NUREG/CR-5944

ORNL-6734

A Characterization of Check

Valve Degradation and

Failure Experience in the

Nuclear Power Industry

Prepared by D. A Casada. M, D. Todd

Oak Ridge National Laboratory

Prepared for

U.S. Nuclear Regulatory Commission.

.
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NUREG/CR-5944

ORNL-6734

R9, RM, RV

A Characterization of Check

Valve Degradation and

Failure Experience in the

Nuclear Power Industry

Manuscript Completed: August 1993

Date Published: September 1993

Prepared by

D.A. Casada, M. D. Todd

J. J. Burns, Jr., NRC Project Manager

Oak Ridge National Laboratory

Operated by Martin Marietta Energy Systems, Inc.

Oak Ridge National Laboratory

Oak Ridge, TN 37831-6285

Prepared for

Division of Engineering

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Washington, DC 20555-0001

NRC FIN B0828

Under Contract No. DE-AC5- 84OR21400
Abstract

Check valve operating problems in recent years have

resulted in significant operating transients, increased cost

and decreased system availability. As a result, additional

attention has been given to check valves by utilities

(resulting in the formation of the Nuclear Industry Check

Valve Group), as well as the U.S. Nuclear Regulatory

Commission and the American Society of Mechanical

Engineers Operation and Maintenance Committee. All

these organizations have the fundamental goal of ensuring

reliable operation of check valves.

A key ingredient to an engineering-oriented reliability

improvement effort is a thorough understanding of

relevant historical experience. A detailed review of

historical failure data, available through the Institute of

Nuclear Power Operation's Nuclear Plant Reliability Data

System, has been conducted. The focus of the review is

on check valve failures that have involved significant

degradation of the valve internal parts. A variety of

parameters are considered, including size, age, system of

service, method of failure discovery, the affected valve

parts, attributed causes, and corrective actions.

iii
Contents

Abstract .......... iii

List of Figures ........... ii

List of Tables ........... .. ix

Acknowledgments .............. xi

List of Acronyms .......... .. xiii

1 Introduction.1

1.1 Background.1

2 Study Methodology..

2.1 Scope .5

2.2 Limitations in the Filtering Methodology and Inherent Structure of the Data Base .5

2.3 The Characterization Process .6

2.3.1 Failure Mode .. 6

2.3.2 Extent of Degradation .. 6

2.3.3 General Detection Method .. 8

2.3A Specific Detection Method .. 8

2.3.5 System Usage .. 9

2.3.6 Failure Area or Source .. 9

2.3.7 The Normalization Process .. 10

3 Analysis Results.11

3.1 Component and Plant Age . . .11

32 Valve Size...1

3.3 System ......................... .. 14

3.4 Manufacturers...14

3.5 Nuclear Steam System Supplier (NSSS) . ........................ . 14

3.6 Normal System Usage . .. 15

3.7 Failure Mode...16

3.8 Failure Area...17

3.9 General Detection Method ... 17

3.10 Specific Detection Method ...................... 17

3.11 Discovery Process ................. 17

3.12 Extent of Degradation .................................. .. 17

3.13 Cross-Correlation Results .................................... 19

3.13.1 Valve Age Group Cross-Cofelations .................................. . 19

3.13.2 Valve Size Group Cross-Correlations .................................. 22

3.13.3 System Cross-Correlations .................................... 25

3.13.4 Manufacturer Cross-Correlations .................................. 29

3.13.5 NSSS Cross-Corelations . ........................... 30

3.13.6 System Usage Cross-Correlations ........................... 30

3.13.7 Failure Mode Cross-Correlations ........................... 32

3.13.8 Failure Area Cross-Correlations ............................ 32

3.13.9 General and Specific Detection Method Cross-Correlations ............................................ 33

3.13.10 Discovery Proce Cross-Correlations ss ............................................ 34

3.13.11 Extent ofDegradation Cross-Correlations............................................................................................ 35

3.14 Results of Selected Plant Review......................................................................................................................37

4 Summary, Conclusions, and Recommendations .................................... 39

4.1 Summary .................................. 39

4.2 Conclusions .................................. 39

4.2 Recommendations39

v
References. . . . . . . . . . . . . . . . . . . . . . . . . .

Appendix: Charts of Study Results ...................... 41

v
List of Figures

1.1 Comparison of failures from Scott paper and valves in service ............................................................ 2

1.2 Comparison of all check valve failures and valves in service ............................................................ 2

1.3 Comparison of normalized failure data ........................................................... 3

3.1 Relative failure rate by component age group ........................................................... 11

32 Relative failure rate by plant age group ........................................................... 13

3.3 Relative failure rate and population by size group ........................................................... 13

3.4 Relative failure rate by system for the ten systems with the highest overall failure rate ........................................... 14

3.5 Relative failure rate and population distribution by manufacturer ........................................................... 15

3.6 Relative failure rate and population distribution by NSSS ........................................................... 15

3.7 Relative failure rate by system usage ........................................................... 16

3.8 Distribution of failures by failure modes ........................................................... 16

3.9 Distribution of failures by failure area or source........................................................................................................ 17

3.10 Distribution of failures by general detection method .1

3.11 Distribution of failures by specific detection method .18

3.12 Distribution of failures by general discovery process .18

3.13 Distribution of failures by extent of degradation .18

3.14 Cross-correlation of valve age and size groups .19

3.15 Cross-correlation of valve age group and system for four systems with the highest overall failure rate .20

3.16 Cross-correlation of valve age group and normal system usage .20

3.17 Distribution of failures by failure mode and valve age group .21

3.18 Distribution of failures by failure area and valve age group .21

3.19 Distribution of failures by discovery process and valve age group............................................................................ 22

3.20 Relative failure rate and extent of degradation for valves in < 2-in. size group .22

3.21 Relative failure rate and extent of degradation for valves in > 2- and 4-in. size group .22

3.22 Relative failure rate and extent of degradation for valves in > 4- and < 10-in. size group .23

3.23 Relative failure rate and extent of degradation for valves in >10-in. size group .23

3.24 Relative failure rate by valve size group and system usage .23

3.25 Fraction of failures by valve size group and failure mode .24

3.26 Relative failure rate by valve size group and failure area/source .24

3.27 Distribution of failures by valve size group and failure discovery process . 25

3.28 Relative failure rate by valve size group and extent of degradation .25

3.29 Relative failure rate (by extent of degradation) and valve population distribution for

ESW system check valves for the five manufacturers with the highest failure rate

within the ESW system.26

3.30 Relative failure rate (by extent of degradation) and valve population distribution for

diesel starting air system check valves for the five manufacturers with the highest

failure rate within the diesel starting air system .26

3.31 Distnbution of failures by failure mode for four systems with the highest overall failure rate .27

3.32 Distribution of failures by failure area for four systems with the highest overall failure rate .27

3.33 Distribution of failures by specific detection method for four systems with the highest overall failure rate. 28

3.34 Distribution of failures by discovery process for ten systems with the highest overall failure rate .28

3.35 Distribution of failures by extent of degradation for ten systems with the highest overall failure rate .29

336 Relative failure rate by manufacturer and valve size group for ten manufacturers

with highest overall failure rate .29

3.37 Distribution of failures by general detection method and NSSS .30

3.38 Relative failure rate by system usage and failure mode .31

3.39 Distribution of failures by system usage and extent of degradation .31

3.40 Distribution of failures by failure mode and general detection method .32

3.41 Distribution of failures by failure area and discovery process .33

3.42 Distribution of failures by failure area and extent of degradation .33

3.43 Distribution of failures by general detection method and extent of degradation .34

3.44 Distribution of failures by specific detection method and extent of degradation .34

3.45 Comparison of discovery processes for different type facilities .35

3.46 Comparison of discovery processes for different system usages .35

3.47 Relative failure rate, by discovery process, for failures designated as sigificant.

Systems shown are the ten systems with the highest relative failure rates ............................................... .................. 36

3.48 Distribution of failures by general detection method and extent of degradation .36

3.49 Relative failure rate by valve size group and system usage for failures classified as significant .37

3.50 Average text length for check valve failure narratives characterized vs. failure year .38

vii
List of Tables

2.1 Failure modes descriptions and normal classification .......................................... 7

2.2 General detection method .......................................... 8

2.3 Specific detection methods ........................................... 9

2.4 Operating status of plant systems ........................................... 9

2.5 .10 Description of failure areas......................................................................................................................................... 

3.1 Characterization method charts .......................................... 12

3.2 Summary of results of plant review of ORNL characterizations .......................................... 37

3.3 Summary of failure area plant review .......................................... 38

ix
Acknowledgments

The authors wish to acknowledge the efforts and

contributions of the following individuals, who

contributed to the study in a variety of ways, and

without whom the study could not have been

completed:

* Nathan Wood of ORNL who meticulously

QA'd the initial characterizations for

consistency.

* Frank Grubelich of the NRC, for his

recognition of the need for the study and his

ongoing support and review

* The OM-22 Working Group for their

recommendations on parameters to consider

and approaches to take.

* Mike Robinson of EPRI and NIC, who

coordinated the individual plant reviews of

the ORNL characterizations.

* Ken Hart of Pennsylvania Power & Light and

NIC, who carefully and thoughtfully reviewed

both the study methodology and the plant

feedback and offered helpful, positive

criticism.

* Daryl Cox of ORNL, who supported the data

acquisition and carefully reviewed the results.

Finally, the financial support provided by the

Division of Engineering, Office of Nuclear

Regulatory Research of the NRC, along with the

encouragement and coordination efforts by NRC

Technical Monitors Bill Farmer and Jack Burns,

is gratefully acknowledged.

xi
List of Acronyms

AFW Auxiliary feedwater

ASME American Society of Mechanical Engineers

BWR Boiling water reactor

CCW Component cooling water

CVCS Chemical and volume control system

EPRI Electric Power Research Institute

ESW Emergency/essential service water

HPCI High pressure coolant injection

HPCS High pressure core spray

HPSI High pressure safety injection

LPCS Low pressure core spray

NIC Nuclear Industry Check valve group

NPRDS Nuclear Plant Reliability Data System

NRC Nuclear Regulatory Commission

NSSS Nuclear steam supply system

OM Operations and Maintenance (Committee of ASME)

ORNL Oak Ridge National Laboratory

PWR Pressurized water reactor

RCIC Reactor core isolation cooling

RCS Reactor coolant system

RHR Residual heat removal

WG Working group

xiii
1 Introduction

Oak Ridge National Laboratory (ORNL) has conducted a

review of historical check valve failure data under the

sponsorship of the Nuclear Regulatory Commission's

(NRC's) Nuclear Plant Aging Research Program. The

study involves the review and characterization of failure

records from the Nuclear Plant Reliability Data System

(NPRDS) data base. Failures in which significant

internals degradation was detected are being characterized

in detail. Parameters that are being considered include

the age of the plant when the failure occurred, valve size,

manufacturer, system of service, method of discovery,

affected valve parts, attributed failure causes, and

corrective actions.

1.1 Background

The American Society of Mechanical Engineers (ASME)

Committee on Operation and Maintenance (OM) of

Nudear Power Plants has established a Working Group

on Performance Testing of Check Valves in Light Water

Reactor Power Plants (OM-22), which is chartered with

developing check valve performance test requirements.

The Working Group (WG) met for the first time in June

1990.

Early on, the OM-22 membership recognized that a

thorough understanding of historical failure patterns was

critical to several aspects of the code development

activities being pursued. A literature search by the WG

found that while some historical failure data studies had

been completed and documented, the studies were

normally not oriented toward providing the kinds of

information needed in code development activities.

One study that was initially selected by the WG as a basis

for consideration in the development of disassembly and

examination requirements (note that these requirements

would apply only to valves that could not be properly

tested) was a paper presented by M. L. Scott at the EPRI

Power Plant Valves Symposium 1. Scott reviewed

NPRDS failure records for events occurring during the

years 1985-1987. Moderate seat leakage and external

leakage events were then eliminated from the data.

Failure rate vs. valve size, valve service time, and plant

system were discussed. One of the conclusions drawn by

Scott was that there was a tendency for a large number of

failures relatively soon after installation, followed by a

period of fewer failures during the 4- to 9-year service

period, and then subsequently followed by a sharp

increase in failure occurrences. The sharp increase was

attributed to wear-out of the check valves.

As OM-22 deliberated on the establishment of appropriate

disassembly and examination intervals, the conclusion in

the Scott study regarding the sharp increase in failures

beginning at about 9 years was noted. The WG used this

study as the basis for formulating requirements for 8-year

disassembly and examination limitations for those valves

that could not be properly tested.

During the WG's consideration of the paper and its

application to code development, some questions arose

concerning the technical validity of the WG's basis. As a

result, ORNL was asked to conduct a preliminary review

of failure data. This review was conducted by nonqualitatively tabulating NPRDS reported failures and

valve populations during the years 1985-1987 (the years

of the Scott study) as well as the years 1984-1990.

The preliminary review indicated that the age-related

aspects of the study appear to have been heavily

influenced by the age of plants in operation during the

years considered. Figures 1.1 and 12 illustrate the basis

for this observation.

Figure 1.1 provides comparative plots of the number of

valves in service during the period of the study and the

failure data from the WG basis study. The similarity of

the traces indicates that the failures-vs-age trend noted in

the study is strongly affected by the valve population in

existence during the study period.

Figure 1.2 shows comparisons of all check valve failures

(regardless of failure nature) and population during the

same period. It provides further indication of the

importance of the valve population to overall valve failure

rate.

To provide a preliminary indication of the nonpopulation-influenced valve failure-age relationship,

normalized plots of the WG basis study and all check

valve failures during the 1985-1987 period are provided

in Figure 13. There do not appear to be strong,

conclusive trends from the data shown, based on

preliminary review.

The results of the preliminary review substantiated

concerns about the use of the WG's basis study

conclusions for further use in code development activities.

The NRC's Nuclear Plant Aging Research Program asked

ORNL to conduct a more thorough assessment of the

historical failure data. This report documents the results

of the study.

1 NUREGtCR-5944
Introduction

ORNL-DWG 93-7283

Data for 1985-1987:

1800 Valves in service 35

1600 Failures from WG -30

basis study

1400- -25

1200 

20

600 -10

400 ~~~~~~~~~~~~~~~~~

0 5 10 15

Plant age/age at failure (years)

Figure 1.1 Comparison of failures vs age at failure (WG basis paper) and valves in service vs plant age

ORNL-DWG 93-7284

160 1800 -~ ~ ~ ~ ~ ~ ~ I 1800 -~Valves in service 

1600 -All check valve failures14

1400-12

1200~~~~~~~~~~~~~~~~~~2

~~~~~ 1200~~~~~~~~~~~~~~0

800-~~~~~~~~~~~~~~~~~~0

100 - 0

800 40 

Plant age (years)

Figure 1.2 Comparison of all check valve failures and valves in service

NUREG/CR-5944 2
Introduction

ORNU-DWG 93-7285

20- Data for 1985-1987:

18- ---/ \ All cbec valve failures X a-25 

[ _Failures from WG basis

1 16 -study:

14 - -200

i 6- V '. ,' 1 - 10 S~~~~~~t 

> 12 -~ ~ ~ ~ ~ ~ ~ ~ 1 

JI I _

4- ,, l s 10

5

10

Plant age (years)

Figure 1.3 Comparison of nornalized failure data

3 NUREG/CR-5944
2 Study Methodology

2.1 Scope includes those vacuum breakers which are reported as

check valves in the NPRDS data.

A primary goal of this study is to identify any apparent

correlations of valve failure rates with plant age, valve

size, system of service, manufacturer, and other

characterizations that are not inherent in the NPRDS data

base, such as the affected valve parts, the method of

failure detection, and extent of degradation.

Narratives and other pertinent information, such as

manufacturer, system of service, and component service

and failure dates, were initially downloaded for all check

valve failures, yielding an initial data base with 4680

failure records. This data base contained all failures that

had occurred through the end of 1990 and entered into

NPRDS as of May 28, 1992. The data were then filtered

to eliminate failures that did not involve internals

degradation (for example, external leakage at the valve

bonnet gasket) or for which only very minor seat leakage

existed.

After eliminating the nonsignificant failures, it was

decided to only consider failures that occurred between

1984 and 1990, inclusively. Failure reporting to NPRDS

improved dramatically beginning in 1984, and it appeared

that use of prior years' data would not reflect the reporting

practices employed thereafter. Failure events occurring in

1991 and afterward were not considered because at the

time the data was downloaded, all failure reports for 1991

were not filed. Future updates to this study will address

failures occurring in 1991 and subsequent years.

After this filtering process that eliminated insignificant

failures and failures occurring outside the study period

1984-1990 was completed, a data base containing 1227

failure records remained, or about 33% of the overall

failures occurring during the period (3761 failures). This

compares with our estimate of slightly over 20% of all

failures deemed to have been significant by Scott.l

Of the 1227 failures, 1081 (or 88%) affected valves listed

in NPRDS as safety-related. Failures of valves in the

feedwater, condensate, and diesel systems were

responsible for half of the remainder (which included

valves classed as non-safety related and other). Because

of the relatively small group that were not designated as

safety-related, as well as the fact that many of those so

classified are typically either included in the IST or other

plant check valve programs, all valves were included in

further review. It should also be noted that 88% of the

population of check valves currently included in the

NPRDS system are classified as safety-related. In

summary, results achieved from a study of all NPRDS

data should not be significantly influenced by the small

non-safety related portion of the population.

Vacuum breakers are included in the NPRDS check valve

data, which is appropriate, since most vacuum breakers

are check valves in a physical design sense. This study

2.2 Limitations in the Filtering

Methodology and Inherent

Structure of the Data Base

Some failures records have minimal information about the

nature of the failure, noting only that certain parts were

replaced. It should also be noted that some of the

eliminated failures may have technically made certain

valves inoperable. For example, minor seat leakage may

have been discovered during a containment isolation

valve leak test that technically made the valve inoperable.

Alternatively, significant external leakage may render

certain valves inoperable.

The primary area of interest in this study is the assessment

of check valve failures that involve significant wear or

other degradation of valve internal parts. In the cases

where the only valve problem is external leakage or minor

internal leakage that results in failure of the valve to meet

administrative leaktightness limitations, the problems

could reasonably be expected to be routinely detected by

current means (i.e., visual observation of external leakage

and seat leakage measurement testing).

As noted above, one of the intents of the initial filtering

was to eliminate those failures that only involved minor

internal leakage. Because the narratives do not clearly

define the extent of leakage in most cases, it was not

practical to apply hard criteria to this aspect of the

filtering process. As a result, there are almost certainly

some failures that were retained for further evaluation that

are no more significant than some that were eliminated.

On the other hand, because of the extensive number of

failure narratives that were initially reviewed, it is likely

that some failures that should have been retained were

filtered out.

It must also be recognized that reporting practices vary

from plant to plant, as well as with time and individuals at

the same plant. This feature also makes the data base not

particularly useful from an absolute failure rate

standpoint.

Another factor that certainly affects the results of this

review is the growing level of utility attention to check

valve problems in recent years. This is exemplified by the

formation of the Nuclear Industry Check (NIC) Valve

group, which has sponsored a series of test of nonintrusive monitoring techniques. Further, the NIC group

is in the process of developing various documents to assist

utilities in optimizing maintenance and test programs for

check valves. Two likely results of the significant

increase in attention to check valve concerns have been an

enhanced awareness of problem valves and a reduction in

the threshold for what qualifies as a failure.

5s NlJREG/CR-5944
Methodology

In this context, it is important to point out that the term

"failure," as applied throughout this report is a generic

term and does not mean, in many cases, that the valve was

totally incapable of performing its required functions.

Generally speaking, the "failures" only involve a

degradation of one or more valve functions.

One of the parameters considered in the characterization

process was age. Both plant age at failure and the age of

the component were considered. These ages were derived

as follows:

Plant age = Time from initial criticality to failure start

date

Component age = Time from component inservice date to

failure start date

There is minimal uncertainty associated with plant age;

however, the component age calculated per the above can

be misleading. Specifically, it does not reflect the

replacement of parts (or even the entire valve, if replaced

with an identical valve) when either preventive or

corrective maintenance is performed. Thus, the

component age at failure is not a perfect representation of

time to failure.

In close relation to the component age limitation, repeat

failures were not analyzed, primarily due to time

limitations. The results of repeat failures analysis could

provide valuable information, and should be considered

for future studies.

Another feature that was not explicitly considered was

design failures that were corrected early in life. It is

almost certain that some design problems are identified

fairly early in plant life and corrected by either using a

different valve design, changing system operation, or

other action. This area may also be worth exploring

further in future studies or by others.

Failure of a valve that has generic implications (either

industry-wide or for a particular plant) often results in

inspections performed expressly to determine if the same

failure mechanism has affected other valves. For

instance, if a valve which was identical to 10 other valves

at a particular plant were found with a missing lock wire,

it is likely that the other valves would be inspected. Thus,

several failures may be detected in a relatively short

period of time. This pattern was noted in some cases, but

not specifically evaluated.

In light of the limitations noted above (and others), the

use of the filtered data to determine absolute failure rates

is not only not feasible, but any such use would be

misleading.

Note also that several utilities reviewed the ORNL

characterizations of the failure data. ORNL discussed

individual failure narratives with two utilities. These

reviews and discussions reinforced the limitations

associated with lack of familiarity with plant specific

design and, in some cases, either a misinterpretation of the

narrative or the inadequacy of information in the

narratives upon which to adequately complete the

characterization. However, even with these limitations in

mind, it is believed that the results presented herein

provide at least general indicators of importance of the

various characterization parameters, particularly those that

are inherent in the NPRDS data base, such as valve size,

age, and system of service (because interpretative errors

and biases are not a factor for these parameters).

The fact that the data cannot be used for absolute failure

rate determination does not, however, inherently limit the

usefulness of a failure review process, if it is recognized

that the data must be considered in a relative sense rather

than an absolute sense. This approach was used in this

study, and will be discussed in more detail below.

2.3 The Characterization Process

Several of the characterization parameters of interest are

inherent in the NPRDS data base. Those parameters

chosen for consideration in this study, which are

specifically inherent in the NPRDS data, include:

* System

* NSSS

* Valve size

* Manufacturer

* Component age

* Plant age

In addition to considering these inherent parameters,

several additional parameters were developed during the

failure data review. These parameters include:

* Failure mode

* Extent of degradation

* General detection method

* Specific detection method

* System normal operating status

* Failure area or source

Brief discussions of each of these additional parameters

follow.

2.3.1 Failure Mode

Failure modes were classified in seven categories. Brief

descriptions of each and the general characterizations of

the extent of degradation for the failure mode are given in

Table 2.1.

2.3.2 Extent of Degradation

Extent of degradation is not a judgment about the

significance of the effect of the valve degradation/failure

upon the system or plant, from either a safety significance

or availability standpoint Rather, it is intended to be an

indicator of how seriously degraded the particular valve

NUREGICR-5944 6
Table 2.1 Failure modes descriptions and normal classification

Abbreviated

name Extent of

Failure mode used In charts Description degradationi

Corrosion, general Improper This category includes all failures in which the valve failed to properly seat (excluding the Moderate

wear, foreign material seating stuck open and restricted motion cases), whether due to seat erosion or corrosion, lack of full

and/or misalignment seat/disk contact, or unknown causes of reverse flow leakage. The leak rates vary - from

resulting in improper those that were relatively minor to those that were substantial in nature. As a result, these

seating and excessive type failures were generally categorized as Moderate in severity. In reality, the extent of

leakage degradation varied from light to significant. A few of these failures were categorized as

Significant, but only If the circumstances surrounding the failure so dictated (such as some

other piece of equipment failing to perform as required due to the failure).

Disk/other part off or Disk/other part Either the disk to other internal part has come loose from the assembly or a valve internal Significant

broken off or broken part was found to be cracked or broken.

Free or loose (not Loose/damaged Some portion of the assembly, generally in the hinge pin or disk stud area, was found to be Moderate

detached) or part loose or otherwise not in a proper assembly condition (with no other attendant problems,

impact/friction such as stuck open, etc.).

damaged part

Examples are:

* A valve with anti-rotation lugs was free to rotate due to improper installation.

* Seat ring was loose or improperly positioned

* Substantial hinge pin or disk stud wear

* Hinge arm/backstop impact damage

Restricted motion or Restricted Free motion of the valve is restricted. In some cases, this resulted in reduced flow through Significant

reduced flow motion/flow the valve.

Stuck closed Stuck closed Valve will not open when forward pressure is applied. Significant

Stuck open Stuck open Includes valves in which the disk is clearly stuck open or cocked, including, for example, Significant

cases where foreign material prevented the valve from fully closing or the disk cocked in the

seat due to wear of the disk stud. Note that there are some cases where the reverse flow rate

is extremely high (such as where a pump is rotating backwards that are in the "Corrosion,

general wear..." category because the narratives did not explicitly state the valve was stuck

open, cocked, etc.). However, the extent of degradation would be the same (Significant).

Miscellaneous failure Miscellaneous A failure which did not fit any of the above categories. Moderate

A The normal characterization for the various failure modes is shown. A very limited number of failures were accorded the other rating. IA

OQ0
Methodology

was. As is indicated in the table, the failure modes Stuck

open, Stuck closed, Restricted Motion or Reduced Flow,

and Disk/otherpart off or broken were generally

classified as Significant, while failure modes Corrosion,

general wear, foreign material and/or misalignment

resulting in improper seating and excessive leakage, Free

Or Loose (not Detached) or Impact/Friction Damaged

Part, and Miscellaneous were generally classified as

Moderate. The Moderate classification takes in quite a bit

of territory, and includes failures which, no doubt, were

relatively innocuous, as well as failures that were quite

serious. With this classification means, a stuck open

valve in a critical high pressure safety-injection system

application would be classified as the same significance as

a stuck open valve in a balance of plant, non-safetyrelated system. Again, the classification of significance is

not significance to plant operation, but rather a judgment

of the extent of valve degradation.

Two examples of the implementation of this approach are

as follows:

Cage I

A 12" reactor coolant system pressure boundary isolation

valve was found to leak just in excess of the technical

specification limit (normally 5 gpm for this size valve).

The plant was shut down to repair the soft valve seat.

Case 2

A non-safety related service water pump discharge check

valve stuck open. There was no impact on the plant, in

terms of technical specification action statement entry,

forced shutdown for repair, etc.

For Case 1, the failure was categorized as Moderate,

while for Case 2, the failure was deemed Significant.

While the results of this type of analysis are therefore

inherently not geared toward system or plant effect, they

a= useful in a component sense. Any attempt to quantify

system or plant effect would of necessity require not only

much more detailed knowledge on a plant specific basis,

but would mandate considerations that were not

appropriate in this study, such as failure modes and effect

analyses and probabilistic modeling. It is recommended

that additional consideration along this line be given for

future study.

2.3.3 General Detection Method

The first detection method approach was more general,

dividing the failures into those discovered by

programmatic monitoring and those discovered by other

means. By programmatic monitoring it is meant that

some scheduled test or maintenance procedure, e.g., leak

test, inservice testing, scheduled disassembly and

examination, etc., was the means by which the failure was

detected. Non-programmatic detections include such

events as routine observations by operators or observation

of abnormal equipment operation that alerted the presence

of a check valve problem. Table 22 lists and briefly

describes the general detection means.

2.3.4 Specific Detection Method

The second detection method approach deals more

specifically with the method of detection used, regardless

of whether the problem was detected as part of a planned

test or not. Table 2.3 lists and briefly describes the

specific detection means. It should be noted that certain

specific detection methods are not independent of the

general detection method. For example, leak tests are

normally used during surveillance or in-service tests.

Table 2.2 General detection method

General detection

method Description

Programmatic

Routine observation

Abnormal equipment

operation

Special inspection

Miscellaneous or unclear

Observed during the conduct of a surveillance test, in-service inspection or test, leak rate test,

or periodic preventive maintenance(test, scheduled inspection, etc.).

Observed off-normal plant instrumentation, such as level/pressure, etc., during the course of

normal operation. Includes such observations as elevated AFW pipe temperature by feeling of

piping.

Observed off-normal operation of plant equipment, such as reverse rotation of a pump,

frequent cycling of a compressor, or lifting of a relief valve.

Found degraded condition during an inspection performed due to failure of a similar valve at

either the plant in question or some other plant (such as an inspection performed as a result of

an NRC Notice on some particular manufacturer's valve), or as a part of an inspection process

that was not routine in nature.

Did not fit any of the above categories. Includes failures found as a result of correcting other

valve problems (such as finding a disk/seat clearance problem when replacing a leaking

gasket). Also included those failures for which the general detection means were not defined.

NUREG/CR-5944 8
Methodology

Table 23 Specific detection methods

Specific detection

method Description

Disassembly and/or

inspection

Other maintenance

Nonhydraulic

indication

Leak test

Nonintrusive test

Not specific

Hydraulic indication

Pump/comp. rotation

Degradation/failure discovered when the valve was disassembled and examined or a special

inspection was performed; includes both inspections conducted as a part of a programmatic

disassembly and examination effort, plus inspections performed for other reasons.

Degradation found when conducting maintenance on another component, or when correcting an

unrelated check valve problem (such as replacing a leaking bonnet gasket).

Observation of some indication, such as unusual noise or difficulty in operation of a stop check

valve or failure of a power operated valve to stroke, that the valve was not functioning properly.

Degradation/failure found during the conduct of a local leak-rate or other leak-type test.

Degradation/failure found by use of nonintrusive means (primarily radiography).

The specific indicator was not included in the narrative; either no indication or a generic

indication such as "... an operator noticed that the valve was not seating...".

Operator or other person noticed abnormal hydraulic indication, such as higher than normal

pressure, level, or temperature upstream of a valve that should be closed.

Operator observed a pump or compressor rotating in reverse.

23.5 System Usage 2.3.6 Failure Area or Source

The normal system operating status or usage was also

ascribed. This characterization indicates whether the

system is (1) normally operating, (2) infrequently

operating (in support of startup and/or shutdown), or (3)

used in automatic demand or testing situations only.

Table 2.4 indicates the assignment of the various plant

systems to their operating status; PWR and BWR systems

are combined where system general functions are

common.

The failure area or source was identified to designate what

portion of the valve was affected; alternatively, if the

problem was due to the presence of foreign material, it

was so identified. The failure areas and abbreviated

names used in charts are provided in Table 2.5.

Table 2A Operating status of plant systems

System Normal status System Normal status

AFW Shutdown support Feedwater Normally operating

CCW Normally operating HPCI Standby

Combustible gas control Standby HPCS Standby

Condensate Normally operating HPSI Standby

Containment fan cooling Normally operating LPCS Standby

Containment isolation Normally operating Main steam Normally operating

Containment spray Standby RCIC Standby

Control rod drive Normally operating RCS Normally operating

CVCS Normally operating Reactor recirculation Normally operating

Diesel cooling water Normally operating RHR Shutdown support

Diesel fuel oil Standby Standby gas treatment Standby

Diesel lube oil Normally operating Standby liquid control Standby

Diesel starting air Standby Suppression pool support Standby

ESW Normally operating

9 NUREGICR-5944
Methodology

Table 2.5 Description of failure areas

Failure area/source Description

Hinge pin

Disk stud/hinge arm

Seat

Penetration

General wear

Degradation or failure in the hinge pin or the portion of the hanger arm that interfaces with the

hinge pin, including bushings

Degradation or failure of the disk stud or of the portion of the hanger arm that interfaces with

the disk stud, including nuts, washers, and antirotation lugs; also includes the backstop area

Degradation or failure of the disk in the area where it interfaces with the seat, the seat itself,

and/or disk/guide areas

Degradation of a body penetration, such as packing or a stem which interferes with proper

valve functioning

Applied to cases where there was wear of a general nature and specific affected areas were not

identified

Degradation in which the presence of foreign material caused the valve to not function

properly. Foreign material is clearly not an "area"; its presence can cause degradation of any of

the above listed valve parts.

Self explanatory

Foreign material

Unknown/other

2.3.7 The Normalization Process

As discussed previously, questions previously arose

concerning the technical validity of the WG's basis.

Because the data showed, for example, that the number of

failures vs age was heavily influenced by the population

of valves in service over the time period considered

(Figures 1.1 and 1.2), a normalization process is used

herein to account for both population sizes and service life

of the valves. Generally speaking, the process involves

dividing the number of failures for a given category

within a field (e.g., valves 52 in. in size) by the number of

valve-years of service for that category of valves during

the years 1984 to 1990. The number of valve-years of

service is determined by looking at the period of service

of each individual valve in the time period and summing

the totals for all valves in a particular category. For

example, if a particular valve was placed in service in

1982 and remained in service through 1990, it would have

accumulated a total of 7 valve-years of service during the

1984-1990 (inclusive) period. Alternatively, if the valve

was placed in service in 1987, it would have accumulated

4 valve-years of service.

The first step in the normalization process is to determine

the overall failure rate for all valves. This is determined

by dividing the total number of failures characterized

(1227) by the total number of valve-years (123,204). The

result, 0.00996, is the normalizing value that is applied to

the individual category failure rates to determine the

"Relative Failure Rate." As an example, there were 338

failures of valves • 2 in. in size. There are 47,852 valveyears experience for this category. The failure rate for

this category of valves is calculated to be

47852= 0.00706.

The relative failure rate for 5 2-in. valves is then

calculated to be:

0.00706

0.00996 = 0-71-

Because of a considerable number of factors, not the least

of which is the variability in plant reporting practices in

NPRDS, it is deemed inappropriate to report absolute

failure rates. Furthermore, the numeric results generated

in this study are not intended to represent absolute

reliability factors, so to address these concerns, most

results are presented as relative failure rates.

By normalizing, a good indication of how a particular

category (e.g., 5 2-in. valves) within a field compares

with other categories in the field is developed; a relative

failure rate of unity indicates that the particular category's

failure rate is equal to the failure rate of the population as

a whole. In the above example, < 2-in. valves fail at a rate

roughly 71% of the rate at which the population as a

whole fails. The normalizing process used in this study

thus accounts for variables such as population size or

service life, which have been shown to influence the

number of failures, as well as to allow easy comparison

across a field with numbers that are less likely to be

misinterpreted or misapplied.

Some cross-correlations of parameters did not lend

themselves to the normalization process described above.

For example, when cross-correlating failure mode and

affected area or detection method, the valve-year

methodology clearly does not apply. For such cases, the

normalization method is applied to yield an indication of

the relative importance within one of the

characterizations. This type of normalization process

might be used to show, for example, the relative

likelihood of a failure in the hinge pin area to cause

improper seating in comparison to failures in all areas

combined.

NUREG/CR-5944 10
3 Analysis Results

As discussed in Chap. 2, both inherent and ascribed

charcterizations of the failure data were considered. This

chapter will present the results of the tabulation of the data.

Most information will be presented in a normalized fashion,

based on the normalization process described in Chap. 2.

In some cases, the normalization process could not be used;

in such cases, the results will be reported in another

fashion. In a few other cases, the normalization process

applied uses a lower level normalizing factor instead of the

overall failure rate; in these cases, the specific process will

be describe.

The results of the characterizations were developed not

only for the variety of the individual parameters, but in a

cross-correlation fashion as well. The cross-correlations

provided unique insights that could not be seen at the top

level. However, when a variety of parameters are crosscorrelated, each against the other, the size of data to be

considered grows exponentially with each layer of review.

To avoid excessive involvement in all aspects of the crosscorrelated data, this chapter will address only the top-level

results and soie of the more interesting cross-correlation

results. There are certainly notable features that will not be

discussed. For reference purposes, a more complete set of

top level and cross-correlated results are provided in the

appendix as full-page charts. It is also suggested that the

reader refer to the appendix for more detail as well as

somewhat expanded views.

Table 3.1 provides figure numbers applicable to the

individual characterizations and cross-correlations. Both

the appendix and this chapter's figure numbers are shown,

where applicable. It should also be noted that because the

perceptibility of trends can depend upon the means of

presenting cross-correlated data, many cross-correlations

are presented in two formats in the appendix. For example,

if one were interested in finding the charts that display the

results of the cross-correlation of age and size, Table 3.1

indicates that Figures A.1.3 and A.2.2 of the appendix are

applicable, as is Figure 3.14.

It should be noted that the specific valve type (e.g.,

conventional swing check, lift check, etc.) may have a

significant influence on failure rate for certain applications.

Unfortunately, the NPRDS database does not specify the

specific valve type, thereby precluding study of this effecL

3.1 Component and Plant Age

Figure 3.1 presents the results of the characterization of

relative failure rate by the age group of the valve. As can

be seen, there is a moderate increase from the first 5 years

to subsequent age groups; however, the trend is not

particularly strong. Note that valves over 20 years in age

are not shown due to the limited service experience of

valves in this age group.

ORNL-DWG 93-7286

1.2 

I 

a 0.8I

M 0.4 -

0.2

<5 US and <10 a15 10 and <1e and 20

Valve age group, yrs.

Figure 3.1 Relative failure rate by component age group

Figure 3.2 shows the relative failure rate vs. the plant age

group. A somewhat more observable trend is seen that

appears to be linear with plant age. The exact reason for

the different appearances of Figures 3.1 and 3.2 is not clear.

One possibility is that valve applications that have been

severe enough to warrant valve replacement (and thus put

the valve application into a younger category) have also

resulted in failures of the changed design. This possible

explanation was not verified. Clearly, the failure rate-age

relationship is not strong, regardless of whether considering

plant age or component age. However, the trend seen with

plant age merits monitoring.

11 NUREGICR-5944
Cis0

q.A

f

Table 3.1 Characterization method charts

General Specific

Manuf- System Failure Affected detection detection Discovery Extent of

Age Size System acturer NSSS usage mode area method method process degradation

3.1, 3.2, 3.14, 3.15, 3.16, 3.17, 3.18, 3.19, 3.20, 3.21,

Age A.1.1, A.1.3 A.1.4 A.1.5 A.1.6 A.1.7 A.1.8 A.1.9 A.1.10 A.1.11 A.1.12 3.22, 3.23,

A.1.2 II A.1.13

3.3, 3.24, 3.25, 3.26, 3.27, 3.28,

Size A.2.2 A.2.1 A.2.3 A.2.4 A.2.5 A.2.6 A.2.7 A.2.8 A.2.9 A.2.10 A.2.11 A.2.12

3.4, 3.29, 3.30 3.31, 3.32, 3.33, 3.34, 3.35,

System A.3.2 A.3.3 A.3.1 A.3.4 A.3.5 N/A A.3.6 A.3.7 A.3.8 A.3.9 A.3.10 A.3.11

3.36, 3.5,

Manufacturer A.4.2 A.4.3 A.4.4 A.4.1 A.4.5 A.4.6 A.4.7 A.4.8 N/A N/A N/A A.4.9

3.6, 3.37,

NSSS A.5.2 A.5.3 A.5.4 A.5.5 A.5.1 A.5.6 A.5.7 A.5.8 A.5.9 A.5.10 A.5.11 A.5.12

3.7, 3.38, 3.39,

System usage A.6.2 A.6.3 N/A A.6.4 A.6.5 A.6.1 A.6.6 A.6.7 A.6.8 A.6.9 A.6.10 A.6. 1

3.8, 3.40,

Failure Mode A.7.2 A.7.3 A.7.4 A.7.5 A.7.6 A.7.7 A.7.1 A.7.8 A.7.9 A.7.10 A.7.11 A.7.12

3.9, 3.41, 3.42,

Affected area A.8.2 A.8.3 A.8.4 A.8.5 A.8.6 A.8.7 A.8.8 A.8.1 A.8.9 A.8.10 A.8.11 A.8.12

General 3.10, 3.43,

detection A.9.2 A.9.3 A.9.4 N/A A.9.5 A.9.6 A.9.7 A.9.8 A.9.1 N/A N/A A.9.9

method

Specific 3.11, 3.44,

detection A.10.2 A.10.3 A.10.4 N/A A.10.5 A.10.6 A.10.7 A.10.8 N/A A.10.1 A.10.9 A.10.10

method

Discovery 3.45, 3.46, 3.12,

process A.11.2 A.11.3 A.11.4 N/A A. 11.5 A.11.6 A.11.7 A.11.8 N/A N/A A.ll.1 A.11.9

3.49, 3.47, 3.48, 3.13,

Extentof N/A A.12.2 A.12.3, A.12.5 A.12.6 A.12.7 N/A A.12.8 A.12.9 A.12.10 N/A A.12.1

degradation - A.12.4
Results

7 4 ORNL-DWG 93-7287

1.2

4 0.8-

~0.

1 0.4-

0.2

1 11 | | I1 

0

<5 25 and <10 21 e and < 

Plant age group (years)

215 and <20

Figure 32 Relative failure rate by plant age group

3.2 Valve Size

Higure 3.3 provides both the relative failure rate and the

population distribution as a function of valve size groups.

There is a very clear correlation between failure rate and

valve size, inasmuch as the valves that are > 10 in. nominal

size experienced a failure rate that was about double that

for the smaller size groups. Another important feature is

that there are almost twice as many very small (! 2 in.)

check valves in service as the other three group sizes

selected. One could logically conclude that the highest rate

of return for improvements in monitoring and preventive

and predictive maintenance would clearly be in the largest

valves.

ORNL-DWG 93-7288

2 -- 0.4 

2 - 0.35 X

E 1.5 -- 0.3

2 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~05

;0.15 '

*i3 0.5~~~~~~~~~~~~~~~~~~~00

0 0 

!92 >2 and!54 >4 and <10 >10

Valve size group (in.)

Relative failure rate -- Population

Figure 3.3 Relative failure rate and population by size group

13 NUR.EGCR-5944
Results

3.3 System

Figure 3.4 indicates the relative failure rate by system of

service, ordered from highest to lowest Only systems with

more than 1000 valve-years of service were included. Four

systems - emergency or essential service water (ESW),

feedwater, diesel starting air, and main steam - had

significantly higher relative failure rates than did the other

systems. The relative failure rate for ESW was more than

2.6 times that for all systems. Note that three of these four

systems (ESW, feedwater, and main steam) are normally in

service, have a significant number of relatively large

valves, and contain either high energy fluid or raw water.

The fourth, diesel starting air, is significantly different in

that it contains only relatively small valves, is not normally

operating (assuming the check valves hold receiver

pressure to keep the compressors from cycling), and

handles air.

3.4 Manufacturers

Figure 3.5 shows the relative failure rates and population

distribution for manufacturers with more than 1000 valveyears of accrued service during the study period. While

certain manufacturers have a significantly higher failure

rate than others, the conclusion that valves made by these

manufacturers are inherently failure prone would certainly

be inaccurate. It was noted that some manufacturers' valves

tend to be used in applications that are particularly severe,

and as a result, have a significantly higher failure rate. The

results shown in this chart should be considered in the light

of other information, and not as stand-alone conclusive

evidence. Some of the non-design related reasons why

some manufacturers have much higher than average failure

rates will be discussed in section 3.13.4, which deals with

cross-correlations between manufacturer and other

parameters.

3.5 Nuclear Steam System Supplier

(NSSS)

Figure 3.6 indicates the relative failure rate and population

distribution by NSSS. Interestingly, boiling water reactor

(BWR) plants showed a slightly higher relative failure rate

than did the three pressurized water reactor (PWR) plant

types, which had almost identical relative failure rates. As

discussed earlier under the section on manufacturers, other

factors must be considered. One particularly pertinent

factor is that, generally speaking, BWR plants have more

valves that are included in the in-service test programs than

at PWRs, and a greater number of valves are leak tested.

As a result, failures that would not otherwise have been

detected are more likely to be manifested, resulting in an

apparently higher failure rate. Section 3.13.5 will discuss

this in more detail.

ORNL-DWG 93-7289

3-

2.5 -

2-

2

§ 1.5-

310

0.5 -

Only systems with more

than 1000 valve-years

experience were considered

0-

AvnLy

IMI MR&8, I

ESW Feedwater Diesel

Starting

Air

Main HPCI Contain.

Steam Isolation

RCIC Suppress.

I Pool

Support

AFW Awn

Figure 3.4 Relative failure rate by system for the ten systems with the highest overall failure rate

NUREG/CR-5944 14
Results

ORNL-DWG 93-7290

Includes manufacturers with

more than 1000 valve-years

service during the study period.

12

'-

L)

10 *s

4

2 3

I'

I Relative failure rate Population distribution (valve-years %)

Figure 3I Relative failure rate and population distribution by manufacturer

ORNL-DWG 93-7291

1.2 50

0

1 .40 I

1 0.8 -3 

,A0.6 30

4 - 20 0

-Z'V ~~~~~~~~~~~~~~~

~0.2 l 

~O.1 1--I0 1

0 01110

BW CE GE w

[ _M Relative faiure ate e Populaon distribution (valve-year %)

Figure 3.6 Relative failure rate and population distribution by NSSS

3.6 Normal System Usage

'he normal system usage is an important factor in the

service life of check valves. Three classes of system usage

were identified for this study

* normally operating,

* used in support of shutdown operations, but not during

normal operation, and

* essentially used only in testing or in response to

transient/emergency conditions.

The designation of normal system usage for both BWR and

PWR systems is provided in Table 2.4.

Figure 3.7 indicates relative failure rate by normal system

usage. While normally operating systems do have a clearly

higher relative failure rate than shutdown/testing type

systems, it is not dramatically higher, as might have been

expected, and is certainly not representative of the service

hours seen under flow conditions.

15 NUREGICR-5944
Results

ORNL-DWG 93-7292

1.2 --

.§ 0.4 

a

0

Nomly -eda pr4i hudw

Normally operating Used at shutdown Testing only

Figure 3.7 Relative failure rate by system usage

3.7 Failure Mode

Figure 3.8 provides the distribution of failures by failure

mode. This is not based on relative failure rates; rather, it

provides a picture of the extent to which each failure mode

was prevalent in the population of failures characterized.

Clearly, Improper seating was the most likely failure mode.

The term Improper Seating is an abbreviated term which

refers to the failure mode included in Table 2.1 as

Corrosion, general wear, foreign material and/or

misalignment resulting in improper seating and excessive

leakage. Many of the failures that fell into this category

were difficult to characterize in terms of extent of

degradation, failure area, etc. The second largest failure

mode was Stuck open, which comprised 28% of all failures.

Disk/otherpart off or broken accounted for 10% of the

failures, while Restrictedflow/motion and Stuck closed

conditions were responsible for 7% each.

Perhaps the most surprising result was the number of Stuck

closed valves. Stuck closed valves were found in several

systems and applications. For example, stuck closed valves

were found in 18 different systems. The main steam, diesel

starting air, and ESW systems had the most stuck closed

cases. System chemistry conditions varied and included

treated water (e.g., condensate, feedwater, and CCW),

untreated water (ESW), air (diesel starting air), and steam

(main steam). To the extent possible, the specific

application involved was identified. The two most

common applications affected were pump/compressor

discharge check valves and vacuum breakers. It should be

noted that most of the cases in which vacuum breakers

stuck shut were found during testing which measured the

required force/pressure to open. For these valve

applications, relatively tight restrictions are applied for

opening pressure. All four valve size groups were affected,

but over half of the stuck closed failures were in the

smallest size group (? in.).

ORNL-DWG 93-7293

0 Disk/other part off or broken

0 Looseldamaged part

E Miscellaneous

MIl Restricted motion/flow

E Stuck closed

E Stuck open

7%

Figure 3.8 Distribution of failures by failure modes

NUREG/CR-5944 16
3.8 Failure Area

Figure 3.9 indicates the distribution of failures by failure

area. The sum of the fraction exceeds one because some

failures affected multiple areas. As expected, the seat area

and general wear, followed by hinge pin area degradation,

Results

were tie leading sources, and were followed by disk

stud/hinge arm and foreign material. The area labeled as

Penetration applies to failures related to a movable valve

body penetration (such as the valve stem for stop check

valves).

ORNL-DWG 93-7294

0.3 T

0.25 4-

0A

0U

0.2 

0.15

0.1

0.05

0.

Hinge pin Disk stud/

hinge arm

+

Seat Penetration General

wear

Foreign Unknown/

material other

-i

Figure 3.9 Distribution of failures by failure area or source

3.9 General Detection Method

Figure 3.10 shows the distribution of failures by the general

method of detection. Slightly over half of all failures were

detected by programmatic means, such as local leak rate

testing or in-service testing. Nineteen percent of the

failures were detected by the observation of abnormal

equipment operation (such as a pump rotating in reverse).

3.10 Specific Detection Method

Figure 3.11 provides the distribution (no normalization) of

failures by the specific detection method. About one-third

of the failures were detected by what is termed Nonspecific,

which means that the exact way in which the valve

degradation / failure was manifested was not described in

sufficient detail to place it in one of the other categories.

The next largest group of failures was detected by Leak

test, followed by Disassembly andlor inspection, Hydraulic

indication, andNonhydraulic indication. Only about 2% of

the failures were detected by use of Nonintrusive tests, all

but one of the failures detected under the Nonintrusive test

category were found by radiography; the remaining failure

was detected acoustically (in late 1990). It should be

remembered that during the majority of the period covered

by this study, several currently used non-intrusive

techniques were not available.

Note that there is not always a direct connection between a

specific discovery method and the general discovery

method. For instance, hydraulic indication (pressure, flow,

level, or temperature) could be observed during the general

discovery process of programmatic monitoring, routine

observation, abnormal equipment operation, etc. On the

other hand, all leak tests (a specific discovery method)

would be considered to fall within the general discovery

method category of Programmatic.

3.11 Discovery Process

Figure 3.12 indicates that about 54% of the failures were

detected programmatically (note that this corresponds

specifically to the programmatically detected failures

identified under the general discovery method section

above. The remainder of the general discovery method

categories are combined under the title of

Nonprogrammatic for this level of consideration.

3.12 Extent of Degradation

A top level indication of the distribution of failures by the

extent of degradation is shown in Figure 3.13, which

indicates that the failures considered in this review were

approximately equally split between the somewhat arbitrary

categories of Moderate and SigUficant.

17 NUREG/CR-5944
Results

ORNL-DWG 93-7295

6%

16%

Proammatic

E Abnonnal equipment operation

E Miscellaneous or unclear

M Routine observation

mI Special inspection

54%

Figure 3.10 Distribution of failures by general detection method

ORNL-DWG 93-7296

3%2%

11%

12%

DIM

13% )ncy33%

so Not specific

0 Leak test

H Disassembly and/or inspection

19 Hydraulic indication

in Nonhydraulic indication

0 Pump/compressor rotation

1 Other maintenance

0l Nonintrusive test

Figure 3.11 Distribution of failures by specific detection method

ORNL-DWG 93-7297 ORNL-DWG 93-7298

46%

54%

E3 Nonprogrmmnatic MProgrammatic

53% Mo ert

El Significant a Moderate

Figure 3.12 Distribution of failures by general

discovery process

NUREG/CR-5944

Figure 3.13 Distribution of failures by extent of

degradation

18
As discussed in Chap. 2, the extent of degradation

characterization is not intended as a judgment of the effect

on the system or plant, but rather an estimate of overall

valve degradation. Its sole purpose is to help identify,

inasmuch as possible, false positive indicators. A good

example of the usefulness of this characterization will be

presented in the discussion on system vs other parameter

cross-correlation results (Section 3.13.3), where the extent

of degradation by system provides a useful indication of

relative system experience.

3.13 Cross-Correlation Results

Cross-correlations of all of the above discussed

characteization methods were made to gain insights into

dominant effects. The appendix shows the results of all

cross-correlations, from the perspectives of both

parameters. Due to the extensive nature of the appendix,

only a few of the results are presented below, and from only

one parameter's perspective. Refer to the appendix for

additional cross-correlations, as well as different structures

for presenting the results of each cross-correlation.

Results

3.13.1 Valve Age Group Cross-Correlations

Figure 3.14 shows the result of the cross-correlation of

valve age and size groups. While there are no dramatic

trends, the fact that the larger valves are most failure prone

is seen in all age groups. Interestingly, as the component

age increases, the relative failure rate of the smallest valves

increases in comparison to the larger valve sizes. For

instance, in the first 5 years, the relative failure rate of >10-

in. valves is about three times that for <2-in. valves.

However, in the 15 to 20 year time frame, the ratio is less

than 2.

Figure 3.15 provides the results of the cross-crelation of

valve age and system for the four systems with the highest

overall relative failure rates. Note that the distribution

changes significantly from the younger to older component

age groups. For instance, although ESW has a high relative

failure rate for all valve age groups, it does Dot uniformly

increase with valve age, while feedwater valves show a

continually increasing failure rate with component age and,

in fact, have a higher relative failure rate than ESW valves

in the >15- and 20-year age group.

ORNL-DWG 93-7299

2.5

2

.2

E 1.5

!9 I

X05

0

Valve size group (in.)

|*E 2 0>2and 54 W >4and 10 >10

2115 and < 20

+ 4 4

210 and < S

Valve age group (years)

Figure 3.14 Cross-correlation of valve age and size groups

19 NUREGCCR-5944
Results

ORNL-DWG 93-7300

3.5 -

3-

E 2.5- 

.12

> 1.5

.0 

0.5

0 4 -i

<5 >5 and <10 210 and <15

Valve age group, yrs.

>15 and <20

I RAEW E Fdar E Diesel Starting Air Main Steam I I ESW Feedwater

Figure 3.15 Cross-correlation of valve age group and system for four systems with the highest overall failure rate.

Figure 3.16 shows the results of the cross-correlation of

valve age group and system usage. This chart indicates that

the relative failure rate for normally operating systems

increases after a few years of operation but remains

relatively stable thereafter. Alternatively, the relative

failure rate for systems that are primarily used in testing

only is seen to increase with valve age, such that the

relative failure rate for older valves, which primarily see

service only for testing, is similar to that for valves that are

used in normally operated systems.

Figure 3.17 shows the results of a cross-correlation of

failure mode and valve age. This chart is presented

specifically because there are no particularly striking

features relative to valve age. That is, there is little or no

correlation between age and any of the identified failure

modes.

Figure 3.18 shows the relationship between valve age group

and the area or source of failure. The only failure area that

appears to have a continuous trend in failure rate as a

function of age is the disk stud/hinge arm area. Failures in

the disk stud/hinge arm area and those occurring due to the

presence of foreign material were noticeably higher in the

15-20 year time period.

Figure 3.19 indicates the distribution of failures by the

process being used at the time of discovery. It is

particularly noteworthy that for the oldest valve group,

programmatic monitoring was responsible for a

significantly higher fraction of the detected failures than

was the case in earlier years. The explanation for this is not

clear but could possibly be attributable to lessons learned

on a plant specific basis.

ORNL-DWG 93-7301

1.4 . 1 Normally operating 3 Used at shutdown Im Testing only I

1.2 

I

4-

0u

I0.8 -.

0.6 -.

04- + + -I

0.4 -+

0.2 

0 -_ -4- A

<5 Ž5 and <10 >10 and <15

Valve age group (years)

Ž15 and <20

Figure 3.16 Cross-correlation of valve age group and normal system usage

NUREG/CR-5944 20
Results

: ORNL-DWG 93-7302

0.5

0.45

0.4

0.35

E 0.3

I

; 0.25

X 0.2

0.15

0.1

0.05

0

Valve age group (years

El<5

0 25 and <10

I 10 and <15

* 15 and 20

Figure 3.17 Distribution of failures by failure mode and valve age group

ORN D-nWG. Q`3-730

2.5

Valve age group (years)

2 | @Ž5<5 25 and <0 E 210 and <15 215 and <20|

.5

La 0.5 

Seat area General Hinge pin Disk stud/ Foreign

wear area hinge arm material

area

Figure 3.18 Distribution of failures by failure area and valve age group

21 21 ~~~~~NUR.EGKCR-5944
Results

ORNL-DWG 93-7304

0.7 

0.6 -I j Programmatic | mmatic

0.5 ,,

4..V0.4 ar 0

0

I= .3 

0.2 

0.1 

0 <5Ž?S5and < I Ž0 and <15 Ž15 and <20

Valve age group (years)__ _ _

Figure 3.19 Distribution of failures by discovery process and valve age group.

3.13.2 Valve Size Group Cross-Correlations

Figures 3.20 to 3.23 show the relative failure rates for the

five systems with the highest relative failure rate within

each valve size group. Also shown is the distribution by

failure significance. Only those systems with more than

500 valve-years of service within the specific valve size

group were considered.

ESW has either the highest or second highest relative

failure rate within each of the size categories.

Another interesting feature of these figures is that,

generally spealdng, the valves in the two larger size groups

tended to have a greater fraction of their failures

characterized as Significant, in terms of extent of

degradation.

It is expected that cross-correlations such as those shown in

Figures 3.20-323 could be useful in helping prioritize those

valves to which more attention is merited. Of course other

factors are important, but the valve size and system

application appear to be two particularly worthwhile areas

for consideration.

ORNL-DWG 93-7305

25 -

.9

1.5 .

.1

0.5

Diesel ESW RCIC Cont. HPCI

Starting Isolation

Air

I M Significant E3 Modwate 

Figure 3.20 Relative failure rate and extent of

degradation for valves in S 2-in, size group

ORNL-DWG 93-7306

1. - -91.6--

5 14 4

1.2--

-1 I

0O.8 

>~ 0.6 

69.0.2 

ESW Cont AFW Main HPSI

Isolation Steam

I Ell Significant lB Modaate |

Figure 3.21 Relative failure rate and extent of

degradation for valves in > 2- and 4-in.

size group

NIJREG/CR-5944 22
Results

ORNL-DWG 93-7307 ORNL-DWG 93-7308

3--

-9 2.5 

en 25- .X.:

4g .5 1

0.5 

0 

ESW Main Feedwater CCW RCIC

Steam

3.5--

S 3 -

= 2 - 1 

g 0.5 -

Main ESW HPCI LPCS

Sea _ .

Figure 3.22 Relative failure rate and extent of

degradation for valves in > 4. and < 10-hi.

size group

Figure 3.23 Relative failure rate and extent of

degradation for valves in >10-in, size

group

Figure 3.24 provides the results of the cross-correlation of

valve-size group and normal system status. The relative

failure rate for valves used in normally operating systems in

the two smaller valve-size groups was comparable to that

for valves used in the less frequently operated systems.

However, for the two larger valve-size groups, the failure

rate for valves used in normally operating systems was

about twice that seen in the less frequently used systems.

Furthermore, there is a clear tend in failure rate with valve

size for normally operating systems. For the other system

types, there are no clear trends.

Figure 35 shows the results of the cross-correlation of

valve size groups and failure mode. While Improper

seating is the leading failure mode in all four size groups, it

is much more dominant for smaller valves. For the two

larger valve size groups, Stuck open category occurs almost

as frequently as Improper Seating. Also note that

Disk/otherpart offor broken is much less significant in the

smallest valve size group. Not surprisingly, Stuck closed is

more likely to be a problem for the smaller valves, but there

were Stuck closed cases for all valve size groups.

Figure 3.26 shows the results of a cross-correlation of valve

size and failure area. Failures involving degradation in the

seat area are prevalent in all valve size groups, but

somewhat more problematic for the largest valve sizes. On

the other hand, hinge pin area wear and disk stud/hinge arm

area wear are much more significant in larger valve sizes.

Foreign material is more likely to be a problem for smaller

valve sizes, which may be a reflection of the fact that a

given amount of foreign material can have a greater effect

on a smaller valve size.

ORNL-DWG 93-7309

2.5 

2+

U)

I-

.)

3)

1.5 

1 .

MNormally operating

E Shutdown support

E Testing only

-

0.5

0

>2 and S4 >4 and S10

Valve size group (in.)

>10

Figure 3.24 Relative failure rate by valve size group and system usage

23 NUREG/CR-5944
Results

ORNL-DWG 93-7310

0.6

0.5

c

2 0.4

.2

'6 0.3

U

VV 02

0.1

0

to Improper seating

0 Restricted motion/flow

0 Stuck open

ID Stuck closed

an Disk/other part off or broken

[ Loose/damaged part

>10

4

•2 >2 and s4 >4 and 10

Valve size group (in.)

Figure 3.25 Fraction of failures by valve size group and failure mode

ORNL-DWG 93-7311

2.5

2e

9 1.5

.> 1.

0M

Q0.5 

0 P

stud/hinge material

am area

Valve size group (in.)

| : 2 E23 >2 and S4 E3>4 and 10 1 >10|

Figure 3.26 Relative failure rate by valve size group and failure area/source

The smaller fraction of failures in which General wear was

attributed in the larger valve sizes is primarily due to the

fact that in many cases, the smaller valves were simply

replaced without further investigation into the specific

cause or area of failure.

Figure 327 indicates that programmatic monitoring was

more likely to be the method of failure/degradation

discovery for the smaller valve size groups, while failures

in the largest valve size group were more likely to be

NUREG!CR-5944

discovered nonprogrammatically. This is, no doubt, a

reflection of difference in the system effect of failure of a

large valve compared to failure of a small valve.

Figure 3.28 shows the relative failure rate by valve size

group and extent of degradation. While the relative failure

rate of both moderately and significantly degraded valves

generally increase with size, the relationship of more

significant failures to valve size is more distinct

24
Results

ORNL-DWG 93-7312

0.7.

9 0.6.

A 0.5.

00A

.9 0.3.

0.2.

0.1.

0 

Pogrammatic

@ Nonprogrammatic

-1

>2 and 4 >4 and 510

Valve size group (in.)

>10

Figure 3.27 Distribution of failures by valve size group and failure discovery process

ORNL-DWG 93-7313

2.5 .

2 || __ Mdate __ Significant 

2§ 1.5 -_ _ _ _ _ _ __-_ _ _

Z

0-

S92 >2 and l4 >4 and <10 >10

Valve size group, Mn.

Figure 3.28 Relative failure rate by valve size group and extent of degradation

3.13.3 System Cross-Correlations

Figures 3.29 and 3.30 provide relative failure rates and

population distributions by manufacturer for the five

manufacturers with the highest relative failure rates within

two sample systems, ESW and diesel starting air. Only

those manufacturers with more than 200 valve-years

service in the respective system during the study period

were considered There are significant variations among the

manufacturers, which are no doubt partially attributable to

different applications within the systems and other factors;

nevertheless, the extent of variation in relative failure rate

indicates that the valve manufacturer should be a

consideration in any prioritization efforts relative to valve

monitoring and predictive/preventive maintenance

programs.

Also note that the distribution of extent of degradation

(Moderate or Significant) is substantially different for the

two systems. For example, the highest relative failure rate

for any manufacturer in each system is between 6 and 7;

however, for ESW, the majority of these failures were

deemed Significant, while for diesel starting air, a similar

majority were deemed Moderate.

Figure 332 shows the distribution of failures in the same

four systems by affected area. Considerable variations

from system to system can be seen. For example, about 18

and 23% of the ESW and diesel starting air failures,

respectively, involved the presence of foreign material in

the valve, while relatively few feedwater or main steam

valve failures were related to foreign material presence. On

the other hand, about 30% of the failures in the main steam

system involved penetration area problems, while the other

three systems had few or no failures in that area.

25 NUREG/CR-5944
Results

ORNL-DWG 93-7314

7 6- 7\^- 

63 4" . ./Z 6"

7

.83 l0 m 3 

0

0 0>~~~~~0

Valve manufacturer

oe U Valve-year %

t_~~Significantl

broken, as might be expected. More than 10% of the

failures in the diesel starting air and main steam systems

involved stuck shut conditions. It is important to point out

that of the 16 cases in which main steam valves stuck shut,

12 involved failure of vacuum breakers in main steam

safety relief valve discharge lines to open at the required

torque. All 12 failures were observed at a single unit.

Eleven of the twelve failures occurred (i.e., were

discovered) within a month of each other, at about the same

time the unit went commercial. All the vacuum breaker

failures were attributed to hardened packing and long

periods of time between valve operations. Thus, these

failures within the main steam system occurred in unique

applications that are not typical of steam system conditions.

Figure 3.33 indicates the distribution of failures within the

four systems by specific detection method. The most

obvious observation to be made is that for many of the

failures (over half in the diesel starting air system), the

specific method that was used to detect the failure was not

discussed. Note that over one-third of the feedwater

failures were detected by leak tests, in contrast with less

than 5% for the other systems. Of these leak test detected

failures 80% were at BWR units, the remaining 20% were

at two PWR units. This is likely due to differences in leak

test requirements, generally speaking, between BWR and

PWR plants for main feedwater systems.

Figure 3.29 Relative failure rate (by extent of

degradation) and valve population

distribution for ESW system check valves

for the five manufacturers with the highest

failure rate within the ESW system

ORNL-DWG 93-7315

7 14

6 12

5 X >X 10

Z4 8~~~~4~

0 ~ ~ ~ 0

3 .. . 6

Valve manufacturer

Modate Valve-year %l

|-~Significantl

Figure 3.30 Relative failure rate (by extent of

degradation) and valve population

distribution for diesel starting air system

check valves for the five manufacturers

with the highest failure rate within the

diesel starting air system

Figure 3.31 shows the distribution of failures by failure

mode for the four systems with the highest overall failure

rates. About 70 to 80% of the failures occurring in ESW,

feedwater, and diesel starting air systems involved either

improper seating or stuck open conditions, whereas in main

steam, less than half the failures involved these modes. The

two higher energy systems, feedwater and main steam,

showed a higher tendency for disk or other parts becoming

NUREGICR-5944

Figure 3.34 shows the distribution of failures by the process

used for discovery in the ten systems with the highest

overall relative failure rate. It is interesting to note that four

systems (HPCL containment isolation, RCIC, and

suppression pool support) had significantly higher fractions

of the failures detected programmatically than did the other

systems. Three of the four systems (HPCI, RCIC, and

suppression pool support) are exclusively BWR systems,

while the containment isolation valves are exclusively at

PWR plants.* The relatively high rate of programmatically

detected failures in these systems is attributable to required

leak testing for many valves used therein.

The distribution of failures by extent of degradation for

these ten systems is shown in Figure 335. Considerable

variations in extent of degradation can be seen. For

example, about two-thirds of the ESW and main steam

failures were deemed Signftcant, while only about onefifth of the containment isolation failures were so

designated This result is not unexpected in light of typical

service conditions as well as variations in typical test

methodologies.

* Clearly, many valves in a variety of BWR and PWR

systems function as continent isolation valves. In NPRDS,

containment isolation is a system into which valves that act

as containment isolation valves, but do not fit in any other

NPRDS system are placed.

26
Results

ORNL-DWG 93-7316

0.7

0.6

0.5

co

* 03

;

4

02

0.1

0

1 Improper seating

E Stuck open

EM Disk/other part ofbroken

* Restricted motion/flow

[m Stuck closed

O Loose/damaged part o3 miscellaneous

ESW Diesel Starting Air Main Steam

Figure 3.31 Distrbution of failures by failure mode for four systems with the highest overall failure rate

ORNL DWG 93 7317

0.4

0.35

0.3

1 0.25

0

.E 0.15

0.1

0.05

0

ESW Feedw Diesel Starting Air Main Steam

W Seat area 3 General wear D Hinge pin area 0 Disk stud/inge

arm aa

m Foreign matial Unknown/other UI Penetration area

Figure 3.32 Distribution of failures by failure area for four systems with the highest overall failure rate

27 NUREGJR-5944
Results

ORNL-DWG 93-7318

0.6

0.5

1 0.4

LL.

'8 0.3

0.2

0.1

0

ESW Feedwater Diesel Starting Air Main Steam

Not specific 0 Leak test Eli Disassy. &/or 3 Hydralic

inspea indication

m Non-hydraulic m Pmnp/comp. 0 Other maintenance M Non-intrusive test

indication rotation

Figure 3.33 Distribution of failures by specific detection method for four systems with the highest overall failure rate

ORNL-DWG 93-7319

100%

90%

80%

70%

1 60%

8 509

~4%

30%

10%

0%

ESW FeedwaMer Diesel Main

Starting Stean

Air

HPCI Contain. RCIC Suppress. AFW CCW

Isolation Pool

Support

I Non Pmatc Progammatic

Figure 3.34 Distribution of failures by discovery process for ten systems with the highest overall failure rate

NUREG/CR-5944 28
Results

I ' '; A ,' -ORNL-DWG 93-7320

I

.

0

5

c:

80% -

60o -

40o -

20% -

0%.

ESW Fedw Diesel

Saring

Ai

I i E444 "L j 

Main HPCI Contain.

Steam Isolation

IC Suppress. AFW CCW

Pool

Support

-I

.

|r 3 Moderate f Significant I

Figure 335 Distribution of failures by extent of degradation for ten systems with the highest overall failure rate

3.13.4 Manufacturer Cross-Correlations

When comparing the relative failure rates of specific

manufacturers, special care should be exercised. This is

clearly manifested by re-examining Figures 3.29 and 3.30,

which provide relative failure rates by extent of degradation

for the five manufacturers with the highest relative failure

rates in the ESW and diesel starting air systems. While the

overall relative failure rates are similar, the extent of

degradations vary considerably.

Figure 3.5 provided the relative failure rates for all

manufacturers with more than 1000 valve-years of service

during the study period. Figure 3.36 provides the relative

failure rate, by valve size, for the ten manufacturers with

the highest overall relative failure rate. From this figure, it

can be inferred that the two manufacturers with the overall

highest failure rate were significantly affected by the fact

that they had relatively few small valves in service (no

failures of the •2-in. size group). Further investigation

showed that, in fact, valves supplied by these two

manufacturers combined provided <5% of all operating

experience during the study period for all valve sizes

combined, but over 15% of the operating experience for the

>10-in. valve size group.

ORNL-DWG 93-7321

5.

4.5.

4.

i' 3.5.

3

: 2.5.

1 2.

i 1.5.

1.

0.5*

0 

Valve size

0

1. E 1j.J.S. 01~~O >

e gop,n

!and S4

[and S10

Im

Mt

ml

FM

U S

S075 A585 W030 0 I I

C684 A391 M360

Valve manufacturer

a a

P032 V135 VOSO G202

Figure 3.36 Relative failure rate by manufacturer and valve size group for ten manufacturers with highest overall

failure rate

29 NUREG/CR-5944
Results

In addition to the influence associated with size , the system

application affects the relative failure rate. The two

manufacturers with the highest overall failure rate not only

had a disproportionate number of larger size valves, they

also bad a disproportionate number of valves in feedwater

and main steam system service. Recall that these two

systems are among the four highest failure rate systems.

Over 15 and 20% of the experience for feedwater and main

steam system check valves, respectively, was provided by

these two manufacturers, which, as noted above, provided

<5% of the overall operating experience.

Thus, while these manufacturer's valves do appear to have

relatively high failure rates, the population distribution by

valve size, system application, and other variables have a

significant bearing on the overall relative failure rate.

These examples show the potential for drawing erroneous

conclusions from the top-level assessments. Even with the

cross-correlated analyses shown here, there are a variety of

factors that influence failure rates for the individual

manufacturers, such as severity of service duty; thus, the

manufacturer results (in particular) should be used

circumspectly.

3.13.5 NSSS Cross-Correlations

As was noted previously, BWR units had a higher overall

relative failure rate than PWRs (see Figure 3.6). One of the

reasons for this discrepancy is shown in Figure 3.37.

Clearly, BWR plants detect a significantly higher fraction

of failures by programmatic means than do PWRs. This is

likely a direct result of the fact that not only do BWRs

include more valves in their in-service test programs, they

also typically leak-test a greater number of valves. Figure

3.37 illustrates the potential for drawing improper

conclusions from the data and reinforces the importance of

carefully examining any apparent trends or features to

ensure that causal factors are understood.

ORNL-DWG 93-7322

0.7 -

0.6 - -

1 0.5- 

j 0.4- 

'4

= 0.3-

e 0.2

0.1

IB&W CE W

E Programmatic 0 Abnormal equipment operation I Misc. or unclear

Routine observation [m Special inspection

Figure 3.37 Distribution of failures by general detection method and NSSS

3.13.6 System Usage Cross-Correlations

In Figure 3.8, it was shown that almost half the failures

were associated with improper seating; thus this failure

mode has a significant impact on the overall failure

distribution. From Figure 3.38 it can be seen that although

the relative failure rate for improper seating failures is

essentially the same for all three types of system usages,

there are significant differences in other failure modes.

Stuck open, Disk/other part off or broken, Stuck closed, and

Loosetimpact damaged part failure modes generally

represent more significant degradation than does Improper

NUREG/CR-5944

seating. The relative failure rates for these failure modes

certainly vary according to system usage. For instance, the

relative failure rate for normally operating valves in the

Stuck open failure mode is about twice that for systems

used in shutdown support or in testing only. However,

systems used for testing only are more likely to be affected

by Stuck closed failures than are normally operated

systems. This observation is even somewhat understated in

that a significant number of the Stuck closed cases for

normally operating systems involved vacuum breakers that

are infrequently exercised, and thus they are similar in

usage to most testing only systems valves.

30
Figure 3.39 shows the overall distribution of extent of

degradation within each of the three system usage

categories. While not dramatic, there is a slight trend

toward an increased proportion of failures that are more

significant in nature with increased system usage (i.e., the

Results

normally operAting systems have a slightly greater fraction

of significant failures than shutdown support systems,

which in tn have a slightly greater fraction than testing

only systems).

ORNL-DWG 93-7323 .

1.0 * _

1.4 +

1.2 ± 

0

4

1

0.8

0.6

OA

02

0 4 + V- 4I

Improper seating Stuck open Disk/other part

off or broken

Restricted

motion/flow

Stuck closed Loose/impact

damaged part

N @ Nmally peaing M Shutdown support IMl Testing nly

Figure 3.38 Relative failure rate by system usage and failure mode

ORNL-DWG 93-7324

10 -

90- 

go70- ISip1icatI

'.pa60g s nlModerate

5 40-

9 30-

20- 

10- 

0 I

Normally Shutdown Testing

Operatings support only

Figure 3.39 Distribution of failures by system usage and extent of degradation

31 NUREGACR-5944
Results

3.13.7 Failure Mode Cross-Correlations

Figure 3.40 shows the fraction of failures by failure mode

and general detection method. This figure indicates that the

types of programmatic monitoring historically applied have

been more successful at detecting improper seating, stuck

closed, and loose/damaged parts than the other failure

modes, particularly disk/other part off or broken. However,

opportunity for improving the programmanatic detection of

all the failure modes exists.

For the d/other part off or broken failure mode, special

inspections have been the second most successfully applied

technique. Further review indicated that about one-third of

the programmatically detected failures were detected by

disassembly and examination (conducted as part of a

preventive maintenance or other routinely applied

inspection program); thus almost 40% of the disk/other part

offor broken failures were found as the result of valve

disassembly and inspection.

Figure 3.40 Distribution of failures by failure mode and general detection method

3.13.8 Failure Area Cross-Correlations

Figure 3A1 provides the distribution of failures by failure

area and discovery process. Degradation due to the

presence of foreign material and seat area-related problems

was most likely to be detected programmahically. Disk

stud/hinge arm area problems were least likely to be

detected programmaticaiy. Figure 3.42 shows that the two

areas for which the extent of degradation was judged to be

greatest were the penetration and disk stud/hinge arm areas.

The combination of these two charts (along with the raw

number of failures classified as significant in nature)

indicates that the area in greatest need of improved

monitoring is the disk studhinge arm area.

NUREG/CR-5944 32
Results

ORNL-DWG 93-7326

A8

50

0

'Z 40

& 20

±t

1+

0+- -4-

Seat

.ZZZZZZZ4 f V ZIKey i m fL

General Hinge pin Disk stud/

wear hinge arm

-4-

Foreign Unknown/ Penetration

material other

-I

I Programmatic U Nonprorammatic

Figure 3.41 Distribution of failures by failure area and discovery process

ORNL-DWG 93-7327

100.

I

0

to

0)

80 ..

60 .1

40 .

20 4.

O0_ +I

Seat

.VZ,ZZZZAI r57A'A WZZ I 

General Hinge pin Disk stud/

wear hinge arm

+ VzIxzz~dA rzz i xsxm

Foreign Unknown/ Penetation

material other

AI

I Moderate U Significant 

Figure 3A2 Distribution of failures by failure area and extent of degradation

3.13.9 General and Specifc Detection

Method Cross-Correlations

Figue 3.43 provides the distribution of failures by general

detection method and extent of degradation. As expected, a

relatively high fraction of failures discovered as the result

of abnormal equipment operation (e.g., pump reverse

rotation) were judged to be significantly degraded. Another

general detection method with a relatively high fraction of

significant failures was special inspection.

Figure 3.44 shows the extent of degradation by specific

detection method. Other than those failures for which the

specific method of detection was indetenninate, leak testing

was the most frequent detectcr of degraded internals.

However, as indicated in Figure 3.44, over 80% of the

failures detected by leak testing were classified as moderate

in extent of degradation. On the other hand, a substantial

portion of failures detected by several other specific

detection methods, such as nonintrusive testing,

disassembly and inspection, and pump/conmpressor reverse

rotation involved a more significant level of degradation.

33 NUREGICR-5944
Results

ORNL-DWG 93-7328

100 

4.

0

4)

.

80 

60 .1.

40.1

20

0 _. -l- l-4-

Programmatic Abnormal

equipment

operation

Misci Special

unclear inspection

Routine

observation

Figure 3.43 Distribution of failures by general detection method and extent of degradation

ORNL-DWG 93-7329

100

90

80

1 70

*g 60

o6 50

9 40

0

a30

20

10

0 vZA,,,, I ,,,,^

Leak test Disassy.

and/or

inspect.

-I- +h

Hydraulic Nonindication hydraulic

indication

Pump/comp. Other Non- Not specific

rotation maintenance intrusive

test

| Moderate E Significant

Figure 3A4 Distribution of failures by specific detection method and extent of degradation

3.13.10 Discovery Process Cross-Correlations

Several of the previous cross-correlation sections have

provided indication of discovery process correlations with

the other parameters. This section will cover some aspects

that were not previously addressed.

Figure 3.37 showed that BWR plants were more likely to

detect failures programmatically than their PWR

counterparts, when the failure data was cross-correlated

NUREGICR-5944

with the general detection method. Another perspective on

the relative levels of degradation detection processes is

provided by Figure 3.45, which highlights the distinction

between the discovery processes at BWR plants and PWR

plants. Reference was made to the fact that BWR plants

typically include more valves in in-service test programs, as

well as leak testing a greater number of valves. In addition,

it has been observed that, generally speaking, BWR plants

simply made better design provision for in-service testing

34
,:'-;17 \ 1 A: t '71

than did many PWR Units (for example, generically

providing full-flow test lines for safety-related pumps).

Figure 3.46 indicates that there is no correlation between

the percentage of failures discovered progsainmatically and

the type of system in which the failed valve is used. This is

somewhat surprising, inasmuch as it would appear

reasonable to presume that failures of valves in normally

operating systems would tend to manifest the failures more

readily than would less frequently used systems. The

explanation may lie in the fact that improper seating is the

type of condition that would most readily manifest itself

outside of testing, and the likelihood of this failure mode

was found to be not particularly dependent upon the system

usage (refer to Figure 3.38).

ORNL-DWG 93-7330

Results

3.13.11 Extent of Degradation CrossCorrelations

Figures 321 through 3.23 show that for a given system,

there are variations in the extent of degradation distribution

according to size. For example, about one-third of the

ESW failures in the 52-in. size group were classified as

Significant, while about two-thirds of the ESW failures in

the >10-in. size group were Significant in nature.

Figures 3.21 through 3.23 show there are variations in

extent of degradation from system to system within the

individual size groups. For example, in the 2-in. size

group, diesel staring air valves have the highest overall

failure rate; yet the rate of failures that were more

significant in nature was highest for HPCI valves, which

had the fifth highest overall failure rate for the size group.

Figure 3.4 shows the relative failure rate for all failures

chaacterized in this study. Figure 3.35 shows the variation

in distribution of failures by extent of degradation for the

ten systems with the highest overall failure rate. The

systems in Figure 3.35 are arranged from left to right in

descending order of relative failure rate.

Figure 3.47 provides the relative failure rates by system for

only those failures that were categorized as Significant.

ESW is still the system with the highest relative failure rate;

in fact, the relative failure rate for Significant failures in

ESW is greater than its relative failure rate overall. It can

also be seen that the relative failure rate for the diesel

starting air system is reduced when considering the

Significant failures only, such that only three systems -

ESW, main steam, and feedwater - are noticeably higher

than the remainder. Also note that less than half of the

failures for these three systems were detected

programmatically.

Figure 3.48 shows the distribution of failures by general

detection method and level of significance. More of the

Moderate failures were detected programmatically than the

Significant failures. Alternatively, more Significant failures

were detected as the result of abnormal equipment

operation than moderate failures. The latter is not

unexpected, because the likelihood of abnonnal equipment

operation should increase with increased valve degradation.

Figure 3A9 shows the relative failure rate by valve size and

system usage for failures classified as Significant only. A

pattern seen for all failures (Figure 3.25) was found to hold

true for this subset as well; that is, for the smaller valve

sizes, the relative failure rates for the three system usage

categories are similar, but for the larger valve sizes,

normally operating systems were much more likely to have

failures. In fact the pattern is somewhat more dramatic for

the Signficant failure class.

Figure 3.45 Comparison of discovery processes for

different type facilities

ORNL-DWG 93-7331

100 I I

E 80 :I 3-

Z 40 

0 

Normally Shutdown Testing

Operating support only

I 0c ftgmmtc || Nnprogrammatic 

Figure 3.46 Comparison of discovery processes for

different system usages

35 NUREG/CR-S944
Results

ORNL-DWG 93-7332

3.5 

3.

Values shown reflect the relative failure rate of

Signficant failures, where the relative failure rate

forSignificant failures in all systems is one

0

LI

I

2.5 

2- .

1.5 +

1-.

0.5 +

0 _-

ESW Main Feedwater RCIC

Steam

ESW~ MIi Fedae RI Comb Diesel HPCI CCW Suppress. Contain.

Starting Pool Cooling

Air Support

Comb.

Gas

Control

Relative failure rate, by discovery process, for failures designated as significant. Systems shown are the

Figure 3.47 Relative failure rate, by discovery process, for failures designated as signg/iant. Systems shown are the

ten systems with the highest relative failure rates

ORNL-DWG 93-7333

5% 4% 8%

20% .; I . .. 14%

9 % t% 4 646%

62%

Moderate Significant

I Programmatic 3 Abnormal equipment operation El Misc. or unclear

E Routine observation 101 Special inspection

Figure 3.48 Distribution of failures by general detection method and extent of degradation

NUREG/CR-5944 363
Results

ORNL-DWG 93-7334

3

2.5 

2 

'

a

.Zo

.i

In Normally operating

E Shutdown support

E Testing only 1.5 .

1 -I

0.5

>2 and 04

-4 4

>4 and S10 >10

Valve size group, in.

Figure 3A9 Relative failure rate by valve size group and system usage for failures classified as Signifiant

3.14 Results of Selected Plant Review

In order to provide a measure of i racies in the ORNL

characterization of the failures, failure narratives and

charactizations for seven plants (12 units) were reviewed

by plant personnel, using the related maintenance work

order packages. ORNL was present during one of the

reviews, and subsequently, with the help of NIC personnel,

reviewed and tabulated the results. Two specific

charactrizations were tabulated: extent of degradation and

failure area. Other parameters were also discussed, but a

measure of accuracy for these two parameters was

particularly sought Tables 3.2 and 3.3 summarize the

results of the plant specific review. Note that the sum of

the net changes shown in table 3.3 do not equal zero, since

some failures affect multiple areas.

Table 3.2 Summary of results of plant review of ORNL characterizations

Failures Failure area Extent of

Plant reviewed changes degradation changes Comments

A 13 1 2 Both changes in extent went fromn moderate to significant

B 11 3 0

C 16 5 2 Both changes in extent went frcn significant to moderate

D 6 2 0

E 19 6 1 (marginal) Extent change, if made, would be from significant to moderate

F 10 5 0

G 16 2 2 Both changes in extent went from significant to moderate

Total 91 24 6 (pus one marg.) Net change of 2 to 3% in the direction of reduced significance

37 NUREG/CR-5944
Results

Table 3.3 Suunary of failure area plant review

Hinge Disk stud/ General Dirt/foreign

Affected area: pin hinge arm Seat Penetration wear material Unknown

Number failures in

which area was

deemed affected by 23 17 28 1 14 11 15

the ORNL

characterization

Net changes

suggested by plant 2 4 -2 1 -2 4 4

personnel

Percentage change 9 24 -7 100 -14 36 -27

Note that there were initially a substantial number of extent

of degradation characterizations to which plant personnel

took exception (mostly where the plant personnel felt the

assignment should have been Moderate instead of

Significant). During subsequent follow-up review with

NIC personnel, however, it became evident that almost all

of the exceptions were due to the plant personnel having

considered the degradation in safety for the system or plant

rather than the extent of valve degradation. The figures in

Table 3.2 reflect the results of the follow-up review.

These results suggest that the extent of degradation crosscorrelation results should be relatively accurate, but the

results associated with failure area characterizations should

be viewed with some suspicion.

Two obvious limitations of the characterizations are (1) the

accuracy and thoroughness of the narratives and (2) the

ability of the reviewer to correctly interpret the narratives.

During the course of the review, it became very clear that

utilities have substantially improved the length and quality

of narratives submitted to the NPRDS data base during

recent years. To check the validity of this observation, the

average length of text in the narratives for failures

occurring in the years 19841990 was calculated The

results are shown in Figure 3.50.

ORNL-DWG 93-7335

800 -

a U

> 700 .

*1 

3 00-

r 400 .

300.1 i i *

1984 1985 1986 1987 1988 1989 1990

Failure year

Figure 3.50 Average text length for check valve failure narratives characterized vs failure year

With the additional length of narratives, there also appeared

to be a trend toward higher quality, though this was not

quantifiable. It can be concluded that the thoroughness of

the narratives is improving, thereby paving the way for

improvements in the quality of reviews of the nature of this

study in the future. However, to address the second area of

limitation noted above, it would greatly enhance the ease of

use and accuracy of the data base if means were provided to

directly code in parameters such as the affected area of the

valve. Alternatively, if utility personnel who are

responsible for submitting the failure records were made

aware of the need to include such information in the

narratives, the information could be obtained indirectly

(and with more difficulty).

Discussions with NIC personnel resulted in the

identification of the desirability of exploring possible

changes in either the NPRDS database itself, or in the

reporting practices within the existing structure. NIC

indicated that they will pursue this independently.

NUREG/CR-5944 38
4 Summary, Conclusions, and Recommendations

4.1 Summary

This study was conducted to identify failure patterns

associated with check valves used in nuclear power plants

in the U.S during the years 1984-1990. The source of

data for the study was the NPRDS database. The failure

data from the database was filtered to remove those

failures that involved external leakage as well as those

that clearly involved only minor internal leakage.

In order to provide results that were not biased by

population sizes, the data was nonnalized to the relevant

population group. A "relative failure rate" was developed

for the design and failure characteristic parameters

evaluated. This relative failure rate, along with other

measures, was used to develop and present the data in a

normalized fashion.

The study found some parameters that yielded relatively

strong failure trends, while there were no apparent trends

or correlations for other characterized parameters.

There was minimal relationship found between failure

rate and valve or plant age.

Large valves were found to be more likely to degrade and

more likely to degrade significantly than smaller valve

sizes. This relationship was particular true for valves used

in systems that are normally operating. Valves that are

greater than 10 in. and used in normally operating ystems

were twice as likely to fail as the valve population as a

whole.

Valves used in service water, main steam, feedwater, and

diesel starting air systems were found to be two or more

times as likely to fail as the valve population as a whole.

However, the diesel starting air system valve failures

were, on the average, less extensively degraded than were

the valves in these other three systems.

Significant differences in failure rates by manufacturer

were found. Factors such as the severity of duty for

specific valve applications, which were beyond the scope

of this study, likely had a significant impact on these

rates.

valve size. In addition, valves used in nomally operating

systems were about twice as likely to fail stuck open as

those not normally in use. On the other hand, valves used

in systems used only during testing were more likely to

stick shut.

Degradation of the disk stud and/or hinge arm area was

the least likely area to be detected programmatically;

failures in this area were also among the most significant

in extent of degradation.

4.2 Conclusions

This study has shown that failure rates for check valves

are clearly related to certain characteristics and features.

Specific plant and system features which are beyond the

scope of this study are also influential in degradation and

failure rate; thus, the results presented herein should be

considered as only part of the picture.

These analysis results may be useful to those seeking to

optimize the use of resources. The results may also be

useful as baseline information for several types of

comparisons, such as individual plant experience with that

of the industry as a whole, and trending industry

performance with time. The latter may be particularly

pertinent during the next few years, to determine how

successful advances in monitoring techniques and

programmatic controls are in improving valve reliability.

4.3 Recommendations

It is recommended that periodic updates of this study be

performed to provide an indication of industry trends. It

is further recommended that, to the extent feasible,

additional parameters be considered in future reviews,

either as a part of the periodic update process or as a

separate review. Parameters that merit consideration

include:

* valve type (swing, lift, tilting disk, dual disk, etc.),

* valve orientation (horizontal, vertical, distance from

upstream disturbances, etc.), and

* monitoring or maintenance programs for specific

valves (such as IST).

BWR plants had a higher overall relative failure rates;

however, this was clearly the result of the fact that BWR

plants are better structured to detect failures

programmatically failure rates for all detection means

other than programmatic were lower for BWRs than for

PWRs.

Valves used in systems that are normally in service did

not experience significantly higher failure rates overall

than did valves used in infrequently used systems (used in

support of shutdown operations or for testing only).

However, as noted above, the failure rate for valves used

in normally operating systems had a strong relationship to

39 NUREG/CR-5944
Reference

1. M. L. Scott, "Check Valve Failure Trends in the

Nuclear Industry," EPRI Power Plant Valves

Symposium II, Charlotte, N.C., July 1989. Available

for purchase from the Research Reports Center, Box

50490, Palo Alto, CA 94303.

NUREG/CR-5944 40
Appendix

Charts of Study Results

41 NUREGICR-5944
ORNL-DWG 93-7336

1.2 -

1 -_

0.8 -

0.6 -

.

0.4 -_

0.2 -_

O - l4

<5 Ž5 and <10 210 and <15 Ž15 and <20

Valve age group (years)

Figure A.1.1 Relative failure rate by valve age group
(. ORNL-DWG 93-7337

1.2 r

1 +

0.8 4-

I

aE

0.4

0.2 4-

O - I I I - <5 25 and <10 210 and <15 215 and <20

Plant age group (years)

Figure A.1.2 Relative failure rate by plant age group
ORNL-DWO 93-7338

Valve size group, in.

2.5 -

2 -

5 2

3 >2 and -S4

5>4 and 10

M >10

i1.5 -

tb.i

a 1-~

"I

-0

I I

215 and 20

0.5 +

-_

-I- ±L A

<5

A

I I 25 and <10 210 and < 15

Valve age group (years)

Figure A.1.3 Relative falure rate by valve age group and valve size group

V

I.
I

ORNL-DWG 93-7339

3.F.) _ _

2.5

2

1.5

0

0.5

0

n

<5 25 and <10 k10 and <15 5 and <20

Component age group (years)

M ESW M Feedwaier E Diesel Starting Air ES Main Steam m HPCI

i0 Containment Isolation 0 RCIC M Suppression Pool E AFW i ccW

Support

Figure A.1.4 Relative failure rate by valve age group and system for ten systems with the highest overall relative failure rate
ORNL-DWG 93-7340

6

S

4

The high failure rate for P032 in the

15- to 20-year age group is affected

by the fact that there were few valve-years

service for that manufacturer in this time frame

2

-J

1

0

<5 25 and <10 210 and <15 215 and <20

Valve age group (years)

| S075 A585 E W030 1 C684 ID A391 iD M360 EI P032 *0 V135 * V080 ElG202 J

Figure A.1.5 Relative failure rate by valve age group and manufacturer for ten manufacturers with the highest overall relative failure rate
I, ORNL-DWG 93-7341

2.5

The relatively high failure rate for B&W valves

in this age group is partially attributable to the

minimal operating experience in this class during

the study period

2

lBW

CE

E GE

#.'

1.5

1

0.5

0 -I- +I 4- AI

<5 25 and <10 >10 and <15 Ž15 and <20

Valve age group (years)

Figure A.1.6 Relative failure rate by valve age group and NSSS
ORNL-DWG 93-7342

1.4 -

1.2 -

1 -

l Normally operating M Shutdown support 1 Testing only

-I

0.8 

.It 9 0.6 -

A

a OA 

0.2 -

0 -- + + - <5 AS and <10 210 and <15 215 and <20

Valve age group (years)

Figure A.1.7 Relative failure rate by valve age group and system usage
I

Lh

El

ORNL-DWG 93-7343

0.5 -

0.45 -

0.4 -

0.35 -

'A

0.3 -

'8 0.25 -

z 0.2-

0.15 -

0.1 -

0.05 -

0 -

p

t0

EL

<5 25 and <10 210 and <15 215 and <20

Valve age group (years)

1 mproper seating M Stuck open E Disk/other part off or * Restricted motion/flow

broken

l Stuck closed M Loose/impactdamagedpart 0 Miscellaneous

Figure A.1.8 Distribution of failures by age and failure mode
ORNL-DWG 93-7344

0.3

0.25

0.2 jCa

Ie 0.15

0.1

F F

n

tA

0.05

0

<5 25 and <10 210 and <15

WXI I

215 and <20

Ii

Valve age group (years)

* Seat area * General wear U Hinge pin area U Disk stud/ I Foreign material

hinge ann area

o Unknown/other Penetration area

U Figure A.1.9 Distribution of failures by valve age group and failure area
.I

ORNL-DWG 93-7345

0.7 

0.6

0.5 -

.4-4

0

0.4

0.3

tJI 0.2

0.1 -

0- I +

<5 25 and <10 210 and <15 215 and <20

Valve age group (years)

| Programmatic M Abnormal equipment El Routine observation M Special inspection B Misc. or unclear

operation

Figure A.1.10 Distribution of failures by valve age group and general discovery method
ORNL-DWG 93-7346

0.4 -

0.35- 

0.3-

0.25-

t, 0.2i -L ~

0.15 

(y

0.1 

0.05-

Valve age group (years)

1N Not specific M Leak test 0 Disassy. and/or inspect. * Hydraulic indication

m Non-hydraulic indication Punp/comp. rotation J Other maintenance M Non-intrusive test

Figure A.1.11 Dtribution of failures by valve age group and specific discovery method

f
IA\0

ORNL-DWG 93-7347 I

0.7 T-

| Non-programmatic 0 Programmatic I

0.6 +

0.5 -

g

Ij

0.4 -

0.3 

0.2 

0.1

0- +- - 4± -I

<5 25 and <10 210 and <15

Valve age group (years)

Figure A.1.12 Distribution of failures by valve age group and discovery process

:15 and <20
ORNL-DWG 93-7348

1.2 

1.-

0.8 -

.44 0.6 +

LA

tA OA +

0.2 +

0 -- -4-

<5

-4--0000000 I _

25 and <10 210 an

Valve age group (years)

13 Significant Moderate

--I

d <15 215 and <20

Af

Figure A.1.13 Comparison of relative failure rates by valve age group and extent of degradation
I

ORNL-DWG 93-7349

2 -

The population for the

smallest valves is about

twice that for the larger

valve size groups 1.8 +

1.6 +

1.4 +

I4

i

1.2 +

* 0.4

- 0.35

- 0.3

- 0.25 8

- 0.2 a)>

18

0.15 *1g

M

0.1

- 0.05

1 +

0.8 + or1

0.6 +

0.4 +

0.2 +

0 -I- 0

•2 >2 and 4 >4 and S10 >10

Valve size group (ii.)

I Relative failure rate i * Population I

Figure A.2.1 Relative failure rate and population distribution by valve size group
ORNL-DWG 93-7350

2.5

Valve age group (years)

2 +

in 5

25 and <10

* 1 0and < 15

1 15 and < 20

I

1.5 -t

LA

1 -

0.5 -

0 - +I - AI

>2 and •4 >4 and •10 >10

iO

Valve size group (in.)

Figure A.2.2 Relative failure rate by valve size group and component age group
ORNL-DWG 93-7351

3.5 

w 3 -- ~~

2.5--

0 .5--

00~~~

•2 >2 and 4 >4 and 510 >10

Valve size group (in.)

M ESW M eawar 0 Diesel Starting Air E Main Seain ED HPCI

EW Containment Isolation 0 RCIC i Suppression Pool U AFW 13 ccw

Support

Figure A.2.3 Relative failure rate by valve size group and system
5 ORNL-DWG 93-735

4.5

4

3.5

Includes only manufacturers with greater than

3 1000 valve-years operation during study period

~2.5

'0 ~~~1.5

1

0.5

0*

:92 ~~>2an 4 and1 >10

Valve size group (in.)

MS075 A585 0 W030 C684 [ A391 EB M360 P032 V135 U1 V080 23 G202

Figure A.2A Relative failure rate by valve size group and manufacturer for I ~ manufacturers ~~~~~~~~~~~~~~~ten with the highest overall relative failure rate

S2
I! ORNL-DWG 93-7353

2.5 -Tr -- - _

2 - IBW CE GE W

. 1

I 1.5 -

I 11-

iel I 

1191111 1

ii*iwH S S111111111

.........

.........

111111111

.........

Em

§11111111 388gffi

. z

>10

8

0.5 +

0 +I + + 4

•2 >2 and S4 >4 and•510

Valve size group (in.)

Figure A.2.5 Relative failure rate by valve size group and NSSS
ORNL-DWG 93-7354

2.5 -

2

0 .5 - -

0.5

0

I~~~~ 

kw Normally operating 0 Shutdown support H Testing only

I _!//// Ia _ =MMMRFFR IMQMMZllllllH4ll A

>2 and!54 >4 and 910

Valve size group (in.)

Figure A.2.6 Relative failure rate by valve size group and system usage

>10
ORNL-DWG 93-7355

0.6 

0.5 --

0.4 --

~Oa

023

0% ~ ~ ~~. 

0~~~~~~~~~~.

<2 >2 and 54 >10

Valve size group (hi.)

M Improper seating 0 Stuck open WI Disk/other part off or H Restricted motion/flow

broken

ID Stuck closed 0 Loose/damaged part 0 Miscellaneous

Figure A.2.7 Distribution of failures by valve size group and failure mode
ORNI-DWG 93-7356

0.35 -

0.3 -

E I~~~~~I.

0.25-

g 0.2 I

0

0.1 

0) 0.1 

0.05-

0 - 10

>2 and!

f,

54 >4 and V10 >10

Valve size group (in.)

Seat area M General wear 8 Hinge pin area * Disk stud/hinge arm area

OI Foreign material Unknown/other Penetration area

Figure A.2.8 Dstribution of ahiures by valve size group and failure area. The values shown reflect the fraction of failures I within the designated size group In which the specified area was affected. The sum of the values within each size group exceed one since some failures affected multiple areas I

I I
ti

ORNL-DWG 93-7357

0.7

0.6

0.5

Valve size group (in.)

0

0

0.4

0.3

• <2

M >2 and •4

E} >4 and •10

>10

0.2 -

0.1 -

0 - +

Programmalic Abnormal

equipment

operation

Misc. or Routine Special

unclear observation inspection

Figure A.2.9 Distribution of failures by valve size group and general detection method
ORNU-DWG 93-7358

0.45

0.4

0.35

0.3

i 0.25

0.2

0.15

0.1

.1S

0.05

0

0%

I

>2 and 54 >4 and 10 >10

Valve size group (in.)

EI Not specific u LeaD test Em Disassy. or inspect. e Hydrulic indication

1I Non-hydraulic indication El Pump/comp. rotation O Other maintenance M Non-intrusive est

Figure AX110 Distribution of failures by valve size group and spedific dbscovery method

us I
I

ORNL-DWG 93-7359 I

0.7 -r0.6 4-

0.5 4-

I

0.4 -

0.3 +

0.2 -

0.1 -I0 +- 4- 4- 4- -I

•2 >2 and 4 >4 and !10 >10

Valve size group (in.)

Figure A.2.11 Distribution of failures by valve size group and discovery process
ORNL-DWG 93-7360

100 -

90 -

80 +

70 

gI4w

60 +

50 

0z

40

30

20 +

10 

0 - 1 -- I -I I

!92 >2 and•54 >4 and 10

I Significant Moderate

Figure A.2.12 Distribution of failures by valve size group and extent of degradation

:I

>10
ORNL-DWG 93-7361

I 3

2.5

Includes only those systems with

Ž 1000 valve-years of accumulated

experience during the study period

2

~1.5

00

0.5

W Cr~~~~~~~~~~~~~.

C.D; ) 1 h d j X | D e b ! - Mj S E D it a a S 

Figure A.3.1 Relative failure rate by system
ORNL-DWO 93-7362

3.5

Valve age group

3

0 5 and <1

2.5 - _10 and <

* 15 and <

1.

1

0.5

0

ESW Feedwatr Diesel Main Steam HPCI Containment RCIC Suppression AFW C(

Starting Air Isolation Pool

Support

Figure A.3.2 Relative failure rate by system and component age group for ten systems with the highest overall failure rate
ORNL-DWG 93-7363

I:f

3.5

3

2.5

a 2

I1 1.5 --0D

1

0.5

0

ESW Feedwater Diesel Main Steam

Starting Air

HPCI Containment RCIC Suppression AFW CCW

Isolation Pool

Support

Figure A.3.3 Relative failure rate by system and valve size group
ORNLDWG 93-7364

7 0.2

6-

94 M3 0.11

-a2 l ;

A

I0

Emergency Service Water Feedwater

-4

8

9

rA

4)

4

0t-. I

19

U.

i

II

Dfesei Starting Air l _= Relative failure rate

-U-- Fraction of valve-years

Main Steam

IAFigure A.3A Relative failure rates and operating experience for manufacturers with more than 200 valve-years experience In the respective

system during the study period. The fraction of valve-years Is for the designated system only. Results sorted by relative failure rate
ORNL-DWG 93-7365

Q 4.5 _

3' Ihi

3,5 -- :

3 +F

2- 

--j

1

0.5 --

0 | , , , , |ltq#1111888&~ V :V/Y 4

ESW Feedwaer Diesel Starting Air Main Steam

I * BW CE IGE W

Figure A.3.5 Relative failure rate by system and NSSS for four systems with the highest overall failure rate
ORNL-DWG 93-7366

0.7

0.6

0.5

0.4

O0.3

0.2

0.1

0

,

-,. E

. ...

ESW Feedwatr Diesel Starting Air Main Steam

Improper seating E Stuck open E]Disk/otherpartoff/broken IlRestrictedmotion/flow

ID Stuckclosed E Loose/damaged part E Miscellaneous

IO Ffgure A3.6 Distribution of failures by system and failure mode for four systems with the highest overall failure rate
I

ORNL-DWG 93-7367

0.4 -r

0.35 -

0.3 -

.t406

0.25 -

0.2 -

0.15 -

-I

0.1 -

0.05 -

04o ±

ESW

Seat area 0 General wear M Hinge pin area M Disk stud/binge arm area

Foreign material 0 Unknown/other M Penetration area

Figure A.3.7 Distribution of failures by system and failure area for four systems with the highest overall failure rate
ORNL-DWG 93-7368

0.6

0.5 -

AA - V.s

W

'4a8

j3

.

.

At

0.3 ±

-j

0.2

0.1 .

0 -- T iIESW Feedwafer Diesel Starting Air Main Steam I Pron ama tc Abnormal equipment W Misc. or unclear 1 Routine observation Il Special inspection

operation

Figure A.3.8 Distribution of failures by system and general detection method for four systems with the highest overall failure rate

I

I
ORNI4-DWG 93-7369

0.6 

0.5 --

0.4 1..

19.~~~~~~~~~~~~1

ON ~~0.2 -

0.1 -i

0 

ESW Feedwaer Diesel Starting Air Main Steam

U3 Not specific 3 Leak test E Disassy. and/or inspect. l Hydraulic indication

ID Nonhydraulic indication W Pump/comp. rotation 13 Other maintenance 0 Non-intrusive test

Figure A3.9 Distribution of failures by system and specific detection method for four systems with the highest overall failure rate
ORNL-DWG 93-7370

0.9 -

0.8 -

0.7 -

0.6 

1 0.5 - ki-a

0,

aZ 0.4 -

0.3 -

0.2 -

0.1 -

-J

0 - MMM YX1 MMA I * OWMIA * P ZZA I MMMMA * W=VMA MWOJ .ZZZf |M PAWZ fMEM

ESW Feedwatr Diesel Main Steam HPCI Containment RCIC Suppression AFW CCW

Starting Air Isolation Pool

Support

I M Non-programmatic 3 ProgrammaticI

Figure A.3.10 Distribution of failures by system and discovery process for ten systems with the highest overall failure rate

*1

A
I ORNL-DWG 93-7371

3 

2.5

2

Si

00

1.5

1

0.5

0 -

ESW Feedwaer Diesel Main Steam

Starting Air

HPCI Containment

Isolation

4 ! Iz 04

RCIC Suppression

Pool

Support

I- - AI

AFW CCw

|0 Modemkt a Significant

Figure A3.1 1 Allocation of relative failure rate by system and extent of degradation for ten systems with the highest overall failure rate
ORNU-DWG 93-7372

3.5

3

2.5

Excludes manufacturers with

<1000 Valve-years of accumulated

experience during the study period

I

-j'.0

2

1.5

1

0.5

0

12

10

8 8

a

6 '

4 C

2

0

Valve manufacturer

Relative failure rate * Population distribution 1

(Valve-years %o)

Figure A.1 Relative failure rate and service population by manufacturer I

I
6

The high failure rate for P032 in the

15- to 20-year age group is heavily affected

5 by the fact that there were few valve-years

service for that manufacturer in this time frame

4

00

2

S075 A585 W030 C684 A391 M360

Valve manufacturer

ORNL-DWG 93-7373

Valve age group (years)

M.< 5

0 Ž_ 5and <10

u 10 and <15

l 15 and <20

Figure A.4.2 Relative failure rate by manufacturer and valve age group for the ten manufacturers with the highest overall relative failure rates
ORNL-DWG 93-7374

5

4.5 Valve size group (in.)

4 - _2

>2 and •4

3.5

W>4 and•510

3 - >lo

I I .

j2.5

0~

S075 A585 W030 C684 A391 M360 P032 V135 V080 G202

Valve manufacturer

Figure AA.3 Relative failure rate by valve manufacturer and size for the ten manufacturers with the highest overall relative failure rates
ORNL-DWG 93-7375

00

I

4.5 ---- 0.2

3.5- 

2.5-- 

>~ 15

0.5 I

0 I I I0

Ms a n 4 n (" II g P 9

w u w 2 u P. C.)° 

Emergency Service Water Feedwater

SS

9430

2 

1 2-

0 - I I -_

> u ¢ ¢ 22 U 

0

j

6

44

rg3

2

1

0

0.2

U

>

0.1 >

a) ~~~~~~~~~~~0

~~~~ 2 0~~~~~~~~

Diesel Starting Air Main Steam

Relative Failure Rate

- Fraction of valve-years

Figure AAA Relative failure rates and operating experience for the ten manufacturers with the greatest valve population in

the respective systems during the study period. Results sorted by manufacturer population
ORNL-DWG 93-7376

5- 

4.5 -

4

3.5 -

1 3 -

1 2.5- 

00 1.5

0.5- 

0~ I~~~~~. S075 A585 W030 C684 A391 M360 P032 V135 V080

Valve manufacturer

I B &W M CE A9GE SO W I

Figure AA.5 Relative failure rate by NSSS for ten manufacturers with the highest overall failure rate.

Sorted by overall relative failure rate

G202
nBlW octets an 7177,77

3.5 LIiLLW J-h

I~~~~~~

0.5

S075 A585 W030 C684 A391 M360 P032 V135 V080 G202

Valve manufacturer

[ X Nonnally operating M Shutdown support M Testing only

Figure A.4.6 Relative failure rates for the ten manufacturers with the overall highest failure rate by normal system status

I
ORNL-DWG 93-7378

0.5

0.45--

~~~~~~~~~~~~~N 4'

0.4--

0.35--

g0.3--

0.2 

00 ~~0.15--

0.1 

0.05--

S075 A585 W030 C684 A391 M360 P032 V135 V080 G3202

Valve manufacturer

IM1 Improper seating Disk/other part off or broken ID Loose/damaged part Miscellaneous

IID Restricted motion/flow aMmtu closed O3 tuck open

Figure AA.7 Distribution of failures by manufacturer and failure mode for ten manufacturers with the overall highest failure rate. I The sum of the values shown for each manufacturer equals one
Ih ORNL-DWG 93-7379

0.35 T

0.3 -

0.25 -

Go

0.2 -

0

8

0.15 -

00 0'

0.1 -

0.05 -

0- -4

S075 W030

Valve manufacturer

Hinge pin area 1 Disk stud/hinge arm area M Seat area *I Penetration area

ID Unknown/other 1 General wear 0 Foreign material

Figure AA.8 Fraction of failures by manufacturer In which the designated valve area was affected. Manufacturers shown are the

five manufacturers with the highest overall relative failure rates. Note that the sum of the fractions for each manufacturer

may exceed one due to multiple areas being affected In some cases
ORNL-DWG 93-7380

100% -

90%-

80%

70o -

609bw

IS 50%I-

'l0 409 -

30% -

20%-

10%-

0% -

I .

00-J

aMMMA ZZZZ mmM 000MA I WIMmm I KZZA ZZA I VZZMAf IMM"M I WIZ/M 1m

S075 A585 W030 C684 A391 M360 P032 V135 V080 a,

Valve manufacturer

I I Modert E Significant

Figure AA.9 Distribution of failures by extent of degradation for ten manufacturers with highest overall failure rate

AI

202

VD
I ORNL-DWG 93-7381

1.2 T- -r- 0.5

1 -

0.8 -

- 0.45

- 0.4

- 0.35

- 0.3

- 0.25

- 0.2

a

r, 0.6 -

0000

0.4+ 

/

-HI

2!~

C11

S8

0.2 

- 0.15

* 0.1

- 0.05

0 4I-- iH -0

BW CE GE W

I Relative failure rate F Fraction of Valve Population

Figure A.5.1 Relative failure rate and operating experience by NSSS
ORNL-DWG 93-7382

2.5 -

Valve age group (years)

2 _ <5

l 5 and <10

ES lO and <15 1 -,,

1 1.5 - I IM 15 and 20

.

0.5 

0 h

BW CE

Figure A.5.2 Relative failure rate t

GE

by NSSS and valve age group

I MMWMi///// I

w

i
IAi

ORNL-DWG 93-7383

I

R.

2.5 

Valve size group (in.)

I M:92I

2 

a

LI

9

5

I

04

1.5 

1 +

BW

0. +

M >2 and 54

E3 >4 and1o

0 >10

A_

S00002 EEB8 ffl

t t tt0000 

l l!. i_ g

| | .m_

I m .

_ |g g ,

CE

hF

I

F ooze

moo

HHEH_

mum_

1 Ed A. A._

_

GE w

0 4 4 + 4

Figure A.53 Relative failure rate by NSSS and valve size group
ORNL-DWG 93-7384

4.5

4

3.5

2 5

.~ 2

1.5

1

0.5

0

BW CE GE W

| I ESW 0 Feedwater Diesel Starting Air E Main Steaml

Figure A.5A Relative failure rate by NSSS and system for four systems with the highest overall failure rate
ORNL-DWG 93-7385

IAf

4- 35

3.5 30 i

* 3.S- 1! / \) 1 

25 

§ 2.5- .-20 

1.5 15.4.

0.5 m 5 

N.M. ~~~~1. Q

i6-

I)

16 .4

12 a

U) z

8 0

4 Cg

n

s 't WI a w | R n

: !2 d I U W 9 9

II&W

S g W% > m wo n U ff 2 Q 2 2 > 5 

CE

3.5 10

3-

i 2.5 8

I. 2z .6 2

i 1.5 / -

2 a

0.5 0 

0 . . . .

4.5

4

1 3.5

3

2.5

2

i53 1.5

04 

0.5

4.5 ~ ~ ~ ~ ~ ~ ~ .5 

2 ~~~~~~z . / gU11 

I af 0 f 00

W tn 14t8 0 W " 00 m 00 't P N!2;516RU` -

GE Relative failure rate

* - Valve-year percentage

W

Figure A.55 Relative failure rate and population percentage for ten manufacturers with highest overall

failure rate within the NSSS. Sorted by relative failure rate
ORNL-DWG 93-7386

1.4 -

1.2 +

1

-

It

;w.z 0.8 +

0.6 + wc

0.4 +

0.2 -

0 - B&W

t*is I+Hmt+HI W-Y7lolaff "*+"1 IN

CE GE

I M Normally operating E Shutdown support m Testing only I

Figure A.5.6 Relative failure rate by NSSS and system status.

-1

W

I
Ifit

ORNL-DWG 93-7387

0.5 -

0.45 -

0.4 -

0.35 -

g 0.3

'8 0.25 -

2 0.2 -

0.15 -

0.1 -

0.05 -

0-

n

IT I. =Mi z14 .

B&W CE GE W.

* Improper seating M Stuck open 11 Disk/other part off or 1 Restricted motion/flow

brken

m Stuck closed 0 Loose/damaged part O Miscellaneous

Figure A.5.7 Disiribution of failures by failure mode for NSSS
ORNL-DWG 93-7388

0.4 -

0.35 -

0.3 -

I

0

t

01

NO

0.25 

0.2 -

0.15 -

0.1 -

0.05 -

0- tJ I1

BW CE GE W

| sent E area 0 General wear En Hinge pin area 0 Disk stud/hinge ann area

m Foreign material 0 Unknown/other gI Penetration area

Figure A.S.8 Distribution of failures by failure area for NSSS. The sum of the values for each NSSS exceeds I one because some failures affected more than one area
I~ ORNL-DWG 93-7389 ;a.

0.7 r

0.6 +

0.5 -

I

OA -4-

0.3 -

0.2 -

0.1 -

0 - -

B&W GE w

M Programmatic MF Abnormal equipment Misc. or unclear 1 l Routine observation E Special inspection

operation

Figure A-59 Distibution of failures by NSSS and general detection method
ORNL-DWG 93-7390

0.45 

0.4 -.

0.35 _

0.3 -

1 0.25

0

*0 0.2 -

0.15 _

0.1 - _

0.05 _

0 

..

x r _ $

D .,@

~S

BW CE GE W

M Not specific E Leak test El Disassy. and/or inspect. I Hydraulic indication

IM Nonhydraulic indication D Pump/comp. rotation 0l Other maintenance 0 Nonintrusive test

Figure A.5.1O Distribution of failures by NSSS and specific detection method A
I

w

ORNL-DWG 93-7391

100

90

80

0

.S

70

60

50

NO 40

30

20

10

0 I I IH - BW CE GE

I M Programmatic U Nonprgammatic 

Figure A.5.11 Distribution of failures by NSSS and discovery process

w
ORNL-DWG 93-7392

0.7 -

0.6 +

0.5 +

0.4 -

J0.3 -i0.2 

0.1 +

O 4- l- 4- l- -- B&W CE GE w

I M Moderate M Significant |

Figure A.5.12 Distribution of failures by NSSS and extent of degradation
I

ORNL-DWG 93-7393

1.2 r

I 4-

0.8 +

, 0.6-

0.4 - _

0.2 -4-

1- I I

Normally operating Shutdown support

Figure A.6.1 Relative failure rate by system usage

Testing only
ORNL-DWG 93-7394

1.A -r- Component age group (years)

1.2 -

lj

0.8 --

0

T0.6 -_

I< 5

M ks and <10

E210and<15

15 and <20

0.4 4- i\, -

.;

.4,

0.2 -_

0 -- +I -I

I Normally operatlnj I Shutdown support

Figure A.6.2 Relative failure rate by system usage and valve age group

resting only
I ORNL-DWG 93-7395 I

2.5 r

2 +

1.5 -

-

I -

0

Valve size group (in.)

E| 52 M >2 and54 E; >4 and 510 12 >10

0.5 -_

0 -- ± 4- -I

Nonnallyoperating Shutdown support

Figure A.6.3 Relative failure rate by system usage and valve size group

Testing only
ORNL-DWG 93-7396

3.5

3

C4 2.5

2

e 1.5

.~1

0.5

0

10

9

8 

7

6 L

4 & 53 3 It 2

O

I

4) .

:£4

`)

4) aM

4 S

4)0 0

O

An system Normally operating systems

2.5

)l 2 .20 2 - 12

1.5 - ~~~~15 ~:1.5 e

~~~~~L. ~ ~ ~ ~ ~ .

~0.5 5 0.5

00 0 

Shutdown support systems Testing only systems

I

all= _ Relative failure rate * Valve-years percentage

Figure A.6A Relative failure rate and portion of operating experience by system status for the ten manufacturers with the highest

relative failure rate within the speciled type of systems. Includes only manufacturers with 2500 valve-years operation

In the specfied system staus type (21000 valve-years for All systems chart)
I(

ORNL-DWG 93-7397

1.4 -

1.2 -

1

i 0.8

0.6

0.4 -

0.2 -

0 - +I -h -I

Nornally operating Shutdown support

I B38W CE AGE MW

Figure A.6.5 Relative failure rate by system status and NSSS

Testing only
ORNL-DWG 93-7398

0.6 

0.5 +

I

.

0.4 -

0.3 -

0.2 -

0~

a'

0.1 -

0- *= * . -

Normally operating Shutdown support Testing only

Improper seating M Stuck open W Disk/other part off or M Restricted motion/flow

broken

ID Stuck closed D Loose/impact damaged part a Miscel1aneous

LA Figure A.6.6 Distribution of failures by system status and failure mode
I ORNL-DWG 93-7399

0.35 -

0.3 -

.8 78 0.25

ag >

a 0.2

*t 0.15

0.1

0.05

0

-; -

-I. -i -i

Normally operating Shutdown support Testing only

* Seat area General wear 1 B Hinge pin area E Disk stud/hinge arm area

DI Foreign material M Unknown/other Penetration area

Figure A6.7 Fraction of failures by system usage and failure rea/source. Values shown are the fractions of failures In

a particular system usage category In which the designated area was affected
ORNL-DWG 93-7400

0.6 -r0.5 +

0.4 -II

t4.

'4-

081

M

0.3 -1-

0~

-4 0.2

0.1 4-

0 +I

Normally operating Shutdown support Testing only

IA A.6.8 Distribution of failures by general detection method for the three system usage categories
I

I

ORNL-DWG 93-7401

0.45 -

0.4 -

0.35 -

0.3 -

2

:S0.25 -

3- 0.2 -

0.15 - 0

00

0.1 -

0.05 -

JI

Normally operating Shutdown support Testing only

1 Not specific 3 Leak test E Disassy. and/or inspect. * Hydraulic indication

DI Nonhydraulic indication NI Pump/comp. rotation 0Other maintenance H Nonintrusive test

Figure A.6.9 Distribution of failures by specific method of detection for the three system usage categories
ORNL-DWG 93-7402

100

90

80

70

60

50

40

0

I

30

20

10

0 -H--- -

Nommilly operating Shutdown support Test

Programmatic M Nonprgrammatic

Figure A.6.10 Distribution of failures by system usage and general discovery process

ing only

I
I.

ORNL-DWG 93-7403

100 -

90 +

80-

70 -

0

I

60 +

50 

a- 0 40 +

30 +

20

10

I lH- - -I

Nonmallyoperating Shutdown support Testing only

I M Moderate M Significant I

Figure A.6.11 Distribution of failures by system usage and extent of degradation
ORNL-DWG 93-7404

Stuck open

28%

Improper seating

45%

I-&a-'

DaStuckclosed

7%

Ada~~~:

Restricted motion/flow

7%

Miscellaneous 2%

/ 10%

Loose/danaged part Disk/other part off or broken

Figure A.7.1 Distribution of failures by failure mode I 
I ORNL-DWG 93-7405

2 Valve age group (years)

1.8

1.6

1.4

1.2

1

M;25 and <10

I* 10 and <15

2 15 and <20

I- 0.8

0.6 -

0.4 -

0.2 -

0 - t + + + -i

Improper

seating

Stuck open Disk/other

part off or

broken

Restricted

motion/flow

Stuckclosed Loose/impact

damaged pait

Figure A.7.2 Relative failure rate by failure mode and age group. Normalization structured such that the

service weighted average failure rate for each failure mode is one
ORNL-DWG 93-7406

3 T

Valve size group (in.)

2.5 4-

52

M >2 and •4

2 4-

q 1.5 -

a- OE >4 and 0O

0 -

0.5 -

I - 4 -I

ImProwe

seating

Stuck open Disk/other part

off or broken

Restricted

motion/flow

Stuck closed Loose/damaged

pan I Figure A.7.3 Relative failure rate by failure mode and size group. Normalization structured such that the

service weighted average failure rate for each failure mode is one I
I ORNL-DWG 93-7407

7-

6 4-

5-

.-I

a

Aw

4 4

3

2

1

0 9

h-per

seating

Stuck open Disk/otherpart

off/bwoken

Restncted

motion/flow

Stuck closed Loose/damaed

paS

M ESW 0 Feedwar l Diesel Staring Air B Main Steam 

Figure A.7A Relative failure rate by failure mode for four systems with the highest overall failure rate. The rates Indicated

are based on a normalized failure rate of one for all systems within the designated failure mode. Thus, ESW valves

were slightly more than twice as likely to have failed due to Improper seating as the population as a whole
ORNL-DWG 93-7408

6

8 4

*3

02

1

0

10 1

*8 Y

*6 0

*4 V

O0 I

10

8

36

4

2

I

I

V h -4 - - I a S

CT 8 w g R ffi S ! en . co _2 Q o g 

W) Q 2 | I I <; Uf > 

Disk/other part off or broken

40 1

0 I. 0~~ 

Stuck closed

Figure A.7.5 Relative failure rates and percentage of valv I are sorted by relative failure rate within the I

Restricted motionfreduced flow

3.5--

3 

42) 

Cd 0.5

0 I i Ii 

I

I

;r0

t

I

I Relative Failure Rate Stuck open

Valve-year percent

population service life for ten manufacturers for four failure modes. The charts

particular failure mode
0F

ORNL-DWG 93-7409

1.4 -

1.2 4-

1

0.8

0.6

b0.4

0.2

0 4 f

hnProper

seating

Stuck open Disk/other part

off or broken

Restricted

motion/flow

Stuckclosed loose/damaged

part

| B&W M CE UGE W-1

Figure A.7.6 Relative failure rate by failure mode and NSSS. The rates shown Indicate the relative failure rates by NSSS within

the designated failure mode. The valve-years welghted average of the values for any failure mode category equals one
ORNL-DWG 93-7410

1.6 -

1.4 -

1.2 -

".4.

1

0.8

0.6

0.4

0.2

-

I'

I-.1

4 ' 0 I

Improper

seating

Stuck open Disk/other

part off or

Restricted

motion/flow

Stuckclosed Looselimpact

damaged part

Miscellaneous

broken

IM Normally operating M Shutdown support I Testing only

I Figure A.7.7 Relative failure rate by failure mode and system status. The valve-year weighted average of the values for

any failure mode category equals one
I"

ORNL-DWG 93-7411

0.18 -

0.16 -

0.14-

,0.12-

o 0.1-

* 0.08.

0.06.

0.04-

0.02 -

0O

0.3

0.25 -

43 0.2 - - 14-0 01

80.15 -

X 0.1 

0.05 -

Seatarea General Hinge pin Disk

wear aea stud/bhinge

armarea

i I N I

Foreign Penetration

material area

0 _13 XV . ' . I I *1-

Seatarea General Hinge pin Disk

wear aea studmhinge

armarea

. 128MleI

Foreign Penetration

material aea

Jh

Stuck open Stuck cosed

00

0.45

0.4.

' 0.35

0.3.

a 0.2S

.Q2

0.15 

0.1

0.05

0

0.3

n .ic g .1 1

i 0.2 'd

0c3 0.1S 

0.1

0.05

0

IF

F

Seatarea General

wear

Hinge pin Disk Foreign

area stud/hinge material

annarea

Penetration

area

Seatarea General Hinge pin Disk

wear amea stud/hinge

armarea

Foreign Penetration

material area

Disk/other part off or broken Restricted motonlreduced flow

Figure A.7.8 Fraction of failures for selected failure modes n which selected areas were affected.

Not all failure modes and failure areas shown
ORNL-DWG 93-7412

0.7

0.4-

t4.

0O.3-

'0 ~0.2-

0.1

0 

leProPer Disk/otherpart Looe/damaged Restricted Stuck losed Stuck open

seating off or broken part motion/flow

X Programmatic Abnormalequipment 0 Misc. or unclear M Routine observation M Special inspection

operation

Figure A.7.9 Distribution of selected failure modes by general detection method
5 ORNL-DWG 93-7413

0.7

0.6 

0.5 

0A4

'15

Improper Stuck open Disk/other pat Stuck closed Restricted Loose/

seating off or broken motion/flow damaged part

m Not specific 3 Leak test 0 Disassy. and/or inspect E Hydraulic indication

m3 Nonhydraulic indication H3 Pump/comp. rotation EJ Other maintenance U Nonintrusive test

Figure A.7.10 Fraction of failures for selected failure modes by specific detection method
ORNL-DWG 93-7414

0.7 T

0.6 -

0.5 -

go

OA -

0

S 0.3

0.2 -

0.1 -

0-

Improper

seating

I _ MM!i 1 - 2 _ _ [ I!

Disk/other part LosedMged Miscellaneous Restricted Stuckcli

off or broken part motion/flow

| * Nonprogrammatic Programmatic l

Figure A.7.11 Distribution of failures by general discovery process and failure mode

+ -I

Dsed Stuck open

I
I ORN1,DWG 93-7415

100

90

80

70

60

50

40

30

20

10

0 -4- -- I

Improperseating Disklother part

off or broken

Looddamaged Miscellaneous

Pint

Restricted

motion/flow

Stuck closed Stuck open

Modeie U Significant

Figure A.7.12 Distribution of failures by failure mode and extent of degradation
ORNL-DWG 93-7416

0.3

0.25

0.2

%'4

'~0.15

0.1

0.05

Hinge pin Disk stud/ Seat Penetration General wear Foreign material Unknown/

hinge arm other

Figure A.8.1 Fraction of failures affecting designated areas. The sum of the ractions exceeds one

because some failures affect more than one area

-1
I

ORNL-DWG 93-7417

I 2.5 T

Valve age group (years)

2 - E135

M 25 and <10

O10 and <15

0 215 and <20 I 1.5 -

1-

0.5 -

I4 + f AI

Seat area Genal Hinge pin Disk stud/ Foreign

wear am hingearmarea material

Figure A.&2 Relative failure rate by failure area and age group for selected failure areas/causes. Normalization structured

such that the service weighted average failure rate for each failure area for all age groups combined Is one
ORNL-DWG 93-7418

2.5 Valve size group (in.)

M 52

M >2 and •4

M >4 and 10

M >10

2 4

- ....

1.5 -

I 1 

0.5 -

0- q + 4 -*1

Seatarea GCoerA

wear

Hinge pin

mam

Disk stud/

hingeartmarea

Foreign

material

I

Figure A.83 Relative failure rate by failure area and valve size group for selected failure areas/causes. Normalization structured

such that the service weighted average failure rate for each failure area for all size groups combined Is one
I

ORNL-DWG 93-7419 I

8-

7 

6 4-

5 4-

4

3 +

2-

1-

0 - Penetration

aea

Seat area General wea Hinge pin area Disk stud/

hinge arm area

Foreign

material

Unkiown/other

| M ESW M Feedwaker IM Diesel Starting Air MMain Steam

Figure A.8A Relative failure rate by failure area for four systems with the highest overall failure rate. The rates Indicated are based

on a normalized failure rate of one for all systems for the designated failure area. For example, ESW valves were about

3.5 times as likely to have disk stud/hinge arm area degradation as was the valve population as a whole
ORNL-DWG 93-7420

3 10

2.5--

jLg 1.5 1

0.52 

0 I0

6 -- 4

~~~~~~~~~L. ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ .

4)~~~~~~~~~~~~~~~~~~~~~~~~~~~~4

S07 28 P32 W00 20

C684 A391 W030 A585 S075

Hinge pin area Disk stud/arm area

!-4 3 -- 10 14 -- 12

2.5 -- 12 10lo

~1.5--

I) 4)

4 ~ -~ ~ ~ ~ ~~~. 

2 2~~~~~~

0 0 0 0

A585 A391 V080 S075 C684 A585 S075 A391 W030 R340

Dlsk seat area

-. 3- I

U

Relative Failure Rate

Valve-year percent

Valve penetration area

Figure A.85 Relative failure rates and percentage of valve population service life for the five manufacturers with the highest failure

rate In the four listed failure areas. The charts are sorted by relative failure rate within the particular failure area
IA

ORNL-DWG 93-7421 I. 0.4

0.35

0.3

'4

0.25

0.2

0.15

0.1

0.05

0 I

Seat area General wear Hinge pin area Disk stud/hinge Foreign material Unknown/olher Penetration area

arm area

I MBW CE GGE W I

Figure A.8.6 Relative failure rate by failure area and NSSS. The rates shown indicate the relative failure rates by NSSS for the

designated failure area. The valve-years weighted average of the values for any failure mode category equals one
ORN1-DWG 93-7422

1.6 

1.4 4-

1.2 -

1

5 0.8

i 0.6

0.4

0.2

0

i- ? ' -

+ 4 + AI

Seat area General wear Hinge pin area Disk stud/hinge Foreign material Unknown/other Penetration area

armarea

I IMNormallyoperating MShutdownsupport n Testing only |

Figure A7 Relative failure rate by failure area and system status. The failure rate values are relative to the overall failure rate within the

given failure area category, such that the service-weighted average of the failure rates within that category equals one

9
I

I

ORNL-DWG 93-7423

tIA5 T I,

OA4

0.35

0.3

A 0.25

0.2

0.15 b-.

0

0.1 -

0.05 -

0-

Seat area General wear Hinge pin area Disk stud/hinge arm area Foreign material

1 Improper seating M Stuck open M Disk/other part off or broken M Restricted motion/flow

ED Stuck closed 3 Loose/damaged part 03Miscellaneous

Figure A8 Fraction of failures in which the designated area was affected for selected failure modes and areas
ORNL-DWG 93-7424

0.7

0.6

0.5

g0.4

9 .

" 0.3

I,

0.2

0.1

0

Hinge pin area Disk studhinge

armarea

Seat area Penetration area General wear Foreign material Unknown/other

t

f

Figure A.9 Fraction of failures by general detection method for selected failure areas
I~ ORNL-DWG 93-7425

0.4

0.35

0.3

1 0.25

0.2

M 0.15

0.1

0.05

0 1.

Seat area General

wea

Hinge pin

am

Disk

stud/hinge

armarea

Foreign

material

specif gE1Not 1 i Leak test e E Disassy.candorinspect. e Hydraulicindicaion

m Nonbydrauuc indication [I Pump/comp. rotation O3 Other maintenance M Nonintrusive test

Figure A.8.10 Fraction of failures detected b specific detection methods for seected failure areas
ORNL-DWG 93-7426

100 -

90 +

80 -

70 +

I

A

60 4-

50 -

40 +

IU)

U)

30 4-

20 4-

10

0- + 4-

Seat area General Hinge Disk stud/ Foreign Unknown/ Penetration area

wear pinarea hinge arm area material other

Programmatic INonprogrammatic

Figure A.8.11 Distributlon of failures by discovery process and affected area F
I ORNL.DWG 93-7427 I

100-

90 _

80 -

70 -

I

60-

50 4-

40 4-

30

20 -4-

10 - z

0- -4-

Seat area General Penetration area

wear

Hinge

pinarea

Disk stud/

hinge arm area

Foreign

material

Unknown/

other

| Moderale Significant

Figure A.8.12 Distribution of failures by failure area and extent of degradation
ORNL-DWG 93-7428

Special inspection

69'

Misc. or unclear

16%

Progrnmatic

549%

Abnonnal equipment opemon

19%

I Figure A.9.1 Distribution of failures by general detection method
W

ORNL-DWG 93-7429

Valve age group (years) I

1.8 T

1.6 +

<5

3 5 and <10

M 10and<15

215 and <20

1.4 +

1.2 I

M

9!

G

P.

-1

I

1 -

0.8 -

o-A

. | j . j s 

| | S 

| | B 

| g g . I | | I E , m . g § , , . . . S : , : : : :

| i , . . . . | § , . .

. i . . .

. E , . .

0.6 -

0.4 -

0.2 -

0 - +1 + -i

Programmatic

Figure A9.2

Abnormal

equipment

operation

Routine

observation

Special

inspectioll

Misc. or

unclear

Relative failure rate by general detection method and valve age group. The age group population weighted average

within each detection means equals one
ORNL-DWG 93-7430

3 r

2.5 +

Valve size group (in.)

El<2

E >2 and :4

D >4 and S10

>1o

2 +

a

LI

93

.,I

i .ti

1.5 -

-

0.5 -

0- 1- + + 1- i

Programmatic Abnormal

equipnent

operation

Misc. or

unclear

Routine

observation

Special

inspection

IA Figure A.9.3 Relative failure rate by general detection method and valve size group. The size group population weighted average

within each detection means equals one
£ 4.5 -

W9 4 - _ -

3.5 -

3- 

2.5 -

2 -4

00 ~ ~

00~~~~

Programmatic Abnormal Misc. or

equipment unclear

operation

ORNL-DWG 93-743 1

Routine

observation

R ar zzj&nor

Special

inspection

| M ESW E Feedwawer 01 Diesel Starting Air 10 Main Steam I

Figure A.9.4 Relative failure rate by general detection method and system for four systems with highest overall failure rate.

The rates indicated are based on a normalized failure rate of one for all systems for the designated general detection method.

For example, ESW valves experienced programmatically detected failures at just over 2.5 times the overall population
ORNIDWG 93-7432

1.8 

1.6 

1.4

I1.2

0

10.8

0.6

0.4-

0.2-

0

Programatic Abnormal Misc. or F

equipnent unclear Ob

operation

I 13 B&W CE m GE EW

Figure A.9.5 Relative failure rate by general detection method and NSSS. The val

for any general detection category equals one

V/1

II

routine Special

;ervation inspection

Ive-years weighted average of the values
I ORNL-DWG 93-7433 I

2.5 -r-

, 1.5

0.5

,4-

*1- 4 +

Programmatic Abnormal

equipent

operation

Msc. or

unlear

Routine

observation

Special

inspection

Nomally operating M Shutdown support E Testing only

Figure A.9.6 Relative failure/detection rate of general detection methods by system usage. The rates shown indicate how many failures

were detected by the desginated detection method within the specified system usage category, in relation to how well the

method was used overall. The valve-years weighted average of the values for any given detection method equals one
ORNL-DWG 93-7434

4.5

4

3.5

3

2.5t

~1.5

1

0.5 

0

Programatic Abnormal Misc. or Routine Special

equipment unclear observation inspection

Operation

IN Improper seating 0 Disk/other part off or broken 0 Loose/damaged part 1 Restricted motion/flow

m0 Stuck closed EB Stuck open

Figure A.9.7 Relative historical success rato otselected general detection methods i discovering selected failure modes.

The values shown represent how well a partcular detection method has been In finding the designated failure mode In

8 comparison to all detection methods. The weighted (by number of failures) average of all failure modes for each general 3 detectHon method equals one >

X ~~~~~~~~~~
I

9

3 -

ORNL-DWG 93-7435

The fact that special inspections have been, on a relative basis,

successful in finding problems in the disk stud/hinge arm area

does not suggest special inspections are the primary means

for observing disk stud/hinge arm area degradation. Rather,

it suggests that special inspections have been more likely to find

degradation in this area than in other areas

2.5 +

*1

0

2 +

1.5 +

bt.J

1

0.5

0 t -I

Programmatic Abnormal

equipment

operation

Misc. or

unclear

Routine

observation

Special

inspection

| Hinge pin area a Disk studihinge arm area E Seat area

| Penetration area ml General wear ED Foreign material

Figure A.9.8 Relative historical success rate of general detection methods In discovering selected failure areas.

The values shown represent how well a particular detection method has been In finding the designated failure area in

comparison to all detection methods. The weighted (by number of failures) average of all failure areas for each general

detection method equals one
ORNL-DWG 93-7436

100 

90 +

80 +

70 +

g

i

44.

60 4-

50 -

4 0 t P"

J-

w

30 -

20 -

10 +

Proramatic Abnormal

equipment

operation

Misc./

unclear

Special

inspection

Routine

observation

[ Moderate Significant 

Figure A.9.9 Distribution of failures by general detection method and extent of degradation

I
I Wionintrusive test ORNL-DWG 93-7437 Other mainenance 7

Pump/comp. rotation 3%

Nonhydraulic indication

11%

Hydraulic indication

12%

Notspecific

33%

13% 1 ......

Disassy. and/or inspect. _20% Leak test

Figure A.10.1 Distribution of failures by spedflc detection method
ORNL-DWG 93-7438

2.5 -

Valve age group (years)

I -- I

2 -

1.5 -

I - I

46

0.5 -

0-

I

Not specific Leak test Disassy. and/or Hydraulic Nonhydraulic Pump/comp. Other Nonintrusive

inspect. indication indication rotation maintenance test

Figure A.10.2 Relative failure rate by valve age group and specific detection method. The age group population weighted average

within each detection means equals one
ORNL-DWG 93-7439

3 5~~~~

E 4-5 Valve size group (in.)

4--

3.5 >2 and:5•4

0>4 and SlO

|2.5

1.5

0

Not specific Lea test Disassy. and/or Hydaulic Nonhydraulic Pump/comp. Other Nonintrusive

inspect. indication indication rotation maintenance test

Figure A.10.3 Relative failure rate by specific detection method and valve size group. The size group population weighted average

within each detection means equals one
ORNL-DWG 93-7440

10

9

8

7

I

I

5

V

CI

6

5

4

3

2

1

0

Not specific Leak test Disassy. and/or

inspect.

Hydraulic Nonhydraulic Pump/comp. Other

indication indication rotation maintenance

Nonintrusive

test

1 ESW M Feedwar A Diesel Stating Air IM Main Steam

Figure A.10.4 Relative fhilure rate by specifc detection method and system for four systems with highest overall failure rate.

The rates ndicated are based on a normalized failure rate of one for all systems for the designated specific detection method.

For example, non-fntrusive means were used to detect ESW failures at over nine times the rate for all systems; note that no I failures of feedwater, diesel starting air, or main steam valves were detected non-intrusively
ORNL-DWG 9

* 3- _

2.5

2

~1.5

0

00~~~~

Not specific Leak test Disassy. and/or Hydraulic Nonhydraulic Pump/comp. Other Nonin

inspect. indication indication rotation maintenance U

| EJBW AdE BGE S~W|

Figure A.10.5 Relative failure rate by specific detection method and NSSS. The valve-years weighted average of

the values for any specific detection category equals one

3-7441

trusive

Ist
ORNL-DWG 93-7442

1.8 -

1.6 -

1. -

S 1.2 -

0

'9I 

i 0.8-

1 0.6 -

0.4 -

0.2 -

0-

Notspecific Leak test Disassy. and/or Hydraulic inspect. indication

-F 4 I

Nonhydraulic

indication

Pump/comp.

rotation

Oder

maintenance

Nonintrusive

test

Normially operating 0 Shutdown support 0 Testing only

Figure A.10.6 Relative failure/detectlon rate of specific detection methods by system usage. The rates shown Indicate how many

failures were detected by the designated detection method within the specified system usage category, In relation to how I well the method was used overall. The valve-years weighted average of the values for any given detection method equals one

tA
ORNL-DWG 93-7443

z

1 r

2

1.8

1.6

i 1.4

0.2

0

Improper Stuck Disk/other Stuck Restricted Loose/

seating open part off or closed motion/ damaged

broken flow part

3

2.5

2

1.5

0.-

Improper Stuck Disk/other Stuck Restricted Loose/

seating open part off or closed motion/ damaged

broken flow pan

Leak test Hydraulic (flow, pressure, etc.) indication

5 -r 3 r

LA0 4.5 + 2.5 +

4 

S

N

-

to

N

3.5 +

3.

2.5

2 

1.5

1

0.5

0*

0

.

V.

1.5 +

0.5*

1M MR

Improper Stuck

seating open

. 18998O .

Disk/or Suclc

part off or closed

broken

2 W O 1 0

Restricted

motion/

flow

Le

dhmagedl

part

Improper

seating

I MMMWI4

Stuck Disk/other

open part off or

broken

I . . I

Stuck Restricted

closed motion/

now

Loose/

damaged

part

Disembly and examination Pump/compressor reverse rotation

Figure A.10.7 Relative failure rates for selected failure modes and specific detection methods. The values shown reflect the fraction

of failures for the particular detection method In which the failure mode was detected, relative to the fraction of failures the specific

detection means found overall. Not surprisingly, leak testing was relatively good at Indicating Improper seating, while disassembly

and examination was more effective at finding broken, loose, or Impact damaged parts
ORNI-DWO 93-7444

1.8 .

1.6 - tlX 14 A -_§

" 1 2 -1

~M0.8 

0.6 

~0.4--

0O.2--

0 I

Seatarea General Hinge pin Disk

wear am stud/hinge

armarea

1 1.2

1

I 0.8-

g 0.6-

0.4

M 0.2

0 

Foreign

mana Seatrea Geeal

I FORRIMM I

Hinge pin

mm I

4- -1

Disk

sud/hinge

annarea

Foreign

material

Leak test Hydraulic (flow, pressure, etc.) Indication

LA

1 0.5

D |: I I It

Seatarea General Hinge pin Disk Foreign

wear mam stud/hinge material

annarea

1.8

1.6 -

X 1.4-

12

v 0.8-

* 0.6-

A 0.4-

0.2-

Seatarea, Geera

wer

- - 4- i'

Hinge pin Disk

area stud/hinge

armarea

Foreign

material

Disassembly and examination Pump/compressor reverse rotation

IA

Figure A.1O.8 Relative failure rates for selected failure areas and specific detection methods. The values shown reflect the fraction

of failures the particular detection method found In the specified areas, relative to the fraction of failures the specific detection

means found overall. Not surprisingly, leak testing was relatively good at indicating seat area degradation, while disassembly

and examination were more effective at finding hinge pin and disk stud/hinge arm area wear
I ORNU-DWG 93-7445

100.

90.

80.

70.

Ca 'I

60 

50 -

40 -

30 -

20.

10.

0-

Not specific Leak test Disassy. and/or Hydraulic Nonhydraulic Pump/comp. Other

inspect. indication indication rotation maintenance

I Non-Programatic 0 Programmatic |

Figure A.10.9 Distribution of failures by specific detection method and general discovery process

Nonintrusive

test
ORNL-DWG 93-7446

90%/

809%

70%

j6%

a 50%

30%

20%

109%

0%

Leak test Disassy. and/r Hydraulic Nonhydraulic Pumnp/comp. Other Nonintrusive Not specific inspect. indication indication rotation maintenance test

Moderate 12Significt

Figure A.10.10 Distribution of failures by specific detection mnethod and extent of degradation
I

ORNL-DWG 93-7447

Nonprogrammatically detected

degradationsorfailuresinclude

those found due to improper

equipment operation, abnormal

system parameters (not found

during testing), etc.

46%

Nonprogrammatic

Programmatic monitoring includes

in-service and surveillance testing,

preventive maintenance disassembly

and examination, and other practices

that are routinely applied to detect

or avoid degradation and failure

54%o

Programmatic

Figure A.11.1 Distribution of failures by discovery process
ORNL-DWG 93-7448

1.6 T

1A -

1.2 -

10-

0.8 -

Programmatic

0.6 

N"

Lft

LA

, -zzzzzzzzzzzzyx X X X x W x rr | g X X rTT_

-zZZit ---------Tr

_

_

r

Nonprogrammatic

OA -_

0.2 -_

0-

Valve age group (years)

| 1<S M 5 and <10 EW210and<15 M15and<20

Figure A.11.2 Relative allure rate by discovery process and valve age group. The normall7adon Is structured such that the

average of the programmatic and nonprogrammatic values equals the relative failure rate for the age group as a whole I

Uf
I

ORNL-DWG 93-7449

2 -

1.8 -

1.6 -

1.4 +

1.2 -fII.

I -

b' 0.8 -

1111111111 w

Illlrnlll +H

[TTTTTTtll m I l l ......... IIIIIIITI :

+ : +Ht

: i* l .III1

[TTA I J >

| _ 11 m M M | | | _ | a///S 1 1 1 1 1 1 1 I r _ S 1 g

S l_ | BY00000S b l l l l ^ B

0 _g '// 111111111 S tX | R _ Y0000000 l l l l l l l l l . ef X $8

| l_ EY////S 111111111 .m l g

| | E M- g | |

. | | | S .l lE

Ptoc

Valve size group (in.)

03>2 and:4

>4and|10

M >10

0.6 -

OA +

0.2 -

O 4- +-I -4

Nonpiogrammatic

Filgure A.11.3 Relative failure rate by discovery process and valve size group. The normaUization Is structured such that the

average of the programmatic and nonprogramnuatic values equals the relative failure rate for the size group as a whole
ORNL-DWG 93-7450

5 -

4.5 +

A higher value Indicates a more successful testing/monitoring

program. Three of the four systems with significantly

higher ratios than the remainder are used exclusively at

BWR plants.

a

t

4

3.5 +

3 + ,:

2.5 + -

2

-J

1.5 -

1 

0.5

0 - 4

ESW Feodwatr Diesel Main Steam

Starting Air

HPCI Containment

Isolation

RCIC Suppression

Pool Support

+ -i

AFW CCW

Figure A.11.4

0A E

Ratio of programmaticafly detected failures to nonprogrammatically detected failures for ten systems with the

highest overall failure rate. A high value Indicates that failures are more likely to have been detected programmatically
U

ORNL-DWG 93-7451

2 -r1.8 +

I

I

1.6 +

1.A +

1.2 +

1 

00 0.8 +

0.6 +

0.4

I 0.2 -IO 4- IV -IBW CE GE w All NSSS

Figure A.11.5 Ratio of progranmuatically to nonprogranmatcally detected failures by NSSS. GE plants have

detected a significantly higher fraction of failures progranunatically than have the PWR plants
ORNL-DWG 93-7452

1.2 -

1 -

0.8 +

I

UI

0.6

0.4 -

0.2 -

- IH -HProgtM atic Nonprogrnamatic

| M Normally operating M Shutdown support M Testing only l

Figure A.11.6 Relative failure rate by general discovery process and system usage. The normalization Is structured such that

the service-weighted average of the failure rates for a given discovery process equals one

Uf U
ok

ORNL-DWG 93-7453 *

2.5 -1-

I

A

II

a

.t

Hi

2 +

1.5 +

1 +

0.5 +

0 +-

seating

Diskother part

off or broken

ENE I L

Loose/damaged Miscellaneous

part

4± -I4

Reaicted

motion/flow

Stuckclosed Stuck open

Figure A.11.7 Ratio of programmatically to nonprograumnatically detected failures by failure mode
ORNL-DWG 93-7454

1.4 -r

1.2

1

I4

0.8

0.6

I

o.A0% 0.4

0.2

0 -I

Prgrmmac Nonprograwmadc

| Seat am General 1 IM Hinge 1 Disk stud/ {m Foreign M Unknown/ 8 Penetration area

wear pin area hinge armarea material other

I

U

Figure A.11.8 Relative Ailure rate by affected area and discovery process. The values shown indicate how well failures In the

designated areas were detected by the specified discovery process, relative to how all failures were discovered. For example, degradation

from foreign material was about 259 more likely to be found programmatically than degradations in general, while degradation

In the disk stud/hinge arm area was about 20% less likely to be detected programmatically than all degradations combined
ORNL-DWG 93-7455 I*

100

90

A

4

0)

80

70

60

50

40

30

20

10

0 -I

Nonprograminatic Programmatic

I 3M modale M Significant I

Figure A.11.9 Distribution of failures by extent of degradation and discovery process
ORNL-DWG 93-7456

- ----------------- -------------------- --------

Modemte

469o

Significant

53%

IA

: .. F-

.A

_ 

*.4

..

Figure A.12.1 Distribution of failures by extent of degradation
I ORNL-DWG 93-7457

2.5 TValve size group (in.)

I S2 2 -

M>2 and 54

IH >4 and 10

1.5 -

1-

I >l 1 IN I 

.. ....-. ,..

,

| b

_

Illlllllllmm iiiHillllH _U

_

nn,,,,,i mllllnn rl | I I I I rTrrTrl

Sigifit

0.5 -_

o 4- I4 -.- I

Modenule

Figure A.12.2 Relative failure rate by extent of degradation and size group. The normalization Is structured such that the average

of the programmatic and nonprogranuatic values equals the relative failure rate for the size group as a whole
ORNL-DWG 93-7458

3.5

3-

2.5 -

I

2-

1.5 -

oA

1-

0.5 -

- 4IModerate Significant

INESW M lFbedwalr I Diesel Starting Air B Main Steam 11l HPCI

0 Containment Isolation O RCIC M Suppression Pool UI AFW a CCw

Support

Figure A.12.3 Comparison of relative failure rates by extent of degradation and system for ten systems with the highest overall failure rate

4
I

ORNLDWG 93-7459

2.5 T2 +

#II

I

1.5 +

1 +

0.5 -

0

ESW Feedwater Diesel Main Steam HPCI Containment RCIC Suppression AFW CCW

Starting Air Isolation Pool Support

Figure A.12.4 Ratio of number of significant to moderate failures by system for ten systems with the highest overall failure rate

-i
ORNL-DWG 93-7460

4.5 -

4 -_

3.5

3

§ 2.5 

1.5

*'I 2 -

-1

_" 4

a4 1.5 

0.5 

0 -_

I~~~~~

Madef Significant

I S075 M A585 M W030 * C684 lI A391

ire A.12.5 Relative failure rate by extent of degradation for five manufacturers with the highest overall failure rate. The values

shown reflect the rate of failures of the manufacturer's valves compared to all valves for each of the two categories
0.7 ORNL-DWG 93-7461

0.7- -

| ~0.6 - E

0.5 -

1 0.4- 

j0.3 -

0.2

0.1 -_

O - H-I Hi

Moderate Significant

| B&W 0 CE I GE 1 W

Figure A.12.6 Distribution of failures extent of degradation and NSSS
ORNL-DWG 93-7462

1.4 r

1.2 +

1 4-

I

0.8 -

*a

40.6 

1 0.4

4- . ., 1

--- I

i0.2 -_

0 -I*-- I1- -F--

A

Nomiallyoperating Shutdown support

Figure A.12.7 Ratio of significant to moderate failures by system usage

Testing only
LAf

ORNL-DWG 93-7463

1.8 T

1.6 -

1.4 -

1.2 -

I

It

1 +

0.8 

X

s | , | | | | .! t R

R s ^zzzzzig/

| | | 0000m R

0000m FH

m 

mmmmmS 

1>

. g

h~~~~~~. .

0.6 +

I--j

0 0.4 -_

0.2 - -

- _ +f -I

Mode Significant

M Seat aea M General ED Hinge 1 Disk stud/ mO Foreign

war pinarea hinge arm area material

| Unknown/ M Penetration area

I other

Figure A.12.8 Relative failure rate by failure area and extent of degradation. The values represent the relative population

of failures of the specified extent of degradation within the designated failure areas, compared to the entire failure population.

For example, failures involving the seat area were almost 60% more likely to be moderate In nature than the failure population

as a whole
ORNL-DWG 93-7464

1.6 -

1.4 -

1.2

i0.8

* 0.6- 

'-

OA - _

0.2 -_

0

I~~~~Fg

%A~Do

f ~ s

... I

I

'I

, . I

I . I

I

IJ .1

ModeIe Significant

Misc./ 0 Abnormalequipment W Programmatic U Routine JlUl Special

unclear operation observation inspection

re A.12.9 Relative failure rate by extent of degradation and general detection method. The values represent the relative population

of failures of the spedfled extent of degradation for the designated general methods of detection, compared to the distribution

for the extent of degradation distribution for the entire failure population
I ORNL-DWG 93-7465

2 

1.8 -

1.6 -

1A -

.9

V

8

4 I

1.2 -

1 +

0.8 +

0.6 -I_

0.4 -

0.2 +

0 - -i

Modgate Significant

| Notspecific 1 Leak test El Disassy. and/or inspect. M Hydraulic indicaion |

[| Nonhydraulic indication EB Pump/comp. rotation 0 Other maintenance M Nonintrusive test

Figure A.12.10 Relative failure rate by extent of degradation and specific detection method. The values represent the relative population

of failures of the specified extent of degradation for the designated specific methods of detection, compared to the distribution

for the extent of degradation distribution for the entire failure population
NUREGICR-5944

ORNL-6734

Dist. Category RV

INTERNAL DISTRIBUTION

1. C. W. Ayers 28. G. A. Murphy

2-20. D. A. Casada 29. C. E. Pugh

21. D. F. Cox 30. R. H. Staunton

22. E. C. Fox 31. N. L. Wood

23. R. H. Greene 32. ORNL Patent Section

24. H. D. Haynes 33. Central Research Library

25. J. E. Jones, Jr. 34. Document Reference Section

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EXTERNAL DISTRIBUTION

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173
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64. M. K. Au-Yang, B&W Nuclear Technologies, 155 Mill Ridge Road, Lynchburg, VA 24502 4341

65. B. Jenewein, Enertech-Check Valve Services, 2950 Birch Street, Brea, CA 92621

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174
NRC FORM 335 US.NUCLEAR REGULATORY COMMISSION . cREPORT NUI))BER NRCFOR 33 IAntgned byv NRC. Add Vol.. Supp.. Rev..

32013102. BIBLIOGRAPHIC DATA SHEET NUREGICR- 5944

(See instructions on the rverse} ORNL-6734

2. TITLE AND SUBTITLE

A Characterization of Check Valve Degradation and Failure

Experience in the Nuclear Power Industry 3. DATE REPORT PUBLISHED

MONTH V 'EAR

September 1993 4. FIN OR GRANT NUMBER

B0828

5. AUTHOR (S) 6. TYPE OF REPORT

D. A. Casada Technical

M. D. Todd 7. PERIOD COVERED lnclusv.eas

8. PERFORMING ORGANIZATION -NAME AND ADDRESS 0/NRC. pvnide iision. Office of Region. U5. Nucla Regulrory Commsson anailig addres: it contracto r provide name and miling addess.)

Oak Ridge National Laboratory

Oak Ridge, TN 37831-6285

9. SPONSORING ORGANIZATION - NAME AND ADDRESS (If IVRC. type ape reP: if consactorprovide NRC Civasson. Office erRegion. U.& Nuclear Regulatory Corn nijision.

9. PONSORING ORGANIZATION -NAME AND ADDRESSl WNRC. type b ame s ove-ifirontactor. provide RC Diision Ofice oRegion U. Nuck rRV~u1&torYCommi*"t.

and mailing addre.)

Division of Engineering

Office Of Nuclear Regulatory Research

U. S. Nuclear Regulatory Commission

Washington, DC 20555-0001

10. SUPPLEMENTARY NOTES

11. ABSTRACT 200 words or M)

Check valve operating problems in recent years have resulted in signifiant operating

transients, increased cost and decreased system availability. As a result, additional attention has been given to check valves by utilities (resulting in the formation

of the Nuclear Industry Check Valve Group), as well as the U.S. Nuclear Regulatory

Commission and the American Society of Mechanical Engineers Operation and

Maintenance Committee. All these organizations have the fundamental goal of

ensuring reliable operation of check valves.

A key ingredient to an engineering-oriented reliability improvement effort is a

thorough understanding of relevant historical experience. A detailed review of

historical failure data, available through the Institute of Nuclear Power Operation's

Nuclear Plant Reliability Data System, has been conducted. The focus of the review

is on check valve failures that have involved significant degradation of the valve

internal parts. A variety of parameters are considered, including size, age, system

of service, method of failure discovery, the affected valve parts, attributed

causes, and corrective actions.

12. KEY WORDS/DESCR:PTORS {List wordsor prases teat will a oeters in locating the rport. I 13. AVAILABI LI TY STATEMENT

check valves Unlimited

reliability 14. SECURITY CLASSIFICATION

relialu idta frile

failure data Unclassified

(rhis Repor)

Unclassified

15. NUMBER OF PAGES

16. PRICE

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