experience for PORV and BV failure

events. The survey yielded 230 events occurring from 1971 to mid-1986,

including PORV, PORV BVs, and their associated controls. One hundred

and one events involved mechanical failure or degradation of the PORV;

91 events were attributable to the PORV controls. -There were 32 BV

failure events of which four involved BV controls. Six events involved

the design or fabrication of PORVs.

Although the root cause of the majority of the identified failures

could not be determined, the proximate cause. appears to be wear, galling, or steam/water cutting of the valve disk and seat. The nine B&W

plants accounted for adisproportionate number of mechanical failures in

comparison to W and CE plants. The B&W plants use the Dresser/Crosby

type PORV design and accounted for 45% of the PORV mechanical failure

events. The close tolerances and greater number of moving parts exposed

to steam in those designs can make them more susceptible to failure.

Careful selection of materials and proper design for the expected

service conditions are necessary. New pilot-operated PORV designs from

Crosby and Target Rock appear to be more reliable and are qualified as

safety-grade components. The air-operated (spring-closure) type PORV

designs appear less susceptible to catastrophic (stuck-open) failure

than the pilot-operated relief design. However, note that a substantial

number of events (over-'70%), describing failed or 'degraded PORV controls, involved problems with the air/nitrogen control components

required to operate the air-operated (spriing-closure)'PORV.

Seventy-six percent of the PORV mechanical'failures surveyed in the

report were judged as degraded. Operator and maintenance errors were

involved in only 18% (41) of the events; of these, 6 events were drawing

or administrative error, and 25 were mechanical or electrical maintenance mistakes. An improvement in operations and maintenance QA could

effect some reduction'-in these'types errors. '
27

8. CONCLUSIONS

Based on a review of the failure events, 'it is concluded that, the

greatest safety benefit could bejachieved by using PORV designs that are

resistant to sticking open. Upgrading the PORVs,' operators, or control

components to safety-grade status could each effect a reduction' in PORV

failures. A new PORV design from Target Rock and improvements incorporated in the new Crosby/Garrett"design may provide higher reliability,

but 'neither has been in service long' enough'to provide long-term operating experience.

BV reliability could best be enhanced by upgrading them to safetygrade status, where'more rigorous testing,' 'diagnostics, and maintenance

are required. The QA normally 'applied to maintenance on safety-grade

components may reduce the incidence of maintenance-induced failures. A

summary of EPRI-recommended testing, diagnostic, 'and 'maintenance

practices is contained in Appendix E.

The most common mechanical failure mechanism for PORVs appears to

be degradation of the seat/disk interface or other internal' parts by

high-pressure steam and/or water. ,No reported. events mentioned: boron

incompatibility as contributing' to PORV or' BV failure. However, an

event that involved a stuck-open' PORV' occurred at Oconee 3 in June

1975. The causes of the failures given in the sources of information

reviewed included: (1) heat expansion, (2) boric acid crystal'buildup

on the 'valve lever (on the exterior of the' valve)', (3) rubbing of the

lever against the solenoid brackets, and (4)' bending 'of the solenoid

spring bracket. This was the only reported event that specifically mentioned boric acid crystals. No events found listed'boron incompatibility with ORV materials as a cause'of failure. '

Internal leaking was the most common failure mode apparent from

this study. Of the seven failure-to-close events, four occurred at B&W

units and were considered to be serious challenges to safety (especially

the TMI-2 event).

Most PORV BV failures involved torque switch failure or misadjustment. Proper coordination of valve packing adjustment, operator maintenance, and setup of motor-operator torque switches, limit switches,

and torque-bypass limit switches would considerably enhance MOV reliability. A more thorough analysis of MOVs is contained in Ref. 7.
28

9. REFERENCES

1. Letter, James P. Knight, Washington, D.C., to Guy A. Arlotto, "RES

Assistance on Generic Issue No. 70 - PORV and Block Valve Reliability (July 1985).

2. PWR Safety and ReZief Valve Test Program-VaZve SeZection/Justification Report,. EPRI NP-2292, Electric Power Research Institute, Palo

Alto, Calif., December 1982.

3. W. W. Weaver, "Estimating Failure-to-Close Probabilities for Pressurizer Valves," NUREG/CR-0027, Proceedings of the International

Meeting on Thermal Nuclear Reactor Safety, American Nuclear Society,

February 1983.

4. LER Summary Report on Valves, Report EGG-EA-5125, NUREG/CR-1363,

Vol. 1, June 1980. -

5. Reliability/Availability Data CoZlection and Analysis System, Report

NPGD-TM-378, Babcock and Wilcox, Lynchburg, VA, 1981.

6. R. J. Borkowski et al., The In-PZant Reliability Data Base for Nuclear Plant Components: Interim Report - The Valve Component,

NUREG/CR-3154, December 1983.

7. W. L. Greenstreet, Aging and Service Wear of Motor-Operated Valves

in Nuclear Power Plants, NUREG/CR-4234, June 1985.

8. E. G. Silver, The 21/55 Data Base Users' Manual, NUREG/CR-4011,

July 20, 1984.
29

Appendix A

DATA BASE SEARCH PARAMETERS

Gross Number of

Source Search strategy number of events after

events screening

NOACRECON Keywords: VALVES, MAIN COOLING 185 110 PORV

SYSTEM, REACTOR COOLANT, 32 BV

REACTOR PWR, "PORV," "POWER

OPERATE" + "PILOT"

NOACSCSS System: Pressurizer; PORV and 363 74 PORV

BV Failures 22 BV

NPE NSSS: CE, B&W, and W 202 78 PORV

System: RCS 12 BV

Component: safety/relief valve,

control valve

NPRDSa NSSS: CE, B&W, and W 78 13 PORV

System: RCS 0 BV

Component: pressure relief

valves, pressure control

valves

aNo specific PORV (motor-operated) BV events could be obtained from

NPRDS because the structure of the NPRDS does not permit searching by

component function, that is, PORV or PORV BV. A compilation of MOV

failure data taken from NRDS is contained in Reference 7.
31

Appendix B

EVENT TABLES
go

Table .l. UW PORV events - mechanical falalr.m

Event MM~~~~~~~~~~~~~~~PR Utility

Plant date lecrIptlon/iallure cuse Severity Manafactatrer/ valve Corrective action

model No. 1.1.

AlO-I 9/7'. POltV lifted and tuck open; F D*reaserlll533VX-l0 PSV-00 Redesign location here the

pilot vent line design faulty 1/2-In. vent lne joins te

*-In. PORV discharge pipe

lUpped pilot and ain sent

Crystal RIver 3

Davis-besse

Oconee I

1118/19

118180

612319

I11/22/8 5

9/241/7

10/fl

,S 5578

10126/19

2118182

6/9/8 S

2/3/75

Loaks; wear of Internal*.

Bad disk aeat

Seat leak at sating aurfaces

PORV failed to open on demand, and another PORV

transferred open

POxV lifted nine tmes; pilot tem filed

close relay missing

Pilot tem clearance problems

Broken valve ate.

Pilot valve and main disk leaking

Lek. through ; - -

POxV failed to close on third actuation;

failure cause undetermined

leaks; manufacturing and/or InstallatIon

error

Lltt box failure

Scarred valve seat

L.aks pst seat, worn disk

Seat scarred

Pilot leakage

leak abnormal wear on seat of main

valve and pilot

Leaks; trash under seat

worn est

Valve seat and disk scratched, leaks pst

seat

Carbon buildup on cotl contacts (coil

located on the valve)

D

D

D

F

Diresser/31IM3V-10

Dresser/3l SIMY-30

Dressternii IV-lf lApped nd rebuilt

0 CrosbvyitPV-SN Repalrs made

1019/16

1/19/77

1/21/i7

10//77

Oconee 2 11/73

5/26/77

8/23/78

6/29/79

7/1/82

I . . - . . ./2 2/9

I11/22/83

D Crosby/IIPY-SM

F Crosby/HiPV-SN.

0 Crosby/HIPV-Slt

0 .Crtoby/HiPV-N.

F Croisby/RIPV-S

o Dresser/3153VX-30

.0 Drosser/3153MV-30

D Dresser/3153VX-30

D Dresser/31333VX-30

D Dresser/31533VX-30

0 Dresser/31533VX-30

D Dresser/31533VX-30

0 Dresser/31533VX-30

0 Dresser/31533VX-30

O Dreaaer/315lIYX-30

IF Dresser/3153]VX-30

RC-ZA

RC-ZA

RC-ZA

RC- 2A

IC-2A

Stem and bonnet Were replaced

Lpped pilot and main disk

replaced all gaskets

Rteplaced internals

Pending

1apped

Replaced IlIit box

lUpped

Replaced dsk

Lpped

WwA

21 C-66

Cleaned nd repaired

2RC-66

21c-66

Lapped the valve seat and

disk

Cleaned the coil eontacts
Table .l. (continued)

PORV Utility

plent tdaetnet Description/failure cause Severity Kanufacturer/ valve Corrective .'tion -ate MAPI No. I.D.

Ocone3 6/74 Vent failed to open r Dresser/315)3VX-30 IRC-66

2/5/75 Leaks D Dre,.er/3lS)1VX-10 Lapped

6/13/15 Vent failed to open; boric acid builidup; F Dresser/l1513VX-30 3RC-66 Valve repaired

bent lever on pilot valve

7/20/16 Leak; seat worn badly D Dreaaer/3133VX-30 Repaired

Rancho Seco 6/11/18 PORV and V leaking D Dresser/lISIVZ30. PV-21511 Replaced POIV and the disk'

seat was lapped on the block

valve

9/19/83 Position Indicator weight caused pilot F Dresaer/l1iIVXIO rv-21511 Poaltion Indicator was valve to open. opening POKV removed, and a different

method of position

Indication was used

TMI-I 8/31/82 PORV Internals corroded F Dresser/lMllMVX)0 IC-RV2 Installed spare. POXV was

refurbished

2/11/83 ORV Intarnala rusted and pitted; traces F Dresser/3153)VK)0 RC-lV2 Refurbished POKV (from

of sulfur on Internals; pilot valve 8/31/82 event) was re- disk was stuck; mIn valve disk was Installed

stuck closed

TKa-2 3/28/19 POXV stuck open F Dresser/31533VX-30 RC-l2

a 6/23/79 PORV leaked D Dreseer/11533VX Lapped seat and rebuilt valve

"Wo plant dentification available.

Li

C
I 

Table B.2. B&W PORV events - control failures

Plant ~Event Plant + Edae Description/failure cause Severity Corrective action,

Crystal River 3 11/75 Stuck solenoid F

2/26/80 Power supply was lost; PORV open due to a F

faulty circuit design In the NNI; PORV

could not be closed

6/3/82 Position indicator was out of tolerance' D Preamplifter was recalibrated

Davis-Besse 9/24/77 Missing seal-in relay caused PORV to cycle F PORV was reworked; seal-in

9 times, then stick open relay installed(?)

Oconee 2 -8/73 Wiring error F

5/12/82 Hook-up wire blocked control relay contact F Rerouted hook-up wire

2/21/84 Coil contacts had carbon build-up F Cleaned coil contacts

Rancho Seco 3/20/78 Operator changing a light bulb dropped F

light bulb and shorted out NNI power; PORV

disabled

TMI-2 3/28/78 Loss of power to PORV actuation channels F

9/78 Failed to open F
Table .). V PORV events - echanical failures

Event Plant date

leansu 8/20/14

Callabay I 12/11/84

Connecticut Yankee 1917

3/12/83

Cook I 1/24/84

Description/lfailure cause

Stuck open; fractured valve yoke

Excessive PORV leakage; Ve had to be

closed

PORVS were deteriorating causing ecesaive

leakage and loss of operbillity

Seat leakage; disk cracked

Seat leakage; cause unknown

PORV sect leakage; PORV was isolated

POIV lifted bt leaked on reseat; seated

after pressure reduced

Opening times were 2.5 longer than

permitted

Gasket failed

Valve will not operate; bent stem

Volve will not open; diaphragm failed

Seat leakage; wear

Sect leakage; Incorrect Installation

Farley 2

Ginna

Indian Point 2

Kewaunee I

4/26/81

6/19/83

I/19/81

9/19/15

6/10/76

1/22/71

8/6/83

12/5/84

PORV Utility

Severity manufacturer/ valve Corrective action

model No. I.D.

F

D Garrett/stralght

through or

Copes-Vulcan

D-IUO-160

D Crosby

D Copes-Vulcan/

D-100-160

D Hasonelln/

38-20771

D Copes-Vulcan/

D-100-160

D Copes-Vulcan/

D-100-160

D Copes-Vulcan/

D-100-160

D hasonellan/

3-20721

F Masoneilan/38-20721

r Hasoneilan/38-20721

D ?lasonelln/

38-2072

D Hasonellan/38-20721

PR-570

NRV-I 51

445 A

430

PCV-4 56

PR-2A

PR-28

PK-21

PR-2A

PR-2A

Replaced Crosby valves with

Copes-Vulcan air-operated

valves

Disc welded nd machined to

fit

Replaced plug, stem, packing.

seat ring and gasket; reset

stroke

PORV repaired when plant conditions permitted

Valve was cycled open. then

shut

Replaced gasket and lapped

valve seat

Installed new valve internals

Raplaced diaphragm

Replaced steam, plug. eat

and gaskets

Replaced plug stem, seat ring

and gskets

W

aN

., 
6.

table .3. (continued I)

Plant

?fcCutre I

North Anna I

date Description/failure cause

1/3/82 PORV ieat leakage; V ws closed

4/2/82 PORV seat leakage; bMe were closed

12/22/85 PORV out-of-celibrstion and fail to open

- 3/80 PORV tailed to actuate

11/82 PORV we echanically blocked" n the

open positton; the steel "block" fell

out and left valve closed

9/21/84 Sent leakage; proper adjustment of vlve

stem

6/24/80 Cocked bearing In valve operator; PORV

inadvertently opened and then failed to

close; maintenance unknowingly cocked

the bearing; the event we attributed to

an inadequate procedure

3/15/76 Valve lecked through; plug and seat cut

Severity

0

D

F

F

PORV

anufacturer/

model No.

Control components/

drag valve

Control componenta/

drag valve

North Anna 2

Point Beach I

I . .

D Hasoneilan/

38-20721

F Hasoneilen/

20.000 series

0 Copes Vulcsn/

D-100-160

D Copes Vulcan/

D-100-160

D Copes Vulcan/

D-100-160

D Copee-Vulcen/

D-100-160

Utility

valve

l. D.

NC-32

NC-34

PCV-1456

I RCPCV1456

PCV-2456

1-431C

Corrective action

PORV repaired during 2/82

outage

PORV repaired

A ore substantial "blocking'

device was to be designed and

provided

24 tem threads showing;

screwed down 6 threads and

leaking stopped

The cocked bearing was

corrected and the spring

pressure readjusted

Reachined and lpped plug

and seat; reinstalled with

new gaskets

Adjusted valve stem downward

Reaachined cage and plunger.

repacked valve

Installed a new plug, cage.

gaskets. and packing

W

4/18/77

6/25/77

7/2/83

Stem out of adjurtment; valve leaked

Valve leaked through; cage and plunger worn

Seat leakage; degraded cage and plug
Table .]. (continued)

EIvtRV UtilIty

Plant Description/falture cause Severity Manufactrirer valve Corretive .¶cti2n date m)del o. 1.11).

Robinson 2. S/18/79 PORVa had long troke times; scored valve )

Sale I

Salem 2

Sequoysh I

Sequoyah 2

4/29/13

6/81

t/S/82

1/1/82

6/22/80

5/15/81

atems

POV ftailed during teating; galling f plug

to cage

POtV leakage due to team cutting of valve

cage

POV leaking through

PORV would not open in manual

Foreign material or dryetroking cause4

valves not to reseat

PORV leakage caused by galling of the plug

6/18/81 POIV seat leakage; generic problem

7/9/81 Valve leaked through

1/21/83 POXV seat leakage; generic problem

1/25/84 POkV failed to reset during test,

BV slow to close

10/26/81 POlV leaked due to Improper adjustment of

*te coupling

4/21/83 POET leakage

9/12/83 Valve feled to open; leaking through; valve

not fully closed

11/9/83 POE? leakage; crack n valve seat

D Capes-Vulean/

D-1no-1ho

n Canre-Vuleanl

n-mo(-u^(n

n) cope-vul *an'

F Cnpes Vlean/

) Copes-Vl canI

n- 11)0- I

D CopeaVulcan/

D-100-160

D Copes-Vulcan/

D100-160

0 Copes-Vulcan/

D-100-160

D Copes-Vulcan/

D-100-160

D Copes-Vulcan

D-100-160

D asonellan/

20.000 series

D Masoneilan/

20.000 erits

F

0 Copes-Vulcan

D-100-160

RC-4%C

I PRI

I PRI

I PR. P0RV disissembled nd waitIng parts

Parts were refurbished

2 PRI PORV were odified by Installing plugs of a different

material

2 PRZ PORV was Isolated

2 PRZ Scheduled for repair during

next refueling outage

The POIV plugs were scheduled

for replacement

All damaged cmponents were

rep I ced

The valve cage ws rplaced

2 PR2

I -PVC68-340

I-PVC-68-

340

PCV-68-340

2-FCV-68-

340

Stem coupling was readjusted

POEV* scheduled for replacement

PoRVs scheduled for replacement during 12/83 refueling

outage

Valve vendor replaced seat

4
9

Table .3. (continued)

PORV UtIIity

Plant Edvent Desrtption/failure cAuse Severity ManufActurerl valve Corrective action

date ~~~~~~~~~~~~~~~~~~~~model 'Jo. 1.0.

Summer 10/20/82 POY sest leakage; steam impingement on 0 PCV-445k Valve scheduled for repair

seat PCV-4453

2/17/83 POR seat leakage D PCV-4458

4/10/84 Seat leakage; cage deformed; design error D Copes-Vulcan/ PCV-444h Ileavy wall cage pacer and

D-100-160 new trim ssembly were nitalled

- 7/3/84 Seat leakage; cage deformed 0 PCV-4458

Surry I 1/26/82 Leaking FORV and V D Copes-Vulcan/

D-MO-160

10/2/82 Leaking diaphragm 0 PCV-1455C PORV was overhauled

2/4/83 PORV would not cycle F PCV-1455C

Zion 1 1/20/76 Seat leakage D Copes Vulcan/ PCV-455C Install new plug, stem,

D-100-160 cage, spacer, gasket. and

diaphragm

7/22/84 Seat leakage; wear plus possible radiation 0 Capes-Vulcan/ PCV-455C lapped n plug and seat; redamage 0-100-160 packed, set stroke

Zion 2 12/18/83 Seat leakage; wear D Copes-Vulcan1 PCV-456 Replaced valve stem, stem

D-100-160 assembly seat, and gaskets;

repacked valve; set stroke

and preload

a 3/23/75 Plug scored, cage frozen; valve would only F Copes-Vulcan/ Installed new sten, plug.

stroke 1/4 n.. frozen open D-100-160 cage, and gasket

a 3123/75 Bonnet leak; plug scored, cage frozen; F Copes-Vulcan/ Installed new stem, plug.

valve frozen shut D-100-160 cage, and gasket

a 7/7/75 Seat leakage; cage fits tight 0 Copes-Vulcan/ Durting outage, replaced stem

D-100-160 and dise assembly; cage

reconditioned

a 1/14/76 Seat leakage D Copes-Vulcan/ Seats relapped - valve still

D-100-160 leaks; scheduled for repair

net outage

0

11 plant identification available.

%D
Table B.4. W PORV events - control failures

Plant Event Description/fallure cause Severity Corrective action

Connecticut Yankee 8/13/79 PORV and BV opened due to failure of pressure

controller

D

2/4/80 PORV actuated due to dirty contacts

4/3/81 Pressurizer pressure controller malfunction;

PORV and V opened

11/1/83 Loss of control air; filter leak

11/28/83 Loss of control air; filter leak due to

worn threads

1/8/83 PORV emergency air actuation system failure;

allowed PORV to drift closed during test

D A connector was reinstalled

properly

F Isolated leak, incorrect

0-ring was installed, correct 0-ring was then Installed

F Replaced entire filter

canister

F Regulators were readjusted

to a higher pressure to ensure the valves would remain

open

0 Cook 2

7/3/83 Lack of air supply for PORVs due to administrative errorF Air supply was restored

10/8/83 PORVs drifted closed; air supply

regulator set low

2/17/83 PORV controller failure; defective driver

card

D Regulator adjusted to a

higher pressure

Farley 2 F Installed new card
a

Table .4. (continued)

Plant

Ginna

Indian Point 2

McCuire 1

McCuire 2

North Anna I

Event

date

5/6/80

1/2 5/82

1/19/81

4/3/81

3/26/82

6/5/82

4/1/83

3/78

12/31/80

3/18/81

Description/failure cause

Both PORVs inoperable; DC power switches

in the "off" position

PORV stuck open due to faulty pilot solenoid

valve

Opening time 2.5 seconds long; nitrogen

supply valve closed

PORV actuation setpolnt set too low

PORV position ndication light failure

PORV. position ndication lost due to pinched

cable at limit switch

Low pressure:signal to PORV; air trapped

in pressure transmitter

PORV failed to open; pressure interlock not

jumpered out; procedure error

PORV nitrogen supply low due to frequent

cycling during preparation for refueling

PORV tanks leaked

SevcerIty

F

Corrective action

F Solenoid valve was replaced

D Nitrogen valve reopened

F Pressure was reduced

D Socket contacts were adjusted

to contact bulb, and the

socket will be replaced

F The-wire and conduit were

repaired

F Transmitter was bled

F Revised procedure

P Design and modifications have

been undertaken

F Both PORV nitrogen low-temperature overpressurization

systems were repaired

-':
Table 8.4. (continued)

Plant Event Description/failure cause Severity Corrective action date

North Anna I

(continued)

10/7/81 PORV nitrogen supply low F A temporary nitrogen supply

was used

5/10/82 PORV nitrogen supply low

5/19/82 'A' PORV declared inoperable; two days later

'B' PORV was found to be inoperable for an

indeterminant time; nitrogen isolation valve

closed for indeterminant time

5/19/82 PORV nitrogen supply low

F A design study has been

completed and the system

will be modified

F

F Manual blocks were installed

on both relief valves

5/25/82 PORV nitrogen supply low

6/82 PORV would have opened 20.5 psi above limit;

pressure transmitter drifted low

12/7/82 PORV nitrogen supply low

12/11/83 PORV nitrogen supply accumulator relief

valve failed

F A design study has been

completed and the system

will be modified

D Transmitter was recalibrated

F Nitrogen relief valve was

repaired

F Nitrogen relief valve was removed, inspected, and reinstalled
Table .4. (continued)

Plant Event Description/Failure cause Severity Corrective action

date

North Anna 2 8/80

8/14/80

,. .I

9/2/80

1112/80

.. .- .j

6/20/81

8/6/81 &

8/17/81

Nitrogen supply low

PORV nitrogen supply low

; : - , . ...

Low nitrogen due to high plant usage

PORV nitrogen supply low

PORV nitrogen supply low

PO.V nitrogenupply low

PORV nitrogen supply low

PORV nitrogen supply low

Stroke times were 2.4 a long; Improper setting of nitrogen pressure

regulator

PORV nitrogen-supply low

F Nitrogen tanks recharged

F Gas supply recharged; design changes expected

F Nitrogen supply tanks recharged; recommended actions

have been-proposed to fix

entire nitrogen supply

system

F Future corrective actions

will be based on the Investigation In' progress

F Repairs to'reduce leakage

have'been made

F A full nitrogen tube truck

was ordered and used to repressurize the tanks

F Gas supply tanks refilled

F A design study has been completed, and the system will

be modified

D Regulator readjusted

F A design study has been completed, and the system will

be modified

3/8/82

5/16/82

5/26/82

-6/5/82
Table B.4. (continued)

Plant Event Description/failure cause Severity Corrective action date

North Anna 2

(continued)

7/10/82 PORV nitrogen supply low

8/20/82 & PORV nitrogen supply low

8/28/82 three times on 8/28/82

10/82

1/8/83

4/6/83

Acoustic monitor failed

Lost valve position indication for PORVs

PORV nitrogen supply low

F A design study has been completed, and the system will

be modified

F A design study has been completed, and the system will

be modified

D Passive channel put In

service; action channel to

be repaired during a

subsequent outage

D maintenance-performed on a

remote valve indicator for

solenoid valve SV-2551A

F A design study has been completed, and the system will

be modified

5/15/83 PORV nitrogen supply low F Regulators were reset

Point Beach 1

Point Beach 2

6/28/83 No position Indication; circuit breaker was

open

9/25/82 Valve in instrument air line closed; PORV

was Inoperable

D Closed circuit breaker

F Instrument air line opened;

bad procedure

4
Table B.4. (continued)

Plant Event Description/failure cause Severity Corrective action date

Robinson 2 11/4/83 PORV failed to meet required cycle time;

limit switches msadjusted

D The limit switch was repaired

and a small leak on the operating diaphragm was repaired

Salem 2

12/15/84 Both air and nitrogen to PORVs were isolated; system drawings and procedures

in error

3/1/82 POP.valves were closed, which rendered both

PORVs . inoperable.,

1/22/83 POPS declared inoperable due to excessive

leakage

1/26/83 PORV control-air system failed; surge

caused excess flow check valve to close

8/30/83 POPSvalve failedto demonstrate operability

due to problems with valve position ndicator

F

F Valve reopened and operator

was counseled, -,

F Problem investigated during

current outage',

D Control air system was.returned to normal lineup; the

vent was restored

D The controls of the PORVS

have been modified to

function as POPS valves

vow

San Onofre I 6/18/81 PORV controller settings caused cycling

during transients

D PORV control was placed in

manual mode; will repair.

automatic controller

Sequoyah 4/21/83 Valve failed to open;,failed coil in ASCO

Model LB831654 solenoid

F Scheduled for repair at

first outage

4/2/84 PORV bistable alarm lights mswired F Both PORVs on both units were

.- rewired
Table 8.4. (continued)

Plant

Sequoyah 2

Summer I

Event

date

4/2/84

6/6/83,

7/7/83

Description/failure cause

PORV bistable alarm lights miswired

PORV.nitrogen supply pressure regulator

drifted (PCV-445ZA-RC)

PORV nitrogen supply pressure regulator

drifted PCV-448-RC)...

Possible inadvertent opening of PORV

upon loss of power

Low back-up air pressure

Both PORV.control air supplies were

degraded

Se v

8/31 /83

10/2/82

2/9/83

!rity Corrective action

F Both PORVs on both units were

rewired

F The limit switches and the

regulator were adjusted

D Nitrogen supply header pressure control regulator was

replaced

D Design needs to be corrected

F Air bottles were replaced

D Replaced-backup air bottle

for one PORV, and emergency

air bottles were replaced

for the other

D Check valve reinstalled

correctly

F

Surry 1

4'

Surry 2

2/11/83 Instrument air check valve installed

backwards

5/27/80 Accumulators for both PORVs were vented, and

the instrument air source was isolated;

PORVs inoperable

5/21/81 Due to a wiring problem the pressure inputs

to the PORVs were eliminated

F
t " a

Table .4. (continued)

Plant Event Description/faI lure cause Severity Corrective action

Turkey Point 4 11/28/82 Overpressure mitigating system failed to F

operate; pressure transmitter isolation

valve closed

Zion 2 6/18/80 Accumulators for both PORVs were vented and F Changed procedures to block

the instrument air source was isolated; open PORVs during integrated

-'PORVs inoperable leak rate test

2/26/75 Air line to PORV leaking D Installed new air hose on air

operator

aPlant identification not available.

.I 11
Table .5. CE PORV events -echanical Wa lures

FORV Utility

Plant Description/faiure cause severity Hanufacturer/ valve Corrective action

model No. I.D.

Calvert Cliffs 1 7//19 PORV failed to seat after test D Dreamer/3153VX-30 RC-402-ERV The pilot valve stroke was

adjusted

10/18/80 Set pressures adjusted incorrectly by D Uft pressures were

manufacturer (both valves) readjusted

3/1/81 POIV leaked due to low RCS pressure D RCS pressure was increased

and PORV stopped leaking

Calvert Cliffs 2 8/22/77 Leak D Dresser/153VX-30 Cleaned

Millstone 2 12/29/83 PORV seat leakage; foreign material on seat 0 Dresser/31533VX-30 2-RC-404 The valve was successfully

flushed

Palisades Early PORV seat leakage (ll PORVa) D Dresser/1511VX-30 PORVs were disassembled,

1972 lapped, and the connecting

piping modified to reduce

stresses on the valve body

8/30/80 PORV leakage. PORV pilot was held open by F 10423 The spring guide was brazed

the solenoid plunger; plunger spring slipped back onto the guldeplate

St. Lucie 2 4/28/83 Possible failure of PORV pilot solenoid valve D PORV was retested with dusmy

signal to pilot valve and

PORV operated normally

5/14/83 POSV position Indication magnet lost agnetism D Garrett/Angle Valve 1475 The magnet was replaced

due to high temperatures

5/23/83 PORV position Indication magnet lost mag- D Garrett/Angle Valve 1474 The magnet was replaced

netie- due to high temperature

6/3/83 POXV position indication magnet lost D Garrett/Angle Valve 1475 The magnet was replaced

magnetism due to high temperature

7/4/83 POXV position indication magnet lost D Garrett/Angle Valve 1474 The magnet was replaced

a 7/22/76 Seat leakage D Dresser/31533VX Replaced disc, guide, rings

a 11/28/19 Pilot valve and main valve seating surface D Dresser/31533VX-30 I-ERV-404 Replaced pilot and main valve

cut discs

a 1/25/80 Pilot valve and main valve seating surfacee D Dresaer/31533VX-30 1-ERV-402 Replaced pilot disc and

cut lapped main valve disc

a 12/9/80 Valve lifted, failed to reseat tightly; D Dresser/31533VX Lapped seat and reinatalled

seat leakage

4Plant Identification not available.
.

Table .6. CE PORV events - control failures

Plant I Event Description/failure cause Severity Corrective action date

Calvert Cliffs I 1/80 PORV actuated on erroneous signal; bumping

of pressure transmitter cabinet

D This over-pressure protection

circuitry was disabled, and

PORV actuation was a function of the RPS during normal operation

7/16/81 PORV actuated on erroneous signal; bumping

of pressure transmitter cabinet

4/26/83 While troubleshootinga short circuit

caused loss of control power to PORV; short

circuit due to technician error

D A mechanical stop was installed to protect the

-- transmitter -

F Control power was restored

CalvertCliffs 2 1/18/81 PORV opened due to pressure transmitter

failure

F

40

2/3/83 PORVs opened when two RPS channels were

inadvertently de-energized -

D Wiring error corrected

8/24/84

Ft. Calhoun I 12/20/78

Override handswitches were in the "override"

position and PORVs would not open

Defective procedure; technician pulled

recorder fuses which opened both PORVs;

operator closed PORVs

F The procedure has been

changed to require operator verification

D MVe closed; design changes

considered so that removal

of recorder fuses will not

disable PORVs
Table B.6. (continued)

Plant Event Description/failure cause Severity Corrective action date

Maine Yankee 11/83 PORVs may not actuate due to single relay D Design modifications

failure under LTOP procedures initiated

Palisades 9/71 PORV opened; technician de-energized the F Closed.BV, corrected nonRPS breakers, which de-energized the feed standard drawing notation

to the PORV pilot valve solenoids.

11/23/81 Licensed operator error (Administrative); D Procedures will be reviewed

valves were declared operable without

following procedures

8/13/83 PORVs do not provide LTOP when shutdown D The LTOP system will be

cooling system Isolation valves are open evaluated and modified as

necessary to allow PORV

opening

St. Lucie 1 3/23/81 PORV acoustic flow position indicator was D A spare transducer and cable

inoperable were installed

St. Lucie 2 4/24/83 Pressure transmitter was erroneously F A valve lineup was performed

isolated by.unidentifled personnel to ensure no further instrumentation was isolated

in

a

4 4
Table 8.7. PORv Y Event,

Event Description/ Valve Utility Motor operator Plant date failure cause Severity manufacturer/ valve manufacturer/ Corrective action

model o. I.n. model So.

ANO-2 (W) 6/79 Failed torque avitch; V F NV-32196 Limltorque/ The switch was replaced

Beaver Valley I ()

Calvert Cliffs I (CE)

Connecticut Yankee

(U)

failed to close

4/28/81 V operator limit switch damaged; bent pinion gear and

shaft

Sm-n

NOV-tC-5, Limitnrque Replaced limit switch

11/13/81 hV packing leak Backseated valve; valve was repacked during subsequent refueling outage

Operator overrode the open signal8/13/79 DV and PORV opened a a result

of the pressurizer pressure controller

2/80 tV opened on spurious signal from

pressure controller; dirty

contacta

4/3/81 tV and PORV opened spuriously;

pressurizer pressure controller

connector came loose

F MOV-5h9

F MOV-569

F MOV-569 The connector was reinstalled

LnI..

Crystsl River 3 (W) 9/27/83 Torqueasvitch failed; V failed

to close

F RCV-I I Linitorque Replaced torque switch

Cook I (W) 1/20/86 tV packing leak D NM0-151 Valve was repaired

McGuire 2 W) 4/27/83 DV packing leak, eye bolts failed D Borg Verner 2NC-]lt ROTORK Repairs are scheduled for 6/83
Table B.7. (continued)

Event Dacription/ Valve Ut ity Motor operator Plant Severity manufacturer/ valve manufacturer/ Corrective action date failure cause model o. 1.D. model No.

Millstone 2 (CE)

North Anna I (W)

Oconee I (BJW)

Robinson 2 (W)

Sales 2 ()

San Onotre I (W)

6/10/79 body-to-bonnet seal failed

9/28/81 body-to-bonnet seal ring leakage

12/6/81 tY motor operator electrical

failure due to torque switch

3/4/82 tV body-to-bonnet joint leaked

until RCS temperature and pressure raised

7/82 BVs suffered packing leakage

3/1/83 tV leakage Into containment

11/19/82 BV control cable connections

loose; BV could not be opened

12/19/73 H.D. failure; valve stuck open

11/30/81 DV operator did not receive proper

PM; BV failed to close

6/25/83 BV packing leak

7/25/84 DV slow to close; broken wire In

the valve operator circuit

6/4/85 BV filed to close fully;

actuator diaphragm leaked. part

of diaphragm was missing

0

D

I.

Velan/SA-182

Veln/SA-182

Velan/SA-182

2-RC-405

2-RC-403

2-RC-403

Limitorque/

SMB-000

Limitorque/

SMB-000

Limttorque/

SMB-000

The valve gasket and spacer

ring were replaced

Replaced seal ring

Motor torque switch and geared

limit switch ssemblies were

replaced

D Velan/SA-182 2-RC-403

0

D

F

F

F

D

D

Velan 2-RC-403 &

2-RC-405

2-RC-40S

Replaced seal ring

MOV-1 536

Velan/3-6SBSN

Loose connection tightened

Override thermal /L to close

valve

Limitorque/ Valve repaired under vendors

SHB-OOO-5 direction

Scheduled for repacking at

cold shutdown

Limitorque Readjusted

Actuator diaphrsgm was replaced

U'

Velan

Anchor Darling

RC-536

2 PR 6

CV-530

'J I I .J 1
Table .7. (continued)

Event Descipio/ Valve Utility Motor operator Plant date ;elrp on %everity manufseturer, Us Imauacurer/ Corrective action

drdel No. I.D. model No.

Sequoyah 2 () 11/10/81 tV poattton limit switch gear D 2-FCV-6R-331 Limit switch was replaced

broken; DV position could not be

verified

3/21/82 RV operator torque switch setting F 2-FCV-68-333 Linttorque Torque switch setting was

too low for operational conditions; increased

sV would not close

Sumer I () 10/1/82 tV would not reopen after teat; F MVG-800'. Stem packing was replaced

packing too tight; overtorque on

opening

10/10/82 IV packing leak n MVG-8000C Packing was replaced

12/16/83 Packing leak D MVG-8000A Valve packing was replaced

Surry I () 1/26/82 sV would not close coqpletely; re- D Velan MOV-1536 Ltitorque DV was cycled satisfactorily

quired manual assistance at cold shutdown; however,

- - torque switch was replaced

6/18/82 DV would not close completely D MOV-1536

either remotely or anually; RV

was closed by overriding the

torque and limit switches

St. Lucie I (CE) 4/16/81 RV packing adjusted too tight; F Velan MV-1403 Packing gland adjusted and

sV would not close maintenance cautioned

8/2/81 NV would not close due to failed F nV-1403 Loose electrical connection

limit switch; excessive leakage was tightened

through packing

2/26/82 BV would not shut F Velan/P35036-2 MV-I403 Closed manually n 57 mIn

Turkey Point 3 () 12/30/84 sV would not close completely; D Velan MOV-3-535 Torque switch was replaced

faulty torque switch

n

W
Table .8. PORV events -design/fabrication failures

Event Description/ PORV Utility Plant date De au e Severity manuf ac trer/ valve Corrective action

model No. 1.1).

Ginna (W) 5/79 Valves had Incorrect discharge D Copes-Vulcan/ Copes-Vulcan wasexpediting delivcoefficient (Cv - 42 Instead of D-1(0-160 ery of properly sized Internals;

Cv 50) scheduled for installation during

the next cold shutdown so that

valves could be isolated

Indian Point 2 () 8/78 Newly Installed valves had D ropes-Vulcan During the 1979 refueling outage.

Incorrect discharge coefficient D-100-160 the existing valve trim sets were

(Cv - 38.5 instead of C - 50) removed and replaced with the

proper trim sets

Indian Point 3 () 8/78 Newly installed valves had D Copes-Vulcan During the 1979 refueling outage,

Incorrect discharge coefficient D-100-160 the existing valve trim sets were

(Cv - 38.5 Instead of C - 50) removed and replaced with the

proper trim sets

Prairie Island I (W) 2/80 Discovered in 1180 that addi- U Copes-Vulcan Ordered material; scheduled repair

tional conax fitting required D-100-160 for planned outage

to meet environmental qualification for PORV

Prairie Island 2 () 2/80 Discovered in 11/80 that addl- D Copes-Vulcan Ordered material; scheduled repair

tLonal conax fitting required D-100-160 for planned outage

to meet environmental qualification for PORV

Salem 2 () 8/80 Limit switches on PORV were D Copes-Vulcan Limit switches were to be replaced

not seismically and environ- D-100-160 at next cooldown with qualified

mentally qualified limit switches

.1 -C

I
. .

55

Tablee - -Plant

Appendix C

'HUMAN ERROR EVENTS

Table C.1. Human error events

"Event dat , -Evet Description

Operators

3/20/78 Operator dropped light bulb -

* . shorted NNI power 

7/3/83 Lack of air supply for PORVs due

to administrative error

2

4

Rancho Secc

Cook 2

'4 !' Ginna 5/6/80 Power switches off

4 Indian Point 2

4 North Anna li

4- North Anna 1-

4- Point Beach 1

4 Point Beach 2

4 Salem'2

6 Palisades

: , . I

1/19/81 N2 supply valve closed

3/78 'PORV failed to open; pressure

interlock not jumpered out;

procedure error

5/19/82 N2 supply valve closed

6/28/83 .. Circuit breaker open

9/25/82 Instrument air line valve

. closed-faulty procedure

3/1/82 POP valves were closed, which

rendered both PORVs inoperable

11/23/81 Licensed operator error (ad-

.ministrative) - valves were

declared operable without following procedures . '.. . I - ..

-1 ''11- Maintenance/I&C

- 2/3/75 'Possible installation'error . . . I I 1 '' Oconee 1

2 Crystal River 3

2e 2 . - - I

2 Oconee 2

6/3/82 Position indicator out of

tolerance

5/12/82 Hookup wire blocked contacts
I

56

Appendix C

Table C.1 (continued)

Event Table Plant date Description

2 Rancho Seco 3/20/78 Operator changing a light bulb

dropped light bulb and shorted

out NNI power; PORV disabled

3 Kewaunee 1

3 North Anna 1

3 North Anna 1

3 North Anna 2

3 Salem 2

3 Sequoyah

4 Connecticut

Yankee

12/5/84 Seat leakage; incorrect installation

9/21/84 Seat leakage; improper adjustment of valve stem

11/82 PORV was mechanically "blocked"

in the open position; the steel

"block" fell out and valve

closed

6/24/80 Cocked bearing in valve operator; PORV inadvertently opened

and then failed to close; maintenance unknowingly cocked the

bearing; the event was attributed to an inadequate procedure

6/22/80 Foreign material or dry stroking

caused valves not to reseat

10/26/81 PORV leaked due to improper adjustment of stem coupling

2

4/3/81 Mis-installed connector

4 North Anna 2

4 Point Beach 2

4 Robinson 2

4 Sequoyah 1 and 2

4 Surry 1

5/26/82 Improper regulator adjustment

9/25/82 Valve in instrument air line

closed; PORV was inoperable;

bad procedure

12/15/84 Both air and nitrogen to PORV

were isolated; system drawings

and procedures in error

4/2/84

2/11/83

PORV indicating lights miswired

Instrument air check valve installed backwards
57

Appendix C

Table C.1 (continued)

Table Plant Event Description date

6 Calvert Cliffs

6 Calvert Cliffs 1

6 Calvert Cliffs 1

6 Ft. Calhoun 1

6 Palisades

6 St. Lucie 2

7 Robinson 2

7 St. Lucie 1

7 Summer 1

1/80 PORV actuated on erroneous signal; bumping of pressure transmitter cabinet

4/26/83 While troubleshooting, a short

circuit (due to technician

error) caused loss of control

power to PORV

7/16/81 PORV actuated on erroneous signal; bumping of pressure transmitter cabinet

12/20/78 Technician pulled recorder fuses

which opened both PORVs; Operator closed PORVs; defective

procedure

9/71 PORV opened; technician deenergized the RPS breakers,

which de-energized power supply

to the PORV pilot valve solenoids; nonstandard drawing

notation

4/24/83 Pressure transmitter was erroneously isolated by unidentified

personnel

11/30/81 BV operator did not receive

proper PH; BV failed to close

4/16/81 BV packing adjusted too tight;

BV would not close

10/1/82 BV would not reopen after test;

packing too tight; overtorque on

opening
59

Appendix D

PORV MANUFACTURERS INTERVIEW SUMMARY

Four PORV manufacturers were contacted and asked to informally

respond to a list of questions provided by NRC. The four manufacturers

are:

Dresser Industrial Valve-Operations

Copes-Vulcan ' ' '

Target Rock Corporation

Crosby Valve and Gage Company

Alexandria, LA

Lake City, PAEast Farmingdale, NY

Wrentham, MA

Each was visited and interviewed on an informal basis to obtain

their response on questions related to PORV manufacturing, installation,

testing, maintenance, and operation.

This Appendix contains the questions from the NRC and a summary of

the responses from the personnel contacted at each facility. The

responses do- not necessarily reflect- individual corporate 'policy, but

are the result of interviews conducted in an informal, conversational

manner.

. .

. . . .

: -

:, ' - . : '

s

. . . . .

..

. * . ............... .
1. Since 1971, are PORVs constructed to Section III of the ASME Boiler and Pressure Vessel Code? Prior

to the introduction of the 1971 Edition of Section III of the Code, were PORVs constructed to codes

and standards such as the Draft ASHE Code for Pumps and Valves and ANSI B31.1.0?

COPES-VULCAN: CopesVulcan PORVs are constructed to ASME Section

III pressure-retaining

requirements. Prior to

1971, Copes-Vulcan used

ASME pump and valve code.

CROSBY: Older versions

(HPV-SN) were built to

ASME Section III requirements; these are the only

PORVs Crosby built for

nuclear units. Crosby has

a new design (a modified

Garrett design) but none

have been ordered.

DRESSER: PORVs are

constructed to ASME

Section III pressureretaining capabilities

but not to Code relieving

capacity requirements.

Prior to 1971, Dresser

PORVs were built to 1968

Article 9 Code.

TARGET ROCK: Yes;

Target Rock did not make

any PORVs prior to 1971.

All have been constructed

to ASME Section III Code.

2. Are PORVs Code stamped? If they are not code stamped, what is the reason for not stamping?

COPES-VULCAN: All CopesVulcan PORVs for nuclear

application are N-stamped

ASME Section III, Class

I.

CROSBY: Crosby PORVs are

code stamped.

DRESSER: Dresser PORVs

are N-stamped as pressure

boundary. All pre-1971

PORVs are not N-stamped;

AEs (NSSS) did not

require it in specs.

TARGET ROCK: All PORVs

supplied by Target Rock

to date have been Nstamped: Bellefonte,

Sequoyah, Watts Bar,

Midland are also qualified to IEEE-382 (1972),

-323 (1974), and -344

(1975).

0%

0

3. Are PORVa constructed to Seismic Category I requirements?

COPES-VULCAN: CopesVulcan supplies Seismic

Category I if the

customer requests it;

Copes-Vulcan provides

calculations for seismic

design. They have run

IEEE qualification tests

for certain customers.

CROSBY: Old design had

no seismic requirements

specified by utility/-

NSSS. New design is

qualified to Seismic

Category I requirements.

DRESSER: Dresser PORVs

were not constructed to

Seismic Category I

requirements;. NSSS did

not ask for it.

TARGET ROCK: Midland and

TVA valves were all

qualified to Seismic

Class I requirements.

I} f U
4 VA

4. Are PORVe constructed in accordance with a Quality Assurance Program in conformance with 10 CFR 50,

' ,1 , Appendix B?

'COPES-VULCAN:''Nuclear

* PORVs (ASME'Section.III)

are constructed to.

10,CFR 50 Appendix Bwhen

* specified by customer.

CROSBY: Crosby has a QA

program in conformance to

10 CFR 50, Appendix B. All

nuclear PORVs are

constructed to these

requirements.

5. Are the design features f PORVs for nuclear

not, describe the differences.

COPES-VULCAN:' Nuclear CROSIBY: Old.version -

PORVs are identical to nuclear and fossil

similar relief valves in designs arethe same

other ervice. Nuclear except for class H

units have mate ial insulation for solenoid.

traceability, NDE, etc. New version - unique

to meet QArequirements design for nuclear use -

and ASME Sction II1. not used in fossil units

Design features and-, due to cost.

materials meet ASME

requirements.

DRESSER: Since 1971,

Dresser has applied QA

requirements meeting

10 CFR 50 Appendix B.

service identical to those

DRESSER: The basic

design and principle of

operation is the same for

Nuclear PORVs and

commercial-grade PORVs.

Nuclear valves have

material traceability,

NDE, etc. to meet QA

requirements and ASME

Section III.. Most nuclea

PORVs have a bellows in

the pilot valve to

preclude packing leakage

to environment.

TARGET ROCK: All Target

Rock nuclear PORVs are

constructed in accordance

with 10 CFR 50 Appendix B

requirements.

for nonnuclear service? If 

TARGET ROCK: The design

,features are similar;,

-however, most non-nuclear

service valves are-

,subjected to higher.

temperatures, and as such

-utilize different

materials.
6. Are there differences in the construction of PORVs for nuclear service compared with the construction

of PORVs for non-nuclear service other than that associated with the Quality Assurance Program that

is in conformance with 10 CR 50, Appendix B?

COPES-VULCAN: Nuclear

PORVs are identical to

similar relief valves in

other service. Nuclear

units have material

traceability, NDE, etc.

to meet QA requirements

and ASKE Section III.

Design features and

materials meet ASME

requirements.

7. What modifications

modifications made

CROSBY: Old version -

nuclear and fossil

designs are the same

except for class H

insulation for solenoid.

New version - unique

design for nuclear use -

not used in fossil units

due to cost.

DRESSER: The basic

design and principle of

operation is the same for

Nuclear PORVs and

commercial-grade PORVs.

Nuclear valves have

material traceability,

NDE, etc. to meet QA

requirements and ASME

Section III.

TARGET ROCK: Nuclear

service valves are

qualified to IEEE

standards as stated above

in 2. PORVs for nonnuclear service receive

the same QA program

(10 CFR 50, Appendix B) as

nuclear service valves.

have been made to PORVs since they have been used in nuclear service? Were these

because of nuclear service?

COPES-VULCAN: CopesVulcan experienced minor

problems with early units

(mid 60s) with trim

parts - came out with a

"quick-change" trim and

resolved problem. No

significant modifications

made for conditions

unique to nuclear

service. Copes-Vulcan

feels that ASME material

requirements limit

improvements in nuclear

PORVs. They believe they

can make a better PORV

with newer materials but

Code does not allow use

of new materials, so

nuclear designs are

essentially unchanged.

CROSBY: New version -

since acquiring the

Garrett design, Crosby

modified the bonnet joint

gasket configuration and

the pilot valve seat

design to provide better

sealing.

DRESSER: PORVs at Oconee

and TMI were equipped

with heavier springs to

allow use down to 50 psi

versus nominal 2300 psi

design operating pressure; an improved

latching device for

bottom plug was added on

-2 and -3 models.

Otherwise no other

significant design

changes.

TARGET ROCK: Only

modifications are to

assure compliance with

IEEE requirements (2

above) requires radiation-resistance solenoid

insulation. (Supercritical fossil applications are actually

tougher, valves than

nuclear service other

than solenoid.)

Q f .
I a

8. Are any future modifications anticipated for PORVs used in nuclear service?

COPES-VULCAN: No future

modifications are planned

due to Code restrictions

(see 7 above) and diminishing nuclear market.

CROSBY: No modifications

planned at this time.

DRESSER: Dresser has

developed an improved

PORV design to'meet IEEE382, but no prototypes

have been made or tested

yet; no demand for

Environmentally Qualified

valves from utilities.

Dresser is presently,,:

redesigning commercial

version of Electromatic -

mostly for simpler

maintenance and better

TARGET ROCK: No modifications are planned;

present Target Rock

nuclear PORV is considered by Target Rock to be

superior to other

designs.

I . .

- !r ., ,,,I.,1; I,

reliability (fewer . - . or parts)._

9. Is there feedback from utilities, architect engineers, or nuclear steam system manufacturers with

respect to operational or maintenance problems of PORVs? 0'

WA

COPES-VULCAN: Some early

units experienced gasket

problems, but CopesVulcan resolved these

problems long ago. No

other feedback from

utilities. They rarely

hear from AEs or NSSS

suppliers.

CROSBY: Utilities -

little feedback excep

occasionally through

field service personn

or sales representati

AEs - no feedback.

NSSS - some feedback

during start-up phase

plant operation, but

little after that.

t

DRESSER: Utility

feedback is variable;

they don't always get the

el complete story on

ves, problems that occur, as

they (Dresser) hear of

problems long after they

of occur. Some utilities

communicate regularly;

others are never heard

from. AE firms do not

order PORVs, hence no

feedback.' Dresser,

interfaces with NSSS

suppliers on new reactors

- they'specify valve.

TARGET ROCK: Operational

or maintenance problem

feedback (if any) comes

from utilities. AEs and,

NSSSs are out of the

picture by the time the

PORV is operational.

Target Rock deals with

utilities mostly in spare

parts and maintenance.
10. Are you requested by utilities to perform maintenance on PORVs?

COPES-VULCAN: CopesVulcan has a force of

service engineers who do

perform field maintenance

when requested.

CROSBY: Occasionally

called in on back-fit

jobs, but not on older

PORV versions.

DRESSER: Dresser has a

field service group that

is frequently called to

work on PORVs, but at a

test facility (like

Wyle). They rarely go to

plant to work on valves.

TARGET ROCK: On occasion. mostly during

start-up to make sure

valve is ready for

service after handling

during shipping, storage,

inspection, construction

installation,, and hookup.

Target Rock has experienced cases-where valve

was shipped in sealed,

clean condition only to

find valve installed with

loose or missing parts,

dirt, etc. which has

compromised all QA

applied by Target Rock to

assure unit meets

specifications.

11. Do you know if utilities perform maintenance

the manufacturer?

on the PORVs in accordance with your recommendations as

COPES-VULCAN: CopesVulcan has no feedback

from utilities concerning

use of Copes-Vulcan

procedures/maintenance

manuals supplied with

valve.

CROSBY: Crosby offers

in-house or on-site

training for utility

personnel for repair and

maintenance. They provide

all maintenance manuals

and procedures for PORVs.

They have only experienced one case where

utility did not follow

Crosby procedures.

DRESSER:. All utilities

are given Dresser maintenance procedures and

should base their maintenance procedures on the

Dresser Manual.

TARGET ROCK: Utilities

are provided maintenance

instructions as part of

the contract, but work to

date, however, has been

conducted by Target Rock

personnel.

4 'I <
12. Do you know if utilities utilize replacement

original manufacturer of the PORV?

parts for PORVs other than those supplied by the

COPES-VULCAN: CopesVulcan knows of only a

few utilities that have

purchased non-CopesVulcan parts, but only on

other in-plant valves,

not PORVe. Pressure

boundary parts ust be

NPT stamped anyway and

Copes-Vulcan can provide

these. Some "pirate"

manufacturers have

produced inferior parts

(per Copes-Vulcan) but

Copes-Vulcan knows of

none used in nuclear

plants or PORVs.

13. Are you aware f

COPES-VULCAN: CopesVulcan has not heard of

any cases of boroninduced failure or

incompatibility of PORV

materials with boron.

CROSBY: Crosby has

experienced no problems

with "outside" replacement parts for PORVs at

domestic plants -

utilities use vendorsupplied parts.

DRESSER: Dresser knows

of no cases where nonDresser parts were used

In their valves.

TARGET ROCK: For Nstamped valves, no; they

(utilities) don't

normally hold an N-stamp

to make parts for PORVs.

o any indications of boron induced failuresor incompatibility with PORVs?

U' a

CROSBY: In 1974 or 1975,

Davis-Besse PORV (old

Crosby design) had, some

boron precipitate buildup in discharge passages

of pilot valve - it was

cause of valve sticking

open. Seat leakage

through a relatively cold

valve caused precipitation. No problems

experienced on new units

to date.

DRESSER: Dresser has,

observed no cases of

boron-induced failures

their PORVs; but field

service personnel only

see valves at test.

facility, where it has

been cleaned and

decontaminated for

shipping and testing.

TARGET ROCK: Target Rock

has no information

regarding boron-induced

failure of their PORVs.

in
14. Does orientation, location or nuclear service operating environments/operations of the PORV in the

reactor coolant system present a concern from your viewpoint as a PORV manufacturer?

COPES-VULCAN: Some

piping configurations in

nuclear plants (a "U"

bend before PORV) cause

water to collect in bend.

When PORV lifts, relatively cool water passes

through valve followed by

two-phase steam/water at

higher temperatures and

supersonic velocity. Such

conditions seriously

stress valve internals

and can lead to leakage.

Problem is generally

plant-specific.

CROSBY: Crosby designs

valve to specifications.

Most specs call for

"upright" orientation, so

no problems with orientation.

Location -\valve should,

be located to see either

full steam pressure (loop

seal) or water (300'F)

with a loop seal configuration. If there is a

loop seal that permits

water greater than 300'F

to collect, when the PORV

is operated, the two-phase

water/steam flow through

the valve can wire-draw

the seat. On the other

hand, a loop seal that

upon operation introduces

cool water first, then

progressively hotter

water, then steam, can

place high thermal stress

on valve. Preferred

location is with no loop

seal so only steam passes

through valve.

DRESSER: Dresser PORV is

designed to operate in

specified system and

environmental conditions.

In early years, some

utilities operated valves

in 'environmental temperatures hgher than

specified by NSSS, but

this is no. longer a

problem. (Mostly affected

safety valves, not

PORVs.) The construction

practice of "acking"

piping into place to mate

with PORV has caused

problems in the past.

TARGET ROCK: PORV

orientation is important

for Target Rock units.

Target Rock prefers a

mounting that positions

solenoid about 10°

below horizontal (or

better) to allow water to

collect in bonnet, which

keeps solenoid cooler

than if mounted vertically upward. Other nuclear

service conditions are

not considered a problem.

as

a'

9 ,
15. To what extent have human factors considerations, such as procedures and maintenance practices,

affected PORV failures?

COPES-VULCAN: No

experience or feedback

regarding human factors.

CROSBY: Only one case

Crosby knows of -

maintenance people did

not read Crosby procedure. Have heard of cases

where "generic" procedures were used on PORVs

- with consequential

problems.

DRESSER: Dresser field

service personnel stated

that they rarely see

cases of mismaintenance;

only recalled one

instance of a valve

damaged by poor maintenance.

TARGET ROCK: Since there

is no periodical maintenance required on TargetRock PORVs, there is

little chance of human

error in normal operation. Most problems occur

during construction and

start-up phase (see 10).

16. What are the failure mechanisms of the PORVs?

COPES-VULCAN: Galling, CROSBY: Human-induced DRESSER: Observed

disk/seat leakage mismaintenance - cases failure mechanisms-have

(thermal transients), where generic",proce- been:. pilot leakage

seat cutting from two dureswere used on PORVs (rare), pilot bellows

phase flow' - - with consequential leakage (rare), seat

problems. leakage, pin corrosion

-: i,. , - -- , (rare), binding of

solenoid bearings.

17. What are the failure modes of the PORV9?

TARGETROCK: Target Rock

considers seat/disc "wire

drawing"-as mostcommon.

0%

-j

COPES-VULCAN: Leakage

mostly -no cases of

stuck open or' closed.

CROSBY: In the case of

human-induced mismaintenance - the valve stuck

open.

DRESSER: Observed

failure odes have been

seat leakage, failure to

operate (solenoid burned

out or. insufficient.power

to operate solenoid).

TARGET ROCK: Seat/disc

"wire drawing" causing

seat leakage.

I, :.
18. Is the control system for the PORV supplied as part of the PORV overall system?

COPES-VULCAN: CopesVulcan does not provide

control systems.

CROSBY: Crosby does not

provide control systems

for nuclear PORVs.

DRESSER: Dresser has not

supplied PORV controls

for PWRs; they do supply

them for commercial

applications.

TARGET ROCK: Not on

nuclear applications.

19. Do you know if utilities use control systems that are supplied by other than the PORV manufacturer?

COPES-VULCAN: Controls

usually provided by NSSS

supplier.

CROSBY: Controls usually

provided by NSSS supplier. ,

DRESSER: PWR utilities

have PORV controls

generallydesigned by

NSSS supplier and

supplied by NSSS.

TARGET ROCK: Nuclear

utilities usually. have

their PORV controls 

designed by NSSS and/or

AE.

20. To what extent would upgrading of control systems for PORVs to safety-related status provide an

increase in the reliability and operability or PORVs?

COPES-VULCAN: CopesVulcan had no comment.

CROSBY: No comment -

Crosby does not provide

control systems for

nuclear PORVs.

DRESSER: On PWRs, only

portion of PORV Dresser

would have to upgrade

would,be the solenoid -

possibly use a redundant

(dual) solenoid design.

Dresser has not provided

nuclear PORV controls.

0'

TARGET ROCK: Target Rock X

has no opinion - feels

their valve as supplied

is extremely reliable.

Designation of safetyrelated would have no

effect on design - they

are already ASME Section

III and IEEE-qualified;

also Seismic Category I.
a

21. To what extent would upgrading of PORVs to safety-related status provide an increase in the

reliability and operability of PORVs?

COPES-VULCAN: Upgrading

PORV itself would not

effect any change In

design or materials -

valve would be the same.

CROSBY: New version

Crosby PORVs meet IEEE323, 344, & 382 standards

for safety-related

components. Crosby feels

that new version (modified Garrett design) is

extremely reliable.

DRESSER: Possible

improvement using

redundant solenoid - but

in their experience,

solenoids have not failed

very often.

TARGET ROCK: Little

difference in safetyrelated valves; Target

Rock feels their PORV is

reliable as is.

22. To your knowledge, are your installation, operating and preventive

followed?

COPES-VULCAN: Copes-. CROSBY: Yes in most DRESSER: Yes.

Vulcan'has'no feedback on cases; see #15 above.

this subject., -

maintenance instructions

TARGET ROCK: Installation procedures- see

#10. Operating and '

preventive maintenance

instructions are generally'followed - occasion-

'ally'Target Rock provides

special instructions if

asked by utility.

. - _ Z

.I .

0' 'Is

%0 .
23. Give a brief description of the level of equipment qualification that has been performed on your

PORVs. Please list the standards, such as EEE-323, iEEE-344, etc. to which you have qualified your

PORVs and the approximate dates of completion of your Environmental Qualification program.

COPES-VULCAN: Although

PORV as a whole has not

been tested in IEEE-323,

various supplied components are qualified -

limit switches, solenoid

valves, etc. Some

actuators are qualified,

but they were used in

other nuclear systems,

not PORV.

CROSBY: Crosby PORVs

(new version) meet IEEE323, 344 and 382 standards.

DRESSER: No Environmental Qualification has

been done on PORVs from

Dresser - was never part

of specification.

TARGET ROCK: The Target

Rock PORV has been

qualified to IEEE 323-

1974, 344-1974, and 382-

1972 and 1980. The Target

Rock Solenoid Valve

Qualifications are

directly applicable to

the Target Rock PORV, and

in addition, the PORV was

subjected to a separate

qualification program for

B&W.

24. Of the PORVs you have supplied, were any purchased specifically to perform safety-related "active"

functions; that is, they must open and/or close under normal, upset, and faulted-conditions? -4

0

COPES-VULCAN: Only one

AE specified the PORV as

safety-related - it was

for a foreign plant. No

domestic plants'have

specified a safetyrelated PORV from CopesVulcan.

CROSBY: All new version

PORVs supplied perform

"active" functions and

meet safety-related

requirements (see 21).

DRESSER: None. TARGET ROCK: The valves

supplied to TVA were

required to perform

safety-related functions.

"I $I .*.
r

25. Do you, as a PORV manufacturer, have any suggestions or recommendations regarding the use of PORVs

for safety-related service in PWRs? Do you feel they are suitable for this type of service?

COPES-VULCAN: CopesVulcan has better

materials available for

PORVs, but Code and ESpecs do not allow use.

Same materials have been

used in PORVs for years.

See 7.

CROSBY: Correct maintenance is key to PORV

reliability - Crosby

feels most problems come

from mismaintenance.

DRESSER: Dresser

suggests use of Environmentally Qualified

solenoids or redundant

solenoids; otherwise no

changes. They feel their

valves have operated

satisfactorily and are

suitable for nuclear

service. Operating

conditions are not

significantly different

from commercial units.

TARGET ROCK: Target Rock

feels that more frequent

testing while in service

will result in higher

reliability. The Target

Rock valves are designed

specifically for this

service and will not

suffer deleteriously when

subjected to frequent

testing.

-4

I- -> ;.
73

Appendix E

SUMMARY OF EPRI-RECOWMENDED TESTING, DIAGNOSTIC, AND

MAINTENANCE PRACTICES FOR PORVs AND BVs

* Use of a planned maintenance/refurbishment program based on detailed,

written procedures which are either furnished by the valve manufacturers or written by the plant maintenance personnel based on manufacturers' guidelines.

* Bench testing to verify operability and leaktightness of the valves

before they are reinstalled on the pressurizer to permit deficiencies

to be corrected without affecting plant availability. Note that the

bench testing should simulate as-installed valve conditions (e.g.,

valve orientation, valve body temperature) as close as practicable.

* Engineering tracking and evaluation of valve failures at the plant

and applicable experience at other plants in order to identify

required modifications to achieve more reliable performance.

* Performance of valve surveillance tests based on the requirements of

ASKE Section XI, Subsection IWV. This periodic exercising during

plant shutdowns permits valve operational deficiencies to be identified in a manner which minimizes the impact on plant operations.
75

NUREG/CR-4692

ORNL/NOAC-233

Dist. Category AN, RM

Internal Distribution

1. H. E. Trammell 17. H. D. Haynes

2. J. R. Merriman 18. D. Hendrix

3. J. R. Buchanan 19. ORNL Patent Office

4. G. T. Mays 20. Central Research Laboratory

5. D. M. Eissenberg 21. Document Reference Section

6. W. L. Greenstreet 22-33. Laboratory Records Department

7. A. P. Malinauskas 34. Laboratory Records (RC)

8-10. J. W. Cletcher II 35-37. Nuclear Operations Analysis Center

11-16. G. A. Murphy 38. J. A. Getsi

External Distribution

39-41. J. R. Zahorsky, Crosby Valve Company, 43 Kendrick Street,

Wrentham, MA 02093

42-44. Vito Liatonio, Target Rock Corporation, 1966 East Broadhollow

Road, East Farmingdale, NY 11735

45-47. N. E. Matson, Copes-Vulcan Inc., P. 0. Box 577, Lake City, PA

16423-0577

48-50. Steve Danielson, Dresser Industries, P. 0. Box 1430, Alexandria, LA 71309-1430

51. S. P. Carfagno, Franklin Research Center, 20th & Race Streets,

Philadelphia, PA 19103

52. B. M. Morris, Division of Engineering Technology, Office of

Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission, 5650 Nicholson Lane, Rockville, MD 20852

53-55. J. P. Vora, Division of Engineering Technology, Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission,

5650 Nicholson Lane, Rockville, MD 20852

56. V. P. Bacanskas, Franklin Research Center, 20th & Race Streets,

Philadelphia, PA 19103

57-59. W. S. Farmer, Division of Engineering Technology, Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission,

5650 Nicholson Lane, Rockville, MD 20852

60. F. C. Cherny, Engineering Issues Branch, Office of Research,

U.S. Nuclear Regulatory Commission, Washington, D.C. 20555

61-63. R. Kirkwood, Engineering Issues Branch, Office of Research,

U.S. Nuclear Regulatory Commission, Washington, D.C. 20555

64. C. Michelson, ACRS, 20 Argonne Plaza, Suite 365, Oak Ridge, TN

37830

65. Office of Assistant Manager for Energy Research and Development, Department of Energy, Oak Ridge Operations Office, Oak

Ridge, TN 37831

66-67. Technical Information Center, Department of Energy, Oak Ridge,

TN 37831

68-327. Given distribution as shown in NRC categories AN and RM.
%PC FORM 23 US NUCL9AUNIGt TOPTL~O COPUIOf IOhTOIT NuMg"@ Ij,.br aT IOC ~ V0 

%2CM 1 02NUREG/CR-4692

32xo3N2 aBIBLIOGRAPHIC DATA SHEET ORNL/NOAC-233

Sit ISTRUCTIONSO . mT1 nllIva Dist. Category AN, MI!

2 TITL AIO SUITLI S~t LEAVE SLA~'

Operating Experience Review of Failures of

Power Operated Relief Valves and Block

Valves in Nuclear Power Plants DT*00 COPLTIC

S AUT,.~~~~~~~~~~~~a~~~~sI A. ~~~~~~~July 1987

C. A. Murphy .or.ouSSuw

J. W. Cletcher II* BA W 

*PAI, Incorporated August 1987 ? PSR'ADt.G oA - ^LtAIO* RAME ARO Guis Y ddit LOOhI As~.J C S PUICTTA.o. Io~hIbT t4USA

Oak Ridge National Laboratory FINOR GAbTLI

Post Office Box Y B0828

Oak Ridge, Tennessee 37831

hO SDO INI.OAGANuIZAyTOb4 kA^ ANDAILlADONICSSI.*M C Il TOF REPORT

Division of Engineering Technology

Office of Nuclear Regulatory Research Topical

U.S. Nuclear Regulatory Commission b 011` COVREo lDA{_

Washington, D.C. 20555

'2 UP'L.tE TAF- OT92

*J .S31fl41 .ale .11W

This report contains a review of nuclear power plant operating events

involving failures of power-operated relief valves (PORVs) and associated block

valves (BVs). Of the 232 events identified, 103 involved PORV mechanical failure, 91 were attributable to PORV control failure, 6 events involved design or

fabrication of the PORVs, and 32 events involved BV failures. The report contains a compilation of the PORV and BV failure events including failure cause

and severity. The events are identified as to plant and valve manufacturer.

An assessment of the need to upgrade PORVs and BVs to safety-grade status concludes that such action would improve PORV and BV reliability. The greatest

improvement in reliability would 'result from using newer, more reliable PORV

designs and improving testing, diagnostics and maintenance applied to PORVs

and BVs, particularly the BV motor operator. A summary of interviews conducted

with four PORV manufacturers is also included in the report.

'A O0CU0 .T * AALS. .WORDS OSCINIPTORS

Valves, maintenance, degradation, failure mode, failure cause,

operating experience, relief valves, aging, service wear

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