NUREG/CR-5507

BNL-NUREG-52222

Results from the Nuclear Plant

Aging Research Program:

Their Use in Inspection Activities

Prepared by W. Gunther, J. Taylor

Brookhaven National Laboratory

Prepared for

U.S. Nuclear Regulatory Commission
AVAILABIUTY NOTICE

Avalability of Reference Materials Cited In NRC Publications

Most documents cited In NRC publications will be avaflable from one of the following sources:

1. The NRC Public Document Room. 2120 L Street, NW. Lower Level. Washington. DC 20555

2. The Superintendent of Documents. U.S. Government Printing Office. P.O. Box 37082, Washington.

DC 20013-7082

3. The National Technical Information Service, Springfield, VA 22161

Although the listing that follows represents the majority of documents cited In NRC publications. It Is not

Intended to be exhaustive.

Referenced documents available for Inspection and copying for a fee from the NRC Pubic Document Room

Include NRC correspondence and internal NRC memoranda; NRC Office of Inspection and Enforcement

bulletins. circulars. Information notices, Inspection and Investigation notices: Ucensee Event Reports; vendor reports and correspondence: Commission papers; and applicant and censee documents and correspondence.

The following documents h the NUREG series are available for purchase from the GPO Sales Program:

formal NRC staff and contractor reports. NRC-sponsored conference proceedings, and NRC booklets and

brochures. Also available are Regulatory Guides. NRC regulations In the Code of Federal Regulations, and

Nuclear Regulatory Commission ssuances.

Documents available from the NatIonal Technical Information Service Include NUREG series reports and

technical reports prepared by other federal agencies and reports prepared by the Atomic Energy Commisslon. forerunner agency to the Nuclear Regulatory Commission.

Documents available from pubie and special technical libraries Include al open literature Items, such as

books. Journal and periodical articles, and transactions. Federal Register notices, federal and state legtslation. and congressional reports can usually be obtained from these lbrarIes.

Documents such as theses, dissertations, foreIgn reports and translations. and non-NRC conference proceedings are avallable for purchase from the organization sponsoring the publication cited.

Single copies of NRC draft reports are avalable free, to the extent of supply, upon written request to the

Office of Information Resources Management. Distribution Section, U.S. Nuclear Regulatory Commisson.

Washington. DC 20555.

Copies of ndusta codes and standards used In a substantive manner In the NRC regulatory process are

maintained at the NRC Library. 7920 Norfolk Avenue. Bethesda, Maryland. and are available there for reference use by the public. Codes and standards are usually copyrighted and may be purchased from the

originatig organization or, If they are American National Standards, from the American National Standards

Institute, 1430 Broadway. New York, NY 10018.

DISCIAIMER NOTICE

This report was prepared as an account of work sponsored by an agency of the United States Government.

Neitherthe United States Government nor any agency thereof, orany of their employees, makes any wananty,

expresed or implied, or assumes any legal liability of responsibility for any third party's use, or the results df

such use, of any Information, apparatus, product or process disclosed In this report, or represents that Its use

by such third party would not Infringe privately owned rights.
NUREG/CR-5507

BNL-NUREG-52222

RV

Results from the Nuclear Plant

Aging Research Program:

Their Use in Inspection Activities

Manuscript Completed: May 1990

Date Published: September 1990

Prepared by

W. Gunther, 1. Taylor

S. K Aggarwal, NRC Program Manager

Brookhaven National laboratozy f

Upton, NY 11973

Prepared for

Division of Engineering

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission a c v pip

Washington, DC 2055S

NRC FIN A3270 -Mt¢ ..

141- ' 
ABSTRACF

T he US. NRCs Nuclear Plant Aging Research (NPAR) Program has determined the susceplibllity to aging of components and systems, and the potential for aging to impact plant safety and

availability. The NPAR Program also identified methods for detectingand mitigating aging in components.

This report describes the NPAR results which can enhance NRC inspection actvities. Recommendations are provided for communicating pertinent information to NRC inspectors. These recommendations are based on a detailed assessment of the NRCs, nspection Program, and feedback from

resident and regional inspectors as described within. Examples of PAR epo summaries and aging

inspection guides for components and systems arc included.

iii
CONTENTS

Page

ABSTRACT .. ....................................... i.

LIST OF FIGURES .................................... vi

LIST OF TABLES ..................................... vi

SUMMAARY . *................ i:

1. INTRODUCTION .

1.1 Background and Goals

1.2 The NPAR Program .

13 Strategy .

.............

.............

.............

.............

. . .. ...

. . .. ...

. . .. ...

. . .. ...

1

1

2

4

2. INSPECTION GUIDANCE TO ADDRESS NUCLEAR POWER

PLANT AGING .................................. 5

3. NPAR

3.1

3.2

3.3

3A

3.5

3.6

INFORMATION WITH INSPECTION APPLICATION . .

Component Background Information ...............

Operating Experience .........................

Recommended Maintenance, Testing & Inspection ......

References ................................

Feedback from Regions ........................

Other NRC Input ............................

4. APPLICATION OF NPAR RESULTS TO INSPECTION

ACTVITES ....................................

S. INFORMATION TRANSFER ........................

5.1 Manual of NPAR Results ......................

5.2 Conduct On-Site Inspections .....................

5.3 Personal Computers.

5A Revision of the NRC Inspection Manual.

5.3 Presentation of NPAR Results at Regional Meetings ....

6. CONCLUSIONS AND RECOMENDATIONS.

6.1 Conclusions. ...............................

6.2 Recommendations. ...........................

7. REFERENCES ..................................

APPENDIX A - NPAR REPORT SUMMARIES .................

APPENDIX B - AGING NSPEC17ON GUIDES .................

11

11

12

13

13

14

16

17

18

18

18

20

20

21

22

22

23

24

A-1

B-1

V

_-
LIST OF FIGURES

Page

1 NPAR Input to ESF System Inspection .................. 7

2 NPAR Information Desired by Inspectors ................. 15

3 Preference for Method of Information Transfer .... ......... 15

LIST OF TABLES

1 NPAR Information Areas ........................... . 2

L Published Component Studies ..................... 2

IL On-Going or Planned Component Phase 2 Studies ....... 3

III. Published Systems Studies ........................ 3

IV. On-Going or Planned System Studies ..... ........... 3

2 Research Strategy and Report Outline ..... ......... . 4

3 Use of NPAR Results in Inspection ..................... 10

4 Manual of NPAR Results ........................... 19

vi
SUMMARY

The Nuclear Plant Aging Research (NPAR) Program is a hardware oriented research program

which has produced a large data base of information on equipment and system operating, maintenance,

and testing. A review of the NRC Inspection Program and discussions with NRC inspection personnel

have revealed several areas where the research results from NPAR would be valuable to the inspector. This report describes the NPAR information which can enhance inspection activities, and provides alternatives for making these pertinent research results available to the inspectors.

The emphasis of the NRC Inspection Program is on evaluating the performance of licensees

by focusing on requirements and standards associated with the administrative, managerial, engineering,

and operational aspects of their activities. The Inspection Program recognizes that licensees may

satisfy NRC requirements differently, and therefore expresses inspection guidance in the form of

performance objectives and evaluation criteria. For the resident and regional inspectors, procedures

have been written covering various subjects, such as operations, maintenance, and surveillance. Some

of these procedures contain guidance on aging degradation.

Associated with each NPAR study is the need to determine the role of inspection, maintenance, and monitoring in counteracting the effects of aging andAMRce wear. The role of maintenance in managing aging is an important area where NRC emphasis has been applied. A review by

the NRC of maintenance performed at several plants concluded that Most utilities do not perform

condition monitoring due to inadequate knowledge of degradation mechanisms and the relationship

between measurable parameters and predicted functional capability. The output from NPAR in this

area could provide the needed information not only to assist the inspector in recognizing age-related

concerns.

To obtain a complete delineation of the NRC inspectors' needs, presentations summarizing the

results of the NPAR Program were made to the resident inspectors at three regions. Their comments,

supplemented by a written questionnaire, indicated that NPAR results can be of use to the inspectors

when provided in a format directed to their activities.

The types of information generated by NPAR which were found to be relevant to inspection

needs include the following:

* Functional indicators - NPAR reports identify parameters which can be monitored or

measured to detect aging degradation. Te inspector can apply these results to

enhance vis ims (walkdownsand d to evaluate licensee programs for assuring

equipment and system operability.

* Failure modes. causes, effects - Operating experience data evaluated in NPAR studies

can alert the inspector to the prevalent failure mechanisms of systems and equipment.

The potential for changes in failure rate with increasing age is useful in evaluating

preventive maintenance.

* Stresses which cause degradation - An inspector can benefit from knowing the environmental and operational stresses which cause aging degradation.

vii
Maintenance recommendations - The inspector is required to evaluate the licensee's

maintenance program for several different inspections, including special team inspections. The NPAR reports review current maintenance practices, summarize vendorrecommended maintenance, and make recommendations for preventive and corrective

maintenance which can be used to detect and mitigate the effects of aging.

Based on the feedback from these presentations and from discussions with regional manage.

ment, we concluded that NPAR report summaries and aging inspection guides for each completed

component and system would be the best vehicle for providing concise, pertinent information. Each

summary includes identification of aging-related problems, highlights of the operating experience,

solutions to aging problems, and references likely to be available to the inspector. The aging inspection guide is a more concise document, which specifies licensee activities which should be conducted

to manage the aging of a specific equipment or system. It also notes visual inspection techniques

which may be useful in detecting degradation of the equipment The summaries and guides for

selected equipment are included in Appendix A and B.

viii
1. INTRODUCMION

1.1 Background and Goals

Research conducted under the auspices of the U.S. NRC Nuclear Plant Aging Research

(NPAR) Program has resulted in a large data base of component and system operating experience.

This data base was used in the NPAR Program to determine susceptibility to aging, and the potential

for equipment aging to impact plant safety and availability. The NPAR Program has also identified

methods for detecting and mitigating aging in components and systems.

The NPAR Program's goals are to understand the processes of aging degradation in components, systems, and structures, and to assess methods for detecting and mitigating aging'. This hardware-oriented engineering research program uses a two-phase approach. The phase 1 studies assess

the operating experiences in nuclear power plants to identify and characterize aging modes, mechanisms, and effects, and identify measurable functiona" parameters wich coma DC used w Al Llaplent aging.-I- he 2 research is an in-depth engineering study and assessment of aing detection and mitgation method e on e etg of na a uimet, review of current

majnte¶-'n~pacties i nuclear Powr pn, an a cos nefit analysis 

tions.

The typical output from a two-phase study of a component or system includes information

such as:

a detailed assessment and evaluation of operating experience,

* evaluation of failure modes, causes, and effects,

* review of current maintenance and operating practices,

* summary of past and ongoing regulatory activities in the area including Notices and

Bulletins, and Regulatory Guides,

* summary of industry standards, and

* evaluation of operational stresses which could lead to degradation or premature failure

of equipment.

Associated with each NPAR study is the need to determine the role of inspection, maintenance, and monitoring in counteracting aging and service wear effects. The role of maintenance in

managing aging is an important area that NRC has emphasized. A review by the NRC of maintenance performed at several plants concluded that Most utilities do not perform condition monitoring

due to inadequate knowledge of degradation mechanisms and the relationship between measurable

parameters and predicted functional capability.' In addition, recent NRC team inspections that

examined maintenance programs at nuclear power plants found that management does not consistently

acknowledge the aging issue. Of the twenty-five inspection reports issued, eight specifically state that

aging effects are not adequately addressed.

1
The potential exists for the NPAR Program to provide information which can support the

NRC regional inspections. More specifically, one of the goals of this work is to explore the areas

where NPAR results could enhance the inspectors understanding of the topic and contribute to a

more effective inspection. Other goals are

* to identify NPAR information that can help focus inspections on those components and

systems vulnerable to age-related degradation, and

* to develop a method(s) for integrating research results into the inspection process.

12 The NPAR Program

More than fifty reports have been published via the NPAR Program. The systems and components which have been or are being studied are summarized in Table I. As illustrated, the majority of completed NPAR work is in the component area. Recently, however, the research emphasis has

been towards aging assessments of important nuclear plant systems. These studies provide information

on all of the critical components within the system and their effect on the system performance.

Abstracts of the document products from the NPAR Program have been compiled in NUREG-1377,

'NRC Research Program on Plant Aging: Listing and Summaries of Reports Issued Through May 1,

1990.

Table 1 NPAR Information Areas

L Published Component Studies

Phase 1 Comonent Reports Comonents Date

1.

2.

3.

4.

S.

6.

7.

9.

10.

11.

12.

13.

14.

15.

16.

17.

I&

NUREG/CR4156

NUREG/CR4234, Vol 1

NUREGICR4257, Vol 1

NUREG/CR4302, Vol. 1

NUREG/CR4279

NUREG/CR464

NUREG)CR4597, Vols 1&2

NUREG/CR4257, Vol. 2

PNL-5722

NUREG/CR4819, Vol 1

NUREGICR-4715

NUREGICR4928

NUREGICR-4457

NUREG/CR-4590 Vols. 1&2

NUREGICR4985

NUREG/CR4992

NUREG/CR4692

NUREG/CR-5053

Electric Motors

Electric Motor Operated Valves

In-Containment Cables

Check Valves

Pipe Snubbers

Battery Chargers and Inverters

Auxiliary Feedwater Pumps

Pressure Transmitters

ECCS Pump Room Coolers

Solenoid Operated Valves

Circuit Breakers and Relays

Temperature Sensors

Batteries

Emergency Diesel Generators

Reactor Coolant Pump Seals

Multistage Switches

PORVs and Block Valves

Motor Control Centers

"5

718S

W5

186

6186

7/K6/88

10186

3,^7

6187 7187

9187

9R97

10i87

7/88

1

2
Table 1 (Cont'd)

Phase 2 Conponent Reports - Component

Published

Date

1. NUREGKR-4939, 3 Vols.

2. NUREG/CR-S051

Electric Motors

Battery Chargers & Inverters

1187

g8

II. On-Going or Planned Com-yonent Phase 2 Studies

1. Emergency Diesel Generators

2. Circuit Breakers and Relays

3. Auxiliary Feedwater Pumps

4. Check Valves -

5. Snubbers

6. Solenoid Operated Valves

Ea. Published System Studies

Plant 3s§tem Reports

1. NUREG/CR-4740

2. NUREG/CR-5052

3. NUREG/CR-5268

4. NUREG/CR-4967

5. NUREG/CR-5379, Vol.1

6. NUREG/CR-S419

7. NUREG/CR-S181

Reactor Protection

Component Cooling Water (PWRs)

Residual Heat Removal (BWRs)

High Pressure Injection

Systems (PWR)

Service Water System

Instrument Air

Class E Electrical Distribution

Published

Pate

LOB

7188

6/89

S89

6189

1,90

5/90

IV. On-Going or Planned System Studies

1. Component Cooling Water-Phase 2

2. Control Rod Drive-Phase 1

3. Reactor Core Isolation Cooling(RCIC)-Phase 1

4. Containment Cooling-Phase 1

3
13 Strategy

Several tasks have been accomplished towards integrating NPAR information into the NRC

Inspection Program. These tasks determined which NPAR information is relevant to the inspector,

how the Inspection Program addresses the performance of components and systems, and the format

in which the NPAR information can be presented so that it can be readily accessed and updated.

As illustrated in Table 2, the information flow path includes the following:

1. Determine how the NRC Inspection Program addresses the aging issue.

2. Determine the information needs of the NRC Inspection Program for effective evaluation

of licensee programs.

3. Develop a format for summarizing NPAR results that are pertinent to inspections.

4. Apply the format to NPAR components and systems to access the available information.

5. Assess methods to transfer information to the regions.

Table 2 Research Strategy and Report Outline

RESEARCH APPROACH REQUIRED ACTIViTIES

Review the NRC Inspection Program

Obtain pertinent information from

selected NPAR reports

Determine the- way that the Inspection Program

addresses aging

Develop a format for summarizing the NPAR results

that apply to NRC inspections

Apply guidelines to two NPAR components which

have completed the 2-phase research strategy

Obtain feedback from the regions on their

information needs and methods of transferring

the information

Develop recommendations

Present the information to the regions

Conduct a survey of the inspectors

Validate conclusions at selected plants

Evaluate the feedback from the inspectors, the needs

of the Inspection Program, and the available

resources

4
2. INSPECTION GUIDANCE TO ADDRESS NUCLEAR POWER PLANT AGING

Chapter 2515 of the current NRC Inspection Manual was reviewed to determine the areas of

emphasis, and to ascertain where aging information could improve the inspection goals. The NRC,

through the regional offices, makes independent inspections of equipment, systems, and human performance, as well as audits of each plant's inspection program and results. If necessary, augmented

inspection teams are sent to a plant to resolve special issues and problems.

The emphasis of the NRC Inspection Program is on evaluating the performance of licensees by

focusing on the requirements and standards associated with administrative, managerial, engineering,

and operational aspects of licensee activities. The Program recognizes that licensees may satisfy NRC

requirements differently, and therefore, expresses inspection guidance in the form of performance

objectives and evaluation criteria3 . For the resident and regional inspectors, there are written procedures covering various areas. Some of these procedures contain guidance related to aging degradation.

Team inspections are becoming an integral part of licensee evaluations. Several types of team inspections and several procedures for resident inspector are described in this report, with emphasis on how

aging effects are addressed in the inspection guidance. For the most part, this guidance is general.

Specific details provided by the results from the NPAR Program could enhance this guidance substantially.

The three major areas covered by the procedures for the resident inspectors are plan1operation

maintenance, andjnn olpl. The inspection modules which cover these areas and their relationship

with plant aging are briefly described. Illustration of the aginglinspection relationship is emphasized

for Plant Operations, but applies as well to Maintenance and Surveillance.

Operational Safety Verification'

The overall objectives of Inspection Procedure 71701 are to observe licensee activities and the

status of the safety systems to ensure that the facility is being operated safely and in conformance with

regulatory requirements.

The procedure indirectly addresses the aging issue by providing guidance for the inspector on

equipment degradation that should be assessed. For instance, one of the weekly inspection items is

to ....visually inspect the major components for leakage, proper lubrication, cooling water supply and

any general condition that might prevent ffillment of their functional requirements." Since one of

the goals of NPAR is to identify functional indicators for detecting component and system degradation,

more specific guidance may be useful to the inspector in determining the operational readiness of the

major components inspected.

Some activities recommended in this inspection procedure (i.e., checking for fire hazards) require

access to the interior of electrical panels and breaker cabinets. The inspector is directed to be aware

of cleanliness and signs of overheating. Several NPAR reports have noted that overheating of the

internal penb1 a * dgificant ese of age-related degradation in electrical equipment. Particular

components susceptible to this type of aging include xjlys, Lveryters, ttery chagers, and reactor

3rotegtion system oc cabinets. A knowledge of these facts could substiit lll the inspector

during inspection activities.

5
Engineered Safety Feature System Walkdowrn

Inspection Procedure 71710 associated with Plant Operations aims to independently verify the

status of engineered safety feature systems.

The inspector is directed to ....inspect the interior of breakers and electrical or instrumentation

cabinets for debris, loose material, jumpers, and evidence of rodents.' The guidance provided is that

the inspector should assess the overall conditions during the walkdown to identify problems which

could impact the performance of the system.

his procedure addresses aging to a certain degree in that one requirement (Section 0.201c)

directs the inspector to verify that electrical components are free from signs of overheating and all

solder joints should be shiny, indicating that there is no oxidation.

If the system being inspected was reviewed in the NPAR Program, considerable background

information would be available to the inspector. As shown in the flow chart in Figure 1, NPAR

research results, along with other plant-specific and regulatory information, could be used to plan and

prepare for an inspection. The NPAR results of interest are data on operating experience on the

system, which include dominant failure modes, mechanisms, and effects. The age-susceptible stresses

which contribute most to component and system degradation would also be identified, and would be

useful for selecting inspection areas.

If deficiencies are observed, the NPAR research results could assist the inspector i developing

the technical basis for requiring licensee action. This assistance may be in the area of methods and

techniques for determining aging degradation, vendor-related information, or operational practices

which have been shown to contribute factors to system unavailability. Likewise, the corrective action

proposed or implemented by the licensee could be evaluated using the maintenance recommendations

and evaluations from phase 2 of the NPAR studies.

Maintenance Inspectlons'" -

The monthly maintenance observation, Inspection Procedure 62703,is performed at all plants

to verify iarimaintenance activities for safety related systems and components are being conducted

properly. This procedure states that industry codes and standards should be used by the inspector to

evaluate a licensee's performance. Since the codes, standards, and guides are being written and

revised to reflect aging in components and systems as it impacts equipment qualification, plant life

extension, and good maintenance practices, this NRC inspection procedure indirectly addresses plant

aging.

NPAR research results include an evaluation of existing codes and standards for the component

or system and could, therefore, be used by the inspector as a reference. Other NPAR research results

which could provide an input to maintenance inspection procedures are:

1. NPAR research evaluates the vendor's maintenance recommendations and would assist the

inspector in satisfying inspection requirement 02.02d of Inspection Procedure 62700.

6
Regulation

(iOCFR, Licensee

Commitments)

Research Results

(NPAR)

ESF System Inspection

Infornation

Requirements

4

4

Inspectlon Guidance

(Procedure 71710)

Plant Specific Info.

(Procedures, FSAR

As-Built Drawingsl

Develop Inpetiion cu ne 1

, 

. n

L Perform

Inspection l

I

Def cencies?

Determine

SYea Basis for

>--- Inadequacy

Evaluate

Licensee's Corrective Action

40~~~~ 1~

NPAR Results

(Input (Operating

experience

or materials

evaluation)

NPAR Results

Input (Recommendations for

maintenance)

No

Figure 1 NPAR Input to ESF System Inspection

7
2. Current utility maintenance practices are reviewed in phase 2 NPAR work. Th information,

along with the recommendations resulting from this review, would give the inspector a reference

point from which to evaluate maintenance practices as identified in requirement 02.03d of

Inspection Procedure 62702.

3. Requirement 03.06 of Inspection Procedure 62702 discusses the specific attributes ofmotor

operated valves (MOVs) which should be inspected. A comprehensive study (NUREG/CR4234)

of MOVs was completed in the NPAR Program which gives background information on the

suggested areas of inspection.

4. Inspection requirement 02.0Sa of Inspection Procedure 62704 addresses replacement or life

extension practices for equipment which has a limited service life. This area is the core of the

NPARgrwnm. The inspector is directed to assure that the basis for extension-is oga aM

correct The condition monitoring practices recommended by NPAR could be used by the

inspector to make this judgement.

Surveillance Inspectlons'

The objective of this inspection area (61700 series of procedures) is to ascertain whether surveillance of safety related systems and components is conducted in accordance with the technical specifications. For the most part, the inspection requirements list activities which do not require external

sources of information, such as NPAR results. The possible exceptions to this are associated with the

inservice inspection and inservice testing programs for pumps and valves and some of the complex

surveillances to be reviewed, such as the inspection requirement for the emergency diesel generator

(02.01b of Inspection Procedure 61701).

Safety System Functional Inspection (SSFI)"

Several team inspections are effectively used by the NRC to identify problems regarding the

operational readiness of safety systems. Such inspections provide an in-depth assessment of the licensee's performance by obtaining inspection input on issues in several different functional areas. The

NRC SSFI inspections have identified significant problems in plant design and hardware, such as those

associated with rat v and check valves. For older plants, the SSFI inspections noted

that system desig entation is incomplete.

The objective of the SSFI is to assess the operational readiness of a selected safety system by

reviewing the following system areas:

* design basis requirements

* system design as installed

* maintenance and test records

* abnormal, emergency, and normal operating, maintenance, and surveillance procedures.

* operational experience

I. inspection results provide the NRC with a detailed cross-section of the licensee's perfornjuance in the areas of engineering, management, operation, maintenance, training, and testing.

8
The NPAR research results could be a aluable resource for this detailed inspection. For

example, the SSFI Procedure 93803 states that the inspector should be aware of the stresses imposed

on the system during all modes of operation. i.e., the differential pressure si v an, amflhe rpamp

suction and discsarae ysre eeri d during accident conditions. An evaluation of gpmtional

and environmental stressors is included in an NPAR system study, which could give t s o

insights into areas where there may be design weaknesses.

The SSFI guidance document directs the inspection team to determine the adequacy of the icensee's preventive maintenance program for the system. Appropriate vendor manuals are to be consulted. At both the system and component levels, NPAR results contain the practices generally

employed by the industry, especially those necessary to detect and mitigate the effects of aging.

Because the NPAR program extensively used operating experience data such as LERs, NPRDS,

NPE, and IPRDS, a substantial data bank was developed for systems and components. Important

information on failure causes and effects are available, as well as on changes in failure rate with time

for some components and systems. Risk assessments being developed to factor testing and maintenance into the aging models used in the NPAR program will assist the inspector in determining the

significance of any deficiencies.

Safety System Outage Modifications Inspection (SSOMI)l

The SSOMI program was developed by the NRC in 1985 because of the staffs concern about

the number of safety problems at operating plants which resulted from inadequate design, installation,

and testing of modifications made during outages. The program initially targeted older nuclear power

plants where modifications were made to upgrade equipment or to mitigate aging effects.

While aging is not directly addressed in the SSOMI inspection guidance, the system's performance is reviewed, as well as the changes made to assure the operational integrity of the system. The

NPAR results include details of system design bases and operating experience which could provide

valuable input to this inspection. Some modifications are made because of agin-related wear in the

component or system. In these cases, NPAR insights could be effectively used by the inspector to

evaluate the technical basis of the modification.

SUMMARY

To illustrate where this NPAR information may be used, a matrix (Table 3) was developed,

which shows the primary categories of information applicable to the sample of inspection areas reviewed. However, we note that the inspection procedures give the inspector a great deal of latitude to

perform the responsibilities. For any given inspection or inspector, thelevel of detail required may

differ depending upon the specific circumstances. Therefore, we recommend that as much potentially

useful information as possible be made available.

9
Table 3 Use of NPAR Results in Inspection

NPAA INFORMATION CATEGORIES

Inspection Type | Background | Operating | Maintenance |

(Procedure) Information Exerience Recommendation References

Safety System

Functional X X X X

Inspection

(SSFI)

Safety System

Outage Modifi- X X

cation Inspection (SSOMI)

Operational

Safety IV X X X

Verification

(71707)

Engineered

Safety

Features Xb X Xd X

System Walkdown (71710) .

Maintenance

Inspection Xd X

(62700 Series)

Surveillance

Inspections Xd

(61700 Series)

a - NPAR functional indicators

b - Age susceptible components & stresses

c - Dominant failure modes & mechanisms

d - Evaluation of current maintenance practices

e - Industry standards & guides for various components

f - Stresses associated with testing

10
3. NPAR INFORM&TION WITH INSPECnION APPLICATION

The review of the NRC Inspection Program revealed several areas where NPAR information

could be helpful to the inspector. To obtain the desired information from the NPAR reports

uniformly, and to present the results in discrete categories to the inspectors, four headings of information were defined.

a) Component background

Included under the category of component background are items such as identification of

materials and subcomponents susceptible to aging, design specifications and qualifications, and operating stresses which have effects on the aging of equipment.

b) Operating experience

An important aspect of every NPAR study of components and systems is the assessment of

actual operating experience to determine age-related failure modes, causes, and effects. The operating and environmental stresses are included in this section, with a discussion of problem areas in

design, installation, and testing.

c) Recommendations

Recommendations encompass the major research results including functional indicators and

viable techniques for aging detection and mitigation. Also included is an evaluation of current maintenance practices, vendor recommendations, and the results of any testing performed as part of the

research.

d) References

The fourth category of information that can be applied to inspection activities are selected report

references, such as NRC documents associated with the equipment, as well as related industry standards.

A detailed breakdown of these four information categories are listed below.

3.1 Component background information

a. Boundary- The interface limits of the component are defined; ie., inverter includes input

breaker to output breaker.

b. Related Systems (where used): The major systems where the component is used are

indicated.

c. Types and Sizes: The types and sizes of the component included in the study are listed.

d. Function: A description of the safety-related function of the component is provided.

e. Age-Dominant Materials: ne materials most susceptible to aging are isted.

11
f. Designs and Configurations: The component designs are reviewed, and any alignment

differences are noted.

g. Subcomponents: The subcomponents most susceptible to aging are listed.

h. Subcomponent History: For the subcomponents identified above, any significant age

related information is provided including:

- application to other equipment or systems

- estimates of service life

- design parameters and specifications

i. Specifications: The typical specifications associated with this equipment are given,

including electrical, mechanical, and environmental parameters.

j. OperatingtAccident Parameters: The most limiting operating and accident conditions

affecting this equipment are given.

k. Manufacturers: The major manufacturers and suppliers of this equipment are listed.

3.2 Operating Experience

a. Summary of failure data is given.

1. Number of Failures: Summarizes the operating experience for the component based

on LERs, NPRDS, and NPE giving the period reviewed.

2. Subcomponents Failed: Lists the number of failures attributed to subcomponents.

3. Failure Causes: Lists the causes of failure identified and the number of failures.

4. Failure Effects: Lists the effects of failure identified and the number of failures.

b. Design-Related Problems: Any design and manufacturing errors which have contributed

to component aging are given.

c. Environmentally Related Failures: Describes any age-related failures which were due to

environmental conditions.

d. Operational stresses: Describes the operational stresses which contribute most to the

aging of the component.

e. Change in Risk Impact With Age: Provides the relationship of a time-dependent change

in failure rate with a change in system unavailability, plant risk, or plant unavailability.

12
L Human Factors: Summarizes the failures associated with errors in operations or maintenance.

g. Testings Summarizes the failures associated with equipment or system testing.

h. Installation: Lists installation errors which resulted in premature failures of components.

3.3 Recommended Maintenance. Testing. and nspection

a. Functional Indicators: Descnies the parameters which can be monitored periodically or

continuously to determine the component's health.

b. Age Mitigation Techniques: Describes the practices for detecting or mitigating the effects

of aging on this component. Indicates frequency of performance, where applicable.

c. Vendor Recommendations: Lists the specific vendor recommendations for this component,

and identifies the source of the recommendation, ie., technical bulletin.

d. Storage Recommendations: Lists the storage requirements for the component and cites

the source of the requirement, i.e., ANSI standard.

e. Recommended Maintenance Practices: Summarizes the NPAR report's recommendations

on preventive maintenance. The technical basis for each recommendation is given.

f. Corrective Maintenance Methods: Summarizes important repair practices which should

be employed to reduce age-related failures.

g. Trending Techniques: Suggests component trends which could be monitored to detect agerelated degradation.

h. Results of Testing Performed: Describes the results of any testing performed on naturally

or artificially aged equipment which revealed aging degradation.

i Important Inspection Concerns: Lists the inspection areas which provide the most

valuable feedback to the NRC inspector on the component's operational readiness.

3.4 References

a. Bulletins, Notices, Regulatory Guides: Lists the NRC documents associated with the

component.

b. Reports, AEOD Case Studies: The reports associated with this component which could

be useful to the NRC inspector are listed.

c. Related Industry Standards such as EEE, ASME: Summarizes industry activities

associated with the aging of this component, such as equipment qualification, and plant ife

extension.

13
3.5 Feedback From Rezions

The NPAR results and their potential use was presented to inspectors at Regions 1, 2, and 3.

The major segment of the presentation provided specific examples of NPAR research results and how

they could be applied to inspection activities. Excerpts from the NPAR reports were arranged in four

categories-component background, operating experience, recommendations, and references.

A survey form was given to the inspectors, whose purpose was to:

a. rank the four types of NPAR information;

b. identify components and systems for which information is desired;

c. rank the proposed means for transmitting NPAR information;

d. determine which plants have programs which address aging and

e. solicit comments on the overall program of applying aging research results to the inspection

process.

As illustrated in Figures 2 and 3, this feedback indicated that:

1. The NPAR results are potentially useful to the inspectors, with most people desiring information on operating experience (60% said this would be very useful.)

2. Most insp tors felt that summaries of the MsRE/ ults would be the best method

of alerting inspectors to NPAR results, foMowed closely by pefrig npc ions e f P ! > _ t closed by ~~~performing inispections -X-e

on aging issues. While there was a mixed reaction from the Region 3 resident inspectors

on the usefulness of revising the NRC Inspection Program to include guidance on aging,

Region 1 inspectors felt that including NPAR results as appendices to the inspection procedures could be useful. They added that this may not be as valuable to the resident inspectors because they may not consult the procedures as often as the regional inspectors.

3. The respondents listed many systems and components which were of interest to them from

the perspective of aging. There was only minor commonality indicating that information

needs vary widely depending on the individual's experience, and the problems at the plants

to which they are assigned. For instance, in Region 3 where 17 anpors responded to

the survey, those components for which information was desriRby at least three inspectors

were cable (5), diesel generators and chargershnverters (4), relays, motors, and batteries

(3); The systems identified were service water (4) and component cooling water (3); The

components and systems listed which are not presently covered by NPAR were power

supplies, nuclear instrumentation, air operated valves, radiation monitors, the automatic

depressurization system, and the recirculation system (BWRs).

4. Only a small percentage (<10%) of the inspectors were aware of any actions being undertaken by the utilities to address the aging issue.

14
Info Type

I

Component

Background

Operating

Experience

Recommendatlon

References

I 3.9

I

I

4.2

4.1

- U

3.1

I

NOT

USEFUL

2 3

USEFUL

4 6

VERY

USEFUL

Figure 2 NPAR Information Desired by Inspectors

Method

REPORT

SUMMARIES

AGING

INSPECTION

PERSONAL

COMPUTER

k1kW111,1111,111, 3.9

3.7 I

111111,

II

I

3.2

PROGRAM

REVISION

REGIONAL

SEMINARS

3.0

I

111111,

2.7

I

I

NOT

USEFUL

2 3

USEFUL

4 6

VERY

USEFUL

Figure 3 Preference for Method of Information Transfer

15
3.6 Other NRC Input

To support the NRCs team inspections of maintenance programs at nuclear power plants, a

two-volume Maintenance Inspection Guidance was published in September 1988. As part of the

inspection checklist, the team is expected to evaluate the extent to which management is aware of

plant aging. Of the first twenty ive reports issued on the team inspections, eight (32%) found that

utility management was not aware of the aging issue, specifically making the following points:

* 'No program in place to address plant aging effects.

* "Lack of management attention to aging."

* "No followup to aging failures."

Several inspectors at the regional seminars felt that the utilities must develop programs to

address the aging issue before the inspectors could NAruesults caly, they felt

that the NPAR reports provided inadequate regulatory support foheinspector to obtain corrective

action from the licensees. The need for NPAR results to be moved into the regulatory area, should

be pursued further. In addition, it is apparent that there is a need for utilities to develop programs

to address the aging issue.

16
4. APPLICATION OF NPAR RESULTS TO INSPECMION ACTIVITIES

Supported by the feedback obtained from the inspectors, NPAR reports for selected components

and systems were reviewed, and information was extracted that could be of use to inspection activities.

This information was compiled into two documents called an aging report summary and an aging

inspection guide.

The aging report summary, of approximately 1500 words, has the following format.

a) Summary of Results - This is a brief overview of the study which addresses the question of

whether or not aging is a significant safety concern for the particular component or system.

b) NPAR Reports - This is the reference NUREG report number which provides the basis for

this summary.

c) Aging-Related Problems - This section briefly describes the components most susceptible to

aging, the stresses which affect service life, and the dominant causes of failure.

d) Operating Experience - The failure history of the component or system is discussed. This

operating experience is typically based on the LER or NPRDS data bases, but could include

specific plant data. Significant causes and effects of failure are highlighted.

e) Solutions to Aging Problems - The largest portion of the summary is devoted to the recommendations presented in the NPAR reports for detecting and mitigating aging effects.

Periodic testing, maintenance, continuous monitoring, and routine inspections are some of

the techniques described for the specific equipment or system.

f) References - The summary contains references to the NRC documents and industry standards that are available to the inspector. The NRC documents include AEOD reports,

information notices, and regulatory guides associated with the equipment, while industry

documents include ASME, IEEE, ISA, and NEMA standards and guides.

The aging inspection guide is a concise document focused on the specific inspection activities to

be considered when assessing the operational readiness of the component or system. The guide

contains visual-inspection techniques for detecting aging degradation, including external and internal

indicators, and important operating parameters. In addition, the guide lists those activities associated

with maintenance, operations, design, and testing which the licensee should employ to demonstrate

that aging is understood and is being adequately managed.

Appendix A contains the sample report summaries for several studies of components and systems,

completed as part of the NPAR program. The components addressed are the inver battery charger, motor, and motor control center. The systems included are Component Cooling Water (PWRs)

and Reidual Heat Removal (BWkts). It should be noted that the system summaries are based on

phase 1 work only and could be modified following the phase 2 efforts. Appendix B contains the

aging inspection guides for the same components and systems.

17
5. INFORMATION TRANSFER

Several alternative methods for transferring NPAR results to the regions were presented to the

inspectors for their comment.

* Manual of NPAR Results

* Conduct On-Site Inspections

* Personal Computer

* Revision of the NRC Inspection Manual

* Presentation of NPAR Results at Regional Meetings

5.1 Manual of NPAR Results

It was clear from the survey response that a hard copy of the information is desired, as long as

it is concise and directed towards the inspector's activities. This method has been pursued and is

recommended as the primary method of information transfer. Report summaries and aging inspection

guides for other NPAR components and systems can be completed and organized in a manual that

can be updated as work is completed. A possible layout of a document is depicted in Table 4.

52 Conduct On-Site Inspections

Success was achieved using a team inspection approach (from the regions or headquarters) to

assess the performance of utilities in the areas of maintenance, fire protection, equipment qualification, and system design, among others. A similar approach could be taken to assess a plant's ability

to detect and mitigate aging. Because few plants have a formal program to address equipment aging,

the inspection team would most likely focus on maintenance practices, routine operator activities, and

procedures to evaluate test data. The inspection team would be composed of personnel familiar with

these areas and cognizant of NPAR findings and recommendations.

The disadvantage of on-site inspections is the possible duplication of effort resulting from a

separate NPAR inspection. It is more likely that NPAR information can support maintenance, operations, and routine inspections by the resident inspector, rather than warranting a comprehensive team

inspection. Therefore, it is not recommended as a primary method of transferring NPAR information

to the regions. t can be used, however, on an as needed basis for a special inspection where it is

expected that insufficient attention is being devoted to the aging issue.

18
Table 4 Manual of NPAR Results

GOAJs

Combine the results from related NUREGs into a single document on aging, emphasizing inspection.

A. Eectrical Systems/Oomponents

* Circuit Breakers/Relays

* Batteries

* Chargers/Inverters

* Electric Penetrations

* MOCs

* Cables

* Motors

* Connectors

* Diesel Generators

* Transformers

* Motor Operated Valves

* Solenoid Operated Valves

* Switches

B. ECCS Systems/Components

* HPCI

* RHR

* HPSI (PWR)

* Control Rod Drive

* Auxiliary Feedwater

* PORVs

* Heat Exchangers

* Check Valves

* Snubbers

C Support Systems

* CW

* Service Water

* Instrument Air

* Room Coolers

* RCP Seals

* BOP Systems

D. Instrumentation and Controls

* RPS

* Sensorstransmitters

* Bistables/Switches

* Power Supplies

19
A team inspection plan to evaluate licensee programs to determine that operations, maintenance,

and testing adequately address the effects of equipment and system aging should review the following

areas

1. Corrective maintenance records of age susceptible equipment to determine rates of failure

and evidence of recurring failures.

2. Preventive maintenance program to determine content and frequency of PM and changes

in the program to reflect actual or anticipated increased failure rates.

3. Operating rocedures to determine that precautions are taken to minimize operational

stresses.

4. Operating logp to determine if operating stresses are identified, ie., area temperatures,

unusual noise or vibration, oil or water leakage.

S Maintenance procedures to determine if as found' conditions are identified, if spare parts

controls are in place, and if there is root-cause evaluation of detected wear.

6. Equipment status to determine its condition.

7. Document controls to determine that vendor's recommendations are incorporated in maintenance procedures and are maintained current.

An inspection of this type would provide reasonable assurance that the licensee's programs

effectively consider those aspects of plant aging that affect plant safety.

53 Personal Computers

With the expanding use of personal computers at NRC offices, and the desire to minimize the

paper routinely processed by NRC inspectors, exploring the application of NRC information resources

such as the Safety Information network (SINET) or the Safety Issues Management System (SIMS)

should be considered.

The purpose behind the SINE? initiative is to collect information related to NRC licensees and

their operations into a centralized data base, to which both headquarters and regional staff would

have access.

The overall purpose of SIMS is to provide NRC staff with an effective system to manage information to assure the timely resolution of outstanding concerns, including the aging issued

5.4 Revision of the NRC Inspection Manual

The NRC Inspection Program consists of procedures that provide instructions and guidance for

the resident inspector, team inspections, vendor evaluations, and inspections for equipment qualification.

20
Based on the review of the Inspection Manual, generic NPAR recommendations could be incorporated through a revision of the Manual. Samples of the report summaries and aging inspection

guides were submitted to the NRCs Inspection and Licensing (LPB ) Program Branch for their

information. Several mechanisms, including temporary instructions, are available through LPB to

distribute information and guidance to the regions.

5.5 Presentation of NPAR Results at Regional Meetings

A practical alternative to disseminate NPAR information is to present the results directly to the

inspectors.

Presentan NRC staff and national lborator NPAR representatives were made to ach of

the Reizions ovr the past two years. These presentations provided regional and resident inspection

personnel with an overvew of the NPAR Program and its results. It is conceivable that NPAR results

could continue to be disseminated through this type of meeting. To achieve maximum advantage, a

workshop atmosphere is recommended that would permit a free exchange of information.

21
6. CONCLUSIONS AND RECOMMENDATIONS

The Nuclear Plant Aging Research Program has the potential to support the ongoing inspection

effort conducted by the regions in accordance with the NRC Inspection Program. One objective of

the inspection effort is to ensure that systems and components have not been measurably degraded

as a result of any cause, including aging. The following objectives coincide with this goal as stated in

the NPAR Program Plan:

1. Identify aging effects which could cause component or system degradation and impair plant

safety.

2. Identify methods of inspection, surveillance, and monitoring to detect aging effects before

the loss of safety function.

3. Evaluate the effectiveness of storage and maintenance practices in mitigating aging effects.

To achieve the NPAR Program objectives, research results have included such important inspection attributes as:

1. Compilation of component and system operating experience data.

2. Identification of component and system failure modes, mechanisms, and effects.

3. Identification of the operating and environmental stresses contributing to failure.

4. Evaluation of current industry maintenance and testing practices.

5. Recommendations for inspection, maintenance, and monitoring practices to detect and mitigate aging in components and systems.

This report describes the effort associated with evaluating the potential of integrating the NPAR

results into the NRC Inspection Program: our conclusions and recommendations are summarized in

this section.

6.1 Conclusions

Based on the feedback obtained from regional and resident inspectors, it is concluded that the

use of NPAR results can improve the inspection process. The inspectors are closely involved with

technical issues at the plants and generally agree that equipment and system aging is an issue that

should be addressed by all licensees. Therefore, they are interested in research findings and recommendations that enhance their understanding of the issue.

The review of inspection procedures suggests that the information requirements of the inspector

are vast. We therefore conclude that the NPAR data base can assist the inspector in focusing their

activities on those components and systems most likely to affect plant safety as the plant ages. In

addition, the NPAR data and research results can provide the inspector with criteria for determining

the validity of findings and the completeness of licensees' responses. Evaluating a licensee's administrative programs is another area where NPAR results can provide a reference, especially those reviews

associated with operations, maintenance, and testing.

22
NPAR-generated information which has a direct relationship to the requirements of the NRC

Inspection Program are:

* functional indicators

* failure modes, causes, and effects

* degradation causing stresses

* maintenance recommendations

* component and system risk impact as a function of time.

Examples of inspection procedures reviewed which could benefit from one or more of those

NPAR results are:

* 71707, Operational Safety Verification

* 71710, Engineered Safety Feature System Walkdown

* 62700 series, Maintenance Program Inspections

* 61700 series, Surveillance Program Inspections

* Safety System Functional Inspection (SSFI)

* Safety System Outage Modification Inspection (SSOMI)

6.2 Recommendations

To achieve the goal of transferring useful information from the NPAR program to the regions

we recommend:

1. Summarize the research from NPA reports that are applicable to NRC inspection activities.

A summary of the research results, coupled with an aging inspection guide will provide the

inspector with important insights into the aging degradation of various equipment and systems. The summary for each equipment type and system studied in the NPAR Program

would include the identification of aging-related problems, highlights of the operating

experience, solutions to aging problems, and references likely to be available to the inspector.

The aging inspection guide is a more concise summary of recommendations emphasizing

visual inspection techniques, and activities to evaluate licensee's programs for understanding

and managing aging.

2. Establish a schedule of regular regional seminars by NPAR contractors. Results oriented

discussions by NPAR representatives would be of mutual benefit to the regions and NRC

research. A workshop atmosphere for discussion of components or systems of particular

interest to the region would be of greatest value.

3. Pursue the development of a software supported database. Continuation of work with the

NRC's Data Administration Branch to make NPAR results available through a system such

as the Safety Information Network (SINET). With the expanding use of personal computers

at NRC offices and the desire to minimize the amount of documentation routinely processed

by the NRC inspectors, exploring the application of a data base system is appropriate.

23
7. REFERENCES

1. NUREG-1144, Rev. 1, 9/87, 'Nuclear Plant Aging Research (NPAR) Program Plan."

2. NUREG-1212, Vols. 1 & 2, Status of Maintenance in the U.S. Nuclear Power Industry," 1985.

3. NRC Inspection Manual, 'Policy and Guidance for Development of NRC Inspection Manual

Programs," Chapter 0033, 10/13/87.

4. Inspection Procedure 71707, Operational Safety Verification,' 8(29/88.

5. Inspection Procedure 71710, 'Engineered Safety Feature System Walkdown,' 7/14/87.

6. Inspection Procedure 62700, 'Maintenance Program Implementation," 2/087.

7. Inspection Procedure 62703, 'Monthly Maintenance Observation,' 220/87.

8 Inspection Procedure 62704, 'Instrumentation Maintenance (Components & Systems) Observation

of Work, Work Activities, and Review of Quality Records," 220/87.

9 Inspection Procedure 62705, Electrical Maintenance (Components & Systems) Observation of

Work, Work Activities, and Review of Quality Records,' 220/87.

10. Inspection Procedure 61700, Surveillance Procedures and Records," 9/13/83.

11. NRC Inspection Manual, "Light-Water Reactor Inspection Program-Operations Phase,' Chapter

2515-Appendix D, 8/30/88.

12. Memo: J.O. Partlow to Regional Directors, "Inspection Checklists - Safety System Outage Modifications Inspection Program,' 6/86, 54 pages.

13. NUREG-1145, Vol. 4, U.S. NRC 1987 Annual Report," pps. 172-177.

24
APPENDIX A

NPAR REPORT SUMMARIES

A. Inverters

B. Motors

C. Battery Chargers

D. Motor Control Centers

E. Component Cooling Water (PWRs)

F. Residual Heat Removal (BWRs)

Pare

A-2

A-7

A-14

A-19

A-24

A-29

A-1
AGING REPORT SUMMARY

INVERTERS

SUMMARY

Inverters are used In nuclear power plants to convert de to

ac power for Instrumentation, controls, and other equipment

necessary for power operation and safety. Research has

shown that inverter performance will degrade with time due

to the aging susceptibility of some components and

materials. This degradation can be detected and mitigated

through maintenance, operation, and design activities.

This guide summarizes these recommended practices, and

Identifies areas of inspection Importance.

BASED ON:

1. NUREG/CR-4584, Operating Experience and Aging-Selmic Assessment of Battery Chargers and Inverters

2. NUREG/CR-5051, Detecting and Mitigating Battery Charger and Inverter Aging

3. NUREG/CR-5192, Testing of a Naturally Aged Battery

Charger and Inverter

AGING RELATED PROBLEMS

A large percentage of Inverter failures are due to hardware.

Components susceptible to aging degradation are:

1. FILTER CAPACITORS: These components have experienced a limited service life (approximately

5 years) directly related to ambient temperature,

applied voltage, and ripple current.

2. THYRISTORS (SCRs): Large SCRs used in the power

conversion circuit generate heat which Is designed

to be dissipated through attached heat sinks. Improper torque of the SCR/heat sink connection has

resulted in overheating and failure of the SR.

3. FUSES: Fast acting fuses are used to protect

inverter electronics and are subject to a thermal

fatigue. Depending on internal cabinet temperature

and the proximity of the fuse rating to normal load

current, expected life can vary from 5 to 25 years.

As the fuses degrade, they are more susceptible to

normal plant electrical transients such as starting

motors and switching operations.

A-2
OPERATING EXPERIENCE

INVERTER FAILURE EFFECTS

Number of Event,

Reactor Trip 87

Loss of B/D Cooling a

ROCInop 4

v HPO Inop 

Core Instrumentation 

Ventilation Loss 7

Turbine Aunbeck 7

The operating experience data

demonstrates that Inverter failures

can Impact plant safety and availability. One of the most visible

and dramatic effects of an Inverter

failure Is reactor trip. From 1984

to 1986, 67 reactor trips resulted

from an Inverter failure. In addition, safety injection (SI) system actuations, containment isolations,

and safety system (HPCI & RCIC) Inoperability were directly linked to

Inverter failures.

Containnent IsoL 18

8i Actuation 12 N

Loss of Fewater 11

LERs 1984 - 1986

INVERTER FAILURE CAUSES

Percent of Failure

Electrical Transient 15

Overheating

Loose Connection 7

Wear 6

Personnel Error Ve

The analysis of data on operating

experience accumulated over 12

years Indicates that overheating, electrical transients, and errors

by plant personnel are the leading

causes of inverter failures. Such

stresses cause aging of critical

components. The large percentage of unknown causes may be due to

'normal' electrical switching

where Inverter fuse or circuit

breaker operation results.

Other 8 38

Unknown 3s

LERs 1976 - 1986

A-3
SOLUTIONS TO AGING PROBLEMS

DESIGN

Four basic designs of Inverters are used In the

nuclear Industry. Improvements were made In the

more recently manufactured units, such as:

1. The use of an automatic transfer switch, which

senses an inverter failure and switches to a

backup power source without a detectable loss

of power to vital equipment.

2, The Installation of higher voltage and temperature rated components, especially capacitors

and semiconductors. This makes these

components less susceptible to operationally

induced stresses.

3. Forced air cooling rather than natural convectlon cooled units tend to have less overheating

problems. Several utilities have modified the

inverters in this manner.

4. Additional monitoring capabilities, including

annunciation of abnormal conditions, such as

high temperature, are available In newer units.

MAINTENANCE & MONITORING

Based on the Inverter's Importance and the effects

of Its failure on plant safety and availability, a

comprehensive maintenance program is recommended.

To detect and mitigate the effects of aging on

Inverters, this program should Include inspection,

testing, and preventive maintenance.

(continued)

A-4
MAINTENANCE & MONITORING

INSPECTION

The inspection of an Inverter by experienced

personnel can provide a great deal of Information

about the equipment's overall condition.

1. While operating, observation of cyclical electrical

hum, meter oscillation, or cooling fan noise can

Indicate an Impending failure.

2. Component degradation due to overheating, and loose

electrical and mechanical connections can be

detected when the Inverter Is off-line.

3. Cleaning can minimize the risk of overheating. The

wiping of SCR heat sinks and ventilation flow paths Improves heat transfer away from temperature sensitive components.

TESTING/MONITORING

Periodic testing Is necessary to verify that design

parameters are obtainable under all conditions. The

acceptance criteria for such testing should be based

on specific plant and manufacturer information.

1. Overheating Is an Important cause of stress that

can reduce the expected life of electrolytic cap- acitors, thyristors, and Inductors. It is prudent

to periodically monitor them to detect any Increase

In temperature.

2. The component's performance may change with time

and can Indicate degradation. Two parameters for

detecting aging of electrolytic capacitors are an

Increase In the equivalent series resistance (ESR)

or a decreL.le In capacitance.

3. Capacity testing Is recommended, especially for

standby Inverters. This verifies that the inverter

can supply design loads, and permits inspection monitoring techniques to be applied at rated

conditions.

4. The automatic transfer switch should be tested to

verify it is capable of transferring to the: alternate supply without interrupting power to critical

equipment.

A-5
PREVENTIVE & CORRECTIVE MAINTENANCE

Specific requirements from the manufacturer should be

Incorporated Into the maintenance program. These are

based on the manufacturer's experience or are generated

as a result of equipment qualification. Guidelines are

also provided to restore the Inverter to an operable

condition following a failure.

1. Deviations from equipment qualification requirements require documented engineering analyses. Components which

have been identified as having limited service life Include capacitors, cooling fans, fuses, circuit breakers,

and relays.

2. Replacement power electronics, such as SCRs, should be

remounted to a cleaned heat sink surface at the torque

specified by the vendor.

3. Loose power cable terminal contact surfaces should be

cleaned before tightening.

4. Fuses identical in rating and design should be used.

REFERENCES

These documents provide additional background information on Inverters used in nuclear power plants.

1. AEOD Case Study Report C605, Operational Experience Involving Losses of Electrical Inverters", 12/86.

2. Information Notice 87-24, 'Operating Experience Involving Losses of Electrical Inverters".

3. Information Notice 88-57, Potential Loss of Safe Shutdown Equipment Due to Premature SCR Fallures,.

4. IEEE-650-1989, IEEE Standard for Qualification of Class

1E Static Battery Chargers and Inverters for Nuclear

Power Generating Stations'.

A-6
AGING REPORT SUMMARY

MOTORS

SUMMARY

Motor degradation due to aging and service wear decreases

reliability and Increases the potential for failure. The

Impact of motor failures on plant safety is significant

since motors play a vital role In most safety systems.

The evaluation of motor performance In nuclear and nonnuclear ndustries and laboratory testing of aged motors

has Identified elements for an Improved maintenance

program comprised of comprehensive Inspections and

periodic testing of motor subcomponents.

BASED ON:

1. NUREG/CR-4156, Operating Experience and Aping-Seismic

Assessment of Electric Motors.

2. NUREG/CR-j4939, volumes 1,2,3; Improving Motor

Reliability In Nuclear Power Plants.

AGING RELATED PROBLEMS

For smaller motors (under 200 hp), the stator Insulating

system and bearing assemblies are the subcomponents that

most frequently failed. The major -factors contributing to

large motor failures Include voltage surges and mechanical

stresses due to centrifugal or magnetic forces.

1. INSULATING MATERIAL:

primarily degraded b eate w

due to starting, 

Humid environments produce more rapid degradation In

both cases.

2. BEARINGS: Bearing failures are primarily caused by

deterioration of ubrication or mechanical

misalignment.

3. TEMPERATURE: Thermal effects commonly result from

excessive current which Imposes self-heating and

results IninsuLation fallure.

4. VIBRATION: Vbration can originate from internal and

external abnormalities, and Is often caused by

coupling misalignment, rotor Imbalance, and loose

par ts.

6. MOISTURE: Humidity can reduce properties of electrical

insulation. High humidity promotes dirt buildup on the

windings, leading to overheating.

A-7
OPERATING EXPERIENCE

N

U

m

b

S

r

0

f

F

u

r

e

S

I I M r; I M. I '1 I MO

STAOR WTOR 8CVW ACSSORES WANTDV UKR0N

M VO* moton PWp MWotor, E M. motor

Motor Component Failure Distribution

Regardless of size and

system application, 

motors are subject to

stresses which may eventually cause failure.

Stator-related failures

are the highest having

nearly an equal probability of occurrence for

both pump and valve

motors. Bearing failures

are significantly

higher for pump motors

than for valve operators.

For 250HP motors and

above, class B Insulation systems, which were

used In safety & nonsafety applications at

older plants & nonsafety applications at

newer plants, have

experienced the most

failures. Most newer

plants (post 1980) use

class F or H Insulation

for safety systems.

LARGE MOTOR FAILURES CLASSIFIED BY INSULATION TYPE

IMS LATN lotl 070 tl S? t 74 lo7 7 an T 3 lit

CLASS

A - 413 2 4 1 1---

* 19 19 28 13 28 20 21153120 29 34142

F 3 2 4 4 *2 7 8 3 13 9 7 19

H 1 _ 3 2 1 1 4 - 1

OTHER - 1 _ 2 2 - 2 1 8 1 3 3

TOOAL 23 26 S323 35 29 339 45 43 44 68

Son"ic 4.7 5.7 8.2 5.7 3.8 4.3 3.2 5.1 81 8.2 12

Awags Swvte Ufa * Awage A at TIme of n

A-8
SOLUTIONS TO AGING PROBLEMS

A preventive maintenance program should exist for motors

Important to plant safety and availability. To evaluate the

performance of a motor, the PM program should Include

periodic testing, continuous monitoring, and Inspection

techniques.

PERIODIC TESTING

Periodic tests are In situ tests performed In the plant on

the equipment at scheduled Intervals to detect degradation

and verify operability.

1. Insulation resistance megger) tests are go/no go tests

that are effective for the post maintenance check of a

motor. They indicate the dryness of the insulation but

are not useful for predicting overall Insulation

dielectric conditions.

2. A partial discharge test is used for large motors with a

voltage rating above 500 volts, and can provide results

which are useful for trending. It detects void growth

and corona discharge in the insulation by measuring the

discharge inception voltage, which decreases as the

Insulating material gets older.

3. Power factor or- dissipation factor testing Is used on

high voltage motors and is suitable for monitoring

average insulation condition.

4. During technical specification testing of pumps and

valves, motor running current and bearing vibration

should be mebasur7u M-Mrecorded. Where -available-, the

winding and bearing temperatures should also be measured

and trended.

5. Ac and dc leakage tests (hipot) have proven to be

effective in locating faults, however, they have several .

shortcomings Including the imposition of electrical

stress. If used, it is recommended that the voltages

be applied in small discrete steps up to the test

voltage.

A-9
SOLUTION TO AGING PROBLEMS

(continued)

6. Voltage Impulse or surge testing can detect turn shorts

or hot spots in the Insulating material in low voltage

motors.

7. The chemical analysis of the lube oil will Indicate

excessive bearing wear or contamination within the

lubricating system. r

CONTINUOUS MONITORING

Motors equipped with permanently installed devices should be

monitored regularly. A baseline value should be developed for each parameter. Readings should be evaluated by comparison to baseline readings.

1. Parameters typically monitored are lne/phase current or

voltage, winding and bearing temperatures, lube oil

temperature, and bearing vibration signals.

2. GuidelInes for the frequency of evaluating continuously monitored parameters for safety related motors are:

a. Line/phase current:

b. Winding temperature:

c. Bearing temperature: d. Lube oil temperature:

e. Bearing vibration:

6 to 12 months

3 to 6 months

1 to 3 months

3 to 6 months

1 to 3 months

3. Bearing temperature and vibration measurements are

proven methods for indicating degradation In bearing assemblies. A high temperature or vibration Is a clear

indication of bearing wear, misalignment, or other aging mechanisms.

A-10
SOLUTION TO AGING PROBLEMS

(continued)

INSPECTION

Motors, regardless of their sizes and types, should have a

periodic Inspection to evaluate their condition. The

Inspection program assures the operational readiness of

of motors between scheduled testing or maintenance.

10 POINT INSPECTION PROGRAM FOR MOTORS

1

2

3

GUARD 4

6

AGAINST 6

7

8

9

10

.- *DIRT, DUST, & CONTAMINANTS

MOISTURE, WATER, GREASE & OIL

FRICTION

VIBRATION/MOUNTINGS

EXTREME ENVIORNMENTAL CONDITIONS

CRACKS/CORROSION

ELECTRICAL STRESSES

AGE AND SERVICE WEAR

HUMAN ERROR

LOSS OF INSPECTION DATA

1. Dirt, dust, and contaminants may be removed by wiping

the motor clean with a dry cloth. Regulated compressed

air can be used to reach Inaccessible areas.

2. Moisture intrusion Into motor components significantly

Increases the probability of failures. Space

heaters should be used to thoroughly dry the motor

before It Is returned to service.

3. Excessive belt tension, poor alignment, a bent shaft,

excessive end bell thrust, or damaged bearings can result In

friction and high noise levels.

A-l
INSPECTION

(continued)

4. Winding vibration can be caused by loose rotor bars or

end rings, phase imbalance, or Improper lubrication.

5. Humidity, temperature, radiation, and chemical spray can

effect the motor's service life. When required to

operate in post-accident conditions, the motor should be

shielded as much as possible from potential severe

environmental stresses.

6. Surface corrosion or cracks on the motor's components

can be detected by a thorough visual Inspection. High

frequency vibration can Initiate cracks or voids at high

stress regions.

7. A good visual Inspection of Insulation surfaces for

corona discharge (white and grey deposits) or burn marks

can detect a degrading Insulation.

8. Some components have a finite life because of their age

and service wear, such as seals, bearings, gaskets, and

carbon brushes. A typical life for bearings In small

motors Is ten years.

9. An Inspection checklist performed by trained maintenance

personnel can help eliminate many of the problems

Introduced by the human.

10. Logging the Inspection activities and observations of

motor conditions can provide Insight Into the motor's

per for mance.

A-12
REFERENCES

The universal applications of electric motors has resulted

In a multitude of references. The following list reflects

those which may be more accessible to the Inspector.

1. IEEE Std. 334-1974, Type Test of Continuous Duty Class

1E Motors for Nuclear Power Generating Stations.

2. IEEE Std. 432-1976, Guide for Insulation Maintenance for

Rotating Electrical Machinery.

3. EPRI NP-3416, A Guide for Developing Preventive Maintenance Programs In Electric Power Plants.

4. EPRI NP-3887, Lfe Expectancy of Motors In Mild Nuclear

Plant Environments.

6. Information Notice 88-12,

Bearings.

Overgreasing of Electric Motor

A-13
AGING REPORT SUMMARY

BATTERY CHARGERS

SUMMARY

Battery chargers convert ac to do to provide power to dc

driven equipment and components, as well as to maintain the

standby battery fully charged. The battery charger components most susceptible to aging are agactors, transformers

ndkctos, diodesjand thyristors. High voltage, current,

humidity, or temperature WI,, decrease the life of these

components. A failed or degraded battery charger which is

not detected and corrected In a timely manner could result

In depletion of Its associated battery and a partial los of

station d power.

BASED ON:

1. NUREG/CR-4584, Operating Experience and Aging-Seismic Assessment of Battery Chargers and Inverters

2. NUREG/CR-5051, Detecting and Mitigating Battery Charger

and Inverter Aging 3. NUREG/CR-5192, Testing of a Naturally Aged Battery Charger and Inverter

AGING RELATED PROBLEMS

The small number of battery charger failures reported In the

LER data base which were attributed to component degradation

Indicates that, to date, the aging impact Is minimal. This

may be due to adequate attention being applied at the plant

level. However, the charger contains many components Identical to those found In Inverters, where aging Is Important.

The potential therefore exists for future age-related

failures of battery chargers, Including the following

failure modes:

1. Degraded Voltage: Failures of components within the

voltage regulation circuitry can result in voltage

fluctuations which affect operation of equipment supplied

by dc power. Degradation of potentiometers that

establish the equalize and float voltages can also

have this effect.

A-14
AGING RELATED PROBLEMS

(CONTINUED)

2. Excessive Ripple: Failures In the filter network (capacitors and Inductors) can create'abnormally high ripple

voltages on the charger output. This can result In the

failure of sensitive electronic Instrumentation and can

create overheating of the supplied battery.

3. Loss of Voltage Output: Battery charger fuse or circuit

breaker operation In raction to normal plant electrical

transients and switching have rendered the charger Inoperable. The thermal fatigue of fuses with time could

Increase their propensity to fall in this manner.

OPERATING EXPERIENCE

Chargers are susceptible to failures from overheating and

loose connections. Because of their complexity, failures

due to personnel error are high. For approximately 40%

of the total failures, the cause was not delineated.

IDENTIFIED FAILURE CAUSES

Loose conncn Loose connection ~Personnel 2 error r

25%

Open/short circuit

.4%

... vervotavervoltage

Overheating 10%

20% \ _

Electrical transient

14%

Percent of Failures-LERs 1976 to 1986

A-15
SOLUTIONS TO AGING PROBLEMS

DESIGN

The solid-state type charger Is most widely used,

(75% of chargers) and Is the only type qualified

to Industry standards. The magnetic amplifier and

controlled ferroresonant types comprise the

remaining population. The following design related solutions primarily address the solid

state charger.

1. Battery charger degradation or failure should

be annunclated before a decrease in the dc bus

voltage occurs. Annunciation of high and low

-charger output voltage and current are

appropriate.

2. Because of its susceptibility to stresses from

plant electrical transients, surge suppression schemes should be employed on the power supply

to the charger. Auto or isolation transformers

i.e., SOLA, have been effective.

3. The availability of a standby battery charger increases the reliability for maintaining the

batteries in a fully charged condition.

MAINTENANCE & MONITORING

The battery charger is comprised of several types of subcomponents which require periodic maintenance

and monitoring. These components include filter

capacitors, thyristors(SCRs), transformers, circuit

breakers,-and relays. In addition, output metering should be calibrated to permit accurate, routine

monitoring.

1. Filter capacitors: Capacitors have a limited

service life (5 to 10 years) based on the op- erating temperature and applied voltage. Deg- radation can be detected through measurement of

capacitance or equivalent series resistance, or

by deterioration of circuit waveforms. Periodic

replacement is also effective in lieu of the

detection techniques

(continued)

A-16
MAINTENANCE AND MONITORING'

(Continued)

2. Thyrlstors (SCRs): Large thyrIstors used in

the rectification process are sensitive to

temperature. Hreat sinks are installed to

transfer heat away from these devices. The

heat sink surfaces should be periodically

cleaned to maintain their design rating. In

addition, the connection between the SCR and

heat sink should be torque checked.

3. Magnetics (Transformers and Inductors): The

life of transformers and Inductors (chokes) is

directly related to their insulation condition.

Therefore, the periodic monitoring of

insulation resistance (meggar) and winding

temperature, is recommended.

4. Circuit Breakers and Relays: Periodic manual

operation and calibration of the circuit

breakers and protective relays (high temperature, abnormal voltage) are necessary to ensure

proper operation of these Important devices.

5. Panel Meters: Instrumentation on a battery

charger front panel often Includes output

voltage and load current. These readings are

used by operators on a regular basis to determine equipment operability. Regular calibration Is necessary for reasonable accuracy.

A-17
MAINTENANCE AND MONITORING

(Continued)

PERIODIC TESTING

Technical specifications require that capacity testing be

performed on the station battery and its associated battery

charger. For the charger, the test interval Is typically

every refueling. The capacity test simulates the maximum

possible loads, which generally occur when the charger

must supply the station d loads while recharging the

depleted battery. During capacity testing, the following

additional activitIes are recommended to determine the

charger's condition:

1. The cabinet temperature should be monitored, as

well as selected temperature sensitive components.

2. Monitoring the circuit waveforms is recommended to

verify proper equipment operation. Changes in

waveshape could alert personnel to potential

problems, as well as provide troubleshooting

guidance. Obtaining waveshape and temperature

data at a consistent load Is important for

trending.

3. Measurement of the ripple voltage on the dc output

during periodic testing Is important. This value

should not exceed 2% of the rated voltage. Damage

to the station battery could result.

REFERENCES

1. IEEE Std. 850-1979, "IEEE Standard for Qualification of

Class E Static Battery Chargers and Inverters for

Nuclear Power Generating Stations.*

2. Information Notice 84-84, rev. 1: "Deficiencies In

Ferro-resonant Transformers," 4/85.

3. NEMA PE5-1983, Constant Potential Type Electric

Utility Battery Chargers."

4. Regulatory Guide 1.32; Criteria for Safety

Related Electric Power Systems for Nuclear Plants."

A-18
AGING REPORT SUMMARY

MOTOR CONTROL CENTERS

SUMMARY

Motor Control Centers (MCCs) are low voltage (600 volts)

controllers that start and stop, provide continuous power

to, and protect motors that drive pumps and motor operated

vaIys. Typically, a motor controller unit consists of a

molded case circuit breaker, a magnetic contactor, a transformer, relays and thermal overload devices. Age-related

degradation of these subcomponents has impacted safety

system availability and operation.

BASED ON:

1. NUREG/CR-6063, Operating Experience and Aging

Assessment of Motor Control Centers, 7/88.

AGING RELATED PROBLEMS

Cf A 4

1. The most freQuent cause of MCC failure was the buildup

of dirt or other foreign substances that caused the

electrical device to stick.

2. More failures occurred in systems that function

intermittently rather than continuously.

3. The starter contactor may fall to close due to a nonuniform magnetic driving force caused by impeded armature motion.

4. Most age-related failures are attributed to theirQcjuIt

breaker and relay subcomponents. S ntdriftan

c ntctsurfa e derardaton are two dominant failure

modes.

A-19
OPERATING EXPERIENCE

Operational data on nuclear plant components shows there

have been significant failures of molded case circuit

breakers, relays, and magnetic contactors used In MCCs.

The combination of circuit breakers and relays contribute

to about 50% of all reported MCC failures. Subcomponent

contribution to MCC noperability, along with the breakdown of the dominant failure modes, are illustrated.-

A II JBl MPOEAMAl T FAILR MODE CON~r)TRIBU1TIONA

Circuit Breaker Failed to close - 32%

Tripped - 19%

Would not operate - 17%

Failed to open - 9%

Relays Failed to close - 23%

Failed to open - 21%

Would not operate - 19%

Out. of adjustment - 11%

Transformers

Starter/Contactor

Overload Device

Coll

Short/Ground - 55%

Open circuit - 27%

Failed to close - 43%

Would not operate - 30%

Failed to open - 11%

Tripped - 41%

Failed to close - 8%

Would not operate - 8%

Open circuit - 25%

Short/Ground - 12%

Would not operate - 10%

Control Mechanism Out of adjustment - 39%

Tripped - 26%

Open circuit - 13%

A-20
SOLUTIONS TO AGING PROBLEMS

DESIGN

At least five different manufacturers supply MCCs to

nuclear power plants. Although the outside appearance

varies, the basic elements Inside the compartment and

their designs are the same. Design considerations which

are related to the aging process Include the following:

1. NEMA standards require that the magnetic devices

operate properly at varying voltages from 110% to

86% of the rated coil voltage. Regulating transformers can provide the necessary voltage control

to minimize stresses on key MOO subcomponents.

2. MOO enclosures are classified into four categories

by NEMA. As a minimum, NEMA 2 drip-tight construction should be used. The doors are gasketed and a

drip shield is located on top of the cubicle.

3. For MO0s associated with standby equipment, strip

heaters should be considered for the control of

moisture Intrusion.

TESTING

Several tests are useful in assessing the

performance characteristics of the MCC, such as:

1. Continuity test following repair or replacement of

a component.

2. Contactor mechanical and electrical checks, including verification of pickup and dropout voltages.

3. Verification of circuit breaker trip setpoint.

pare timing with manufacturer's data.

Com4. Testing of time delay relays where applicable.

6. *A final energized operational test of each control

device.

A-21
SOLUTION TO AGING PROBLEMS

(continued)

PERIODIC MAINTENANCE

Based on the Input received from manufacturers and

utilities, several maintenance actions are recommended

to detect and mitigate age related degradation.

MCC COMPONENT MAINTENANCE ACTION

Structure Check for moisture, oil, and

foreign material. Vacuum clean.

Bus Bar Examine for pitting, corrosion,

and overheating. Check

connections for tightness.

Circuit Breaker

Operating

Mechanism

Test and examine for proper

operation.

Exercise ON, OFF, RESET

buttons; verify interlocks.

Fuses Check for arcing or overheating

Starter Inspect contacts and replace if

pitted or corroded.

Overload Heater Manually trip the device and

inspect for proper operation.

Check size of heater.

Metering Calibrate important indicators

All Components Inspect connections for tightness; inspect wiring for signs of

wear and overheating.

A-22
REFERENCES

1. Information Notice 86-66; Potential for Failure of

Replacement AC Coils Supplied by the Westinghouse

Electric Corporation for Use In Class E Motor

Starters and Contactors.*

2. NEMA AB-1; Molded Case Circuit Breakers

3. UL 846; Motor Control Centers

4. IEEE Std. 649; 'IEEE Standard for Qualifying Class 1E

Motor Control Centers for Nuclear Power Plants'

% . . , , 4 -. .

; '- '', ''~~~~~~~~~~~~

A-23
AGING REPORT SUMMARY

COMPONENT COOLING WATER (CCW) SYSTEM-PWRs

SUMMARY

The CCW System In a PWR Is a continuously operating

non-radioactive closed loop system used to remove heat from

plant equipment, and transfer It to an open loop cooling

system such as service water. Aging is a significant factor

In failures of CCW systems (over 70% of the failures

reported were related to aging). Fifty percent of the

the failures resulted In degraded performance of

the CCW system, while 27% caused a loss of redundancy.

Using the time dependent failure rates calculated from the

plant data, Improvements In maintenance and monitorina

r!ethods may be reauired to Drevent sYstem unavailabilit

from reaching an unacceptable level during the later years

of plant life.

BASED ON: NUREG/CR-6062, 0Operating Experience and Aging

Assessment of Component Cooling Water Systems

In Pressurized Water Reactors', 7/88.

AGING RELATED PROBLEMS

iukacie was the predominant mode Of fallure. War was the

Prdominant failure mechanism. On a component level, valva

were the most commonly reported component to fall. These

were dominated by failure of the valve operators, followed

by wear of the valve seats. Pump failures were dominated by

seal and bearing failures, while .ea changer failures

most frequently involved the tubes. Factors contributing to

aging of these components along with the observed effects

are summarized on the next page.

A-24
AGING RELATED PROBLEMS

(Continued)

Under normal operating conditions, the stresses which

contribute to COW system aging, and the part of the system

It most affects are summarized:

AGING EFFECTS

Eroslon, wear, corrosion

Clogging, blocking, reduced

flow

Vibration, misalignment, loose

parts

Binding, distortion, rupture

Electrical short circuits, grounds,

pitting

Setpoint drift, loose connections

COMPONENTS AFFECTED

Mechanical

Mechanical

Mechanical, electrical

instrumentation & controls

Mechanical

Electrical, I&C

Electrical, I&C

OPERATING EXPERIENCE

For each COW component showing a significant number of

failures, the data were examined to identify the specific

subcomponents which failed, As Illustrated below, pump

seals and bearings contributed most to pump unavailability.

Similarly,-valve-operators and valve seats were the leading

*subcomponent- problems eading to COW valve-failures..-

Subcomponent Failures:

- PUMPS: Seals - 57%

Bearings - 25% .

Other - 18%

Operator - 39%

Seat - 31%

Other - 30%

HEAT EXCHANGER: .,1 . . . !

Tubes - 59%

Other - 2.5% 

VALVES: Tubesheet - 16%

A-25
OPERATING EXPERIENCE

(Continued)

The failure modes for the CCW system are diverse.

Leakage Is the most common mode of failure and is typical

for pump and valve failures. The failure modes classified

as "other" include overload, rupture, and disengaged.

LEAKAGE

37%

<

OTHER

11%

DO&S NOT CLOSE 3

INCORRECT

SIGNAL

l B2% SHORT CIRCUIT

3% NOISEIVIBRATION

4% PLUGGED

5 %DOES NOT OPEN

9% 8%

EXCEEDS LIMIT

The predominant failure mechanism for the CCW system is

wear, which accounted for 37% of the reported failures. The

other 63% of the failures were distributed fairly evenly

among the mechanisms listed below. "Fracture includes

events where fracture or crack rowth lead to faillur. The

wcontamination- category includes failures where a foreign

material was introduced into the system causing a blockage

or buildup. Calibrationo includes failures where set point

drift occurred, often resulting in a violation of technical

speci fications.

FAILURE MECHANISMS

) Wear - 37% Corrosion/erosion - 8%

Calibration - 12% Distortion - 7%

Contamination - 9% Deterioration - 7%

Other - 8% Fracture - 2%

A-26
SOLUTIONS TO AGING PROBLEMS

Aging contributes to a significant portion of CCW

system failures. Monitoring methods must, therefore,

Include good functional Indicators which will detect aging

effects while the system operates normally. It would then

be possible to mitigate aging effects.

1. Because leakage Is a typical failure mode associated

with both pump and valve failures, It suggests that

Inspecting and testing for leakage are important

monitoring methods.

2. The variety of failure modes suggests that several

different monitoring techniques would be required to

detect all failures., For example, visual inspections

could only be expected to detect a portion of the CCW

system failures. A good surveillance and monitoring

plan should be diverse, and Include sufficient tests

and Inspections to cover all of the significant failure

modes:

The functional indicators recommended as potentially viable

methods for monitoring and detecting aging degradation are:

STRESSORS AGING FUNCTIONAL

INDICATORS

CCW

VALVES

CCW

HEAT EX.

High temp.

Foreign materials

Humidity, dust

Cyclic operation

High press.

High flow

Service water

exposure

Packing & seat

leakage

Stem binding

Insulation degradation

Erosion/

corrosion

Fouling of

surfaces

Eros ions

corrosion

Blockage

Visual inspection

Leakage tests

Stem torque check

Torque/limit

switch setting

Curren tivoltage monitoring

Visual inspection

Temperature

Acoustic or eddy

current tests

Bolt torque check

A-27
SOLUTIONS TO AGING PROBLEMS

(continued)

STRESSORS AGING

EFFECTS

FUNCTIONAL

INDICATORS

CCW

PUMPS

Vibration

High Temp.

Human Error

Loss of NPSH

Bearing Wear

Distortion

Cavitation

Seal & Packing

Wear

Vibration Rdgs.

Lube Oil Temp.,

Quality, Level

Bearing Temp.

Visual Insp.

for leaks

SYSTEM

LEVEL

INDICATORS

Surge Tank level, system flows

and pressures, HX. outlet temps.

REFERENCES

1. Bulletin 88-04, Potential Safety Related Pump Loss',

5/88.

2. NUREG - 0800, Standard Review Plan, Section 9.2.2;

'Reactor Auxiliary Cooling Water Systems', 6/86.

3. ASME/ANSI OM-1987, Part 2-Appendix D;

Analyzing System Degradations

'Guidance for

4. Generic Issue 5 - CCW Supply to the Reactor Coolant

Pump Seals

A-28
AGING REPORT SUMMARY

RESIDUAL HEAT REMOVAL (RHR) - BWRs

SUMMARY

The RHR System In a BWR serves a variety of purposes

for operation during routine, abnormal, and emergency conditions. While the failure data reviewed covered all phases .,

of operation, the emphasis of evaluating system effects and

operating stresses was on the Low Pressure Coolant Injection-lLfCl and Shutdown Cooling (SDC) oreratlng modes.

Aging has a moderate Impact on RHR component failure rates

(O to 17% per year Increase). Standby systems such as RHR

may be less severely affected by aging, although several

plants exhibit increasing failure trends for certain RHR

components.

BASED ON: NUREG/CR-6268, Aging Study of Boiling Water

Reactor Residual Heat Removal Systemo, 6/89.

AGING RELATED PROBLEMS

Aging is a concern for RHR systems. The evaluation of

multiple data bases showed that more than 50% o the

failures were attriDuted to aging. Different aging

mechanisms are present, related to the operatng status of

the system. While In standby, the aging mechanisms are:

• corrosion

v set point drift

• embrittlement

Aging degradation due to wear takes place while the system

is in the shutdown rcoiIng or taslLng mode. Operational

stresses-are enhanced by the synergistic effects of various

standby stresses. One important source of stress Is

testing. Plants with a common minimum flow line for 2 RHR

pumps, for Instance, should closely monitor pump performance

since aging can degrade performance, and lead to dead-headed

Dmp oeration on one of the pumps. This can result in

overheating and premature failre.

A-29

p
OPERATING EXPERIENCE

The effect of each RHR failure on system performance was

determined from the NPRDS data. Over half of the failures

resulted in degraded operation of the system. This implies

that the system can still perform Its function;

however if left uncorrected, the failure could cause a loss

of system function.

DEGRADED

UNKNOWN

NO EFFEC ~LOSS OF

25% REDUNDANCY

21%

No failures were reported in which the complete loss of LPCI

resulted. However, the complete loss of the shutgw2 cpLing mode HR resulted from some of the component failures. These typically involved a failure of the instruments

controlling the inboard or outboard isolation valves, or a

failure of the valves themselves.

FAILURE MECHANISMS:

A failure mechanism is the physical, chemical, or other

process by which a component or system degrades or falls.

Since the RHR system has standby modes as well as operational modes, there are several different failure mechanisms.

Wear represents an exposure to stresses encountered during

operation, which results in some portion of the component being worn away. The-failure mechanism classified as Other

Inclupes emDrittlement, fatigue, vibration, and fracture.

Deterioration includes failures where a material of construction is broken down physically by the environment

to a point where it can no longer perform its function; i.e.

insulation or gaskets.

A-30
OPERATING EXPERIENCE

(continued)

RHR FAILURE MECHANISMS:

SETPOINT DRIFT 25%

DETERIORATION 4%

CORROSION/

EROSION 4%

DISTORTION 5%

OTHER 20X CONTAMINATION 6%

SHORT/GROUND 6%

FAILURE MODES:

A failure mode is the manner in which a component fails.

The failure modes for the RHR system are diverse.

The predominant modes Include Leakage, Loss of Function,

and Wrong Signal. Leakage includes-Inlernal and eternal

leakage ovalves, along with leakage of pump seals,

piping and pipe fittings. The Loss of Function mode

includes failure of an instrument to operate or failure of

a pump to run. The Wrong Signal mode includes a position

switch indicating a valve is closed when it is actually

open, or a pressure transmitter indicating the incorrect

pressure.

LOSS OF FUNCTION 21% LEAKAGE 26%

WRONG SIGNAL

SHORT/GROUND 2%

15% 15% . :u~m.u::. Ia:-... UNKNOWN 3%

\ , ' ' , OPEN CIRCUIT 3S%

. B; ' z 1 DOES NOT OPEN 4%

DOES NOT CLOSE 5% OTHER 12% EXCEEDS LIMIT 10%

RHR FAILURE MODES

A-31
SOLUTIONS TO AGING PROBLEMS

The operational readiness of the RHR system can best be

assured from three tests:

I. Valve stroke tests

2. Control logic response tests

3. In-service Inspection pump tests

This choice is supported by the data which showed

valves odlne trulmentAton/controls to be the two

predominant types of components In the RHR system which

fail.

The type and amount of periodic testing, preventive maintenance, and corrective maintenance performed on the major

system components are described In the following summary:

RHR PUMPS:

TESTING

During the quarterly testing required by tech. specs.

for RHR pumps, it is recommended that other information

is recorded such as bearing vibration and temperature,

motor amps and voltage, and motor winding temperature.

Bearing degradation can be detected by increasing

vibration and temperatures. Likewise, motor and pump

degradation may be apparent from increasing motor

current or winding temperatures.

PREVENTIVE MAINTENANCE

Due to environmental qualification requirements,

bearings, seals, and gaskets are replaced at prescribed

intervals. Activities such as cleaning and lubrication

should be periodically conducted regardless of whether

the pump is in standby or is continuously operating.

The frequencies at which PM activities are performed

are normally based on the equipment's operating

experience, plant configuration, and the impact of pump

failure on plant risk. The limited PM activities

described may be justified based on the extent of

periodic testing that is performed.

A-32
SOLUTIONS TO AGING PROBLEMS

(continued)

BUR VALVES

TESTING

In accordance with tech. specs., periodic testing is

required for key RHR valves, including measurements of

valve stroke time and valve seat leakage. Technical

specifications also requires that each valve in the

flow path be periodically checked to verify its correct

position. Other periodic testing that utilities have

successfully employed'to monitor valve degradation are:

1. Relief valve setpolnt verification (5 years)

2. MOV signature analysis (18 months)

3. Position indicator functional test (18 months)

As a result of numerous problems with MOVs. further

research is being conducted. Stroke time testing may

be of only limited value, and the frequent oJeratior

required by testing may result in accumulated wear to

the valve seats. NRC Generic Letter 89-10 addresses

this concern.

PREVENTIVE MAINTENANCE

Utility practices for RHR valve PM consist primarily of

Inspection and lubrication. The frequency of this

activity ranges from annually to every four years.

Some utilities also periodically megger the motors on

the MOV. Inspection and lubrication of manual and

check valves are also performed. PM on AOVs and SOVs

is largely based on EQ requirements.

It should be noted that post maintenance testing is

performed for valves, especially MOVs. Following

packing adjustments or torque/limit switch corrections,

stroking the valve is useful to verify proper

operation.

A-33
SOLUTIONS TO AGING PROBLEMS

(continued)

RHR HEAT EXCHANGERS:

TIESTING

In-service testing, such as a heat balance, is a

standard non-intrusive test for determining heat

exchanger capacity. Design calculations assume a

certain amount of fouling; the heat balance determines

the continued validity of the assumption. Other

periodic tests such as a hydrostatic or leak test

verify the integrity of the pressure boundary interfaces. Research is continuing to determine the

effectiveness of other methods such as eddy current

and acoustic testing.

PREVENTIVE MAINTENANCE

The preventive maintenance activities specified for the

RH.R heat exchanger includes Inspection, tube cleaning, and a periodic replacement of gaskets.

REFERENCES

1. Bulletin 88-04, "Potential RHR Pump Loss"

2. Generic Letter 89-10, Safety-Related Motor

Operated Valve Testing and Surveillance"

3. Bulletin 86-01, "Minimum Flow Logic Problems

That Could Disable RHR Pumps"

4. Notice 86-36, "Failure of RHR Pump Motors and

Pump Internals"

A-34
N

APPENDIX B

AGING INSPECTION GUIDES

EVe

A. Inverters B-3

B. Motors B-S

C. Battery Chargers B-7

D. Motor Control Centers B-9

E. Component Cooling Water (PWRs) B-11

F. Residual Heat Removal (BWRs) B-13

B-1
AGING INSPECTION GUIDE-INVERTERS

1. Visual Inspection: Summary

a. External

1. There is no unusual meter oscillation or

electrical hum

2. The input and output parameters fall within

specifications (voltage, current, frequency)

3. The cooling air filters are not clogged

b. Internal

1. There are no signs of overheating

2. The capacitors are not bulging or leaking oil

3. The panel is clean, especially SCR heat transfer

surfaces

I. Understanding and Managing Aging

a. Maintenance Activities

1. Periodic Inspections are performed and include

cleaning and checks of connection tightness

2. Preventive maintenance is conducted at least

once per cycle and includes calibration, EQ

related component replacements, and evaluation

of circuit waveforms. Electrolytic capacitors

should be Included in the EQ program.

3. The personnel responsible for maintenance have

been trained, and use approved procedures which

have incorporated the vendor's recommendations.

b. Operations Related Activities

1. The daily logs or round sheets include recording

the data on or observing Inverter performance

2. The operating procedures address the response to

an inverter failure

3. Periodic checks are made to insure proper

electrical alignment - normal supply from

the station battery

B-3
AGING INSPECTION GUIDE-INVERTERS

(continued)

c. Design/Test Related Activities

1. The loading of the inverter for normal and

postulated accident conditions is within the

equipment's rating.

2. The static switch Is functionally tested to assure

an uninterruptible transfer to alternate supply.

3. Capacity testing, especially recommended for

standby inverters, accurately reflects loads.

4. A protective device coordination exists between the

inverter and its branch circuits.

d. Other Recommended Licensee Activities

1. Replacement or testing of all filter capacitors

should be considered when one fails. (Same stress)

2. The ferro-resonant inverters (i.e., SCI, Westinghouse) use magnetic components for waveform shaping

and voltage regulation. Special ferro tuning

techniques recommended by the manufacturer should

be followed.

3. The pulse-width modulated inverters (i.e., Elgar,

Cyberrex) generate a near sine wave output through

electronic feedback. Photographing the wave shapes

for timing and sequence should provide good trouble

shooting information.

B-4
AGING INSPECTION GUIDE

MOTORS

1. Visual InsDection Summary

a. Operating Parameters Routinely Observed

1. Bearing vibration and temperature

2. Lube oil level and appearance

3. Winding temperature (permanently Installed

detectors may be recorded by plant computer

or data logger)

4. Motor line current-concern for motor overload

5. High noise level-Indicator of poor alignment,

excessive friction

b. External Indicators or Causes of Age Degradation

1. Humidity - the space heaters should be

energized on standby motors

2. Dust & Dirt Buildup - Internal air temperature

may be too high due to blocked air passages or

dirty filters

3. Ambient Temperature - motor Insulation class

(rating) limits safe ambient temperature

4. Corrosion or surface cracks

6. Loose mechanical connections

2. Licensee Proaram Evaluation for Understanding and

Manaalng of AgnAg

a. Maintenance Activities

1. During scheduled downtime, ventilation openings

filters and winding Insulation are cleaned.

2. Vibration levels are measured and evaluated

routinely.

3. There Is a greasing schedule for antlfriction bearings. Oil changes for sleeve

bearings are similarly scheduled.

4. Oil leaks are corrected expeditiously to avoid

winding contamination.

5. Manufacturer recommended maintenance such as

replacing seals or carbon brushes are evaluated

and Incorporated into the maintenance program.

B-5
MOTOR INSPECTION GUIDE

(continued)

b. Operations Related Activities

1. The line current is measured and recorded

periodically during motor operation.

2. Operating rounds Include observations of space

heater energization for standby motors.

3. Operating procedures contain guidance for the

number of starts permitted over a given time.

4. Alarm response procedures address the operator's

action to abnormal motor conditions.

c. Design/Test Related Activities

1. Periodic surge tests or partial discharge (corona)

tests are conducted to monitor age-related

deterioration.

2. Large motor operating hours are monitored (elapsed

hour counter on swltchgear).

3. Motor operating parameters are monitored, recorded,

and evaluated, when performing required surveillance testing on pumps and valves.

4. AC/DC leakage (hipot) testing is not recommended.

5. An engineering evaluation of base-line readings for

bearing vibration, motor winding temperature, and

rated current values has been completed.

B-6
AGING INSPECTION GUIDE-BATTERY CHARGERS

I. Visual Inspection Summary

a. External

1. The Identification of positive output current

2. No unusual meter oscillation or electrical hum

Is apparent

3. The charger output voltage is correct

4. The cooling air filters are not clogged

5. The ambient temperature of the room is less than

90F

b. Internal

1. There are no signs of overheating,

2. The capacitors are not bulging or leaking oil

3. The panels are clean especially SCR

heat transfer surfaces

11. Licensee Program Evaluation for Understandihg

and Managing Aging

a. Maintenance Activities

1. Periodic inspections are performed and include

cleaning & checks of connection tightness

2. Preventive maintenance is conducted at least

once per cycle and includes calibration of panel

meters and alarm/trip relays.

3. The personnel responsible for maintenance have

been specifically trained on this equipment.

b. Operations Related Activities

1. The daily logs or round sheets include recording

of the charger output voltage and current

2. The operating procedures address the response to

a battery charger failure.

3. Periodic checks are made to Insure proper

electrical alignment. The normal supply to the

dc bus is from the charger.

B-7
AGING INSPECTION GUIDE-BATTERY CHARGERS

(continued)

c. Design/Test Related Activities

1. Capacity testing is performed in accordance with

the tech. specs. (typically, every refueling)

2. Circuit waveforms are observed and recorded to

verify proper operation of key components.

Comparison of waveforms to previous testing is

recommended

3. Capacity testing, even for standby chargers,

represents worst case load situations.

d. Other Recommended Licensee Activities

1. Replacement or testing of all filter capacitors

should be considered when one fails. (Same stress)

2. Modifications affecting the dc bus should include

an evaluation of the impact on the battery charger

3. The structural integrity of the chargers should

be periodically checked, based on seismic requirements and vulnerability.

B-8
AGING INSPECTION GUIDE

MOTOR CONTROL CENTERS

I. Visual Inspection Summary

(Primarily Internal)

1. There are no signs of overheating

2. The MOC Is clean, especially the contact

surfaces

3. There Is no moisture, oil, and foreign material

4. The cubicle is In operable status

11. Licensee Program Evaluation for Understanding

and Managing Aging

a. Maintenance Activities

1. A physical inspection of the MCC should be

conducted periodically Including:

check the terminal block condition and

connection tightness.

check the condition of the mechanical linkages

and electrical Insulation.

check that there is no moisture, oil, and

foreign material

examine contacts and fuses for pitting,

corrosion, and signs of overheating.

2. Preventive maintenance should include the

following activities:

• calibration of metering and verification

of the size of the overload heater.

* exercise the operating mechanism, Including

the manual trip button.

* an insulation test (megger) is recommended

following the completion of maintenance.

v check the pickup and dropout voltages to

monitor deterioration of coils

B-9
AGING INSPECTION GUIDE-MCCs

(continued)

c. Design/Test Related Activities

1. A cycle counter is useful for determining PM

frequency. The wear on many parts Is directly

related to the number of operating cycles.

2. The trip setpoint of the circuit breaker should be

checked at least every five years to minimize the

effects of setpoint drift.

3. Because of the effect of the motor applications

on the sizing of the overload heater, documentation

should exist to support the selected value.

4. Tech. Spec. compliance at some plants requires that

a functional test of 10% of the MCCs be conducted

along with preventative maintenance on each MCC

breaker every 5 years. Additional testing is

required If a failure occurs.

d. Other Recommended Licensee Activities

1. The daily logs or round sheets should include

observations of MCC status and condition,

especially those located in harsh environments.

B-10
AGING INSPECTION GUIDE

COMPONENT COOLING WATER SYSTEM

Because there are many variations n the design of COW

systems, the impact of a component failure on the

system's performance will vary. For instance, five 2-unit

sites have a fully shared system with 5 pumps, 3 heat

exchangers, and 2 surge tanks. A single component failure

has little Impact because of the extra redundancy. However,

multiple component failures could affect both units.

Differences In designs results in differences In emphasis

and the priority of licensee resources.

1. Visual Inspection Summary

a. Major valves are monitored for leakage & appearance.

b. Heat exchangers are inspected for leakage,

temperature.

c. Steady state flow to critical loads Is checked:

v Reactor coolant pump ( RCP) seals.

• Residual Heat Removal ( RHR) heat exchangers

and pump seals.

• Safety Injection ( SI) pump & motor coolers.

v Chillers & Containment coolers.

2. Licensee Program for Understanding & Managing Aging

a. CCW Pumps:

a Trend the pump's performance (flow, pressure)

• Monitor the bearing temp. & vibration (operator

rounds) -

• Perform analysis of lube oil quality

b. CCW Heat Exchangers:

Trend the inlet and outlet temperatures

Perform eddy current or acoustic testing (or

equivalent) to determine tube sheet condition

c. CCW Valves:

v Calibrate the control valves, check set points

v Monitor the operator current/voltage

B-il
AGING INSPECTION GUIDE - CCW

(continued)

d. Other CCW System Activities:

v The integrity of the piping should be checked

periodically, especially main headers,

v The instrumentation (controls, indicators)

associated with modulating flow to equipment should

be calibrated regularly.

• The strainers in the system (pump suction) should

be cleaned, based on differential pressure

readings.

• Water chemistry should be routinely checked, and

chemical addition modified as necessary.

B-12
AGING INSPECTION GUIDE

RESIDUAL HEAT REMOVAL SYSTEM

1. Visual Inspection Summary

a. When in the standby mode, the pump areas are checked

for environmental conditions; temp., cleanliness

b. When a pump is operating, vibration levels,

motor amps, and motor winding temps. are observed

c. The major valves are monitored for leakage and

appearance. d. The heat exchangers are inspected for leakage, temperature.

2. Licensee Program for Understanding & Managing Aging

a. RHR Pumps:

• Trend pump performance (flow, pressure)

• Monitor bearing temp. & vibration (periodic testing)

• Perform an analysis of lube oil quality

• Monitor and trend motor performance (amps, windings)

b. RHR Heat Exchangers:

• Trend the inlet and outlet temperatures

v Perform eddy current or acoustic testing (or equivalent) to determine tube sheet condition

c. RHR Valves:

Monitor the operator current/voltage Check the relief valve setpoints Perform post maintenance testing following corrective maintenance activities

Trend the results of the tech. spec. tests

d. RHR Instrumentation

• Routinely calibrate the instrumentation channels,

especially those associated with system actuation,

isolation and permissives.

• Properly fill and vent the nstruments following

testing or maintenance.

B-13
NRC FORM 335 U.S. NUCLEAR REGULATORY COMMISSION 1. REPORT NUMBER

12-89) IAuilifed by NRC. Add Vol.. Sup.. f..

NRCU 1102. VW Addendum NmbM let IW.)

3201.3202 BIBLIOGRAPHIC DATA SHEET

IS" imtrt on Ds the ntnsE NUREG/CR-5507

2. TITLE AND SUBTITLE BNL-NUREG-52222

Results from the Nuclear Plant Aging Research Program:

Their Use in Inspection Activities 3. DATE REPORT PUBLISHED

MONTH Y EAR

September 1990

4. FIN OR GRANT NUMBER

A-3270

5. AUTHORIS) 6. TYPE OF REPORT

William Gunther and John Taylor FINAL

7. PERIOD COVERID t1* lsoate

S. PERFORMING ORGANIZATION -NAME AND ADDRESS it NRC.iovide Ovisobn. Offie o, Reion, U aucla Reguiearv Commisoen-. md tainee uifnsracter prowide ea. and sailtn odd,,sO

Brookhaven National Laboratory

Upton, New York 11973

9. SPONSORING ORGANIZATION -NAME AND ADDRESS f NRC type 5 hSbow" tentrwr opovid. NRCDision. Office er Region. US Nucear Regultory Commiason.

Widma~lng eddMss

Division of Engineering

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Washington, DC 20555

10. SUPPLEMENTARY NOTES

1. ABSTRACT 200 wors or m)

The US NRC's Nuclear Plant Aging Research (NPAR) Program has determined the suscepDtibili

to aging of components and systems and the potential for aging to impact plant safety

and availability. The NPAR Program also identified methods for detecting and mitigating

aging in components.

This report describes the NPAR results which can enhance NRC inspection activities.

Recommendations are provided for communicating pertinent information to NRC

inspectors. These recommendations are based on a detailed assessment of the NRC's

Inspection Program, and feedback from resident and regional inspectors as described

within. Included are NPAR report summaries and aging inspection guides for components

and systems which have been evaluated at BNL.

y

12. KEY WORDSIDESCRtPTORS Lis wordrorjph reset t wieulstr esearchers in amstn the repo". 13 AVAI LABI UTY STATEMENT

Reactor components; reactor components--aging; reactor safety; Unlimited

reactor components--failures; failures-detection; in-service 14. SECURITY CLASSIFICATION

inspection; nuclear facilities--inspection; failures--detection; treil

reactor maintenance; data analysis; communications Unclassified

(TMi RePoit I

Unclassified

15. NUMBER OF PAGES

16. PRICE

NRC FORM 33512491
TllIS DOCUMENT WAS PRINTED USING RECYCLED PAPER.
NUREG/CR-5507

I.-

q

ce

Ywo

I 

RESULTS FROM THE NUCLEAR PLANT AGING RESEARCH PROGRAM:

THEIR USE IN INSPECTION ACTIVITIES

SEPTEMBR 10, .

SEPTEMBER 1990 ." 

2

2maD

Mo(02

c 

cs

z

a

I Ws

WD

ZLW o'fl

co D

0..0

EIL 

-I

a-