NUREG/CR-5404

ORNL-6566/V1

Vol. 2

Auxiliary Feedwater System

Aging Study

Phase I Follow-On Study

Prepared by J. D. Kueck

Oak Ridge National Laboratory

Prepared for

U.S. Nuclear Regulatory Commission

J
. I

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NUREG/CR-5404

ORNL-6566/V1

Vol. 2

RV, RG, RM

Auxiliary Feedwater System

Aging Study

Phase I Follow-On Study

Manuscript Completed: June 1993

Date Published: July 1993

Prepared by J. D. Kueck

Oak Ridge National Laboratory

Operated by Martin Marietta Energy Systems, Inc.

Oak Ridge National Laboratory

Oak Ridge, TN 37831-6285

Prepared for

Division of Engineering

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Washington, DC 20555-0001

NRC FIN B0828

Under DOE Contract No. DE-ACO5-84OR21400
Abstract

The Phase I study found a number of significant Auxiliary

Feedwater System functions that were not tested and verified operable by periodic surveillance testing. In addition,

the Phase I study identified components actually degraded

by the periodic surveillance tests. Thus, it was decided that

this follow-on study would not deal with aging assessments

or in situ examination but would instead focus on the testing omissions and equipment degradation found in Phase I.

In this follow-on study, the deficiencies in current monitoring and operating practice are categorized and evaluated.

Areas of component degradation caused by current practices are discussed. Recommendations are made for

improved diagnostic methods and test procedures that will

verify operability without degrading equipment.

iii
Contents

Page

Abstract iii

List of Figures ......... ............................................................................ vii

List of Acronyms .................................................................................... ix

1 Introduction and Summary ..................................................................................... 1

1.1 Background ..................................................................................... 1

1.2 Summary of Results .................................................................................... 1

2 Deficiencies in Current Monitoring/Operating Practices ..................................................................................... 3

2.1 Mechanical Failure Modes Not Detected by Current Monitoring/Operating Practices ............ ....................... 3

2.2 Component or Group of Components Unable to Perform as Required Because of I&C Failures

Not Detected During Routine Testing ........................ ............................................................. 4

2.3 Component or Group of Components Unable to Perform as Required Because No Design

Basis Function Verification Test Is Performed . ..................................................................................... 4

3 Areas of Significant Component Degradation Caused by Unnecessary or Excessive Test-Related Wear ............ 6

3.1 Degradation of AFW Pumps Caused by Low Flow Operation ......................................... .............................. 6

3.2 Degradation of Valve Actuator Motors ............................. ........................................................ 10

4 Evaluation of Monitoring and Maintenance Practices .................................................................................... 11

4.1 Evaluation of Monitoring/Operating Practices Where Mechanical Failures Are Currently Undetected ........ 11

4.2 Evaluation of Routine Testing in Areas Where I&C Failures Are Currently Undetected ........... ................... 13

4.3 Evaluation of Additional Functional Verification Testing in Areas Where No Functional

Verification Test Is Presently Performed ................................. ................................................... 14

4.4 Evaluation of Alternate Methods for AFW Pump Testing .............................................................................. 15

4.5 Alternate Methods for Valve Actuator Motor Testing .................................................................................... 16

4.6 Evaluation of Alternate Methods for Check Valve Testing ......................................................... ................... 16

4.7 Evaluation of Alternate Methods for TD AFW Pump Testing ......................................... ............................... 17

4.8 Evaluation of Untestable Functions ..................................................................................... 17

5 Recommendations for Alternative Monitoring/Operating Practices to Detect Failure Modes

Currently Undetected .................................................................................... 18

5.1 Recommendations for Improvements in Current Monitoring/Operating Practices to Detect

Check Valve Failures ..................................................................................... 18

5.2 Recommendations for Full-Flow Testing of AFW Pumps .............................................................................. 18

5.3 Recommendations for Improvements in Detection of TD AFW Pump Failures .............. .............................. 21

5.4 Valve Failure to Open or Close .................................................................................... 21

5.5 Recommendations for Alternative Routine I&C Testing in Areas Where I&C Failures

Are Not Detectable ..................................................................................... 22

5.6 Recommendations for Detection of Service Water System Piping Fouling with Subsequent

Flow Reduction .................................................................................... 22

5.7 Recommendation for Full-Flow ESW Test Line ..................................................................................... 23

v NUREG/CR-5404, Vol. 2
6 Recommended Changes to Technical Specifications to Allow Auxiliary Feedwater Pump Testing on

a Quarterly Frequency ................................................................................... 24

6.1 Recommendation for Quarterly Testing .................................................................................... 24

6.2 Recommendation for Full-Flow Testing .......................... ......................................................... 24

6.2 Preferred and Optional Test Method ................................................................................... 24

References ........ .......................... .................................................. 25

NUREG/CR-5404, Vol. 2 vi
List of Figures

Figure Page

3.1 Anticipated useful operating ranges for pumps used in large nuclear and fossil power

generating units ........ ................................................................... 7

3.2 Formation of stall (a) in diffuser and (b) in eye of impeller ............................................................................ 8

3.3 Secondary flow pattern in and around pump impeller stage at off-design flow operation ............ .................. 9

3.4 Head-capacity characteristics of multistage boiler feed pumps ...................................................................... 9

4.1 Swing check valve, exploded view ........................................................................... 11

4.2 Effect of wear on head-capacity curve ........................................................................... 12

4.3 Example pump and system head-capacity curves ................................. .......................................... 12

5.1 ESW full-flow test line added to AFW system ........................... ................................................ 23

.i. NUREG/CR-5404, Vol. 2
List of Acronyms

ACP Auxiliary control panel

AFW Auxiliary feedwater system

AMSAC Anticipated transient without scram mitigating system actuation circuit

AOV Air-operated valve

ASME American Society of Mechanical Engineers

ASE Average system effect

B&W Babcock and Wilcox

BDIV Blowdown isolation valve

BEP Best efficiency point

BMDLCV Bypass motor-driven pump level control valve

BWR Boiling water reactor

CMCV Common miniflow check valve

CST Condensate storage tank

DBE Design basis event

DCV Discharge check valve

DDP Diesel-driven pump

EHOV Electrohydraulic-operated valve

ESF Engineered safety feature

ESW Emergency service water

FC Failure count

FSAR Final safety analysis report

FWIV Main feedwater isolation valve

GV Turbine governor valve

I&C Instrumentation and control

INEL Idaho National Engineering Laboratory

INPO Institute for Nuclear Power Operations

ISCM Inspection, surveillance and condition monitoring

IST In-service test

LCO Limiting condition for operation

LCV Level control valve

LCVCV Level control valve check valve

LER Licensee event report

LOFW Loss of main feedwater

MCB Main control board

MCC Motor control center

MCV Miniflow check valve

MDLCV Motor-driven pump level control valve

MDP Motor-driven pump

MFCV Main feedwater check valve

MFLB Main feed line break

MFSA Magnetic Flux Signature Analysis

MFW Main feedwater

MI Maintenance test-inspection

MOV Motor-operated valve

MOVATS Motor Operated Valve Analysis and Test System"TM

MSIS Main steam isolation signal

MSLB Main steam line break

MSSV Main steam safety valve

NPAR Nuclear Plant Aging Research

NPE Nuclear Power Experience, Stoller Power, Inc.

NPRDS INPO's Nuclear Plant Reliability Data System

NPSH Net positive suction head

NRC Nuclear Regulatory Commission

NSSS Nuclear steam supply system

OP Operating procedure

ix NUREG/CR-5404, Vol. 2
ORNL Oak Ridge National Laboratory

PMTR Periodic maintenance test requirement

PORV Power-operated relief valve

PS Pressure switch

PT Periodic test

PWR Pressurized-water reactor

PZR Pressurizer

RCP Reactor coolant pump

RCS Reactor coolant system

RGSC Ramp generator/signal converter

RHR Residual heat removal

RSD Relative system degradation

SBO Station blackout

SCV Pump suction check valve

SG Steam generator

SI Safety injection

SOV Solenoid-operated valve

SSC Structure, system or component

SSIV Steam supply isolation valve

SSV Steam supply valve

ST Surveillance test

SWS Service Water System

TDLCV Turbine-driven pump level control valve

TDP Turbine-driven pump

TOL Thermal overload

T&T Trip and throttle valve (for AFW turbine)

NUREG/CR-5404, Vol. 2 x
1 Introduction and Summary

The Phase 1 aging study for the Auxiliary Feedwater

(AFW) System dealt less with organic and chemical aging

mechanisms and more with historical failure modes that

could be traced to current maintenance and surveillance

practices. A thorough review of system controls and functions was performed, and several significant deficiencies in

maintenance and surveillance practices were identified,

such as failure to verify many of the safety-related control

functions by periodic testing and degradation of the AFW

pumps by testing at low flow.

This follow-on study categorizes the deficiencies in current

monitoring/operating practice identified in Phase I and

evaluates failure modes and component degradation caused

by these practices. Although the deficiencies identified in

Phase I are for a specific plant, the findings have applicability to all plants in that they point out typical testing

omissions or sources of degradation. This follow-on study

also provides recommendations for alternate methods of

performing testing that will greatly reduce equipment

degradation caused by testing and will greatly improve

verification of system operability. The primary areas where

alternate test methods are discussed are AFW pump testing, instrumentation and controls (I&C) functional verification, and check valve testing. Section 2 of the follow-on

study categorizes the deficiencies in current monitoring/

operating practices. Section 3 discusses areas of significant

degradation caused by current practices. Section 4 provides

a discussion of problematic monitoring and maintenance

practices. Section 5 provides recommendations for six new

monitoring and maintenance practices, and Sect. 6 provides

a recommended change to the technical specifications to

eliminate AFW pump degradation caused by miniflow

testing.

1.1 Background

The Phase I AFW system aging studyl focused on how and

to what extent the various AFW system component types

fail, how the failures have been and can be detected, and on

the value of current testing requirements and practices. For

each of the component types and for the various sources of

component failure, the methods of failure detection were

designated and tabulated and the following findings

became evident

* I&C-related failures dominated the group of failures

that were detected during demand conditions.

* Many of the potential failure sources not detectable by

current monitoring practices were related to the I&C

portion of the system.

* Some components appear to be tested in excess of what

failure history indicates to be appropriate.

e Enhanced testing requirements appear to be needed to

reduce excessive testing while ensuring that thorough

performance verification is conducted periodically.

The goal of this follow-on study was to categorize and

evaluate the deficiencies in testing identified by Phase I

and to make specific recommendations for corrective

action. In addition, this study presents discussions of new,

state-of-the-art test methods and provides a proposed AFW

pump test at normal operating pressure that should do

much to verify system operability while eliminating

degradation.

1.2 Summary of Results

Several significant conclusions of this follow-on study

follow:

1. The present method of testing the AFW pumps at the

minimum flow condition leads to degradation of the pump

and does not provide an adequate indication of pump condition. An alternate method is proposed that consists of

testing at normal operating pressure to eliminate degradation and to verify flow at design conditions. This alternate

test would also allow verification of other component's

design basis operation, such as the steam generator blowdown isolation valve (BDIV) and level control valves

(LCVs). These valves are currently tested only at the lowflow, low differential pressure condition.

2. There are a large number of safety-related control functions that are presently not verified to be operable by the

periodic surveillance testing. This is a significant concern.

It is recommended that the entire set of control wiring diagrams for the system be evaluated against the periodic test

requirements by an experienced engineer to locate all

omissions in testing.

3. Check valve condition is not adequately assessed by the

present test methods. Recommendations are made in the

report for new check valve diagnostic methods, and a

comparison of diagnostic methods is provided.

4. Evaluations of current surveillance and testing are also

made for other AFW components such as the turbinedriven feedwater pump, valve actuator motors, flow

verification of emergency service water (ESW), and so

forth.

I NUREG/CR-5404, Vol. 2
Introduction and Summary

5. Recommendations are provided in Sect. 5 for improved

methods of diagnosing degradation in check valves, AFW

pump testing at full flow, functional testing of control

circuits, improved testing of the turbine-driven pump

(TDP), and assessment of service water system fouling.

NUREG/CR-5404, Vol. 2 2
2 Deficiencies in Current Monitoring/Operating Practices

These areas of deficiency in current monitoring practice

were developed from a Review of Sect. 3.3, "Failure

Modes and Features that Are Not Detectable by Current

Monitoring Practices" of the Auxiliary Feedwater System

Aging Study, Vol. 1, NUREG/CR-5404. 1 The noted deficiencies were categorized into three areas, "Mechanical

Failure Modes Not Detected by Current Monitoring/

Operating Practices," "Component or Group of Components Unable to Perform as Required Because I&C

Failures Were Not Observed During Routine Testing," and

"Component or Group of Components Unable to Perform

as Required Because No Function Verification Test Is

Performed." Although many of the deficiencies noted were

specific to the plant being studied in the Phase I study, the

findings are considered to be generically applicable

because they point out testing deficiencies that can easily

exist at any plant.

2.1 Mechanical Failure Modes Not

Detected by Current Monitoring/

Operating Practices

2.1.1 Check Valve Undetected Failures

Check valve failure to open sufficiently-Degradation

could occur without detection when the valves are not

included in a periodic inspection program, and neither

pump flow nor differential pressure is monitored during

testing. Failure to open to the required position could also

occur if the valve is required to operate under different

pressure conditions than the test conditions. Usually, the

AFW pump flow test, performed at miniflow conditions,

does not verify that design basis flow is available. Correct

obturator movement is difficult to verify using flow and

pressure. (Section 4.6 discusses alternate methods for

check valve testing.)

Examples from Ref. 1 of Check Valve Failure to Open

Sufficiently:

* Table 3.1, Item 2, AFW Pump Suction

* Table 3.8, Item 1, AFW Pump Discharge

* Table 3.11, Item 1, Steam Generator Level Control

Valve

* Table 3.12, Item 1, Steam Generator (SG) AFW to

Main Feedwater

Check valve failure to close-Gradual degradation may

not be detected because not all valves are included in the

periodic disassembly and inspection program. Also, leak

rate testing may allow leakage substantially in excess of

the level required to meet AFW system design requirements. The acceptance criteria for main feedwater check

valves must reflect the AFW system functional

requirements.

Examples from Ref. 1 of Check Valve Failure to Close:

* Table 3.1, Item 3, AFW Pump Suction Check Valves

Failure to Close When ESW Suction Valves Open

* Table 3.13, Item 1, MFW Check Valves Fail to Close to

Ensure that Adequate AFW Flow is Delivered to the SG

Miniflow check valve (MCV) fails in the closed position or

fails to open sufficiently to allow required recirculation

flow. The quarterly testing flow rate is so low that the

valves would not be fully stroked.

Examples from Ref. 1:

* Table 3.6, Item 1, AFW Pump Miniflow Check Valve

Fails Closed or Fails to Open Sufficiently

* Table 3.7, Item 1, Common Miniflow Check Valve

Fails Closed or Fails to Open Sufficiently

2.1.2 AFW Pump Undetected Failures

The motor-driven pump (MDP) fails to deliver required

flow to its steam generators at the required pressure conditions. The pump testing is performed at low pressure. At

high (operational) pressure, the pump head-capacity curve

will intersect the system curve at a different point with

lower flow. In addition, actual flow, steam generator pressure, and developed pump head are not measured. Also, no

testing is done with all pumps operating simultaneously.

Example from Ref. 1:

* Table 3.4, Item 4, MD AFW Pump Fails to Deliver

Required Flow

The TDP failure to develop required flow-Pump condition is not fully monitored; no testing is performed to verify ability of the TDP to deliver required feedwater flow at

a steam supply pressure less than 842 psig. It is important

to recognize that the TDP must be capable of operating at

steam pressures as low as 120 psig. These low pressures

will be present before the reactor coolant temperature is

low enough to start the residual heat removal system.

Example from Ref. 1:

* Table 3.5, Item 4, TD AFW Pump Fails to Develop

Required Flow

2.1.3 Valve Undetected Failures

The LCV fails to open sufficiently to allow adequate flow.

Only flow (not pressure) is monitored during testing.

3 NUREG/CR-5404, Vol. 2
Deficiencies

Under different pressure conditions, valves may not open

sufficiently.

Example from Ref. 1:

* Table 3.9, Item 3, MD AFW Pump Level Control Valve

Fails to Open Sufficiently

• Table 3.10, Item 5, TD AFW Pump LCV Fails to Open

Sufficiently

The BDIV fails to close under blowdown conditions; it is

tested under low-flow, low-pressure conditions.

Example from Ref. 1:

o Table 3.15, Items 1 & 2, SG BDIVs Fail to Isolate

Blowdown Flow

2.2 Component or Group of Components Unable to Perform as

Required Because of I&C Failures

Not Detected During Routine

Testing

2.2.1 Valve Operator Undetected Failures

Valve operator fails to open or close in response to sensed

condition. Failure in control logic is not detected because

logic is not tested in the periodic tests. Pump auxiliary

contacts, station blackout contacts, or limit switches fail to

provide required control inputs to automatically actuated

equipment. Proper function is not verified.

Examples from Ref. 1:

* Table 3.2, Item 1, ESW to MDPs Supply Valves

* Table 3.9, Item 2, MD AFW Pump LCVs

* Table 3.15, Item 1, SG BDIVs

* Table 3.16, Item 3, AFW TDP Steam Supply Valve

* Table 3.16, Item 4, AFW TDP Steam Supply Valve

* Table 3.16, Item 4, AFW TDP Steam Supply Valve

* Table 3.3, Item 3, ESW to TDP Suction Isolation Valve

* Table 3.10, Item 2, TDP LCVs

* Table 3.17, Item 2, TDP Stean Supply Isolation Valves

* Table 3.4, Item 5, MD AFW Pump Auxiliary Contact

* Table 3.5, Item 5, TD AFW Pump Valve Stem Switches

* Table 3.9, Item 1, MDP LCV

* Table 3.9, Item 2, MDP LCV

* Table 3.9, Item 5, MDP LCV

* Table 3.10, Item 2, TD AFW Pump LCVs

* Table 3.10, Item 3, TD AFW Pump LCVs

* Table 3.10, Item 6, TD AFW Pump LCVs

* Table 3.15, Item 1, SG BDIVs

* Table 3.16, Item 1, AFW TDP Steam Supply Valves

* Table 3.16, Item 2, AFW TDP Steam Supply Valves

Valve operator failure to open because of improper thermal

overload actuation-Thermal overload (TOL) bypass had

not been verified. TOL setting had not been verified.

Proper TOL selection will provide motor protection, while

improper TOL selection will result in spurious trips or

motor degradation.

Example from Ref. 1:

. Table 3.5, Item 1, TD AFW Pump T&T Valve Fails to

Open

During extended TDP operation, the ambient temperature

may rise to the point that a steam supply line pipe break

signal is generated. This signal is generated by high ambient temperature. The steam supply isolation valve would

then close. This test is typically performed only over a

short time and may not simulate extended TDP operation.

Example from Ref. 1:

* Table 3.17, Item 1, AFW Turbine Steam Supply

Isolation Valves Spurious Closure

2.2.2 TD AFW Pump Undetected Failures

Turbine electronic overspeed trip function fails to trip

before mechanical overspeed trip occurs. Trip is tested

under simulated rather than operating conditions. No verification is made of auto resetting; the mechanical overspeed set point is not verified at all.

Example from Ref. 1:

* Table 3.5, Item 3, TD AFW Pump T&T Valve

2.3 Component or Group of Components Unable to Perform as

Required Because No Design Basis

Function Verification Test Is

Performed

2.3.1 ESW Function Verification

Flow verification of ESW-This test cannot be performed

because it would introduce lake water into the

condensate/feedwater system. This verification is

important, however, because of the various types of

biological contamination, such as Zebra Mussels, which

can foul ESW piping and reduce flow. There are a number

of measures that can be taken to ensure that adequate flow

is available. These measures are discussed in Sect. 5.6.

NUREG/CR-5404, Vol. 2 4
Example from Ref. 1:

Table 3.2 Item 2, ESW to MDP Supply Valves Open

but Insufficient Flow Is Delivered

Verification of switchover time for ESW-If the transfer

takes place too slowly it could result in air binding of the

AFW pumps because of vortexing on the low condensate

storage tank (CST) level and possible pump damage. This

test also cannot be performed because it would introduce

lake water; however, an alternate test is described in Sect.

4.3.2. The alternate test compares the sum of the switchover times of the various components with the analyzed

maximum time.

Example from Ref. 1:

* Table 3.2, Item 3, ESW to MDP Supply Valves

Switchover Results in Pump Damage

Deficiencies

suction source to the ESW-Excessive friction caused by

corrosion or biological contamination of the ESW lines

may result in inadequate AFW pump suction head. This

test would also introduce lake water and thus cannot be

performed.

Example from Ref. 1:

* Table 3.4, Item 2, ESW to MDP Supply Valves

2.3.2 TDP Function Verification

Verification of TDP LCV opening-The valve operator

may not open or stay open because the ability of the accumulator air supply to stroke the valve and the proper seating of the control air check valve are not demonstrated.

Example from Ref. 1:

* Table 3.10, Item 2, TDP Level Control Valves Do Not

Open or Stay Open

Verification of ability of motor-driven pumps to continue

to operate satisfactorily during and following transfer of

5 NUREG/CR-5404, Vol. 2
3 Areas of Significant Component Degradation Caused by Unnecessary

or Excessive Test-Related Wear

The following three areas of component degradation have

already resulted in some industry attention and are discussed here as the major areas of component degradation

resulting from current test practices.

3.1 Degradation of AFW Pumps

Caused by Low Flow Operation

Degradation of AFW pumps caused by extended operation

at minimum flow condition occurs because of hydraulic

instability within the pump during operation at low flow

conditions. These pumps are usually tested with minimum

flow lines that allow the pump discharge flow to be recirculated to the CST. The flow rates using the minimum

flow lines are sized to pass -10 to 15% of pump best efficiency point flow. (See Sect. 4.4.1 for an evaluation of current test practice.)

As explained in Ref. 2, p. 30, "Operation of these pumps

'far' from the BEP flow induces very strong unsteady flow

conditions within the pump hydraulic passages." In summary, Ref. 2 states that strong unsteady flow conditions

result in very large dynamic forces on pump internals, both

the stationary and rotating parts. The result of these forces

is a high-amplitude vibration that causes rapid wear at critical clearances in the pump because of severe vibrationinduced rubbing. This leads to a rapid increase in stage-tostage leakage and a measurable reduction in delivered

pump capacity. In addition, these large dynamic fluid

forces can break loose pieces of diffuser vanes, impeller

side plates, and impeller vanes. This deterioration of pump

internals will result in considerable reduction in the delivered capacity of the pump as well as eventual structural

failure.

Deterioration of the impeller and diffuser caused by cavitation erosion also degrades performance. The net effect of

the deterioration is a slow reduction in the delivered capacity of the pump.

Hydraulic instability is the term most commonly used to

describe the unsteady flow phenomena that become progressively more severe the farther from best-efficiency

flow that a pump is operated. These unsteady flows are the

most significant contributor to deterioration of pump components because of the dynamic forces they produce.

Figure 3.1 (Ref. 2, Fig. D. 1) shows the stable and unstable

flow regions for various classes (i.e., different specific

speeds) of power plant pumps. This figure is based on a

composite of field experience, shop tests, and laboratory

tests.

Hydraulic instability has also been described by the label,

internal "flow recirculation," which occurs both at the inlet

and discharge regions of a pump stage at off-design operating flows. These flow recirculation cells, as illustrated in

Figs. 3.2 and 3.3 (Ref. 2, Figs. D.2 and 3), are highly

unsteady, producing large vibration excitation forces and

hard-to-control flow pulsations in the entire pump loop.

Figure 3.4 (Ref. 2, Fig. D.4) illustrates hydraulic instability

in the unstable flow regime.

Reference 3, "Notification of IOCFR21 Reportability,"

filed with the Nuclear Regulatory Commission (NRC) by a

pump manufacturer, discusses AFW pump damage experienced by several utilities and is summarized as follows:

After the AFW pump was disassembled, it was found that

some of the cast iron diffuser vanes within the pumps had

broken and had traveled through the pump discharge piping to eventually lodge in the venturi. Considerable corrosion pitting of the cast iron internals was also observed,

and cracklike crevices were noted in a number of areas

along the vane to shroud junctions. The other AFW pumps

of the same design at this plant were inspected and found

to have similar damage.

The IOCFR21 Notification (Ref. 3) concludes, after examination and analysis, that "the primary cause of diffuser

vane inlet edge breakage was the undermining of the vane

inlet ends due to the accumulated hours of operation of the

pump at minimum flow, on the low flow recirculation line

used in inservice testing. The plant had been in commercial

service for 15 years at the time of the subject failure. Based

upon the facts presented above, Ingersoll-Rand concludes

that the damage observed is primarily due to accumulated

operating time on the pump at the minimum flow

condition."

An evaluation of current flow testing is provided in Sect.

4.1.2, alternative testing is discussed in Sect. 4.4, and an

alternate full flow test recommendation is provided in

Sect. 5.2.

NUREG/CR-5404, Vol. 2 6
Degradation

ORNL-DWG. 86-4227 ETD

10

U)

z

U)8

U0

z

U)

0

z

0

LUJ

a-V

U)4

C.,

04

2

0 25 50 75 1WU

PUMP FLOW, % OF RATED

Figure 3.1 Anticipated useful operating ranges for pumps used in large nuclear and fossil power generating units.

(Inner line of design margin area is preferred; if hydraulic Instability occurs at higher flows, various

pump and system problems can be expected.) Source: E. Makay and 0. Szamody, Survey of Feed Pump

Outages, EPRI FP-754, Electric Power Research Institute, April 1978

7
Degradation

ORNL-DWG. 86-4228 ETD

DYNAMIC FORCES

IAT VANE PASSING FREOU.A

(a) DEVELOPMENT OF STALL. CAVITATION DAMAGE AND FINALLY VANE

DAMAGE IN A FIRST STAGE BOILER FEED PUMP VANED DIFFUSER

BLADE

INLET

ANGLE

FORMATION OF STALL IN AN IMPELLER EYE DUE TO

FLOW INCIDENCE ANGLE

IVISUALIZED ON EXPERIMENTAL TEST RIG)

Figure 3.2 Formation of stall (a) in diffuser and (b) in eye of impeller. Source: E. Makay and 0. Szamody, Recommended Design Guidelinesfor Feedwater Pumps in Large Power Generating Units, EPRI CS-1512, Electric

Power Research Institute, September 1980

NUREG/CR-5404, Vol. 2 8
Degradation

ORNL-DWG 86-4229 ETD

4_

Figure 3.3 Secondary flow pattern in and around pump inpeller stage at off-design flow operation. Source:

E. Makay and 0. Szamody, Survey of Feed Pump Outages, EPRI FP-754, Electric Power Research

Institute, April 1978

ORNL-DWG. 86-4230 ETD

125

100

I

a

wj

x

ae 50

DESIGNED TO SATISFY EFF. AT BEP ONLY.---

CORR UN.STABLE SAL z

x . nINCORRECT

.......... m

......... ... . ... /.,........... ...... I

c.~~~~~~~USAL z STABL 

FLOW REGIME :FLOW REGIME : TE

F- z~~U,

/ CURVE F B: Z >:

no / 3 TEST * NO. 1 >O.

// I;,: + TEST NO. 2

/ TEST NO. 3 Bt <

A/ O Jo. I

t ~ ~ ~ ~ c *j LA.

LAU

7 5 ULwU

25 50 75

% BEST EFFICIENCY FLOW

100

Figure 3.4 Head-capacity characteristics of multistage boiler feed pumps. Curve "A" Is correct and desired for stable

system operation. Curve '"B" represents hydraulically unstable impeller-diffuser design. Parallel, as well

as single-pump operation, is difficult In the unstable flow regime. Curve '"C shows design with flat head

curve at part load resulting in control system malfunctioning. Single-pump operation is possible in unstable regime. Designs "B" and "C" are not acceptable for utility applications. Source: E. Makay and

0. Szamody, Survey of Feed Pump Outages, EPRI FP-754, Electric Power Research Institute, April 1978

9 NUREG/CR-5404, Vol. 2
Degradation

3.2 Degradation of Valve Actuator

Motors

Degradation of valve actuator motors occurs quite often

during testing because of the large number of duty cycles

that may be experienced when performing a series of periodic tests. Valve actuator motors are typically provided

with very short time ratings, on the order of 5 to 15 min,

and it is not uncommon for periodic testing to be scheduled

during an outage so that a motor is called upon to stroke its

valve several times within a relatively short period

(perhaps 1 h) so that time to cool down is not provided

between strokes. If the valve has a 30-s stroke time, it only

takes five open/close operations in close succession before

the rating of a 5-min motor is exceeded. In many cases,

TOL protection for the motor may not be provided because

the TOL has been either bypassed or purposely set higher

than the motor's thermal damage point.4 '

5 With no thermal

protection, the motor will be thermally degraded by operation in excess of the duty cycle. In some cases, valve actuator motors are "rotor limited." This means that the thermal

degradation will occur first in the rotor.6 Degradation in

the rotor is difficult to detect with conventional diagnosis

equipment but will result in a significant decrease in motor

torque output. Alternate methods for testing valve actuator

motors to assess degradation are discussed in Sect. 4.5.

10
4 Evaluation of Monitoring and Maintenance Practices

4.1 Evaluation of Monitoring/

Operating Practices Where

Mechanical Failures Are

Currently Undetected

Typically, there are several motor-operated valves (MOVs)

in the AFW system. The issue of MOV actuator operability

is dealt with thoroughly by Ref. 7, "Generic Letter 89-10."

This Generic Letter provides recommended actions for the

testing, inspection, and maintenance of MOVs to provide

assurance they will function when subjected to the Design

Basis Condition. As all nuclear utilities are now in the process of developing MOV maintenance and testing programs to comply with Generic Letter 89-10, there is no

need to expand on the issue of MOV maintenance and testing here except to direct the reader to Refs. 4 and 8 through

14, which provide a general overview of the issues associated with ensuring MOV reliability. Other maintenance

practices that were found to contribute to component failure or that were found to be profoundly inadequate in

detecting component failure in the Phase I study are discussed in the following paragraphs.

4.1.1 Undetected-Check Valve Failure to

Open or Close

Currently, most AFW system check valves are verified

operable by exercising the valve and verifying obturator

movement. A small number of valves at each plant cannot

be tested in this way because flow cannot normally be put

through the valve. The American Society of Mechanical

Engineers (ASME) Operation and Maintenance (OM)

Code, Subsection ISTC,15 states that as an alternative to

testing by exercising, disassembly may be used to verify

operability of check valves. When disassembly is used, it

may provide indications of premature wear or degradation;

however, disassembly should only be used as a last resort

when no other option is available.

If significant degradation is detected in the disassembled

valve, a failure analysis should be conducted to determine

the cause of failure and the appropriate corrective action.

Other check valves that may also be affected because of

similar design, manufacturer, service, size, materials of

construction, orientation, flow instabilities, etc., should

also be inspected or tested.

Nonintrusive testing techniques should be used to verify

operation of check valves. Simply exercising the valve by

putting flow through it does not verify complete obturator

movement. A partially open valve can significantly reduce

flow, as discussed in Sect 4.1.2. There are three basic

diagnostic methods for assessing check valve degradation

without disassembly-acoustic emission, ultrasonic inspection, and magnetic flux signature analysis (MFSA). These

methods are discussed in Sect. 4.6, and recommendations

are made in Sect. 5.1. A typical check valve is shown in

Fig. 4.1.

OSNL-DWO 5-4714 ETD

1. CAP STUD FASTENER NUT

2. CAP STUD FASTENER BOLT

3. SPIRAL WOUND GASKET

4. OBTURATOR FASTENER NUT PIN

B. OBTURATOR FASTENER NUT

6. OBTURATDR FASTENER NUT WASHER

7. OBTURATOR

8. HANGER PIN

D. HANGER

10. CAP

II. CAPPIN

12. IDENTIFICATION PLATE

13. BODY

Figure 4.1 Swing check valve, exploded view

4.1.2 Undetected-AFW Pump Failure to

Deliver Required Flow at Design

Conditions

A key concern regarding AFW pump functionality is that

sufficient operating parameters to establish functionality

are not measured during testing. In addition, the pumps are

often not tested at the required pressure condition, and no

testing is done with all pumps operating simultaneously.

To quote Ref. 16, p. 46, "The primary purpose of an

AUXFP is to deliver flow to the feedwater system to provide secondary system emergency heat removal." It is

essential that pump flow capability be accurately assessed

during periodic testing.

The flow delivered by a centrifugal pump will decrease as

a pump ages and wears and the internal clearances between

11 NUREG/CR-5404, Vol. 2
Evaluation

the impeller and stationary surfaces become larger. When

the internal clearances become too large, the stage-to-stage

recirculation flow becomes a significant portion of the

normal through-flow, and the pump provides less head.

Figure 4.2 shows the effect of this internal leakage increase

on the pump head-capacity curve.16 Undetected degradation of pump internals, such as cracking of diffuser vanes

or impeller blades, will also lead to reduced flow as discussed in Sect 3.1.

ORNL-DWG 88-4008 EMD

Currently, AFW pump flow testing is done at the minimum

flow rate where the effect of wear and increased clearances

is much less obvious. Testing at minimum flow may

demonstrate that the pump does actuate, but it does not

provide assurance that the pump will perform at conditions

of higher flow. In the low-flow portion of the curve, the

change in head caused by wear in the pump is small compared to the change at the typical design basis event (DBE)

condition; therefore, significant degradation may go

undetected.

A centrifugal pump will produce flow at a rate that corresponds to the intersection of its own head-capacity curve

and the system curve for the particular system of piping

and valves in which the pump is installed. As the head on

the system curve is increased, the intersection of the system curve with the head-capacity curve will result in lower

capacities. See Fig. 4.3 for an example of a typical AFW

system curve. Here, it can be seen that the intersection of

the head-capacity curve with the system curve at a static

head curve of 50 psig provides a flow of -950 gal/min. At

a static head of 1000 psig, the same pump will produce a

flow of 600 gal/min. (At typical minimum flow conditions

of 1500 psig, the pump will produce a flow of 100

gal/min.)

ORNL-DWG 92-4176 ETD

I

CAPACITY

Figure 4.2 Effect of wear on head-capacity curve.

Source: Adapted with permission from

Igor J. Karassick, Centrifugal Pump Clinic,

Marcel Dekker, Inc., 1981

0.

1000

Flow, gpm

Figure 4.3 Example pump and system head-capacity curves

NUREG/CR-5404, Vol. 2 12
The 1000-psig value corresponds to the typical DBE system condition. The static head curve for a 50%-closed

globe valve includes the additional friction that would

result from a partially closed valve, a check valve, for

example. One 50%-closed valve is seen to reduce the flow

from 950 to 830 galmin at 50-psig static head.

It is essential that this effect be considered when evaluating

minimum flow test results. To do this, the system curve for

the AFW system and the pump head curve must be evaluated and the DBE flow calculated based on the measured

flow at the actual tested discharge pressure condition.

Section 5.2 provides a table of AFW pump monitoring

methods and a test guideline for full-flow periodic testing

that would eliminate uncertainties associated with minimum flow testing.

4.1.3 Undetected-LCV Failure to Open

Sufficiently to Allow Adequate Flow

These valves are normally closed, and they open on the

loss of air or control power. Per Ref. 1, p. 70, none of the

surveillance tests for the particular plant studied in Phase I

that officially demonstrate the operability of the MDP

LCVs actually put any flow though the valves. The periodic test that is used to demonstrate full stroking of various

check valves does demonstrate that the valves can be

opened (using manual controls) to allow 2220 gal/min to

each steam generator. This flow is provided, however, at

relatively low differential pressure, on the order of 100

psid, when the motor-driven (MD) AFW pump is tested at

cold shutdown conditions. It would be highly preferable,

from the viewpoint of verifying operability, to perform this

test during the transition from hot standby to hot shutdown.

The AFW is normally used in hot shutdown to provide

core cooling after the main feedwater (MFW) is isolated. A

short test performed at hot standby, when the steam

generator is at normal operational pressure, would provide

the opportunity to verify the operability of a number of

AFW components. This test is discussed in Sect. 5.2.

Although this is a plant-specific example of a testing

weakness, this opportunity to verify AFW component

operability at hot standby does exist at all plants.

4.1.4 Undetected-BDIVs Failure to Close

Sufficiently to Isolate Flow

The blowdown valves are 0.2-in. air-operated valves that

close automatically in response to the start of the AFW

pumps. For the specific plant studied in the Phase I study,l

the blowdown valves are tested at low-flow conditions, and

an upstream valve is simultaneously closing to isolate

Evaluation

flow. This does not provide a meaningful test of the

BDIVs. Testing of the AFW pumps at operational pressure

would also provide the opportunity to test the auto close

function of the BDIVs and their capability of closing

against operational pressure. This test of the AFW pumps

is described in Sect. 5.2. Again, this is a plant-specific

example of a testing weakness; however, the opportunity to

test these valves at operating conditions does exist at all

plants.

4.2 Evaluation of Routine Testing in

Areas Where I&C Failures Are

Currently Undetected

4.2.1 Examples of Undetected I&C Control

Logic Failures

In Sect. 2.2.1 are a significant number of examples at the

studied plant of a valve actuator failing to open or close the

valve in response to the sensed condition. In each case, a

failure in control logic had not been detected because logic

had not been tested, in either a periodic test or periodic

maintenance test requirement. These major issues of a

nondetectability discussed in Ref. 1 are as follows:

1. Only one of three possible logic coincidences was verified by testing to result in an open signal to the ESW

to MD AFW pump supply valve.

2. ESW to MD AFW pump isolation valves are not

restroked after reconnecting the control circuit leads

following testing of other valves, thereby creating the

potential for improper reconnection.

3. The automatic de-energization of the MD LCV

solenoids following an automatic pump start is not

tested.

4. There is no testing that the BDIVs close in response to

any AFW pump start.

5. There is no testing to verify that the interlock for the

normally open motor-operated steam supply valve to

the TDP will cause the alternate motor-operated supply valve to close.

6. There is no testing to verify that contacts from the

alternate steam supply valve to the turbine-driven

AFW pump cause the automatic steam supply transfer

sequence.

7. There is no testing to verify automatic closure of the

ESW to the turbine-driven AFW pump suction isolation valves upon receipt of auto close signal.

8. The de-energization of the TDP LCV solenoids is not

demonstrated with the control switches in AUTO.

9. There is no testing to verify that automatic closure of

the TDP steam supply isolation valves will occur on

high temperature.

10. Auxiliary contacts used to provide control signals to

the MD LCVs are not tested.

13 NUREG/CR-5404, Vol. 2
Evaluation

11. There is no verification of the switch that results in

auto closure of the steam generator BDIVs.

12. The ability to transfer the control of the MD LCVs

from automatic to manual in the presence of an AFW

actuation signal is not demonstrated.

13. The turbine-driven (TD) LCV is not verified to close

in response to a faulted steam generator condition.

14. The ability to transfer the control of the TD LCVs

from automatic to manual in the presence of an AFW

actuation signal is not demonstrated.

Many of these examples of failure to test could be broken

down into more examples, but the point has been clearly

made that there are many significant control functions that

are not demonstrated to be operable by test. This is partially because of the fact that, traditionally, solely checking

the operation of the actuation relays was considered to be a

satisfactory operability test of an engineered safety feature,

but another more unsettling observation is that an experienced engineer with the ability to discern all the required

system functions and the authority to include them in the

test procedures had apparently never been tasked with the

responsibility of performing the type of review that was

performed for Ref. 1. These examples are specific to the

plant studied in Ref. 1 but are indicative of a generic need

for a careful review of system logic.

Failure to incorporate all safety-related logic into functional testing can only be prevented by performing a comprehensive review of safety system logic and ensuring that

all logic circuits are completely tested, including all contacts, wiring, actuation devices, and terminal points.

Obviously, this review is a significant and time-consuming

effort, but the large number of examples above are indicative of the fact that serious omissions in safety feature

actuation do remain undetected by current testing programs. This is a serious safety concern.

The manpower resources required to correct this concern

are significant One experienced engineer could reasonably

be needed 1 year for a comprehensive review of all functional logic and wiring diagrams for one safety system

where each system function is checked to ensure that it is

completely tested by the current plant periodic maintenance procedures. After this, the maintenance procedures

would require a significant work-hour effort for revision,

and maintenance staff would require familiarization and

possibly training based on the extent of the revisions.

4.2.2 Undetected I&C Failures-Thermal

Overload (TOL) Setting Not Verified

Proper valve actuator motor TOL setting has received

much attention from both the NRC and industry groups.

The key to proper TOL selection is an understanding of

duty cycle and selection of the motor and TOL to meet this

duty cycle. Generic Letter 89-10 requires that sizing calculations for TOLs be verified,7 and industry guidance (IEEE

741)4 provides detailed instructions for accomplishing this.

Performing adequate research to determine the valve's

intended duty cycle and then selecting both the valve actuator motor and its protection to meet this duty cycle will

eliminate spurious TOL actuation. Again, this review will

require an experienced engineer who is familiar with all

facets of system operation.

4.2.3 Undetected I&C Failures-Turbine

Electronic Overspeed Function Fails to

Trip Before Mechanical Overspeed Trip

Occurs

The electronic trip is tested under simulated, rather than

operating conditions. There is no verification of automatic

resetting, thereby requiring local resetting and preventing

auto restart Testing the electronic overspeed trip by simulation provides no assurance that there is proper coordination between the electronic and manual trip devices. A

controlled, manual turbine overspeed test should be performed; this is discussed in Sect. 5.3.

4.3 Evaluation of Additional Functional

Verification Testing in Areas

Where No Functional Verification

Test Is Presently Performed

4.3.1 Flow Verification of ESW

It is not practical to verify ESW flow by test because lake

water should not be introduced into the condensate/

feedwater system; however, the ESW lines should be

inspected periodically to ensure that design flow will be

available and that the lines are not corroded or blocked by

an accumulation of organic material. Section 5.7 provides a

recommendation for a full-flow ESW test line.

14
Per Ref. 17, NUREG/CR-5379, Nuclear Plant Service

Water System Aging Degradaton Assessment, Phase I, the

following considerations are obvious for the maintenance

of service water systems:

* timely painting of exposed structures,

* replacement of sacrificial anodes in cathodic protection

systems,

* proper attention to material selection in components

prone to failure,

* coating application and repair,

* chemical and/or mechanical cleaning, and

* water treatment.

Thus, as an alternative to actual performance of the ESW

flow test, maintenance attention to cathodic protection,

coating application, and inspection of the service water

lines is essential. A discussion of service water system

fouling is provided in Sect. 5.6. In addition, an analysis of

the untestable flow switchover function should be performed as discussed in Sect. 4.8.

4.3.2 Verification of Switchover Time for

ESW

A single complete functional test of the automatic

switchover to ESW also should not be performed because

it would introduce lake water into the condensate/

feedwater system. However, this is a critical safety function that must be demonstrated as operable. The principal

concern is that a slow transfer could result in a temporary

loss of water flow to an AFW pump with resultant air

binding damage to the pump and loss of the pump at the

time when it is most needed. There are a number of factors

that could result in slow transfer times. These include

degradation of valve actuator motor, degradation of relay

logic, and degradation of sensing circuit.

The maximum allowable ESW switch3ver time should be

determined by analysis so that an acceptable time for the

switchover is established.

Even though the complete functional test cannot be performed, overlapping portions of the sensing and actuation

logic and actual valve stroking should be performed and

the total switchover time determined from the test results.

This switchover time can then be compared to the allowable switchover time, and the operability of the switchover

can be verified.

There is another option worthy of consideration and that is

the addition of an ESW full-flow test line. See Sect. 5.7 for

a discussion of this option.

Evaluation

4.3.3 Verification of TDP LCV

There is one significant failure mode of the TD LCV that is

presently not detected by conventional testing (Ref. 1,

p. 93) as follows: "The ability of the accumulator to stroke

the valve and the proper seating of the control air check

valve for the accumulator are not demonstrated." A test

should be performed that tests the function of the accumulator to stroke the valve for the minimum required cycles

and the seating of the control air check valve for the accumulator. In this test, control air to the accumulator would

be isolated, then a discharge path to atmosphere from the

accumulator would be opened to test the accumulator

check valve. If accumulator pressure stayed constant, then

the TD LCV would be stroked for the minimum required

cycles under operating system pressure to test the ability of

the accumulator to provide an alternate source of power.

4.4 Evaluation of Alternate Methods

for AFW Pump Testing

Several considerations for AFW pump surveillance and

monitoring practices are provided in Ref. 2. These are

summarized in Sects. 4.4.1 through 4.4.3.

4.4.1 Current AFW Pump Surveillance

Practice and Limitations

Unlike equipment used in continuous service, AFW pumps

typically are not provided with vibration monitors or internal temperature sensors. Thus, trending of parameters such

as temperature and vibration during operation is not easily

done. Some newer plants use a nonnuclear safety AFW

pump for startup and shutdown, thus "saving" the nuclear

safety pumps for DBEs. The safety-related pump is still

tested, however, nominally every 3 months, by operation

with the miniflow line. As discussed in Sect. 3.1, this lowflow operation will degrade the pump and has been shown

to lead to pump failure. A IOCFR21 report has been issued

on this concern. In addition, this low-flow test at low head

does not provide the proper operating range of flow or sufficient running time to comprehensively trend AFW pump

performance and operating characteristics, even if complete monitoring were installed. The current status of AFW

pump surveillance practice is concluded then to be not only

harmful to the pump but inconclusive in verifying pump

design basis operability.

4.4.2 Interim Recommendations for Surveillance and Monitoring Practices

In light of this obvious problem of the inadequate and

damaging current flow test practices, Ref. 2 provides

15 NUREG/CR-5404, Vol. 2
Evaluation

recommendations for interim surveillance and operating

practices. These are summarized as follows:

1. AFW systems should be studied for the possibility of

installing permanent full-flow test lines. Full-flow test

lines have been installed by Virginia Power at the Surry

Plant, which was the plant that identified the AFW

pump low-flow failures.

2. Complete monitoring should be periodically conducted

on every AFW pump. Parameters for monitoring should

include rotor orbital motion; oil-film bearing temperature; head, flow, and speed values; rotor axial position;

metal fragment or sound emission detection; and vibration monitoring.

3. A trending data base should be prepared for each pump

for all the monitored parameters. The trending would

help to indicate the need for maintenance, overhaul, and

replacement.

4.4.3 Interim Recommendations for Detailed

Inspection Program

In addition to monitoring and trending, a disassembly and

inspection of the AFW pumps should be carried out at

appropriate intervals, perhaps one pump every third

outage. Each pump would then be disassembled every 10

years. If significant wear were detected in one pump, then

all pumps would be disassembled.

Reference 2 provides a number of procedures and reliability enhancing actions that could be taken during disassembly. These are summarized as follows:

1. replace bearings;

2. replace shaft seals;

3. replace wear rings;

4. replace worn impellers and diffuser vanes;

5. replace any worn journals, bearing surfaces, or thrust

balancing components;

6. inspect sealing joint surfaces;

7. check shaft for run out; and

8. replace any degraded fastener.

The most conclusive option for AFW testing is afull-flow

test during normal operation. This could alleviate the need

for the extensive monitoring devices just described and

perhaps provide the basis for less frequent disassembly and

inspection. Section 5.2 provides a recommendation for a

full-flow method of performing AF`W testing.

4.5 Alternate Methods for Valve

Actuator Motor Testing

Several methods for detecting degradation in valve actuator

motors have been developed recently. Surveillance of

NUREG/CR-5404, Vol. 2

safety-related valve actuator motors, especially the large

frame sizes, is essential because of the many failure modes

associated with these motors.1I The magnesium alloy used

for the cast end rings and conductor bars in the larger

motors is susceptible to failure from overheating or

corrosion. 18

The typical motor tests that have been common surveillance practice over the last 40 years, such as high-potential

testing, winding resistance, megger testing, and polarization index are valuable for testing the condition of the stator but provide little or no information on the condition of

the rotor. The rotor can be examined using a flexible fiber

optic borescope, but this requires a technician to actually

insert the borescope in the motor, which at times can be

quite difficult because of motor location.

A new method of assessing rotor degradation is called

motor current signature analysis. This method has been

tested on a valve actuator motor and was successful in

detecting broken rotor bars before the motor's torque output had been appreciably reduced. 19 This method is based

on the principal that an electric motor acts as a transducer.

When broken rotor bars are present, harmonic fluxes are

produced in the air gap that induce harmonic components

in the motor current waveform. The motor current waveform can be readily converted from a time domain to a

frequency domain using fast Fourier analysis, and the

amplitude of each of the component frequencies can be

evaluated to determine problems both in the motor and in

the driven equipmexnt.

4.6 Evaluation of Alternate Methods

for Check Valve Testing

Check valve testing has become the subject of considerable

attention. Reference 20, NRC Generic Letter on Developing Acceptable Inservice Testing Programs, discusses

check valve reliability and states that, in some cases, an

electrical signal initiated by a position-indicating device

may be used for position verification. Because check valve

testing has developed into a major issue with many methods being offered in the industry, only a brief summary of

some of the techniques can be discussed in this study.

No single diagnostic technique will satisfy all requirements, but a combination of acoustic emission with

either ultrasonic inspection or Magnetic Flux Signature

Analysis (MFSA) will detect most major check valve

operating conditions. The acoustic signature will not

indicate disk position when the disk is stationary in the

fully open and fully closed positions, nor will it detect a

slowly moving disk or disk flutter in midstroke. In all three

tapping modes (seat tapping, backstop tapping, and hinge

16
arm rocking), however, the acoustic signature will detect

the tapping but not the position.

The magnetic signature is a technique of applying external

magnetic fields to the valve and then monitoring disk

movement as it either completes or partially opens the

magnetic circuit. This method does not unambiguously

detect the tapping, but, in conjunction with the acoustic

signature, does identify its location. A discussion of the

diagnostic techniques and a recommendation for detecting

check valve failures are provided in Sect. 5.1.

Aging and service wear of check valves are also discussed

in Ref. 21, which describes several check valve monitoring

methods and identifies their strengths and weaknesses, as

summarized in Table 2.1 of that report.

4.7 Evaluation of Alternate Methods

for TD AFW Pump Testing

The present TD AFW pump test is performed at normal

operating steam generator pressure. The steam supply to

the AFW turbine is taken from the steam generators

through the main steam system. The steam supply pressure

can range from a high that corresponds to the main steam

safety valve relief pressure (-1215 psia) to a low of -120

psia. This low pressure corresponds to a temperature of

-340'F. The AFW system is required to operate until the

reactor coolant temperature is reduced to the point at which

the residual heat-removal system can be started (3501F).

Because the steam generators are a heat sink for the reactor, steam generator temperature typically must be below

3500F. Therefore, it is possible that the AFW turbine could

be operating with steam supply pressures as low as 120

psia. Therefore, the turbine should be tested with steam

supply pressures as low as 120 psia to ensure that adequate

flow is developed. This could be accomplished by performing the pump flow test at startup when the steam supply

pressure is low. This is discussed in Sect. 5.3.

4.8 Evaluation of Untestable Functions

Evaluation

should be independently verified by an alternate analysis to

ensure that an appropriate degree of conservatism exists.

Two examples of these are the flow switchover from the

CST to ESW and the system flow curve for flow from

ESW. As is discussed in Sect. 4.3.1, additional functional

verification testing can be performed to verify portions of

the ESW switchover, but then the individual times must be

summed and compared with the total allowable switchover

time, which is determined by analysis. Because an error in

this analyzed total allowable switchover time could result

in air binding and possible destruction of an AFW pump

and because this function typically can never be tested, it is

crucial that the analysis used to determine an acceptable

switchover time be independently verified by an alternate,

independent analysis to verify that the result is correct.

This is also true for the analysis of the system head flow

curve for the ESW lines. These lines typically can never

actually be tested, but their correct operation is absolutely

essential. Additionally, they are also notoriously susceptible to increased friction from fouling (see Sect. 5.6).

Because of this, the ESW system head flow curve could

easily change with time as the lines became fouled. The

ESW lines must be periodically inspected for fouling, and

the curve should be established as accurate and acceptable

by an independent calculation.

Other potential function failures may be hidden in the

untested portions of the AFW system. An example is the

routing of the ESW line feeding the AFW suction. When

the ESW line is filled, the presence of a high point in the

line may allow a bubble to form if the designer does not

provide a high-point vent. This bubble could remain

undetected and cause failure of the AFW pump if it were

called upon to operate with suction from ESW. To the

author's knowledge, this potential failure caused by a

design oversight has occurred at a minimum of three plants

and was the subject of NRC Information Notice 93-12

(Ref. 22). Potential failures such as these could not be

discovered by testing because the ability to test was not

provided in the system design; they are "caught" only by

carefully analyzing operation of the system function.

In the design of the AFW system, there are some functions

that cannot be tested. The analysis of these functions

17 NUREG/CR-5404, Vol. 2
5 Recommendations for Alternative Monitoring/Operating Practices

to Detect Failure Modes Currently Undetected

The discussion of failure modes provided in Sect. 2 provided the following areas where failure modes were not

detected by current monitoringloperating practices:

1. check valve failures,

2. AFW pump failures at operating pressure conditions,

3. turbine-driven AFW pump failure to provide required

flow at reduced steam pressure,

4. various air-operated valve failures to open or close,

5. I&C failures not observed during routine testing,

6. turbine electronic overspeed trip function,

7. turbine steam supply isolation valve failure to close

correctly,

8. ESW failure to switchover in time, and

9. ESW failure to provide adequate flow.

Recommendations for alternative monitoring/operating

practices to address each of these failure modes are provided in Sects. 5.1 through 5.7 and are summarized in

Table 5.1.

5.1 Recommendations for Improvements in Current Monitoring/

Operating Practices to Detect

Check Valve Failures

Check valves failing to open were a significant AFW system failure mode found in the AFW aging study. 1 In the

aging and service wear of check valves study,21 the discussion of monitoring practices may be summarized as

follows:

There are five primary methods for check valve monitoring: acoustic emission monitoring, ultrasonic inspections,

magnetic flux monitoring, radiography, and pressure noise

monitoring. Radiography and pressure noise monitoring

are limited to special test applications. Acoustic emission

monitoring, ultrasonic inspection, and magnetic flux monitoring provide the best general diagnostic capability, especially when they are used in combination with each other.

Radiography, as a check valve diagnostic, is limited to

inspections for flaws, cracking, or erosion over a specific

valve area.

Pressure noise monitoring requires penetrating the pressure

boundary and installing a transducer. In addition, Ref. 21

(p. 30) states that pressure noise monitoring is influenced

by many system phenomena and sometimes provides nonreproducible results. Acoustic emission monitoring is

excellent for detecting a tapping valve but has the major

drawback that when the obturator is fluttering in midstroke, lodged in one position, or completely broken from

the hinge pin, there will be no tapping to indicate these

conditions. Thus the absence of tapping does not show that

the valve is open and stable.

MFSA is nonintrusive because the magnets or magnetic

coils are typically installed outside the valve. The analysis

of the magnetic field provides a continuous, real-time indication of the obturator position.

A combination of two of the monitoring methods provides

the best overall diagnostic capabilities. Acoustic emission

provides unique information on obturator contact (tapping)

and use of acoustic emission with MFSA will provide

information on leakage (acoustics), impacts within valve

(acoustics), and detecting disk position to assess whether

the disk is open, closed, or partial (MFSA).

One method for detecting check valve leakage is infrared

thermography. This is useful in an operating condition

where one side of the valve is pressurized with hot water.

5.2 Recommendations for Full-Flow

Testing of AFW Pumps

Reference 16 provides a discussion on the problem of

development of minimum flow rate criteria. This discussion concludes that no proven formulas are available to

determine how long a specific pump design can operate at

reduced flow rates and that the continued use of miniflow

testing will, over time, continue to produce possibly damaging effects in the tested pumps.

The alternative, which will both conclusively verify operability and eliminate damage caused by miniflow operation, is full-flow testing. A proposed test guideline is provided in Ref. 16 as Appendix G and is summarized here as

it is a logical alternative to the minimum flow test.

Allowing the AFW pumps to deliver flow to the steam

generator during system operation would require no

NUREG/CR-5404, Vol. 2 18
Recommendations

Table 5.1 Recommended alternative testing practices

Component Test Value Drawback Suggested frequency

Check valve Radiography Verifying integrity

Pressure noise monitoring

Acoustic emission

Ultrasonic inspection

Verifies tapping

Nonintrusive

Magnetic flux signature

analysis

Disassembly

AFW pump Visual inspection

Motor power monitoring

and rotational speed

Dimensional inspection

Developed head

monitoring

Developed flow

monitoring

Vibration monitoring

Balance return line flow

Audible noise monitoring

Verifies position

Allows for assessment of wear and

obturator motion

Will sometimes

detect external

signs of

degradation

Indicates hydraulic

degradation

Indicator of mechanical wear

Essential for assessing hydraulic

degradation

Indicates hydraulic

degradation

Indicates mechanical

degradation

Indicates hydraulic

degradation

May indicate

developing

problem

Indicates mechanical

degradation

Indicates worn

fasteners

Indicates shaft seal

condition

Indicates bearing

wear corrosion or

contamination

No information on

positioning

Overly sensitive

Will not detect stuck or

broken obturator

May not operate over full

range of travel

Relatively new technology

Valve must be removed

from service for

extended period, possibility of error in

reassembly

External evidence must be

present

As needed

Not ordinarily recommended

As needed, in combination

with MFSA

Ordinarily, not

recommended

As needed, in combination

with acoustic emission

10 years

At each flow test (quarterly)

Must be corrected and

trended

Can only be done at

disassembly

Must be corrected for system friction, pump

speed, etc.

Must be corrected for

system condition, static

head, pump speed, etc.

High implementation cost

High implementation cost

Requires experienced

individual

At each flow test (quarterly)

At 10-year interval

At each flow test (quarterly)

and trended

At each flow test (quarterly)

and trended

At each flow test (quarterly)

plus trend

At each flow test (quarterly)

At each flow test (quarterly)

Bearing temperature

monitor

Bolt torque inspection

Leakage inspection

Lube oil analysis

High implementation cost Trend

None At 10-year interval

None At each flow test (quarterly)

None At each refueling outage plus

trend

19 NUREG/CR-5404, Vol. 2
Recommendations

Table 5.1 (continued)

Component Test Value Drawback Suggested frequency

Liquid penetrant

inspection

Hot standby full-flow test

Winding megger

Indicates cracking

caused by stress or

corrosion

Indicates ability to

provide flow at

operating pressure

Indicates insulation

resistance

None At each disassembly (10

years)

Possible cyclic fatigue of

FL system

Test is sensitive to environmental conditions

(humidity)

At each refueling outage plus

trend

At each refueling outage plus

trend

Valve

actuator

motor (ac

& dc)

Winding bridge Indicates windings

are not shorted or

open circuited

None At each refueling outage plus

trend

Valve

actuator

motor

(ac)

LCVs and

BDIVs

MCSA Detects rotor

degradation

None At each refueling outage plus

trend

Turbine

drive

AFWP

Stroke at cold shutdown

Stroke at transition from

hot standby to hot

shutdown

Flow test at low steam

pressure

Chemical analysis of

turbine and governor

oil

Verify electrical and

mechanical overspeed

trips by actually taking

turbine to overspeed

condition

Entire control function, in

overlapping segments,

from sensor to end

component action, for

all functions

Indicates logic is

operable

Indicates valve is

operable at design

basis conditions

Confirm flow is

adequate at point

where RHR is

started

Detect wear

corrosion or

contamination

Confirm

coordination

between two trip

actuations

Confirm safety features are operable

None

Requires special test

procedure

At each refueling outage

At each refueling outage

None At each refueling outage plus

trend

None At each refueling outage plus

trend

Safetyrelated

logic

Turbine must be controlled

manually

Complete review of control logic requires a significant commitment of

resources. Plus, procedures must be revised

and training required

None

At each refueling outage

At each refueling outage

ESW,

service

water

Monitor corrosion with

inspection or ultrasonic

wall thickness testing

Monitor flow to detect

fouling, both organic

and inorganic

Ensure system

integrity

Ensure design basis

flow is available

At each refueling outage plus

trend

Flow instrumentation may

not be installed

Trend

NUREG/CR-5404, Vol. 2 20
hardware changes, unlike increasing the flow through the

miniflow lines. This test would result in additional temperature transients on the steam generators and a small

transient effect on the steam generator system. A significant precaution would be that the source of AFW during

testing (typically the condensate storage tank or refueling

water storage tank) be condensate quality, noncontaminated, and that all noncondensate quality sources of

feedwater be isolated during testing. The test would

typically be performed during refueling outage intervals

during entry into hot shutdown.

Only one AFW pump should be tested at a time. (If one

pump is isolated, the others should be operable and remain

aligned and ready to deliver flow in the event of an automatic start signal.)

The flow rate delivered into any one steam generator typically should not exceed 500 gal/min. A plant-specific flow

rate would have to be determined. Each pump should be

permitted to deliver flow into all steam generators to which

it is normally aligned. At least one point well out on the

head-flow curve, for example, at 80% or greater of the

BEP flow rate, should be verified.

The remote manual flow control valve(s) leading from the

pump to the steam generator(s) may be closed immediately

preceding the test and then opened slowly during the test

until the flow rate reaches the limit (typically 500 gal/min).

This should minimize the transient experienced by the

steam generator and level control systems.

With the pump delivering flow, operators should record

pump discharge pressure, suction pressure, discharge flow,

recirculation flow, flow to each steam generator, turbine

inlet pressure, and pump speed, in addition to other pertinent data. Analysis should be performed to verify that the

pump is operating on its design head-flow curve and that

the system friction, pump motor efficiency, flow from

CST, etc., are within design requirements.

Following testing, operators should verify that each valve

in the AFW system is in its correct position.

In addition to the determination of the plant-specific flow

rate, a review of the following two potential concerns

should be performed before the full-flow test is adopted.

1. There will be a temperature transient on the steam generator system because of the injection of the cooler

Recommendations

auxiliary feedwater. A review of the steam generator

pressure and level control system should be performed

to ensure that no deleterious effects will result from the

test

2. There will be a thermal cycling effect on the feedwater

piping and nozzle to the steam generator. A review

should be performed to ensure that the effect of this

cycling, once per refueling interval, is acceptable.

5.3 Recommendations for Improvements in Detection of TD AFW

Pump Failures

There are four areas of particular importance in ensuring

turbine reliability and are not typically included in periodic

maintenance, as follows:

1. Periodically perform a pump flow test at low steam

supply pressure conditions (e.g., at startup from

refueling). This would verify that TDP flow is adequate

at the point at which the residual heat removal system

can be started.

2. Periodically perform chemical analysis of turbine and

governor oil to reveal the presence of contaminants

and/or oil degradation. The experience of each utility

should be used to determine a time period that will

increase reliability (e.g., annual or semiannual analysis).

3. Calibrate governors on a regular basis.

4. Periodically verify overspeed trip operation by manually taking the turbine to overspeed to verify the function of the electrical and mechanical overspeed trip

mechanisms, including the electrical automatic reset.

Recommendations 2 through 4 are vendor recommendations and will provide assurance that the entire overspeed

trip system is operable.

5.4 Valve Failure to Open or Close

Both of the undetected valve failures noted in the study

were for air-operated valves. The first failure, Sect. 2.1.6,

was for level control valves failing to open sufficiently to

allow adequate flow; the second was for the BDIV failing

to close under blowdown conditions. As discussed in Sect.

4.1.6, the AFW pump level control valves are tested at a

relatively low differential pressure, whereas it would be

possible to perform the test at normal operating pressure by

doing the test during the transition from hot standby to hot

shutdown. Testing during this transition would provide

assurance that the valves are operable during design

conditions.

21 NUREG/CR-5404, Vol. 2
Recommendations

5.5 Recommendations for Alternative

Routine I&C Testing in Areas

Where I&C Failures Are Not

Detectable

As discussed in Sect. 4.2.1, most instances of the failure to

test safety-related logic were because the functional tests

simply had not been incorporated into the periodic logic

verification testing. A thorough and comprehensive review

of the safety system logic requires an engineer who is not

only well versed in the detailed function of the system but

also understands the plant's control wiring diagrams and

the translation of the control logic into functional tests as

provided in the written periodic test instructions. Confirming operation of a single relay or output contact does

not provide assurance that the safety function will operate

as required. The entire function must be tested, in overlapping segments, from initiating sensor to actuated

equipment.

As discussed in Sect. 4.2.1, performance of a system

review to ensure that each logic function is properly written into the periodic test instructions is a significant and

labor-intensive effort. However, based on the number of

instances of failure to test found in the study of a sample

AFW system in Ref. 2, where there existed 14 significant

engineered safety feature design functions that were not

periodically verified to be operable, the author recommends that the performance of a review of the safety system logic be made a regulatory requirement All engineered safety feature logic functions would be identified

and documented and reviewed as being properly designed

into the plant's control wiring and be confirmed to be written into the periodic logic verification testing with the possible exception of older plants.

For the older plants, the work-hours required to perform

this comprehensive testing may be excessive. A large

number of jumpers or circuit modifications may be needed

to perform the test. Use of excessive jumpers could result

in the failure to properly restore the safety circuits after

testing. Extensive circuit modifications could potentially

reduce the reliability of the safety systems. In these cases,

the improvement in reliability provided by the comprehensive testing would be outweighed by the decrease in reliability caused by the jumpers and circuit modifications. In

these cases, this recommendation would not be applicable.

For new plants, and older plants that have upgraded their

I&C systems because of obsolescence, the upgraded

microprocessor-based control systems have diagnostic

capabilities that will allow on-line testing of all input signals, signal conversion functions, logic functions, and outNUREG/CR-5404, Vol. 2

put commands. Overlapping testing can be used to test

complete actuations with relative ease. Plants with the

capability to perform comprehensive safety system logic

functional testing should be required to do so.

5.6 Recommendations for Detection of

Service Water System Piping

Fouling with Subsequent Flow

Reduction

NUREG/CR-5379, Nuclear Plant Service Water System

Aging Degradation Assessment Phase I, provides an excellent study of fouling of service water systems (SWSs)

surfaces. 17 The concern of flow reduction caused by fouling is summarized as follows:

Fouling refers to all deposits on system surfaces that

increase resistance to fluid flow or heat transfer. There

are basically two sources of fouling-organic

(microorganisms e.g., bacteria, and macroorganisms

e.g., Zebra Mussels) and inorganic (scales, silt,

corrosion product).

Fouling deposits result in reduced flow of cooling

water. In addition, corrosion can occur underneath sediment deposits and drastically reduce piping system lifetime. Typically, because ESW piping rarely (if ever)

experiences design flow operation, fouling deposits

may go undetected, and their effect on system friction

and flow rate is unknown. For this reason, it is essential

that the potential for fouling be kept to an absolute

minimum.

Chlorination is the predominant method to control biofoulants, but federal discharge regulations limit the

effectiveness of this method. Other methods include

bromination, backflushing, organic coating, or thermal

shock. Sometimes chemical and mechanical cleaning

methods are used periodically to remove fouling. The

size and extent of SWS piping dictates the requirement

to focus antifouling procedures on areas that have the

most safety significance. These areas must include the

lines that supply ESW to the AFW pumps.

Corrosion in service water lines is often discovered by

leaks or inspections. Although pipe wall thickness is

periodically measured ultrasonically, reduced flow area

from material buildup and pinhole leaks are not

detected by ultrasonic wall thickness measurements.

Trending of corrosion parameters in key locations

would be of great value in ensuring system integrity.

Some of the antifouling procedures that should be practiced for the key SWS lines are as follows:

* coating application and repair;

* chemical and/or mechanical cleaning;

* water treatment and

22
* most importantly, periodic inspection, evaluation, and

trending.

5.7 Recommendation for Full-Flow

ESW Test Line

It is not practical to verify ESW flow because lake water

should not be introduced into the condensate/feedwater

system. However, is it possible to add an ESW full-flow

test line to the AFW system (see Fig. 5.1). It is essential to

provide a test line that can be thoroughly flushed at the

completion of the test to eliminate the possibility of introducing contaminants to the steam generators. As shown in

the figure, the AFW pump discharge could be isolated to

prevent lake or river water from entering the steam generators and contaminating the AFW system piping during the

Recommendations

test. The AFW pump suction would then be isolated from

the CST and realigned to the ESW. The pumps would then

be started and the discharge flow returned to the service

water header via the ESW full-flow test line. A butterfly

valve or flow venturi could be installed to simulate steam

generator backpressure. Following the test, the AFW pump

suction would then be realigned to the CST to flush out the

AFW pump(s) and associated piping. (In some cases, at

plants where the CST has been contaminated by a previous

evolution, an analysis would have to be performed to

ensure that flushing the AFW pump to the service water

header would not introduce an unacceptable level of contamination into the service water header.) After the AFW

pumps and the small section of piping have been thoroughly flushed, the AFW system would then be returned to

service.

ORNL-DWG 92.4177 ETD

Service Water Header

To SGs

CSTAFW Pump

Figure 5.1 ESW full-flow test line added to AFW system

23 NUREG/CR-5404, Vol. 2
6 Recommended Changes to Technical Specifications to Allow Auxiliary

Feedwater Pump Testing on a Quarterly Frequency

As discussed in Sect. 3.2, the present method of performing periodic testing of the AFW pumps at miniflow conditions is producing significant degradation in the pumps

because of the hydraulic instability associated with the

high-head, low-flow operation. This degradation is

leading to premature pump failure.

6.1 Recommendation for Quarterly

Testing

Presently, the typical standard pressurized water reactor

technical specifications23 require operability testing of

the AFW pump on a monthly basis. Because this mode of

operation degrades the pump, it is strongly recommended

that this test interval be increased to quarterly rather than

monthly. There are no age-related failure mechanisms

identified as a result of the Phase I Study that would not

be detected by a quarterly test cycle, and the quarterly

cycle will significantly reduce the present rate of testrelated pump degradation.

6.2 Recommendation for Full-Flow

Testing

In addition, some plant technical specifications specify a

test flow rate and discharge head that correspond only to

miniflow operation. It is strongly recommended that a

flow rate and discharge head that correspond to a fullflow test be permitted by the technical specifications.

including the ability of the check valves and flow control

valves to open at design flow and pressure conditions, as

discussed in Sect. 5.2. This test would also eliminate

AFW pump degradation as a result of low-flow hydraulic

instability. This test would result in a temperature

transient on the steam generator and level control system

because of the injection of the relatively cool CST water,

but by opening the flow control valve slowly and only

performing the test on an 18-month frequency, the effect

of the transient and the number of thermal cycles imposed

on the steam generator would be minimized.

6.3 Preferred and Optional Test

Method

The optimum resolution to the problem of low-flow

testing is the addition of full-flow test lines. With fullflow test lines, a quarterly full-flow test could be

performed to verify pump performance with an 18-month

test of flow to the steam generator to verify complete

system operability. This is the preferred test method.

In cases where installation of full-flow test lines is

impracticable, an optional test method is to perform the

miniflow test on a quarterly basis and only for a period of

30 s or less to verify that the pump operates and that a

predetermined discharge pressure is developed. The

18-month full-flow test to the steam generator would be

performed to verify complete system operability.

A full-flow test to the steam generator on an 18-month

interval would verify complete system operability

NUREG/CR-5404, Vol. 2 24
References

1. D. A. Casada, Martin Marietta Energy Systems, Inc.,

Oak Ridge Natl. Lab., "Auxiliary Feedwater System

Aging Study," USNRC Report NUREG/CR-5404,

Vol. 1 (ORNL-65661V1), March 1990.*

2. M. L. Adams et al., Martin Marietta Energy Systems,

Inc., Oak Ridge Natl. Lab., "Aging and Service Wear

of Auxiliary Feedwater Pumps for PWR Nuclear

Power Plants," USNRC Report NUREGICR-4597,

Vol. 1 (ORNL-6282/V1), July 1986.*

3. Letter from Ingersoll-Rand to the NRC, Subject:

Notification of 1OCFR21 Reportability of a Potential

Safety Hazard from Broken Cast Iron Diffuser Pieces

in Auxiliary Feed Water Pumps, October 199 10t

4. IEEEISTD 741-1990, "IEEE Standard Criteria for the

Protection of Class IE Power Systems and Equipment

in Nuclear Power Generating Stations."'

5. 0. Rothberg, USNRC, "Thermal Overload Protection

for Electric Motors on Safety-Related Motor-Operated

Valves - Generic Issue 1 E.6.1," USNRC Report

NUREG-1296, June 1988.*

6. A. Richards et al., "Motor Overload Protection for

Motor Actuated Valves," IEEE Transactions on

Power Apparatus and Systems, PAS-100 (1), 43-50

(January 1981).**

7. NRC Generic Letter 89-10 to all licensees of operating

nuclear power plants and holders of construction

permits for nuclear power plants from the U.S.

Nuclear Regulatory Commission, Subject: SafetyRelated Motor-Operated Valve Testing and

Surveillance, June 28, 1989.

8. A. J. Weiss, "Application of Signature Analysis for

Determining the Operational Readiness of MotorOperated Valves Under Blowdown Test Conditions,"

in Proceedings of the Sixteenth Water Reactor Safety

Meeting, USNRC Conference Proceeding NUREG/

CP-0097, March 1988.*

9. W. J. Foley et al., Parameter Inc., "Failure of GateType Valves to Close Against Differential Pressure,"

USNRC Report NUREG/CR-3050, September 1983.*

10. M. Subudhi et al., Brookhaven National Laboratory,

"Operating Experience & Aging-Seismic Assessment

of Electric Motors," USNRC Report NUREG/CR4156, June 1985.*

11. H. D. Haynes, Martin Marietta Energy Systems, Inc.,

Oak Ridge Natl. Lab., "Aging and Service Wear of

Electric Motor-Operated Valves Used in Engineered

Safety-Feature Systems of Nuclear Power Plants,"

USNRC Report NUREG/CR-4234 (ORNL-6170N2),

August 1989.*

12. G. A Murphy et al., Martin Marietta Energy Systems,

Inc., Oak Ridge Natl. Lab., "Operating Experience

Review of Failures of Power-Operated Relief Valves

and Block Valves in Nuclear Power Plants," USNRC

Report NUREG/CR-4692 (ORNL/NOAC-233),

October 1987.*

13. J. C. Higgins, "Value-Impact Analysis for Extension

of NRC Bulletin 85-03 to Cover all Safety-Related

MOVs," USNRC Report NUREG/CR-5140, July

1988.*

14. W. Grant et al., MPR Associates, "Application Guide

for Motor-Operated Valves in Nuclear Power Plants,"

EPRI Nuclear Maintenance and Analysis Center,

NP-6660-D, March 1990.

15. ASME OM Code-1990, Codefor Operation and

Maintenance of Nuclear Power Plants.t

16. D. M. Kitch et al., Martin Marietta Energy Systems,

Inc., Oak Ridge Natl. Lab., "Aging and Service Wear

of Auxiliary Feedwater Pumps for PWR Nuclear

Plants," USNRC Report NUREG/CR-4597, Vol. 2

(ORNL-6282/V2), June 1988.*

17. D. B. Jarrell et al., Pacific Northwest Laboratories,

"Nuclear Plant Service Water System Aging

Degradation Assessment Phase I," USNRC Report

NUREG/CR-5379, Vol. 1, pp. 117-121, June 1989.

18. J. D. Kueck, "An Investigation of Magnesium Rotors

in Motor Operated Valve Actuators," IEEE Transactions on Energy Conversion, 3(1), March 1988. **

19. J. D. Kueck et al., "Assessment of Valve Actuator

Motor Rotor Degradation by Fourier Analysis of

Current Waveform'" IEEE/PES 1992 Winter Meeting,

92MM 0794EC.**

25 NUREG/CR-5404, Vol. 2
References

20. NRC Generic Letter No. 89-04, to all holders of LWR

operating licenses and construction permits, Subject

Guidance on Developing Acceptable Inservice Testing

Programs, April 3, 1989.

21. H. D. Haynes, Martin Marietta Energy Systems, Inc.,

Oak Ridge Nall. Lab., "Aging and Service Wear of

Check Valves Used in Engineered Safety-Feature

Systems of Nuclear Power Plants," USNRC Report

NUREG/CR-4302, Vol. 2 (ORNL-6193/V2), April

1991.*

22. NRC Information Notice 93-12 to all holders of LWR

operating licenses and construction permits, Subject

Off-Gassing in Auxiliary Feedwater System Raw

Water Sources, February 11, 1993.

23. M. J. Virgilio, USNRC, "Standard Technical

Specifications for Westinghouse Pressurized Water

Reactors," USNRC Report NUREG-0452, Rev. 4,

November 1981.*

Available for purchase from National Technical Information Service,

Springfield, VA 22161.

tAvailable in NRC PDR for inspection and copying for a fee.

*Available from American National Standards Institute, 1430

Broadway, New York, NY 10018, Copyrighted.

Available in public technical libraries.

NUREG/CR-5404, Vol. 2 26
NUREG/CR-5404

Volume 2

ORNL-6566/V2

Dist. Category RV

INTERNAL DISTRIBUTION

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4. R. H. Greene 21. ORNL Patent Section

5. H. D. Haynes 22. Central Research Library

6. J. E. Jones Jr. 23. Document Reference Section

7-16. J. D. Kueck 24-25. Laboratory Records Department

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27. B. P. Brooks, Electric Power Research Institute, P.O. Box 10412, Palo Alto, CA 94303

28. J. W. Tills, Institute for Nuclear Power Operations, 1100 Circle 75 Parkway, Atlanta, GA 30339-3064

29. R. J. Lafaro, Brookhaven National Laboratory, Bldg. 130, Upton, NY 11973

30. R. P. Allen, Battelle-PNL, MS P8-10, P.O. Box 999, Richland, WA 99352

31. J. P. Vora, U.S. Nuclear Regulatory Commission, Office of Nuclear Regulatory Research, Electrical

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Operations Office, Oak Ridge, TN 37831

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27
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/See instructions on rhe reverse) ORNL-6566/Vl

2. TITLE AND SUBTITLE Vol. 2

Auxiliary Feedwater System Aging Study 3. DATE REPORT PUBLISHED

July 1993

Phase I Follow-On Study 4. FIN OR GRANT NUMBER

B0828

5. AUTHOR(S) 6. TYPE OF REPORT

J. D. Kueck

7. PERIOD COVERED mncluvsie Darest

B. PERFORMING ORGAN IZATION - NAME AND ADDRESS Wll NRC, provide Division. Office or Region, US. Nuclear Regulatory Con n ission and mailing address; i Contracror, pro ino name and mailing address.I

Oak Ridge National Laboratory

Oak Ridge, TN 37831-6285

9. SPONSORING ORGANIZATION - NAME AND ADDR ESS (If NRC. type Same as aboeeif contractor. proeide NRC Dielsion. Office or Region. US. Nuclear Regulatory Commission.

9. SPONSORING ORGAN IZATI ON -NAME AND ADDRESS (fl rRC, tyre-Same*5 booe- tfconracror porovdeNRC Division. Office or Region. U.S. Nuclear Re90srorv CommiwsiOn and mailing addressJ

Division of Engineering

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Washington, DC 20555 -0001

10. SUPPLEMENTARY NOTES

11. ABSTRACT f200mordsor less)

This report documents the results of a Phase I follow-on study of the Auxiliary Feedwater (AFW) System

that has been conducted for the U.S. Regulatory Commission's Nuclear Plant Aging Research Program.

The Phase I study found a number of significant AFW System functions that are not being adequately

tested by conventional test methods and some that are actually being degraded by conventional testing.

Thus, it was decided that this follow-on study would focus on these testing omissions and equipment

degradation. The deficiencies in current monitoring and operating practice are categorized and evaluated.

Areas of component degradation caused by current practice are discussed. Recommendations are made

for improved diagnostic methods and test procedures.

12. KEY WORDS/DESCR! PTO RS (List .ords Or phrases that will assist researchers in locating the report.J 13. AVAILABILITY STATEMENT

Unlimited 14. SECURITY CLASSIFICATION

Irhis Page)

auxiliary feedwater, surveillance, monitoring, pump, flow, aging, NPAR, Unclassified

inspection, operating experience, instrumentation and control (This Report)

Unclassified

15. NUMBER OF PAGES

16. PRICE

NRC FORM 335 (2.891
Federal Recycling Program
NUREG/CR-5404, VoL 2 AUXILIARY FEEDWATER SYSTEM AGING STUDY JULY 1993

UNITED STATES

NUCLEAR REGULATORY COMMISSION

WASHINGTON, D.C. 20555-0001

FIRST CLASS MAIL

POSTAGE AND FEES PAID

USNRC

PERMIT NO. G-67

OFFICIAL BUSINESS

PENALTY FOR PRIVATE USE, $300