NUREG/CR-6043

PNL-8614

Vol. 1

Aging Assessment of Essential

HVAC Chillers Used in

Nuclear Power Plants

- Phase I

Prepared by

D. E. Blahnik, R. F. Klein

Pacific Northwest Laboratory

* Prepared for

U.S. Nuclear Regulatory Commission
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NUREG/CR-6043

PNL-8614

Vol. 1

Aging Assessment of Essential

HVAC Chillers Used in

Nuclear Power Plants

Phase I

Manuscript Completed: July 1993

Date Published: September 1993

Prepared by

D. E. Blahnik, R. R Klein

Pacific Northwest Laboratory Richland, WA 99352

Prepared for

Division of Engineering

Office of Nuclear Regulatory Research

US. Nuclear Regulatory Commission

Washington, DC 20555-0001

NRC FIN B2911
Abstract

The Pacific Northwest Laboratory conducted a Phase I

aging assessment of chillers used in the essential safety

air-conditioning systems of nuclear power plants. Centrifugal chillers in the 75- to 750-ton refrigeration

capacity range are the predominant type used. The chillers used, and air-conditioning systems served, vary in

design from plant to plant. It is crucial to keep chiller

internals very clean and to prevent the leakage of water,

air, and other contaminants Into the refrigerant containment system. Periodic operation on a weekly or

monthly basis is necessary to remove moisture and noncondensable gases that gradually build up inside the

chiller. This is especially desirable if a chiller is required

to operate only as an emergency standby unit.

The primary stressors and aging mechanisms that affect

chillers include vibration, excessive temperatures and

pressures, thermal cycling, chemical attack, and poor

quality cooling water. Aging is accelerated by moisture,

non-condensable gases (e.g., air), dirt, and other contamination within the refrigerant containment system;

excessive start/stop cycling; and operation below the

rated capacity. Aging is also accelerated by corrosion

and fouling of the condenser and evaporator tubes. The

principal cause of chiller failures is lack of adequate

monitoring. Human errors and omission of scheduled

maintenance also contn1bute to failures.

iii NUREG/CR-6043

A
Contents

Abstract .......................................... in

Summary .................................................. ix

Acknowledgments .................................................. Y

Acronyms ................................................... xii

Def .................................................. initions xv

1 Introduttion 1...................

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

1.2 Objective ................................................... 2

13 Equipment Boundary Selection ............... ................................... 2

2 Basic Chiller and HVAC Systems Information ............................................. 5..........

2.1 Chillers in Industry and Commerce .................... .............................. S

2.2 Chillers in LWRs .................................................. 7

2.3 Essential Chiller HVAC Systems in LWRs ............................................... 8...

3 Regulatory, Code, and Standards Requirements for Essential Chillers ............ ...................... 11

4 Centrifugal Chiller Description .................................................. 15

4.1 Chiller Design .................................................. 15

4.2 Materials of Construction .................................................. 15

5 Operating Experience Database Evaluation . .................................................. 25

5.1 Licensee Event Reports Database .................. ................................ 25

5.2 Nuclear Power Experience Database .................................................. 25

5.3 In-Plant Reliability Data System Database .................................................. 25

5.4 Nuclear Plant Reliability Data System Database ................................................. 28

v NUREGICR-6043
Contents

6 Other Operating Experience ..................................................... 29

6.1 Pacific Northwest Laboratory Experience ..................................................... 29

6.2 Westinghouse Hanford Company Experience .................................................... 29

63 Regional Service Company Experience ..................................................... 30

6.4 Cooperating Utility Experience ..................................................... 32

6.5 Experience from Literature Reviews . ..................................................... 32

7 Operating Experience Summary and Discussion ..................................................... 35

8 Conclusions ..................................................... 39

9 Recommendations ..................................................... 41

10 References ..................................................... 43

APPENDIX Au LWR Plant Chiller Systems Description (FSAR Data) ............ ........................ A.1

APPENDIX B: Hermetic Centrifugal Chiller Functional Description ............. ......................... B.1

APPENDIX C: LWR Plant LER Review Summary ..................................................... C.

APPENDIX D: NPE Database on Chillers . ..................................................... D.1

APPENDIX E. IPRDS Database Maintenance Report Summary for Nuclear

Power PlantA ..................................................... E.1

APPENDIX F: Chiller Work Request Summary for Nuclear Power Plant B ......... ....................... El

APPENDIX 0: ANS Paper Comparing Safety and Non-Safety Chillers ........... ......................... G.1

NUREG/CR-6043 vi
Contents

Figures

1.1 Research Boundary for Phase I Essential Chiller Study ............................................... 3

2.1 Reciprocating Water Chiller Description ........................................................... 6

2.2 Screw Water Chiller Description ................................................................... 6

2.3 Absorption Water Chiller Description . ............................................................. 7

4.1 Recent Model of Liquid Hermetic Centrifugal Chiller Manufactured by the Carrier Corporation -

Reference Design . ........................................................................ 16

4.2 Recent Model of Liquid Hermetic Centrifugal Chiller Manufactured by the York

International Corporation ...................................................................... 17

4.3 Recent Model of Liquid Hermetic Centrifugal Chiller Manufactured by The Mfane Company ...... ........ 18

4.4 Reference Centrifugal Chiller Cross-Sectional View Showing Refrigerant Flow Path ...... ............... 19

4.5 Reference Centrifugal Chiller Compressor Cross-Section . ............................................. 20

4.6 Reference Centrifugal Chiller Purge Unit ............................................................ 20

4.7 Reference Centrifugal Chiller Piping and Wiring Illustration .......................................... 21

4.8 Reference Centrifugal Chiller Dimensions and Layout Requirements .................................. 22

4.9 Recent Model of Liquid Open Centrifugal Chiller Manufactured by the Carrier Corporation

(for comparison with hermetic centrifugal chiller shown in Figure 4.8) .................................. 23

7.1 Summary of Chiller Failures (LER and NPE Databases) ............. ................................. 35

7.2 Aging Versus Nonaging Related Chiller Failures .................... ................................. 36

vii NUREG/CR-6043
Contents

Tables

5.1 Summary of Chiller Failures in the LER Database ............ ......................... 26

5.2 Summary of Chiller Failures in the NPE Database ............ ......................... 27

5.3 Summary of Plant A Essential Chiller Failures ..................................... 28

NUREG/CR-6043 viii
Summary

The Pacific Northwest Laboratory (PNL)1 conducted a

Phase I aging assessment of chillers used in essential

safety heating, ventilating, and air conditioning (HVAC)

systems of nuclear power plants. Searches of traditional

nuclear plant databases provided limited information on

chillers. The information was heavily augmented by

non-nuclear operating experience. More direct nuclear

plant information will be incorporated in the Phase 11

portion of the aging study.

Centrifugal chillers in the 75- to 750-ton refrigeration

capacity range are the predominant type used in essential nuclear plant HVAC systems. Other, less-used types

include rotary, screw, and reciprocating chillers. The

three primary manufacturers each have many models.

The chillers used, and HVAC systems served, vary in

design from plant to plant. It is difficult to select a

generic design. This study focused on centrifugal

packaged chillers.

Although centrifugal chillers are relatively complex

equipment packages, they are usually designed for a lifetime of`40 yea They will exceed this lifetime

if operations, maintenance, service water, and operating

environment are properly managed and controlled.

Units that are approaching 60 years of age are still operating in cold storage plants.

Major overhauls and maintenance that require entering

the refrigerant containment region must be performed

carefully by well-trained technicians. A small amount of

contamination, or a damaged or misaligned part, can

cause major damage during operation of the chiller. It

is crucial to keep equipment internals very clean and to

prevent the ingress of water, air, and other contaminants

into the refrigerant containment system. Periodic

operation for a few hours on a weekly or monthly basis

isnecessaxyGo-movemoisture and non-condensable

gases that gradually build up inside the chiller, especially

if a chiller is required to operate only as an emergency

t

0perated for the US. Department of Energ by Battelle Memorial

Institute under Contract DE-ACD6-76RL0 1830.

standby unit. If multiple chillers are available, the

operation should be alternated, and the operating hours

should be balanced. The chiller should be operated as

_cltseoAo I(X capacity aspratcalto optimizeoperatIngparamersandiminimizeaging. Usually chillers are

replaced due to lack of adequate monitoring and maintenance. Other causes for replacement of chiliers

include obsolescence due to 1) change of heat load (usually growth), 2) energy efficiency improvements, and,

currently, 3) incompatibility with the new refrigerants

required by new regulations. In many cases the chillers

can be upgraded by installing adaptor equipment packages provided by the manufacturer.

Chillers used in both nuclear and non-nuclear applications will soon be affected, and in some cases become

obsolete, due to environmental regulations that require

changing to the use of alternative refrigerants. The

impacts of the new refrigerants on the performance and

life of chillers is not completely known. Currently the

main concerns are potential efficiency loss, incompatible

materials and design, and the aggressive nature of the

new refrigerants. Chiller owners are encouraged to

work with the chiller manufacturer to make satisfactory

modifications.

The primary stressors and aging mechanisms that affect

chillers are vibration, operation at excessive temperatures and pressures, thermal cycling, chemical attack,

and poor quality condenser cooling water. Vibration is

inherent in chillers due to high-speed rotation, boiling

refrigerants, etc. Vibration is magnified further by misaligned or imbalanced components and/or operation

below 25% of rated capacity. Aging is accelerated by

moisture, non-condensable gases (e.g., air), dirt, and

other contamination within the refrigerant containment

system. Excessive start/stop cycling and under-loading

of chillers can accelerate aging. Aging is also accelerated by corrosion and fouling of the condenser and

evaporator tubes. The principal cause of premature

chiller failures is lack of adequate monitoring. Human

errors and omission of scheduled maintenance also contribute to failures. Failures due to design, operating

procedures, and manufacturing discrepancies and

ix ix ~~~~~~NUREG/C
Summary

defects usually occur during the start-up, shakedown, or

first year of operation for a particular new chiller model.

The time between recommended major overhauls (3 to

10 years) is usually established by the life of seals and

gaskets.

The essential (safety-related) chillers are important to

cool the control room and other safety-related equipment rooms.

The cooling is needed to prevent degradation and failure of safety-related equipment, to protect safety personnel, and to prevent or mitigate events and accidents.

Control of temperature and humidity in these rooms is

very important. Therefore, the essential chillers play an

important role in nuclear plant safety and warrant a

more in-depth Phase II study.

NUREG/CR-6043x x
Acknowledgments

The authors of this report acknowledge the support and

technical guidance provided by Dr. J. J. Burns, Jr. of the

Nuclear Regulatory Commission (NRC) during the

course of this research under the Nuclear Plant Aging

Research Program. Our thanks go to C Michelson,

member of the Advisory Committee on Reactor Safeguards at NRC, and other NRC staff that provided

information important to the studyi, Oak Ridge National

Laboratory for providing information from their SCSS,

IPRDS, and NPE Databases; B. G. Berglin and J. D.

Fulcher of Westinghouse Hanford Company and

D. D. Hatley and H. D. Steele of Pacific Northwest

Laboratory (PNL) who provided valuable insights by

sharing their experience in the installation, start-up,

operation, and maintenance of chillers; T: W Camp of

Landis & Gyr Powers, Inc for utilizing his 25 years of

experience in 'hands on' trouble-shooting and rebuilding chillers throughout the Pacific Northwest to help

provide a preliminary assessment of chiller aging (he

was also helpful in answering many of our questions on

chillers); regional chiller manufacturing representatives

who provided us with equipment catalogs; and staff at a

cooperating nuclear plant who provided us with a tour

of their plant's chiller HVAC facilities and helpful

Information on their plant's chiller HVAC operating

and maintenance experience.

The authors also wish to thank the following PNL staff

for their contributions to this report: Dr. R. P. Allen for

project management support and technical guidance;

Dr. A. B. Johnson, Jr. and Dr. I. S. Levy for their assistance in the Pre-Phase I prioritization of the essential

chillers for further study, and the Hanford Technical

Library staff who performed an extensive literature

search on chillers.

xi xi ~~~~~~NUREG/CR
Acronyms

ANS American Nuclear Society

ARI Air-Conditioning and Refrigeration Institute

ASHRAE American Society of Heating, Refrigerating, and Air-Conditioning Engineers

ASME American Society of Mechanical Engineers

CCW component cooling water

CFC chlorofluorocarbon

ECW emergency cooling water

ESF engineered safety feature

FFrF Fast Flux lTst Facility

FSAR final safety analysis report

HCFC hydrochlorofluorocarbon

HFC hydrofluorocarbon

HVAC heating, ventilating, and air conditioning

HX heat exchanger

IEEE Institute of Electrical and Electronics Engineers

IPRDS In-Plant Reliability Data System (database)

LCO limiting condition for operation

LER Licensee Event Report (database)

LOCA loss-of-coolant accident

LOP loss of offsite power

LWR light-water reactor

NDT non-destructive testing

NPAR Nuclear Plant Aging Research

xiii xiii ~~~~~NUREG/C
Acronyms

NPE

NPP

NPRDS

NRC

NUDOCS/AD

O&M

PNL

PTS

RG

RIDS

SAR

SCSS

SRP

TIRGALEX

-Nuclear Power Experience (database)

nuclear power plant

Nuclear Plant Reliability Data System (database)

U.S. Nuclear Regulatory Commission

Nuclear Documentation System (database)

operation and maintenance

Pacific Northwest Laboratory

Plant Technical Specification

Regulatory Guide

Regulatory Information Distribution System (database)

safety analysis report

Sequence Coding and Search Systems (database)

Standard Review Plan

Technical Integration Review Group for Aging and Life Extension

NUREG/CR-6043 xiv
age-related failure

chiller

essential chiller

failure

monitoring

non-age-related failure

partially age-related failure

safety-related items

ton, cooling rate

ton, storage

Definitions

failure that results from normal aging degradation caused by wear, corrosion,

vibration, etc.

packaged refrigeration machine used to chill water that is pumped to the HVAC room

cooler to cool room air - The absorbed heat is returned to the chiller, which transfers

the heat to a plant cooling system.

a chiller used to cool rooms that contain safety-related equipment essential to plant

safety

inability or interruption of ability of a system, structure, or component to function

within acceptance criteria

includes both routine process parameter monitoring by operations and a preventative

maintenance monitoring program; both aspects are very important to chiller reliability

and performance

failure that occurs as a result of faulty design, manufacturing defect, misinstallation,

human error, etc.

failure that is a combination of age- and non-age-related factors - Often the failure is

accelerated when factors are combined (e.g., seal made of wrong material fails

prematurally).

defined by 10 CFR 50, Appendix A, as Those structures, systems, and components that

provide reasonable assurance that the facility can be operated without undue risk to the

health and safety of the public' - For details, see 10 CFR 50.49.

standard ton of refrigeration that is equivalent to an air conditioning capacity of

12,000 Btulhr

storage equivalent to the beat of fusion of 2000 lb of ice (2000 lb x 144 Btu/lb =

288,000 Btu to melt a ton of ice)

xtr xv ~~~~~~NUREG/CR-6
1 Introduction

The essential chillers provide chilled water to cool the

control room and other rooms containing safety-related

equipment and personnel at nuclear power plants

(NPPs). Essential chiller operability is mandated by

Title 10, Part 50 of the Code of Federal Regulations and

other regulations that govern habitability of the control

room and operation of the safety-related rooms. The

essential chilled water systems must be available at all

times, have redundancy, and function during and after

simultaneous or individual events, such as a safe shutdown earthquake, loss-of-coolant accident (LOCA), or

loss of offsite power (LOP).

Because the ventilation systems these chillers serve are

safety-related, the chillers are also safety-related. They

must be designed, manufactured, and installed in accordance with Seismic Category I, American Society of

Mechanical Engineers (ASME) Code, Section m,

Class 3 requirements. The system must be powered

from Seismic Category 1E buses.

With the above requirements in mind, work was initiated on a Nuclear Plant Aging Research (NPAR)

Phase I aging study of NPP chillers. The discussion

below outlines the background, objectives, and initial

boundary selected for the study.

1.1 Background

Chillers were first formally Identified as a candidate for

an NPAR study in a Nuclear Regulatory Commission

(NRC) prioritization study (Levy et al. 1988). In

January 1991, work was initiated on a Pre-Phase I study

to determine if a full Phase I study was justified. The

Pre-Phase I study was completed and summarized in a

letter report.

The study recommended that a full Phase I study

proceed, and the NRC concurred. The recommendation

was based upon the following reasons:

The Technical Integration Review Group for Aging

and Life Extension (TIRGALEX) component

prioritization study recommended an aging assessment of chillers. Most U.S. NPPs are affected by

this issue.

* NRC Generic Letter 89-13 stresses the importance

and concern for chiller and room cooler heat

exchanger (HX) performance in safety systems.

* NRC Generic Safety Issue No. 143, Availability of

Chilled Vater Systems and Room Cooling is concerned with the availability of cooling services provided by chilled water, HVAC systems, and related

auxiliaries to provide temperature control in rooms

with safety-related equipment.

* Review of draft reports and general literature indicated the importance of chillers in cooling safetyrelated rooms. High temperatures and humidities

in control rooms affect both personnel and equipment. High temperatures can cause operators to

become uncomfortable and more susceptible to losing alertness and making errors in judgment. High

control room temperatures also cause concern for

premature degradation and failure of electrical and

electronic components, which are often housed in

cabinets with even higher than ambient room temperatures. The newer digital control systems are

even more susceptible to high temperature failure

than the older analog systems. Failure of control

components and spurious alarms make the operators' job even more difficult and could become the

principal cause of a major operating error. The situation is particularly difficult during a limiting condition for operation (LCO) caused by the failure of

one of the chillers. Operators become much more

tense due to a warmer environment and time limitations when the remaining chiller becomes

inoperable.

* Preliminary review of Licensee Event Reports

(LERs), Nuclear Power Experience (NPE), and

In-Plant Reliability Data System (IPRDS) data indicated that chillers are subject to age-related degradation with failures resulting from the degradation.

1 1 ~~~~~~NUREG/CR
Introduction

Each year a few plants must reduce power or shut

down because essential chillers are unavailable to

cool the control room and other safety equipment

rooms.

The full Phase I NPAR aging study was initiated in

October 1991 and completed in September 1992, with

the results summarized in this report.

1.2 Objective

The objective of the Phase I chiller study was to make an

interim aging assessment of chillers. The following

standard research elements were performed in accordance with the NPAR Program strategy (USNRC 1991):

* Review and analyze available information from

chiller designs, specifications, operational parameters, and ongoing research.

* Evaluate chiller operating experience from readily

available databases (e.&, IPRDS, NPE, and LERs).

* Utilize industry practices and the knowledge from

experts on chillers.

* Characterize the aging mechanisms for chillers.

* Interact with key NRC staff involved with chillers.

1.3 Equipment Boundary Selection

A simplified diagram of the major components of a centrifrugal chiller and the interfacing systems is shown in

Figure 1.1. The research boundary selected for the

Phase I study is indicated by the dashed line. The major

components of the chiller are typically a motor-driven

centrifugal compressor, a condenser HX, an expansion

device, and the evaporator-cooler HX The refrigerant

used as heat transfer media is usually CFC-11 or

CFC-12 refrigerant. The chiller waste heat is removed

by the plant service water system or an emergency

cooling water (ECW) system (especially in an accident

or LOP situation). The chilled water from the

evaporator is used to cool rooms that house safetyrelated equipment and personnel. The rooms cooled by

chillers are plant specific, but the control rooms were in

nearly all of the plants reviewed. The chiller and its

interfacing systems (the cooling water system, chilled

water system, and electric motor control center) can

have a large effect on the performance of each other. In

reality, a chiller is much more complex than shown in

Figure 1.1. A chiller has hundreds of components and is

interrelated with many remote safety system-controlled

components.

The typical auxiliary components of a chiller include

* compressor guide vane

* control panels and indicators

* wires and terminals

* purge-dehydrator unit1

* piping and tubing

* seals and gaskets

* base, package support structure, and vibration

dampeners

* lubrication oil system1

* sensors, controls, and alarms

* switchgear, starter, and relays

* flash economizers

* relief valves

* transmission gearbox and couplings .

'These components have numerous sub-components.

NUREG/CR-60432 2
Introduction

I . >Cooler (Evaporator) ,

Electric

Motor _

I Control

Center Motor Compressor Devici

r-- l i Condenser Water

|Auxl liary|| CodneWar

Components Service andlor

I______________3 'Emergency Water System - - - - - - - - - -

I

Ix

I NPAR

I Research

i Boundary

Figure L Research Boundary for Phase I Essential Chiller Study

3 3 ~~~~~~NUREGICR-60
2 Basic Chiller and HVAC Systems Information

Chillers are used for numerous applications and are

used extensively throughout developed portions of the

world. Probably about 250,000 liquid cooling chillers

are in use today. Approximately 80,000 are used in the

U.S. alone. Most of the chillers are used in central

HVAC applications where it is more economical and

efficient to distribute chilled water to remote air handling units than to use large space-consuming air ducts of

a central air handler (Niess 1992). The temperature is

better controlled by modulating chilled water flow

through air-cooling coils than with a direct "on-off"

expansion refrigerant distribution controL

2.1 Chillers In Industry and Commerce

Liquid chillers are used to cool water, glycol mixtures, or

brines for central station air-conditioning systems, refrigeration, or process cooling. Nearly 90% of the chillers used in industry-provide water-based liquids for

central station air-conditioning systems (Stebbins 1991).

The most common chiller systems utilize centrifugal, reciprocating, or screw compressors. Most of the chillers

use freon or ammonia (usually not used in rooms or

buildings occupied by personnel) in a closed refrigerant

cycle. They use air, water or evaporative condensers,

and flooded or direct-expansion evaporators. Hermetic

or open drives, expansion devices, and controls complete the typical package. Other, less common systems

used are the rotary and absorption cycle (water/steam)

chillers.

This study focused on the centrifugal water chiller as a

reference design. The centrifugal chiller is described in

greater depth later in the report and is shown in Figure 4.1. Illustrations of alternative reciprocating, screw,

and absorption water chiller designs are shown in Figures 21, 2.2, and 2.3, respectively.

Centrifugal water chillers, the industry workhorses, provide a broad range of sizes between 75 and 5000 tons or

more. The largest is believed to be 10,000 tons of

refrigeration. The compressor is a variable-volume displacement machine using one or more rotating impellers compressing refrigerant vapor by centrifugal force.

Since they are not constant volume machines, centrifugal chillers offer a wide range of capacities continuously modulated over a limited range of pressure ratios

and can provide a wide range of chilled water

temperatures.

Reciprocating water chillers are available in sizes up to

200 tons. The compressor is a fixed positive-displacement machine using crankshaft-powered pistons working in cylinders utilizing suction and discharge valves.

The compressor maintains nearly constant flow rates

over a wide range of pressure ratios and may be used

when displacement volumes are small. They operate

efficiently at high compression ratios and high condensing temperatures.

Screwwater chillers are available in the size range

between 50 and 750 tons. The compressor is a machine

that provides positive displacement with a nearly constant flow of refrigerant using incremental capacity

modulation. The refrigerant compression results from

the meshing action of precision groove-machined lobes

on the male and female rotors. The machine efficiency

is increased by direct injection of oil into the compression region to seal the spaces between the two rotors

and the rotor/casing annulus.

Absorption water chillers range in size between 100 and

1700 tons. These machines have a total of four heat

exchangers: condenser, generator (concentrator),

evaporator, and absorber. The chillers are usually powered by hot water or low-pressure steam. Water is the

refrigerant, and lithium bromide, a salt that strongly

attracts water, is the absorbent. Heat is transferred from

the chilled water to the cooling water through evaporation and condensation of the refrigerant water.

Most of the chillers used in industrial and commercial

HVAC applications are centrifugal chillers. About 80%

use CFC-11 refrigerant. The CFC-12 refrigerant, also

5s 5 ~~~~~~NUREGICR
Basic Chiller and HVAC Systems Information

i

Figure 2.1 Reciprocating Water Chiller Description (Permission to use this copyrighted material is granted by the

York International Corporation.)

Figure 2.2 Screw Water Chiller Description (Permission to use this copyrighted material is granted by Dunham-Bush,

Inc. The above graphic is from an obsolete Dunham-Bush, Inc. document.)

NUREGICR-60436 6
Basic Chiller and HVAC Systems Information

4-14 t'

Figure 23 Absorption Water Chiller Description (Permission to use this copyrighted material is granted by The ane Company.)

widely used in supermarket refrigeration and automobile air-conditioning, is used in about 15% of the

centrifugal chillers. The balance of the centrifugal chillers use R-500, CFC-114, and HCFC-22 refrigerant

(Niess 1992). The CFC refrigerants (CFC-11, CFC-12,

and CFC-114) will be phased out by the year 2000, to

meet current environmental control regulations established by the U.S. Congress Clean Air Act Amendments

of 1990. The regulations were instituted to reduce

degradation of the stratosphere ozone due to chlorine

(Calm 1992). These regulations will also apply to the

nuclear industry. Alternative refrigerants HCFC-123

will likely replace CFC-11, and HFC-134a will likely

replace CFC-12 (Clark 1991). The replacement for

CFC-114 will likely be HCFC-124, for at least the short

term.

2.2 Chillers in LWRS

General descriptions of chillers and the systems they

serve in light-water reactor (LWR) NPPs are provided

in Appendix A of this report. The descriptions are

based upon information found in final safety analysis

reports (FSARs) of US. NPPs. Chiller information was

not found in many of the FSARs that were reviewed. A

comprehensive survey of all the plants would be

required to get exact, up-to-date descriptions. However,

it is believed that this information is sufficient to be a

representative sample of typical systems that are served

by chillers in the United States.

Most of the plants listed in Appendix A had at least two

essential chillers that serve safety systems in the control

rooms and various equipment rooms. One chiller serves

as a backup. The essential chillers were identified with

an asterisk. The non-essential or non-safety chiller systems were also listed (without an asterisk), but this study

focused on the essential chillers.

Centrifugal chillers were the predominant type of chiller

used in LWRs. Most centrifugal chillers were hermetic

drive (electric drive motor is sealed inside the refrigerant boundary). Some were open drive (sealed outside

the refrigerant boundary and exposed to the chiller

room environment). Other types of chillers used included screw, rotary, and reciprocating chillers. These

7 7 ~~~~~~NUREG/CR-604
Basic Chiller and HVAC Systems Information

latter types tended to be used in older and smaller

plants. One plant used a hot water absorption chiller in

a containment cooling system The NPP chillers that

were found all used liquid cooling.

The essential chillers were sized in the 50- to 750-ton

refrigeration capacity range. Non-essential chillers were

in the 200- to 1500-ton range.

Based upon what was learned from the FSARs, it was

decided to focus on centrifugal hermetic chillers during

the Phase I aging study.

The review of the FSARs in Appendix A also provided

the following information:

* In some cases essential chillers and their chilled

water system are normally on standby for emergency

situations (e.g., LOCA, LOP, etc). During normal

operations, non-essential (non-safety) chillers serve

the control room and other safety-related rooms. In

many cases the essential chillers are used for both

normal operations and emergency situations to cool

just safety-related rooms. Sometimes the essential

chillers serve both safety and non-safety-related

rooms and they reduce their capacity in an emergency to serve just the safety-related rooms.

* Essential chiller condenser cooling water is supplied

by systems and arrangements such as the following:

- Service Water System (both normal and

emergency)

- Service Water System during normal operation

and Emergency Service Water System during

emergencies

- Component Cooling Water System (both

normal and emergency)

- Nuclear Closed Cooling System (normal) and

Emergency Closed Cooling System (emergency)

- Emergency Nuclear Service Cooling Water System during emergencies

- Essential Cooling Water System during

emergencies

- Plant Service Water System during normal

operations and Shutdown Service Water System

during emergencies.

The South 'Ibxas Plants have two chillers serving

each safety-related HVAC train (total of four). The

Perry 1 Plant has three chillers serving two safetyrelated trains. The third chiller is used as a standby

unit. All other plants surveyed have two chillers

capable of serving each of the two trains.

Based upon the results of the above FSAR reviews, it

was determined that generic plant designs do not exist.

Even multiple plant units at a site may have substantial

design differences. A study to determine which design

options work the most reliably might be justified. Plants

like River Bend (discussed later in this report) might be

helped by such a study.

In addition to the chiller systems that serve HVAC

applications (Appendix A), there are other chillers

which serve safety systems in non-HVAC applications.

Examples are chillers used to recover condensible offgas from the primary water system in every plant and to

make and maintain ice for containment safety ice condensers in eight of the Westinghouse LWRs. The

review and aging assessment of those chillers were

beyond the scope of this study.

In addition to chiller cooling of essential safety-related

rooms, some plants have the option to use water directly

from the Service Water System or other intermediate

system in lieu of chiller-cooled water. In one plant, service water is cool enough the year around to keep the

control room below 290C (85WF).

2.3 Essential Chiller HVAC Systems in

LWRs

The primary systems served by the essential chillers are

listed in Appendix A. However, during an emergency

the particular systems served varies from plant to plant.

The control room was served by an essential HVAC system in all of the plants listed. However, the other rooms

served by the essential HVAC system varied from plant

to plant.

NUREG/CR-60438 8
Basic Chiller and HVAC Systems Information

Examples of the rooms and equipment served in various

plants include the following

* Containment Pan Coolers

* Electrical Equipment Room

* Battery Room

* Auxiliary Building Electrical Switchgear Room

* ESF Switchgear Room

* Electrical Penetration Room

* ESF Equipment Room

* ECW Pump Rooms

* Auxiliary Feedwater Pump Rooms

* Reactor Makeup VWter and Boric Acid flansfer

Pump Cubicles

* Relay Room

* Cable Spreading Room

* Computer Room1

* Control Room HVAC Equipment Room

* Relay Room

* Remote Shutdown Room

* CCW, Charging, Safety Injection, and Residual

Heat Removal Pump Room fan/coil coolers

* Essential Equipment Rooms

* Standby Gas Iteatment System Compartment

and Area

* Spent Fuel Pool HX and Pump Rooms

* AuIliary Building ESF Equipment, Switchgear, and

Electrical Equipment Protection Room

* Safety-Related Panel Room

* Emergency Motor Control Center.

1

1n some plants the Computer Room is not considered safety-related.

9 9 ~~~~~~NUREG/CR-6
3 Regulatory, Code, and Standards Requirements for Essential Chillers

The regulatory, code, and standards requirements for

essential chillers are outlined below.

Nuclear Regulatory Requirements

The following nuclear codes and standards apply to

essential chillers and the chilled water system they serve:

1. Title 10 of the Code of Federal Regulations,

Part 50, Domestic Licensing of Production and

Utilization Facilities, Appendix A, General Design

Criteria for Nuclear Power Plants (1OCFR50,

Appendix A). The following General Design Criteria apply:

Criterion 2 - Design Bases for Protection Against

Natural Phenomena

Criterion 4 - Environmental and Dynamic Effects

Design Bases

Criterion 5 - Sharing of Structures, Systems, and

Components

Criterion 19 - Control Room

Criterion 44 - Cooling Water

Criterion 45 - Inspection of Cooling Water

Criterion 46 - Testing of Cooling Water.

2. Codes and Standards (1OCFR50.55a)

3. Standard Review Plan (SRP) (NUREG-0800)

SRP 6.2.2 - Containment Heat Removal

SRP 6.4 - Control Room Habitability Systems

SRP 9.4.1 - Control Room Area Ventilation

System

SRP 9.4.2 - Spent Fuel Pool Area Ventilation

System (few plants)

SRP 9.4.3 - Auxiliary and Radwaste Building

Ventilation Systems (some plants)

SRP 9.4.5 - Engineered Safety Feature Area

Ventilation System (many plants).

4. A Review of Regulatory Requirements Governing

Control Room Habitability (NUREG/CR-3786)

5. Nuclear Regulatory Commission Regulatory Guides

(RG)

RG 1.26 - Quality Group Classifications and Standards for Water, Steam, and RadioactiveWaste-Containing Components of

Nuclear Power Plants

RG 1.29 - Seismic Design Classification

RG 1.32 - Criteria for Safety-Related Electric

Power Systems for Nuclear Power Plants

RG 1AO - Design, Tasting, and Maintenance Criteria for Normal Ventilation Exhaust System Air Filtration and Adsorption Units

RG 1.52 - Design, Testing, and Maintenance

Criteria for Post Accident EngineeredSafety-Feature Cleanup System Air

Filtration and Adsorption Units of LUghtWater-Cooled Nuclear Power Plants

RG 1.68 - Initial best Programs for Water-Cooled

Nuclear Power Plants

RG 1.78 - Assumptions for Evaluating the

Habitability of a Nuclear Power Plant

Control Room During a Postulated

Hazardous Chemical Release

11 11 ~~~~~~NIJREG/C
Regulatory, Code, and Standards Requirements

RG 1.82 - Water Sources for Long-Term Recirculation Cooling Following a Loss-ofCoolant Accident

RG 1.95 - Protection of Nuclear Power Plant Control Room Operators Against an Accidental Chlorine Release.

Plant Technical Specifications

The LCO and surveillance requirements are usually contained in the Plant Technical Specification (PTS). The

technical specification applies to the two emergency

HVAC trains that serve the control rooms, and it

requires that at least one essential chiller be operable

for 7 days. If the second chiller becomes inoperable,

then there must be a Hot Shutdown within 12 hours and

a Cold Shutdown within the next 24 hours.

The PTSs are plant specific, and the above description is

an example only. Other sections of the PTS apply to

ESF pump rooms and equipment rooms. The few PTSs

reviewed for the main control room did not provide criteria about temperature or humidity limitations or surveillance requirements. Temperature requirements are

generally contained in the surveillance portion of the

PTS. The chillers are considered "attendant"

equipment

Nuclear Safety Classification

* oil cooler HX excluding oil piping and valves

* all external water piping and valves associated with

the oil cooler.

Seismic Requirements

The essential chillers are classified as Category I Seismic

Equipment, and they are designed to meet the applicable requirements. The chiller and all its accessories

(including those remotely located from the chiller) are

seismically qualified under the requirements of

IEEE-344 by a combination of analysis and testing. The

chillers are designed to withstand seismic loading in

accordance with the Uniform Building Code (UBC) for

the Earthquake Zone Level at the chiller's geographic

location.

Standards

The equipment complies with all state inspection rules

and laws. All nuclear vessels and components are

designed, constructed, inspected, and tested in accordance with Section III of the ASME Boiler & Pressure

Vessel Code, and the associated safety relief valves must

be registered with the National Board, and so stamped.

The chiller and its accessories, including the control

panel and its related components, are qualified in accordance with IEEE-323, 334, and 344.

The essential chillers are classified as Nuclear Safety

Class 3 equipment. The equipment component regions

listed below are designed and fabricated in accordance

with the ASME Boiler & Pressure Code, Section III,

Code Class 3. An ASME "N-Stamp" is required, as

specified in Paragraph NA 6254.1 of the ASME

Boiler & Pressure Code, on the following item

boundaries:

* evaporator water side

* evaporator refrigerant (shell side only)

* condenser water side

* condenser refrigerant (shell side only)

The materials, design, and construction of the chiller

and its accessories comply with, but are not limited to,

the following standards:

Anti-Friction Bearing Manufacturers Association

(AFBMA)

American National Standards Institute (ANSI) Standards ANSI N1&2, N45.2.2, N5.12, B9.1, B16.5, B31.1,

and B31.5

Air-Conditioning and Refrigeration Institute (ARI)

ARI 550 - Centrifugal Water-Chilling Packages

ARI 560 - Absorption Water-Chilling Packages

ARI 590 - Reciprocating Wter-Chilling Packages.

NUREG/CR-6043 12
Regulatory, Code, and Standards Requirements

American Society of Heating, Refrigerating, and AirConditioning Engineers (ASHRAE)

ASHRAE 15 - Safety Codes

ASHRAE 30 - Methods of lbsting Liquid Chilling

Packages.

American Society of Mechanical Engineers (ASME)

Boiler & Pressure Vessel Code

Section II - Materials Specifications

Section HI - Nuclear Power Components

Section IX - Welding and Brazing Qualifications.

American Society for Testing and Materials (ASTM)

American Welding Society (AWS)

Institute of Electrical and Electronics Engineers (IEEE)

279 -Criteria for Protection System for Nuclear

Power Generating Stations

308 - Criteria for Class YE Electric Systems for

Nuclear Power Generating Stations

323 - Standard for Qualifying Class IE Electric

Equipment for Nuclear Power Generating

Stations

334 - Standard for Type Tests of Continuous Duty

Class IE Motors for Nuclear Power

Generating Stations

344 - Guide for Seismic Qualification of Class IE

Electric Equipment for Nuclear Power

Generating Stations

383 - Standard for Type Tests of Class IE Electric

Cables, Field Splices, and Connections for

Nuclear Power Generating Stations

384 - Independence of Class IE Equipment and

Circuits

603 - IEEE Standard Criteria for Safety Systems for

Nuclear Power Generating Stations.

National Electric Code (NEC)

MG-1 Standard Publication for Motors and Generators

(NEMA)

National Fire Protection Association (NFPA) Standard

90-A

Occupational Safety and Health Administration

(OSHA) Standards Health Act

Steel Structures Painting Council (SSPC) Standards

SP-1, 3, 5,6, and 10

Underwriters Laboratory (UL) Incorporated Standard

UL-723

13 NUREG/CR-6043
4 Centrifugal Chiller Description

About 90% of the chillers found in the NPPs listed in

Appendix A were centrifugal chillers, and most of them

were driven by hermetic electric motors. Therefore, this

study has focused on the hermetic centrifugal chiller. A

discussion of how a typical hermetic centrifugal chiller

functions is provided in Appendix B. Alternative chiller

types are discussed briefly in Section 2, and they will be

reviewed in more detail in the Phase B study.

4.2 Materials of Construction

Based upon information that was gathered from manufacturers' literature, the typical materials used in the

construction of chillers are listed below.

* cooler (evaporator) - shell-and-tube

- shell - carbon steel plate

4.1 Chiller Design - waterboxes - carbon steel plate

A photograph of a recently marketed hermetic centrifugal chiller is shown in Figure 4.1. It is quite similar to

older chillers that are still in service at NPPs. The newer

chillers have advanced controls, and computer control is

now available. Many improvements (e g., solid state

controls, more efficient moisture/air purge units, etc.)

have been made in recent years; and the older chillers

can be upgraded because manufacturers make many of

the new features available in retrofit kits.

The reference chiller shown in Figure 4.1 is a Carrier

Corporation model. For comparison purposes, a York

International Corporation chiller is shown in Figure 4.2,

and a chiller manufactured by The Ttane Company is

pictured in Figure 43. Most of the NPP centrifugal chiller market is divided among these three manufacturers.

A cross-sectional view with the refrigerant flow path of

the reference chiller (Carrier Corporation) is illustrated

in Figure 4.4. The compressor cross-section view is

shown in Figure 45, and a view of a purge unit is shown

in Figure 4.6. lypical piping and wiring are illustrated

in Figure 4.7. Dimensions and layout requirements are

given in Figure 4.&

A liquid open centrifugal chiller is illustrated in Figure 4.9. This figure shows the dimensional envelope

changes compared to the liquid hermetic centrifugal

chiller shown in Figure 4.& The open centrifugal chiller

has a motor that is sealed external to the refrigerant system boundary and is exposed to the chiller room

environment.

- division plates -steel plate

- tubes -1.91-2.54 cm (0.75 - 1.00 in.) diameter

externally finned seamless copper or

copper 90/nickel 10 tubing

- tube sheets - carbon steel plate sometimes clad

with copper/nickel alloy sheet

- tube support sheets -steel plate.

* condenser -shell-and-tube

materials the same as for cooler (evaporator).

* compressor

- drive shaft - heat-treated alloy steel

- impeller - high-strength aluminum casting

- casing - close-grained cast iron

- labyrinth seals - non-ferrous metal

- bearings - aluminum alloy, bronze or babbitt

- pre-rotation vanes - manganese bronze

- shaft seal - carbon ring with elastomer O-ring.

15 15 ~~~~~~NUREG/CR-6043
Centrifugal Chiller Description

2hc=P

F :Rl

,t

I. 1 I

- v-c-- >.' -- .. ->

4.,-

Figure 4.1 Recent Model of Liquid Hermetic Centrifugal Chiller Manufactured by the Carrier Corporation - Reference Design (Permission to use this copyrighted material is granted by the Carrier Corporation.)

NUREG/CR-6043 16
Centrifugal Chiller Description

te J,

Figure 4.2 Recent Model of Liquid Hermetic Centrifugal Chiller Manufactured by the York International

Corporation (Permission to use this copyrighted material is granted by the York International

Corporation.)

* motor V-ring sets - molded teflon

components typical of squirrel cage induction-type

motors with windings that are sealed hermetically

with refrigerant resistant insulation.

* miscellaneous

- O-rings - fluorocarbon rubber, synthetic rubber,

nitrile butadiene, chloroprene

- gauges -steel case, bronze or brass bourdon

tube, monel or stainless steel movement,

chrome-plated steel or brass face ring, and glass

crystal

- oil cooler - steel shell, admiralty tubes, cast iron

bonnets, and steel tube sheets and cross baffles

- isolation pads - molded neoprene.

17 17 ~~~~~~NUREGICR-
Centrifugal Chiller Description

Figure 4.3 Recent Model of Liquid Hermetic Centrifugal Chiller Manufactured by The fTane Company (Permission

to use this copyrighted material is granted by The lIane Company.)

NUREG/CR-6043 18
Centrifugal Chiller Description

-8EARM AND SEAL MOO. - TRAN5wIW4 . -

e-RV~c)J

Figure 4A Reference Centrifugal Chiller Cross-Sectional View Showing Refrigerant Flow Path (Permission to use

this copyrighted material is granted by the Carrier Corporation.)

19 19 ~~~~~~NUREO/CR
Centrifugal Chiller Description

In-line impeller design - In-line impeller design, with diaphragm between stages, allows for more flexi- bility in compressor component selec- tion, which results in first cost savings on other machine components. Also provides higher head capabilities, pre- vents uneven loading and allows for routine, easy maintenance.

LEGEND

1 - Motor End Bearing

2 - Gear Journal Bearing

3 - Driving Gear Bearing To Housing

4 - Thrust Clearance on Gear

Bearing leach side)

5 - Pinion Gear Jouma Bearing

6 - Pinion Gear Besaring To Housing

7 - Thrust Bearing

8 - High-Speed Journal Bearing

9 - Front of Impeller to Volute Wall

10 - ktpaIler Eye to 10 of Inlet Ring

11 - Labyrinth Behind Impeller to Spacer Ring

12 - Labyrinth Behind Transmission

and Motor Shell

13 - End-Bell Bearing Labyrinth

19DH

Figure 4.5 Reference Centrifugal Chiller Compressor Cross-Section (Permission to use this copyrighted material is granted by the Carrier Corporation.)

Figure 4.6 Reference 

Carrier Corporation.)

Centrifugal Chiller Purge Unit (Permission to use this copyrighted material is granted by the

NUREGICR-6043 2

20
Centrifugal Chiller Description

LEGEND

I - Cooling Tower Fan Starter

2 - Condenser Water Pump Starter

3 - Cooler Water Pump Starter

4 - Pilot Relay

5 - Oil Pump Starter

6 - Fused Disconnect for Oil Heater and Thenmostat

7 - Fused Disconnect for Purge System

8 - Fused Disconnect

9 - Compressor Motor Terminal Box

10 - Compressor Motor Starter

11 - Cooler Water Pump

12 - Condenser Water-Pump

NOTES:

1 Wiring and piping shown are for general point-of-connection only

and are not intended to show details for a specific installation

Certified field wiring and dimensional diagrams for specific 19

Series machines are available on request.

2. All wiring must comply with applicable codes.

3. Refer to Carrier System Design Manual for details regarding piping

techniques.

4. A separate 115-volt fused power source for controls is required

unless compressor motor control is furnished with a transformer.

S. Provide a separate fused 11 5-volt power source for oil heater and

thermostat.

Figure 4.7 Reference Centrifugal Chiller Piping and Wiring Illustration (Permission to use this copyrighted material

is granted by the Carrier Corporation.)

21 21 ~~~~~~NUREG/CR-6
Centrifugal Chiller Description

Certified dimension drawings available on request

UNISHELL DIMENSIONS (tt-in.l (im) ____iNOZZLE SIZE (in0

SIZS Lngth Width Height D C Cooler Passes Condenser Passes

19DH A. B C | 1 t 2 |3 4 1)| 2 3 4

4244,46 14-3-3/4 1 4362. 3- 7-1/4 1099 6- 4-3/4 18 i94 61 4 - - 6 j -

505.15,73, 14-33/4 4362 3- 7-1/4 1099 I6-10-1/2 ;096M 3-3-1/8 -994 8; 6 6I - _ 4 _

61,63.65 14-3-3/4 4362 4- 5-1/2 1359 18- 0-1/2 2451 4-1-118 124S 8 6 6 a I 0 8

7172.73 14-3-3/4 4352 4-11-1/4 1t50S; 8- 9-1/2 263i0 4-9-1/8 1465 10 S a 6 10 6

76,77,78 14-3-3/4 4362 4-11-1/4 1505 . 8- 9-1/2 -25W 4--1/i -1451, Z 8 1 B a 12 1

'Length shown is chiller with nozzle on drive end only. For length with nozzles at both ends, add 6-1/4 in. {159 mmn).

SERVICE CLEARANCE FOR MOTORS (ft-in.)

DESIGN SIZE CLEARANCE

CENTER__ __

VOLTAGES Unishel Co r I Motor (in.) I MrI

42 thru 65 12thr 38j AA thru AE

208.230. AE

460.575 S0 thru 78 43 thru 6! CS thru CL 1

ol thru 7 72 thru 981 CO thru Co 3 1

2400 & 416C 161 thru 784S2 thru 68 I CA thru CL 2 / ,61

Service access should be provided per ANSI Standard B9.1, NFPA

70 (NEC) and local safety codes. Clear space adequate for :nspection, servicing and rigging of all major components of the chiller is

required. Selected component removal spaces. with no allowance

for access or rigging are shown in phantom.

MACHINE CONTACT SURFACES WIT

OPTIONAL SOLEPLATES

tm-u~~~~~~7

LINISHELL DIMENSIONS (ft-inJ Iinmi ___

SIZE' ' .____

19 ' : 0H D I E IF ,G

2- 3 0-4 0.1-1/.2 G-4 G- IT-1 425 7 1118102 102, 38 9 102 4

61 65__J 3-_1 4-5 0 30-3I 1-1/21t - 0-0-11/2 i3-10 12387 1b 7O *-1 2 -21{ 384 

71-78 14- 7.1 5-1 10-510-31 0-1 IV51 °-Z 7- 137 1549 127i 751 25 1271 50

'See machine informative plate.

Figure 4.8 Reference Centrifugal Chiller Dimensions and Layout Requirements (Permission to use this copyrighted

material is granted by the Carrier Corporation.)

NUREG/CR-6043 22
Centrifugal Chiller Description

. 4!,.,- o . i i.

Dimensions

TyipicaI ILatbon Aw.semble (Wkbx SpringMcunts

meflnde dhalin AWIW tO 1810 M31) k*n"M W1113 VW

fortvn r"

1. Setvlce SCOMs UWa be pra ddPK ANSI Stsndvd Mil. WPA 10

uWWc1 lond MWlg4e inja G ea~nw809all. folr I r"equired

Wmac atde~aZhih Wm2 ampremc Imust be lWW to be

mmu~ed. go #Ir5wce lot E11nok hbcbjded

WI62ILL ______ m~~M~IESIONS "o~z am gb1.)

IEmS LWMflhA WldM a New~ C __ aiPnmcfdmta

am444 144 am9 24L a1m 6f m 1 234 44 1086 

W.S1,2. 144 =24 214 IIIlS 6-11 M1OB 5 6 6 a

61. 6. 6 14-11 4846 44 1372 6.1 2464 a 3 1

r? ,?2 13 Wil1 4546 30 1524 s-ia 252 10 8 a G 1 it 17. 4-11 4848 5.0 1624 6-10 32= 12 __ ___1 0

Figure 4.9 Recent Model of Liquid Open Centrifugal Chiller Manufactured by the Carrier Corporation (for comparison with hermetic centrifugal chiller shown in Figure 4.8) (Permission to use this copyrighted material is

granted by the Carrier Corporation.)

23 23 ~~~~~~NUREG/CR
5 Operating Experience Database Evaluation

The results of evaluating chiller operating experience

from databases traditionally reviewed In NPAR studies

are provided in this section of the report. A small portion of the data in the tables included information on

alternative types to centrifugal chillers. The chiller

failures listed were significant enough to cause the

chiller to break down or shut down.

5.1 Licensee Event Reports Database

A Summary of the Chiller Licensee Event Reports

(LERs) is given in Appendix C. The summary covers

1981 through 1991. The LERs were compiled from the

Sequence Coding and Search Systems (SCSS), the

Nuclear Documentation System (NUDOCSIAD), and

Regulatory Information Distribution System (RIDS)

databases. Some of these items (11) are common to the

Nuclear Power Experience (NPE) database items discussed later. The results of the evaluation of chillerrelated failures are summarized in Table 5.1.

The largest number of failures (16) were electrical control component failures. Mechanical and electrical control component failures (28) represented about 44% of

the total failures. Electrical component-related failures

(28) occurred about twice as often as those failures

which were believed to be mechanical componentrelated (14). Of the listed failures there were at least S

non-aging-related failures. Three were failures due to

human error, and one each was due to a manufacturing

defect and use of a seal made of the wrong material.

The balance of the failures were due to a combination of

age- and/or non-age-related degradation. Insufficient

detail was available to determine the quantity of just the

age-related failures. Accelerated degradation may have

occurred due to a combination of design, manufacturing,

operating, and maintenance errors coupled with aging.

Many LERs that reported chiller trips were not included

because the events were caused by condenser cooling

water system failures (e.g., filter, strainer, pump, and

valve failures; plugging, air injection, undersize, etc., of

cooling water piping).

Of the listed failures that stopped the chiller, three

occurred outside the chiller boundary in the cooling

water supply system.

5.2 Nuclear Power Experience

Database

Information from the Nuclear Power Experience (NPE)

database search is provided in Appendix D of this

report. The information covers 1978 through 1990. The

chiller failures are summarized in Table 5.2.

The largest number of failures (9) again occurred with

electrical components. Mechanical and electrical control component failures (19) represented about 26% of

the total failures. Electrical component-related failures

(17) occurred about twice as often as those failures that

were believed to be mechanical component related (9).

The total number of failures listed in Table 5.2 was 73,

and all were partially or totally age-related.

There were at least 12 non-aging-related failures that

were not listed in Tible 5.2 because the event description was too general. Three were failures due to human

error, four were due to inadequate procedures, four

were due to inadequate cooling capacity (facility design),

and one was due to inadequate refrigeration load

(equipment and facility design).

5.3 In-Plant Reliability Data System

Database

A list of the chiller failures reported in the In-Plant

Reliability Data System (IPRDS) database is given in

Appendix E of this report. This information is from a

single nuclear power plant called Plant A. Ihe plant

essential chillers are identified as Chillers IA and 1B.

These data cover about the first 5.5 years of operation at

the plant.

25 25 ~~~~~~NUREG/C
Operating Experience Database Evaluation

Table 5.1. Summary of Chiller Failures in the LER Database

Number of

Failure Description Occurrences

Water Leak 1

HX Ibbe Fouling

HX Ibbe Plugging

Inadequate Cooling VWter

Service ater Component Failure

Lubrication Oil Leak

Refrigerant Leak

Refrigerant Plugging

Open Motor Bearing Failure

Mechanical Component Failure

Mechanical Control Component Failure

Electrical/Mechanical Control Component Failure

Electrical Control Component Failure

Electrical Component Failure

Motor Starter Failure

No Failure Cause Determined

Ibtal Failures

I

1

4

1

3

5

2

1

2

7

5

16

7

1

7

641

1 Some of the LERs listed multiple failures.

The failure data for the essential chillers are summarized in Table 5.3.

The category showing the most failures for Plant A was

for electrical control component failures (25). That was

also the largest failure category for the LER data in

Table 5.1. The next largest failure category was lubrication oil leaks (20), which with lubrication oil plugging

(7) made up about 25% of the total failures. The balance between mechanical component-type failures and

electrical component failures was about the same. Of

the failures shown in Table 5.3, the non-age-related failures totaled four. Three were due to human error and

one was due to manufacturing error. The rest of the

failures were a combination of aging and non-aging failures with insufficient detail available for further analysis. The failure ratio of about 10 failures per chiller per

year appears abnormally high. The number of service

hours each chiller had is unknown.

NUREG/CR-6043 26
Operating Experience Database Evaluation

Table 5.2. Summary of Chiller Failures in the NPE Database

Failure Description

MIter Leak

HX lbbe Fouling

HX TDbe Plugging

Inadequate Cooling Water

Service Water Component Failure

Inadequate Chilled Water Flow

Lubrication Oil Leak

Lubrication Oil Plugging

Lubrication Oil Excessive to Evaporator

Refrigerant Leak

Refrigerant Plugging

Open Motor Bearing Failure

Loose Parts Damage

Mechanical Component Failure

Mechanical Control Component Failure

Electrical/Mechanical Control Component Failure

Electrical Control Component Failure

Electrical Component Failure

Spurious Electrical Parameter

Thermostat out of Calibration

Switch or Wlve out of Adjustment

Motor Starter Failure

Low Environmental Temperature

No Failure Cause Determined

Total Failures

I Some of the occurrences listed multiple failures.

Number of

Occurrences

I

1

0

4

0

6

I

1

2

7

0

0

4

5

4

7

8

9

3

2

4

0

1

3

731 .

27 27 ~~~~~~NUREG/C
Operating Experience Database Evaluation

Table 5.3. Summary of Plant A Essential Chiller Failures

Number of Occurrences

Failure Description Chiller IA Chiller 1B Ibtal

Water Leak 1 4 5

HX Thbe Leak 0 1 1

HX Tube Fouling 4 0 4

HX TMbe Plugging 2 2 4

Service Mater System Failure 0 1 1

Chilled Water System Failure 1 0 1

Lubrication Oil Leak 12 8 20

Lubrication Oil Plugging 5 2 7

Refrigerant Leak 7 3 10

Mechanical Component Failure 1 2 3

Mechanical Control Component Failure 1 1 2

ElectricallMechanical Control Component Failure 6 4 10

Electrical Control Component Failure 14 11 25

Electrical Component Failure 6 7 13

No Failure Cause Determined 1 2 3

Total Failures 61 48 109

5.4 Nuclear Plant Reliability Data

System Database

The Oak Ridge National Laboratory search for chiller

events found no records in the Nuclear Plant Reliability

Data System (NPRDS) database.

NUJREG/CR-6043 28
6 Other Operating Experience

6.1 Pacific Northwest Laboratory

Experience

A total of seven liquid hermetic centrifugal chillers are

used to cool Pacific Northwest Laboratory (PNL)

HVAC facilities. Five of the chillers are cooled by river

water from an evaporation pond and two are cooled by

well water from cooling towers. The chillers range in

size from 185- to 450-ton capacity. Some of the chillers

serve laboratories where temperature control is critical.

To ensure the reliability of the chillers, PNL contracts

with experienced service companies that perform major

overhauls and condensor tube eddy current testing

activities. A maintenance program was established

about 12 years ago to improve maintenance practices

and reduce equipment neglect. The service company

selected was considered the best available. They have

used the same service personnel, so the history of the

chillers can be monitored, problems can be anticipated,

and service life improved. The PNL maintenance staff

has been trained to monitor the chillers daily and to

make all the minor repairs. Only the service company

does major repairs inside the refrigerant boundary.

Major overhauls are performed on the schedule recommended by the manufacturers. Because of good routine

maintenance practices and equipment monitoring, it

appears that the time between overhauls can be

increased. The condenser tubes are cleaned annually

and eddy current tested periodically by specialty service

companies. The condenser performance has improved

and little degradation of tubing has been observed.

Only one major failure in one machine has caused unscheduled downtime. The failure occurred in a 13- cm

(0.5-inch) steel pipe that broke due to vibration fatigue.

The root cause was a lack of adequate pipe support.

During overhauls the main tasks are to inspect the components and replace or repair them if needed. The only

major repair required for a PNL chiller was to rebuild

the labyrinth seal and impeller tips where some

unexpected wear occurred. The seals, gaskets, filters,

etc., are routinely replaced during overhauls. The entire

refrigerant system is scrupulously cleaned to ensure all

dirt, moisture, etc., are removed before the system is resealed. Overhauls are recommended at either 3- or 10-

year intervals by the major centrifugal chiller manufacturers. Some of the machines have been upgraded with

more modern purging units to remove moisture, noncondensable gases, etc, from the refrigerant system.

The equipment temperatures, pressures, and other indicated operating parameters are monitored daily. Samples of the lubrication oil are routinely analyzed. Using

the same well-trained maintenance and service company

staff has been an asset in achieving an excellent performance record for the chillers. Conscientious management

and supervision of chiller maintenance have also

contributed to the performance.

6.2 Westinghouse Hanford Company

Experience

The 337 Building has two 250-ton liquid hermetic

centrifugal chillers that are cooled by treated river water

from a cooling tower. The condenser cooling water has

not caused problems. The chilled water system, which

uses an ethylene glycol/water mixture, has also been

problem-free.

The main problems have been with electrical and

mechanical control components damaged by vibration

and overheating of components in the motor control

center cabinet Major maintenance has been difficult in

the past because plant forces are used. Human errors

have been made, which caused subsequent failures.

Recently, increased staff training has reduced problems

and failures.

The cooling tower capacity for the chillers is undersized.

This is a continuing difficult situation for the management of chiller control. There are times when compressor surging is prevalent

The Fast Flux Test Facility (FFTrF) reactor has eight

400-ton chillers that serve a variety of service functions.

The chillers are hermetic centrifugal type. Both the

29 29 ~~~~~~NUREG/C
Other Operating Experience

chilled water and cooling water systems are closed, and

they use glycol/water. There has been virtually no corrosion of the HX tubes or tube fouling. The original water

came from on-site wells.

There have been no major failures except one, which

was due to human error when one of the chillers was

new. A main bearing near failure was discovered during

an overhauL The time between overhauls was reduced

from 17,000 operating hours to 8000 hours, and no

major problems have occurred since then. The overhauls are performed by a regional service company, and

they have done an excellent job. FFIF management is

satisfied knowing full-time overhaul experts are taking

care of their equipment, which results in more reliable

operations. The FFTF maintenance personnel are well

trained and have good procedures that they follow for

routine and minor maintenance work.

Most component failures result from vibration. Many of

the failures are considered a nuisance. Indicator lamp

bulb and terminal and wire connector damage are examples of vibration-induced failures that do not necessarily

cause a chiller to shut down. FFTF maintenance estimates that about a third of the failures are electrical and

the balance are mechanical. Repeated vibration damage

to items like timers, cam switches, and relays could be

reduced if the control cabinets were updated to the

state-of-the-art.

Most of the vibration occurs because the chillers are

often operating at partial or low loads. Vibration problems become more severe when operating below 25%

capacity. Even though the equipment is rated for 10%

capacity, operation at this level becomes intolerable due

to changing conditions. Surging becomes prevalent at

the lower capacities. Ideally, FFTF would like to run

the chillers continuously at full capacity, because they

run smoother and do not have as many component

failures.

6.3 Regional Service Company

Experience

An expert consultant, 'ibm Camp of Landis & Gyr Inc.,

provided insights into failure and failure causes. He has

spent about 25 years trouble-shooting, overhauling, and

doing major repairs on centrifugal chillers while

working for service companies. He has serviced nonnuclear-related commercial chillers throughout the

Pacific Northwest Since he began servicing the PNL

chillers, they have improved and had outstanding

reliability. He helped train PNL staff to care for the

chillers.

Based upon his experience, he made the estimates and

observations listed below.

The general causes for chillers to completely fail are as

follows:

Failure Cause % Failures Comments

Design 1 Poor use of design

performance history

Manufacturing 3 Poor replacement

parts, packaging,

drawings

Installation 11 Lack of coordination

and instruction

Component 5 Friction, heat, nonAging Failures serviceable

component

Lack of 60 Poor O&M manageMonitoring and ment and apathy

Maintenance

Human Error 15 Carelessness and

(O&M) uncleanliness

Other 5 Misapplication

The greatest cause of failure is lack of monitoring and

inadequate routine maintenance. Monitoring and

maintenance steps that will significantly help reduce the

number of failures are as follows:

* Control the water quality supplied to the condenser

and evaporator.

* Routinely analyze lubrication oil to ensure correct

chemistry.

NUREG/CR-6043 30
Other Operating Experience -'4A+' r ~ -,

* Routinely analyze refrigerant to ensure correct

chemistry/need based upon results of lubrication oil

analysis.

* Perform eddy current, non-destructive testing

(NDT) on the tubes to monitor corrosion, etc.

* Periodically examine tubes; clean if necessary on a

schedule.

* Periodically perform vibration analysis using same

equipment

* Heat-scan the electrical components with infrared

temperature-sensing instruments.

* flow switches

* gaskets and O-rings (external leaks).

The components which less commonly fail, primarily

due to inadequate lubrication, chemical attack, maintenance, and age, are the following:

* bearings

* tubes

* guidevane

* oil relief valve

* Visually inspect and record gauge readings on a

daily basis.

* Record daily readings on trending charts. Analyze

the trend and take immediate corrective action if

the trend becomes adverse.

* Perform all routine maintenance and service per

manufacturer's instructions.

* oil pump

* seals

* expansion device

* float valves

* agitator

* Annually service and test components to determine/

ensure reliability. Field strip motor control and

starter contacts, change oil and filters, service purge/

dehydrator unit, change drier, run operation and

safety control tests, inspect HX tubes for fouling

and corrosion, etc.

* Periodically (3 to 10 years) overhaul and inspect all

wearing parts (using an interval based on the shortest life of the materials) within the chiller (typically

the O-rings, gaskets, and carbon seals).

* In all cases, cleanliness and care are most important.

* minimum head control

* purge unit

* motor control center

* motor.

The following stressors and aging mechanisms are

encountered by chillers:

* vibration (normal and excessive due to unbalance,

misalignment, and low loads)

The components that most commonly fail, primarily due

to age-related degradation, are

* pressure switches

* temperature switches

* relays

* excessive heat

* excessive pressure

* moisture

* dirt and contamination

* non-condensable gases (air, etc.)

31 31 ~~~~~~NUREG/C
Other Operating Experience

* corrosion

* tube freeze-up

* mineral contamination

* biological attack and growth

* flow erosion

* external environment (temperature, humidity,

fumes, etc), especially at damaged flanges, joints,

and electrical control and wiring

* friction and wear

* thermal cycling

* misalignment

* start-up torque

* frequent starting/stopping.

6.4 Cooperating Utility Experience

Direct contact was made with one NPP to tour the plant

and discuss chiller performance. A copy of the maintenance request data system was received for two nonessential chillers. The essential chillers are used only for

emergency situations as back-up to service water. The

only major problem incurred by the essential chillers

was that one chiller had its tubes freeze up due to

human error.

The plant is relatively new and only about 4 years of

operating experience were available.

The summary of work requests for the non-essential

chillers is presented in Appendix F of this report. Most

of the activity was related to start-up and upgrade work.

The following items were most notable:

* Thirteen tubes in the condenser and evaporator of

Chiller 1A had to be replaced. The tube holes in the

tube sheets had to be repaired. Crevice corrosion

normally caused by excess moisture and subsequent

vibration failure is suspected.

* Both units had the same manufacturing defect. The

lubrication oil pump solenoid valves were installed

backwards. The manufacturer determined that all

22 of the units for that model had the same problem. Both valves had to be replaced ultimately.

Earlier oil jet pump problems were probably related

to the valve being 180 degrees out of phase.

• A new mist eliminator had to be installed in Chiller

1A, which was probably related to excess moisture

in the refrigerant

6.5 Experience from Literature Reviews

Examples of age-related failures/causes that occur in

chillers were compiled from a literature review. Surprisingly, the discussion of aging and failures in the

literature was sparse for such a large industry. There

apparently is no database available for the HVAC or

nuclear industries to document and compile failure/

cause data. The list of major types of failures/causes is

outlined below.

Major Age-Related Failures/Causes

Excessive moisture in the refrigerant can cause many

problems in the chiller (Traver 1976; ASHRAE 1990).

When the amount of moisture exceeds the refrigerant

saturation level (only a few ounces in 1000 pounds of

refrigerant), the free water reacts with the refrigerant to

form hydrochloric and hydrofluoric acid. The acid

attacks crevices between the tubes and tube sheet Combined with vibration of the tubes, especially from boiling

refrigerant in the evaporator, the tubes widen the

annulus and ultimately fail, allowing water entry to shut

down the chiller and expose the entire system to water.

Other degradation that occurs as a result of the acid

attack includes the following.

* Acid contamination of the lubrication oil causes

attack of the bearing surfaces.

NUREO/CR-6043 332
Other Operating Experience

* The compressor inlet guide vane assembly can

corrode and bind.

* Motor failure can result from insulation breakdown

in hermetic units.

* The purge float valve can get stuck due to bearing

and pivot corrosion.

* The condenser and economizer float valves can

similarly fail.

* Shell scaling can cause clogging between tube fins,

between tubes, and in the mist eliminators. Subsequently, the scale hardens to restrict heat transfer

and flow of the refrigerant

* Copper chloride deposits on upper tubes are caused

by the wettingfunwetting process. These deposits

reduce heat transfer and have hygroscopic properties that make removal of water difficult

Ibbe fouling and corrosion can cause eventual chiller

shutdown due to reduced heat transfer or tube failure

(Banta 1974; Leitner 1980, Blake 1977; Alger 1977;

Starner 1976).

Ikbe clogging can occur if the condenser water is not

filtered, treated, and controlled at the cooling tower or

source (Barber 1983).

Non-condensable gases, such as air, get in the machine

and raise the condenser pressure. This, in turn, raises

the compressor's load and requires more power (Barber

1983). In addition, air can accumulate at the top of the

condenser and combine with the refrigerant to drastically reduce heat transfer (Webb 1986; ASHRAE 1989).

Vibration can ultimately cause seals, gaskets, pipe

joints, and fittings to fail and allow leakage of the

refrigerant. Moisture and air can also enter the previously sealed system by the same route (Esslinger 1988;

ASHRAE 1991).

The complete American Nuclear Society (ANS) 7kansactions Summary (Christie and McDougald 1992) of a

paper presented in June 1992, is included in Appendix G of this report. The plant reliability analysis

indicated that safety-related chillers fail three times as

often as non-safety-related chillers at the River Bend

nuclear power plant. The authors felt that the difference in reliability is due to the more stringent control

requirements imposed on the safety-related chillers.

The information needs to be examined more closely.

NRC Notice 85-89 was addressed primarily at the potential loss of solid-state instrumentation following failure

of control room cooling. The incident resulted in

numerous spurious alarms. Previously the same plant

had experienced similar behavior and numerous component failures and degradation due to high temperatures in control cabinets. The licensee had previously

reported that their chillers develop oil level problems

when loaded at less than full capacity. The heat load

calculated during plant design was too large compared

to the actual heat load resulting in oversized chillers.

The question "When does the final chiller failure

occur?" is not an easy one to answer because there are

many variables to consider. An extensive survey of

building owners and managers was conducted (Akalin

1978). The results indicate that centrifugal chillers

usually have a life of 20 to 30 years with a mean value of

23 years. The ASHRAE Handbook estimates the service life of centrifugal chillers at 23 years, but practical

use for 30 to 40 years has been realized when the equipment is properly maintained (Calm 1992). The PNL

consultant indicated that the major components of a

chiller will last well beyond 40 years if they are properly

cared for and maintained. Chillers up to 60 years old

are in continuous use today. Most chillers fail and are

replaced due to a lack of maintenance and monitoring.

Other causes for replacement of chillers include obsolescence due to

* change of heat load (usually growth)

* energy efficiency improvements

* incompatibility with new refrigerants (result of new

regulations)

- efficiency loss

- design of components

- aggressive nature of new refrigerants.

33 NUREG/CR-6043
Other Operating Experience

Centrifugal chillers have motors that are not designed to

be turned on and off frequently. Rapid cycling will lead

to motor and starter failure. The only safe way to limit

demand for a centrifugal chiller is by modulating the

compressor's pre-rotation vanes, which control the

capacity of the chiller. When the modulation is done, it

is critical that it be done gradually. If not, surging of the

compressor can occur, resulting in serious damage

(Gorzelnik 1977). Prolonged operation in a surging

mode is likely to damage the entire chiller, as well as the

compressor. Surging loads and unloads the motor about

every 2 seconds so that the motor current varies markedly (Ball 1987). Surging deteriorates performance and

heavily stresses the thrust bearings. Surging is most

likely to occur at the lower end of the chiller capacity

range. Chiller manufacturers claim that their units can

unload down to 10% of design loading, but one must

remember that low load operation is conditional upon

having lower condenser temperatures (Harmon 1991).

NUREG/CR-6043 334
7 Operating Experience Summary and Discussion

Review of the databases and literature in Sections 5 and

6 indicated general information on chiller failures

experienced during plant operations. Details were

limited and difficult to analyze from strictly an aging

standpoint Also, not all of the chiller-related LERs,

LCOs, and chiller failures have been found and included

in the results of this study. For example, consider the

numerous failures that occurred in the single Plant A.

Most of those failures caused an essential chiller to trip.

But few, if any, of the Plant A failures are contained in

the LER or NPE databases. Considerably more time

than a Phase I study would be required to get comprehensive failure data for each plant and consequently all

of the plants. More specific information from additional

plants will be sought for detailed aging analyses in the

Phase II portion of the study.

The information shown In Figure 7.1 summarizes the

quantities and failure areas from the LER and NPE

databases. Duplicate failures were removed for this

summary. Only failures that caused the chiller to shut

down were included. About 11% of the failures were

partially caused by flow rate variations in the cooling

and chilled water systems and partially by the chiller

condition (e g., chiller fouling, load and capacity limitations, entrance strainers, etc.). Condenserlevaporator

failures were only about 3% because most of the age

degradation occurs gradually, maintenance access is

usually easier, and it is handled during scheduled downtime. The refrigerant/lubrication oil system-related failures accounted for about 15% of the failures. About

17% of the failures were mechanical and mechanical

control related. Electrical/mechanical control components caused about 9% of the failures. Electrical and

electrical control components made up about 30% of

the failures. Misadjustment and miscalibration resulted

in approximately 8% of the failures, and the 7% balance

Fallure Area Fallure Quantity

0 6 10 15 30 25

Cooling Water System (6.2%)

Chilled Water System (4.a%)

CondenseuEtvaporator (32%)

Refrigerant (10.%)_

Lubrication Off (4.6%)

Mechanical (8.7%)

Mechanical Control (7.9%)

Electrical/Mechanical Control (8.7%)

Eiectrlcal Control (17.%)_

Electrical (12=%)=

CallbrationfAd~ustment (7.2%)

No Cause Given (7.1%)

Figure 7.1 Summary of Chiller Failures (LER and NPE Databases)

35 35 ~~~~~~NUREG/CR-6043
Operating Experience Summary and Discussion

of failures was unknown. Nearly half of the failures

were related to control components.

Using the same failure databases, an attempt was made

to determine the degree to which failures were agerelated. The aging versus nonaging failures are illustrated in Figure 7.2. About 81% of the failures were at

least partially related to aging (time-related degradation). More detailed information would be needed to

segregate the failures which were primarily or solely agerelated. About 12% of the failures were primarily due

to design, manufacturing, installation, procedure, and

human errors. The 7% balance of failures was unknown

or unassignable.

All of the failures discussed above caused chiller trips

and most of the failures caused LCO situations because

one or both essential chillers were inoperable. Both

chillers were inoperable 25 times and resulted in implementation of shutdown procedures. The LCOs were invoked for control rooms, ESF equipment rooms, and

containment. At least five times the reactor power

81.2% Aging Related

(at least partially)

was reduced, and at least two plants had to be shut

down. The exact number of LCOs, power reductions,

and plant shutdowns that resulted from failed chillers is

not known because of the limited information available

to review. As demonstrated in Appendix P, some of the

utilities are concerned about the LCO situation due to

the unreliability and complexity of essential chiller

systems.

The essential control room HVAC systems have increased complexity due to more interfacing systems than

just the chillers. Numerous LCOs occur due to monitoring automatic actuation systems; e g., radiation monitors, combustible gas detectors, chlorine detectors, loss

of power, filter monitors, etc. There are many instances

in which the control room HVAC system was erroneously switched to the emergency mode, and spurious

detector faults were a major cause. Also, some control

room LCOs are caused by failures in the chilled water

system other than chillers (pumps, valves, piping, expansion tank, etc.).

6.% Unknown

12.3% Nonaging Related

FIgure 7.2 Aging Versus Nonaging Related Chiller Failures

NUREG/CR-6043 36
Operating Experience Summary and Discussion

One step that might help to increase the LCO time

limits associated with chiller failures would be to use a

chill/ice storage system with a self-contained chiller that

would provide 12 to 24 hours of extra buffer time before

entering an LCO. The stored ice would provide a passive system for backup cooling. Numerous designs are

available to provide such storage and additional backup

chiller capability. The equipment could be located outside the control building. The back-up chiller could use

air cooling rather than water cooling. The overall

design, complexity, reliability, and practicality of such an

additional system would have to be carefully reviewed

for each plant. These systems have been employed primarily to reduce peak refrigeration power consumption

in commercial buildings.

The review information indicated that preventing serious degradation of equipment in the control rooms and

ESF rooms due to excessive ambient room temperatures

is a concern. One plant had a maximum limit of 250C

(770F) for the control room temperature. Another

plant had a limit up to 490C (1200F7). There is concern

about high temperatures inside electronic cabinets,

which can cause erroneous indications, alarms, etc., that

can hinder control of the plant. Temperatures inside

cabinets are much higher than the ambient room temperature. A cursory attempt to find data on the aging

degradation of electronic components for various levels

of temperatures, humidities, and vibration was not successful. Further research in this area is recommended,

but will not be pursued through this program because

that research is outside the scope of the chiller aging

study.

The higher room ambient temperatures also cause discomfort for the personnel operating the reactor. In

general, the comfort range is between 25% and 65%

relative humidity and 22 to 26°C (72 to 79 0

F) temperature. An operator's tracking skills, vigilance, and

sustained attention become very sensitive with time

when the temperature exceeds 300C (86WF). Operators

should not be exposed to temperatures above 350C

(950F) for a period of more than 1 hour. Very little

other information was found about human factors temperature and humidity criteria for control room operators. It appears that more research should be performed

to determine the effects of high temperatures upon personneL Research in this area is also beyond the scope of

the chiller study.

37 37 ~~~~~~NUREG/CR
8 Conclusions

It is apparent from this study that essential chillers,

which are important to cool the control room and other

safety-related equipment rooms, experience aging

degradation. Chillers are integral equipment currently

being addressed in regulatory issues of concern, which

include Generic Safety Issue 143 and Generic Letter 89-

13. The cooling is needed to prevent degradation and

failure of safety-related equipment, to protect safety

personnel, and to prevent or mitigate events and accidents. Control of temperature and humidity in these

rooms is very important

The chillers used in the nuclear power plants are essentially the same as the ones used in other commercial and

industrial applications. The chillers are a relatively

complex piece of equipment because of all the thermal

and flow balances that need to be maintained. The

essential safety-related chillers have more stringent

standards and codes to meet. The basic equipment must

meet seismic requirements which require some minor

modifications to the components, structure, support

base, and anchoring. The essential chillers have interfacing systems, often with complex interlocking controls.

The analysis of chiller interfacing systems cannot be

made generically because the systems vary from plantto-plant Due to regulations, chillers need to be closely

monitored and carefully operated and maintained. The

essential chillers need to be afforded special care so they

can be reliable and fulfill their safety role.

The review of operating experience indicated that chillers experience aging degradation and failures. The primary aging factors to be concerned about with chillers

include vibration, excessive temperatures and pressures,

thermal cycling, chemical attack, and poor quality cooling water. Aging is accelerated by moisture, noncondensable gases (e g., air), and other contamination

within the refrigerant containment system. Excessive

start/stop cycling and under-loading of chillers can promote aging. Aging is also accelerated by corrosion and

fouling of the condenser and evaporator tubes. The

principal cause of chiller failures is lack of monitoring.

It is important to record and trend on a daily basis the

operating temperatures and pressure, and routinely

analyze the lubricant oil and refrigerant chemistry.

Human errors and omission of scheduled maintenance

also contribute to the failures. Mailures due to design

and manufacturing discrepancies usually occur during

the original start-up, shakedown, or first year of operation for a particular new chiller model.

In the NPP data that was reviewed, the largest number

of failures was related to electrical control component

failures. Both electrical and mechanical control component failures represented almost half of the total failures. The lubrication oil system also had a relatively

high failure rate. Most of the failures were at least

partially age-related. Non-aging-related failures were a

smaller number and were primarily the result of human

error. Lack of monitoring is suspected to be the greatest

contributor to both age- and non-age-related failures.

The data available for evaluation was insufficient in

detail to perform failure root cause analyses.

To minimize and eliminate most of the failures, the

operators of chillers need to carefully follow stringent

procedures and monitor equipment. Equipment performance must be recorded and trended on each shift or

on a daily basis. The routine maintenance staff must be

well-trained and careful. Major overhauls and maintenance that require entering the refrigerant containment

region must be performed by careful, well-trained, and

experienced technicians. It is preferable to use technicians who routinely overhaul chillers. A small amount

of contamination or a damaged or misaligned part can

cause major problems during operation of a chiller. It is

crucial at all times to keep equipment internals very

clean and prevent the leakage of water, air, and other

contaminants into the sealed refrigerant containment

system.

Periodic operation for a few hours on a weekly or

monthly basis is necessary to remove moisture and noncondensable gases that gradually build up inside the

chiller. A few hours of operation will help to provide

the stable operation needed to evaluate the operating

parameter performance, especially if the chiller is

required to operate as an emergency standby unit. If

multiple chillers are available, alternate operation of the

chillers and balance the hours of use. Operate the

39 NLREG/CR-6043
Conclusions

chiller as close to 100% capacity as practical to minimize aging. Usually chillers are replaced due to lack of

good monitoring and maintenance.

In-depth analysis of aging and non-aging failures will

require close cooperation among the chiller industry,

utilities, regulatory agencies, and researchers during the

Phase II study. During the Phase I study it was difficult

to obtain the detailed information that was needed to

perform in-depth analyses of chiller aging. More

detailed information will be sought during Phase II to

address the root cause of failures; provide detailed

information on current maintenance inspection, surveillance, and monitoring methods; and define current

maintenance practices.

NUREG/CR-6043 40
9 Recommendations

The Phase I study determined that chillers play an

important role in NPP safety. Chillers have been contributors to a number of serious safety events where

plants had to reduce power or shut down. Some plant

operators are concerned about a higher number of failures in the essential chillers than non-essential chillers.

The operating experience reviewed so far indicates

that chillers degrade and fail as a result of aging and

other factors. It is recommended that a full-scale NPAR

Phase II aging study be performed. Preliminary recommendations for improved operation, maintenance, and

monitoring of chillers have been included in Sections 63

and 8 of this report.

41 41 ~~~~~~NUREG/C
10 References

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ASHR4AEJournal, October 1978, pp. 40-44.

Alger, J. 1977. 'Treat Your Cooling Water to Cut

Energy Consumption and Increase Production Output."

Plastics Design & Processing, April 1977, pp. 59-63.

ASHRAE. 1989. ASHRAEFundamentals Handbook.

American Society of Heating, Refrigerating, and Air

Conditioning Engineers, Inc., Atlanta, Georgia.

ASHRAE. 1990. ASHRAE Refrigeration Handbook.

American Society of Heating, Refrigerating, and Air

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ASHRAE. 1991. ASHRAEApplications Handbook.

American Society of Heating, Refrigerating, and Air

Conditioning Engineers, Inc., Atlanta, Georgia.

Ball, J. 1987. 'A Micrbprocessor Chiller Controller.'

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April 1987, pp. 36-43.

Banta, V E. 1974. 'Continuous Cleaning Ups Chiller

Performance.' Power, June 1974, pp. 76-78.

Barber, J. 1983. 'How to Improve Efficiency in

Centrifugal Chillers.' Ene)V UserNews, March 7,1983,

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Blake, R. T 1977. 'Correct Water featment Can Save

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pp. 49-52.

Calm, J. M. 1992. 'Alternative Refrigerants:

Challenges, Opportunities.' HeatinglPiping/Air

Conditioning, May 1992, Penton Publication, pp. 38-48.

Clark, E. M. 1991. 'Retrofitting Existing Chillers with

Alternative Refrigerants.' ASHRAE Journal, April

1991, pp. 3841.

Christie, R., and W. McDougald. 1992. 'Impact of

Safety Requirements on Component Availability.' In

Proceedings from American Nuclear Society 1992 Meeting,

June 7-12, 1992, Boston, Massachusetts.

Esslinger, S. 1988. The lkue Cost of Refrigerant

Leaks ASHRAEJournal, November 1988, pp. 27-29.

Gorzelnik, E. . 1977. 'Load Controller Modulates

Chillers.' Electrical World, November 1, 1977, pp. 50-51.

Harmon, J. 1 1991. 'Centrifugal Chillers and Glycol

Ice Thermal Storage Units.' ASHRAEJournal,

December 1991, pp. 25-31.

Leitner, 0. 1980. 'Controlling Chiller Akbe Fouling.'

ASHRAE Journal, February 1980, pp. 40 43.

Levy, L S., J. Wreathall, G. DeMoss, A. Wolford,

E. P. Collins, and D. B. Jarrell. 1988. Priorization of

7TRGALEX- Recommended Componenis for Furwher

AgingResearch. NUREG/CR-5248 (PNL-6701),

prepared for the U.S. Nuclear Regulatory Commission

by Pacific Northwest Laboratory, Richland, Washington.

Niess, R. C 1992. Selection of LarWe-Capachy Water

Chilers in the 1990s. EPRI TR-100537s, prepared for

the Electric Power Research Institute by Gilbert &

Associates, Gloucestor Point, Virginia.

Starner, K E. 1976. 'Effect of Fouling Factors on Heat

Exchanger Design.' ASHRAE Journal, May 1976,

pp. 3941.

Stebbins, W L. 1991. 'Implementing an Effective

Utility Testing Process: A Keystone for Successful

Energy Management." In Proceedings of IEEEAnnual

Textila Fiber, and Film Industry Technical Conference,

Greenville, South Carolina, pp. 1-11.

43 NUREG/CR-6043
References

Traver, D. G. 1976. "Saddle Damage of Cooler IUbes."

ASHRAEJouznal, March 1976, pp. 46-52.

Webb, R. L 1986. "Gas in Refrigerant Condensers."

ASHRAE Journal, May 1986, p. 52.

U.S. Nuclear Regulatory Commission (USNRC). 1991.

NuclearPlantAgingResearch (NPAR) Program Plan.

NUREG-1144, Rev. 2, Washington, D.C

NUREGICR-6043 44
Appendix A

LWR Plant Chiller Systems Description (FSAR Data)
Appendix A

Appendix A

LWR Plant Chiller Systems Description (FSAR Data)

This appendix contains a summnay of chiller information found by reviewing final safety analysis reports

(FSARs) of US. NPPs. Information on plant chillers

was not found in many of the FSARs. Some of

the FSARs reviewed at PNL were not completely up-todate. However, it is believed that this information is sufficient to be a representative sample of typical NPP

systems served by chillers in the United States.

NUREG/CR-6043
z

ti

0

I

Plant

Arkansas 1 & 2

Beaver Valley 1 & 2

Qua

Pi

Browns Ferry 1,2,& 3

Clinton 1

2*

2*

3

2*

2*

2

5

3

LWR Plant Chiller Systems Description (FSAR Data)

,ntity/ Refrigeration

ant Type Cap. ('Ibns) EA

Not Found Not Found

Not Found Not Found

Centrifugal 650

Not Found 171

Centrifugal 200

Centrifugal 500

Centrifugal 1100

Centrifugal 148

Comanche Peak 1 .

(+2 when operational)

Fermi 2

Grand Gulf 1

Hope Creek

Limerick 1 & 2

Millstone 3

2* ea unit

6

3

Centrifugal Hermetic

Centrifugal Herm.(4),

Open (2)

Centrifugal Hermetic

2*

2*

3

2*

2

4

2*

2

2*

3

Centrifugal

Reciprocating

Centrifugal

Centrifugal

Centrifugal

Centrifugal

Centrifugal

Centrifugal

Not Found

Not Found

101

1980 Tital

for Second and

Third System

100

80

850

536

200

1285

250

1500

250

938

System Served

Not Found

Control Building

Chilled Water System

Control Building

Control Room System

Drywell System

Plant System

Service Building

System

Safety System

Second System

Third System

Control Center

System

Control Room

Plant System

Control Area

Reactor Auxiliaries

Turbine Building

Control Structure

System

Drywell System

Control Building

Room

Chilled Water System
LWR Plant Chiller Systems Description (FSAR Data) (contd)

_ , .. . w , ~~~Kerigraio ..

Plant

Nine Mile Point 2

Palo Verde 1,2,& 3

Perry I

Shearon Harris

South 7bxas 1 & 2

7kojan

Vogtle 1 & 2

WPPSS 2

Vaterford 3

Watts Bar I

Quantity/

Plant

2*

3

2*

4

3*

2

3

2*

2

4*

4

2*

2

2*

3

2*

2

3(2*)

2!

Type

Centrifugal Hermetic

Hot Water Absorption

Centrifugal Hermetic

Centrifugal Hermetic

Centrifugal Hermetic

Centrifugal Hermetic

Centrifugal Hermetic

Centrifugal Open

Centrifugal Open

Centrifugal

Centrifugal

Open Reciprocating

Open Helical Rotary

Centrifugal

Centrifugal

Centrifugal Hermetic

Centrifugal Hermetic

Centrifugal Hermetic

Not Found

Refrigeration

Cap. (Tbns) EA

145

400

235

213(1), 800(3)

607

800

200

752

904/847

150(2),300(2)

550

57

230

300

1500

85

150

310

400

System Served

Control Building

System

Ventilation System

Essential Systems

Normal System

Control Complex

'Trbine Building

Containment Vessel

Essential Services

Non-Essential

Services

Reactor Control

Building

Mechanical Aux

Building

Control Building

System

Reactor Aux. System

Essential System

Non-Essential System

Control Room

Emergency

Rad Waste Building

Essential

Building Coolant

13 System

* Indicates essential chillers.
Appendix B

Hermetic Centrifugal Chiller Functional Description
Appendsx B

Appendix B

Hermetic Centrifugal Chiller Functional Description

This appendix describes how components in a hermetic

centrifugal chiller function. It illustrates the refrigeration, motor cooling, and lubrication cycles that occur in

an operating chiller and how the mechanical components interact. The description is from pages 17 to 19 of

the Carrier Corporation's Operations and Maintenance

Instruction manual for their model 19FA chiller

(Form 19FA-ISO - courtesy of the Carrier

Corporation).

BA1 B.1 ~~~~~NUREG/C
Appendix B

GENERAL DATA

Machine Nameplate is located on the cooler

support foot at the suction end of the machine.

Always give machine model, serial number.and

name of owner in corresponding with Carrier.

Compressor Nameplate is mounted on the comn

pressor support foot on the suction end of the

compressor adjacent to the oil pump.

System Components Include cooler, condenser,

economizer, motor-compressor and machine control center. A storage tank for the full refrigerant

charge forms the support for compressor and

control center. Most machines are also supplied

with a machine-mounted pumpout unit.

COOLER - A heat exchanger vessel in which

flashing refrigerant picks up heat from, and therefore chills, the water (or brine) flowing thru its

tubes.

CONDENSER - A heat exchantger vcsscl in which

heat is removed from compressed refrigerant and is

carried out of the system

ECONOMIZER - A vessel at intermediate pressure

between cooler and condenser which returns "flash

gas" to the compressor for greater cycle efficiency.

MOTOR-COMPRESSOR maintains the necessary

pressure differences in the system and moves the

heat-carrying refrigerant from cooler to condenser.

CONTROL CENTER controls machine start and

stop, regulates machine capacity as required, contains machine safety devices, indicates cooler,

condenser and oil pump pressures and records

machine operating hours.

STORAGE TANK supports machine components

and provides a ready storage for the refrigerant

charge during machine service periods and at

extended shutdown.

PUMPOUT UNIT is used for refrigerant transfer,

machine evacuation and machine pressrizing.

NUREO/CR-6043B2 B.2
Appendix B

Fig. 12- 19FA Refri

19FA REFRIGERATION CYCLE

With the exception of the thermal economizer,

which Is used on water chilling duty only, the basic

refrigeration cycle described below is applicable to

either water or brine chilling.

The machine compressor continuously draws

large quantities of refrigerant vapor from the

cooler, at a rate set by the amount of guide vane

opening. This compressor suction reduces the

prcssurc within thc cooler and causes the remaining

refrigerant to boil vigorously at low temperature

(typically 30 to 35 F).

The energy required for boiling is obtained as

heat from the water (or brine) flowing thru the

cooler tubes. With heat removed, the chilled water

(brine) can then be used for air conditioning or for

process liquid cooling.

After removing heat from the water, the refrigcrant vapor passes thru the compressor r.rst stage,

is compressed and moves Into the compressor

second stage. Here It is mixed with flasheconomizer gas and is further compressed.

Compression raises the refrigerant temperature

above that of thc water flowing thru the condenser

tubes. When the warm (typically 100 to 105 F)

refrigerant Is discharged Into the condenser, the

relatively cool condensing water removes some of

the heat and the vapor condenses Into a liquid. In

water chilling machines, further removal of heat

occurs In the thermal economizer at the bottom of

the condenser. Here the liquefied refrigerant Is

igeration Cycle

subcooled by contact with the coolest (entering

water) condenser tubes.

nTe liquid refrigerant drains into the flash

economizer where a valve system maintains pressure intermediate between the condenser and the

cooler pressure. At this lower pressure, part of the

liquid refrigerant flashes to gas, thus cooling the

remaining liquid. The "flash gas" is returned

directly to the compressor second stage. Here it is

mixed with ps already compressed by the first

stage impcller. Since the economizer gas has to pass

thru only half the compression cycle to reach

condenser pressure, there is a savings in power,

hence the term 'economizer.'

The cooled liquid refrigerant in the economizer

is metered thru the lowside foat chamber to the

cooler. Because cooler pressure is lower than the

economizer pressure, some of the liquid flashes and

coots the remainder to cooler temperature. The

cycle is now complete.

19FA MOTOR COOLING CYCLE

Refrigerant liquid from a sump at the bottom

of the condenser (Fig. 12) is subcooled by passage

thru a line immersed in the refrigerant within the

cooler. The liquid then enters the compressor

motor end where It Qmrays on and cools the

compressor rotor and stator. It then collects in the

base of the motor casing and drains back into the

cooler. Refrigerant gas Is vented from the compressor motor casing and returns to the upper

B.3 B.3 ~~~~~NUREG/CR
Appendix B

portion Of the cooler thru a check valve. Differential pressure between condenser and cooler

maintains the refrigerant flow.

19FA LUBRICATION CYCIE

General - The compressor oil pump and oil

reservoir ar located In the compressor base, Ol Is

pumped thru an oil &oler an a filter to rnmove

heat and any foreign particles Part of the oil flow

Is directed to the compressor motor-end bearings

and seal. The remaining flow lubricates the compressor transmission thrust and journal bearings and scaL Oil is then returned to the reservoir to

complete the cycle (FIg 13).

Lubrication Details - Oil Is charged into reservoir

(1) thiu a hand valve (2) which also functions as an

oi drain. If there is refrigerant In machine, a pump

is required for charging. Sight gasses (5) on

reservoir waU permit observation of oil leveL

The motor-driven oil pump (6) discharges oil to

an oil cooler (7) at a rate and pressure controlled

by an oil regulator (8). The differential pressure

(supply versus return) is registered on a gage at the

machine control center.

Water flow thru the oil cooler Is manually

adjusted by a plug cock (9) to maintain the oil at

an operating temperature, at the reservoir, of

approximately 145 F. During machine shutdown.

the oil temperature Is also maintained at 140 to

ISO F by an immersion heater (10) so that

absorption of refrigerant by the oil Is minimized.

OIL LTEM TEMPERATURE SIUFT O5atLXT

$4 SZ1 CUPf -I it80 6kom thR MRR

After it leavs the oil cooler, the oil is filtered

(I I) and a portion flows to the motor-end bearing

(12) and seal. The remainder lubricates the compressor transmission (14) and the thrust and

journal bearings (IS) Thrust bearing temperature

Is indicated on a goa (16) mounted on the bearing

inspection cover. Oil from each circuit returns by gravity to the reservoir.

A demister ( 17) and (18), by centrifugal action,

draws refrigerant Vas from the transmission area to

the motor shelL The resulting pressure difference

prevents oil in the transmission cavity from leaking

into the motor shelL

Several safety devices monitor the lubrication

system:

In the event of power failure, a small oil

reservoir(19) supplicssufrtcient oil reserve to ensure

continued lubrication until all compressor parts

have come to a complete stop.

Solid state sensors (20) monitor motor-winding

and bearing temperatures and shut off machine if

temperature rises above a selected point.

Low-oil cutout (Fig. 14) shuts down machine

or prevents start if oil pressure Is not adequate.

A program timer in the machine control center

ensures proper lubrication at start-up and at

coastdown by energizing the oil pump for approximately 30 seconds before the compressor starts,

and keeping the pump running for almost one

minute after the compressor motor is de-energized.

EsERVO9X MOTO*-NDo FROM

NUREG/CR-6043B. BA4
,- l I i : z 11-4? i t

Appendix C

LWR Plant LER Review Summary
Appendix C

Appendix C

LWR Plant LER Review Summary

This appendix contains a summary of LERs that were compiled using the Sequence Coding and Search Systems

(SCSS), NUDOCS/AD database, and NRC staff sources. Some of these items are redundant with the NPE database.

C.1 Ci ~~~~~~NUREGIC
Appendix C

Chiller LER Review Summary

ivent

LER Plant

81-040 Arkansas 2

83-006 Arkansas 2

90-008 Byron 1

86-003 Catawba 1

86-005 Catawba 1

90430 Catawba I

91-05 Catawba 1

89441 Clinton 1

91-018 Comanche 1

87412 Hatch 2

86-029 Hope Creek 1

88-015 Hope Creek 1

89407 Hope Creek 1

83-056 McGuire 1

87401 McGuire 1

87-023 McGuire 1

86-015 McGuire 2

81-025 North Anna 1

83432 North Anna I

Event

Date Descrip

1146-81 Low freon charge.

02-02-83 High condenser pressure.

Ilion Cause

06-27-90 Chiller malfunction.

01-16-86 Chiller failed to start.

01-17-86 Chiller tripped on low chilled water flow and

later on high motor bearing temperature.

10-23-90 Control room ventilation system chillers

inoperative.

02-12-91 Low refrigerant temperature cut out switch set

point reached on frain A. 1rai B also tripped.

11-22-89 Low refrigerant pressure.

05-28-91 Safety chiller inoperable.

09-16-87 Equipment degradation

06-11-86 Control area chiller tripped on low refrigerant

pressure.

05-26-88 Excess oil in one chiller and the other chiller

tripped.

04-06-89 Both Aand B control room emergency

filtration units became inoperable.

07-14-83 Low refrigerant temperature trip.

01-07-87 Loss of refrigerant.

10-01-87 Loss of essential control power in Train A and

control room air handling unit suction damper

not open causing Train B to be inoperable.

0849-86 Train A tripped.

04-28-81 Improperly operating steam chiller.

05-21-83 Chiller malfunctioned.

Leakingvalve fitting.

Power supply for the pressure indicating controller

was defective.

Evaporator tube leak.

Chilled water compressor motor temperature

sensing module had failed.

Misapplied pump seals and unreliable expansion

tank alarm.

Failed hydrometer and out-of-calibration oil

pressure switch.

M-Ain A, refrigerant leak in compressor power

terminal box. 'ain B, condenserwater auto

control valve failed to open.

Refrigerant leakage, no location

reported.

A faulty oil sump lever switch.

Water chiller fouled by calcium

deposits.

Ball foat valve that controls refrigerant flow

malfunction.

Lack of understanding of seasonal oil migration in

first chiller and defective high side float ball in

economizer of second chiller.

Seal failure in one chiller and failed damper in the

other chiller.

Loose flange on suction side of

compressor.

A leaking threaded fitting on oil cooler.

Blown fuse in rhain A and failure of an actuator

micro switch for Train B.

Blown fuse and chiller start mechanical timer not

operating.

Lack of adequate cooling water.

No cause given.

NUREGICR-6043C. C2
Appendix C

Chiller LER Review Summaqy (cont.)

Event

LER Plant Date Description Cause

83456

85063

81-003

North Anna 2

Palo Verde 1

Ocone 2

07-11-83

09-12-85

03-0281

Chiller tripped on low compressor oil pressure

Los of refrigerant.

High temperature on reactor building chiller

unit.

88-019 Perry 1

88-040 Perry 1

91.008 Perry 1

05-15-88 Chillers inoperable.

10-07-88 Electrical fault in chiller control power.

03-05-91 Low refrigerant temperature

90-002

82459

82.039

81.040

82-173

83412

83-043

Riverbend I

San Onofre 2

San Onofre 2

San Onofre 2

San Onofre2

San Onofre 2

San Onofre3

024-2-90

04407-82

07-16-82

07-19-82

12-28-82

01-08-83

0748-83

Chiller shutdown.

Found during maintenance.

Emergency chiller refrigerant compressor failed

to start

High bearing temperature.

Chiller failed to start.

Chiller failed to start.

Chiller inoperable

No cause given.

No cause given.

Bearing high temperature caused by grease

starvation.

Mechanical failure of a compressor guide vane

linkage connector and an intermittent fault In the

motor starter circuit of the supply fan.

Degradation of wire insulation results in grounding

of control power supply.

Malfunctioning solenoid valve on the thermal purge

unit.

Indeterminate.

Faulty flow control switch.

Defective impellerdisplacement switch.

Faulty high temperature bearing alarm module.

Loose wire on the low lube oil pressure switch.

Faulty program timer.

Either a malfunction of chiller control circuitry or

mechanical malfunction in the power supply

breaker.

Intermittent failure of a trip relay.

Low lube oil.

Mispositioned root Isolation valve on the chiller.

Failure of pump shaft bearing.

Contact otidation and low contact pressure on an

awiiary rel.

Problem associated with starting circuitry of chiller.

Cogging of chillers due to unfiltered river water

flowing through tubes.

90-001 San Onofre 3 01-30-90 High motor/bearing temperature trip

indication.

87-007 Shearon Harris 1 02-10-87 Chiller tripped and was restarted several times.

90-017 Shearon Harris 1 06-20-90 Chiller could not be started.

88039 South IBMas 1 06-16-88 Failure of chiller lube pump oil seal.

89-023 South Mxas 1 12-16-89 Essential chiller could not be

secured.

83-019 Summer 1 03-17-83 Chiller failure.

86-024 Surry 1 08-13-86 Loss of one control room and relay room AC.

chiller.

C3 ca ~~~~~NUREG/CR-
Appendix C

Chiller LER Review Summary (cont)

LER Plant

86-27 SurryI

87403 Surry 1

87-005 Surly 1

87-006 Sury 1

88-007 Surry

88-039 Surzy 1

89-23 Surry 1

91418 Surly I

88-011 Sury 2

87-22 Susquehanna 1

84-014 Susquehazna 2

87-049 ogtle 1

89-004 Vhterford 3

90-008 Waterford 3

event

Date Description

10-09-86 Weo of three control room A.C. chillers

inoperable.

02-13-87 Chiller inoperable because of lack of service

water and another because compressor relief

valve lifted, discharging refigerant.

02-21-87 The chillers tripped due to insufficient service

water now.

03-10-87 Service water pump for B control relay room

chiller tripped.

02-24-88 Insufficient service water flow.

10-11-88 ControVrelay room chiller tripped on high

condenser discharge pressure.

06-13-89 Main controlemergency switch gear chiller

inoperable due to degraded performance.

04-25-91 Contruemergency switch gear mom chillers

inoperable.

04-23-88 Controlhlay room chiller removed from

service to perform minor maintenance.

06-19-87 Chiller experiencing spurious trips.

07-23-84 Problems in the B Reactor Building.

07-22-87 Chiller failure.

03-89 Low pressure valve ball float developed crack

allowing float to fill with freon, sink, and dose

valvet

07-30-90 Compressor motor high temperature.

Cause

One out for maintenance, the other inoperable

because of failed relay.

Cogged suction strainer and eracessive throttling of

compressor service water outlet valve.

Marine growth inside of rotating strainer.

Suspect thermal overload device at the motor

control center activated, tripping the pump.

Bad pressure control valve

A small refrigerant leak in combination with

insufficient servicewater flow.

Impropervalve line-up.

Failed oil pressure/overload reset

relay.

Refrigerant filter/dryer was becoming clogged.

Problems with cycle timer and low refrigerant trip

switch.

No cause given.

Temperature switch failure on chiller.

Intergranular stress corresion cracking.

No cause given.

NUREG/CR-6043 CC-4
Appendix D

NPE Database on Chillers
Appendx D

Appendix D

NPE Database on Chillers

This appendix contains a summary of the NPE database that applies to chillers in NPPs. The information is from Oak

Ridge National Laboratory.

DI1 D.1 ~~~~~~NUREG/C
I

0O

Itj

co

0

OA

N' Nuclear Power Experience (NPE) Database on Chillers 0

plar n

Atkansas One 2

Arkansas One 2

Arkansas One 2

Arkana One 2

Arkanus One 2

Arkansas One 2

Arkansas One 2

Arkansas One 2

Arkansas One 2

Byron I

Calvart Cliffs I

Calveet Cliffs I

Calvert Cliffs 1

Calvest Cliffs I

Calvert Cliffs I

Calvert Cliffs I

Calvert Cliffs 1

Dab

7n79

sns

12/80

2/81

617181

66r/1

71481

11/81

1183

7/83

6M0

1W77

5n78

Bn79

7/16180

7/29/80

smao

sn1so080

Power Level

50%

50%

16%

90%

Hot Standby

Hot Standby

Hot Standby

20%

100%

100%

98%

100%

Shutdown

Shutdown

95%

95%

95%

95%

Description

Chilr failed to statt.

Chber failed to start.

Chiller tailed to stat

Chiller trippd.

Containment temp. exoeed toch spc limit

Containment ltmp. exceeds tech sp UlniL

Containment temp. exceeds toch spc limit.

Chiller failed to star

Chiller cycling excessively.

Chiller tripping due to low iteon.

Containment Chiller B was out of seie for mao

rebuilding. Chiller A tripped on ground oveotucrent

due to wet motor windings. Containment tmp

exceeded 1201F and plant was shut down.t11

Chiller failed to stat.

Chiller 12 failed to ta sIght glas showed no oil.

Chiller tripped.

Both chillers tripped. Control room got to 94¶' 1

)

One chiller tripped.

One chiller tripped.

3 times Chiller tripped on high discharge pressure.

Cause

Casting plug lodged In compressor dIscharge Isolation

valve.

Crankcas oll leak.

Freon migration due to cold ambient temperate effects,

modifications needed.

Expansion valve leak

One chiler of service and backup has motor winding

temp. senoor fId

Pow transformer 1 .1ue.

Clogged oil filter.

Leaky fron valve fitting.

Leaking freon discge relict valve.

Leak found In chilled water line. other unknown.

Evaportor tube lak In Chiller A. Single tube was

plugged w/o falure cause, o reactor could resta.

Fauly trr control relay.

Due to low refrieration load. comprsor oll w

displaced to evaporatot.

Compressor motor winding falled.

High compre disge pressures, Inadequate chir

capa-y.

High compresor motor amperae.

High comptesor motor amperage.

Unloader valve adjusiment required.

-
Nuclear Power

Plant

Calvert Cifs 1

Calvet Cih I

Colve" CliM I

WMn cets I

W Calvert cims I

Calertclfs Catmube 1

Catewba I

Catawba I

Catawba 1

Catawba 1

Davis Besse

& Davis Boene

j9 Farly I

Experience (NPE) Database on Chillers

Date Power Level

9/11/80 9f% Both chillers failed h

Description

I statft't

9/80

elm

. 7M

7/I783

8M

4R9185

412/85

4112/8

1n16/8

1/17/M

7/79

B128/89

100%

95%

100%

100%

1D0%

98%

ftOO

100%

100%

100%

100%

Both essential chillers inoperable.t J

ilant computer failed twice due to high room temps

Chiller No. 12 compreseor tripped.

Chiller No. I1 condenser fan found damaged.

Chiller wouldn't star.

Chiller trip on low chilled water ine flow.

Chmer trip on low chilled wate lIne flow.

Chiller trip on low chilled wter ilne flow.

Chiller tripped twice, once for low chilled water flow

and once for high molor beea temp. along with

CR ventiation problem. LCO event was required.

Plant power was reduced.°

Both chillers had low ohilled water flow end were

Inoperable. Caused LCO event°)

ChMer falled to start.

Chiller would not stait during test

Chiller compressor trip.

Cause

Unloader valt adjusted on men unit and misc. repairs on

other unit Uniprlure valves were replaced by hotWgas

bypass and preeu regulating valves to eliminate 7/168

9/11 problems.

Feuly reset owltoh on one unit and operability check

Inadequate on other unit

Chillers have inadequate cooling capacity.

Set ecrews vibrated loose to drop shaft which damaged

fan drive belts.

Set ecrews vibrated loose to drop shaft to damage

structural support

High pressure switch out of ealibration.

Line compression tank almost empty.

Line compression tank almost empty.

Line compression tank almost empty. Problem wee

dembin water storage tank float device not workn.

Unreliable demin. water storage tank makeup source.

Level transmitter malfunction. Motor temp. sensing

module falned.

Chilled water pump leaked and low level computer alarm

and transmitter had faiures.

Failed thermitors In motor windings.

HP switch had tripped earlier In the month and had not

been ret. Compressor HP transfer set point was

raised.

Solenoid valve linkage on pump-down line out of

adjustmert.

-

918/83
04

Nuclear Power Experience (NPE) Database on Chillers

Plant D[e Power Level Descriptlon CAuSO

Faey I

Grand GUMl

Grnd Gul I

Hatch 2

Hatch 2

Hatch 2

p Hope Crek

12/3-31/83

621=83

702/83

6, 7 & WI7

4/80

5190

5/88

9/82

6/1484

10/17/85

7/3/66

1/7187

100% Chiller compreaw trip.

Shutdown Control too temp. eoceded 77F lilmit. Chiller B

deliciont in cooling.

Shutdown Chiller A shut down to repair 1reon shutlof valve.

Valve unloaded the oompresaor.

72 9% Chlllera seingi dry well tripped.

71.09% Chiller B tripped nd Chiller A failed to cool

adequaeloy.41)

71499% Chiller tripped.

100% Chiller A down for scheduled PM. Chiller B down

for repair. Control room temp. Increased. LCO

entered and pl- shutdown Inibalod.01

60% Chiller B tippd due to high boaing temp. Earlier

in month Chiller A trpped for same reason.

100% Chiller trip due to low ol, both verdilatlon rlains

inoperable. LCO Issued nd plant power reduocd.4t 0

100% Chlill tripped 3 times on low chilled water flow,

other unit down for PM.11 )

Refueling One chiller tripped on low oil level, second ohillr

would not sart due to low chilled water flow, tech

spec LCO applied. Control room temp. 19, 1m

100% Chiller B tripped on low tergernt te"mp. Earlier.

Chiller A faild to start LCO event intaed.

Control room. maxed out a 83FatW

Freon leak a HP valve.

Maunctioning condensor ooing water flow control

valve. Lrnc switch on valve needed adjudment

Valvo tailed due to normal wear. Three compressor Inlet

strainr wore blown hrough, damqging two compressor

Personnel trippkn ador swapping chillers.

Chiller B oil pump fallad and Chiller A guWe vane arm

failed.

SW flow throwing by operators causd high head

prsure In chiller.

Chiller A problem causd by seasonal oil migration due

to lower loadk. Chiller 8 problem caused by compresor

floa design deficiency (weld failure susceptibl). Design

was modified.

Excessive oii added due to procedural rror. Oil was

removed and procedure was modified.

Chiller underlobad, oil deposited In evaporator, due to

oversized chillers.

Cause of trip notl found.

Low oi level due to chiller being operated below 100%

capacit, a design problem to be solved by modifying

valve settings on hot ga bypass Low chilled water flow

problem required control circut modifications and

numerous other beam.

Chiller B tripped due to chilir thermostat being set too

ow. Chiller A had fron leak through the oil cooler

threaded fiting.

MoGulr I

MGuire I

MoGuire 1

McGuire I

McGuire 1
Nuclear Power Experience (NPE) Database on Chillers

Plant Date Power LeA Decpon Cause

Mo~ull' 162

ulme 18&2

7/814/8

8(24/8

Various

89%

Chi trip on low o, control room Mp. iseo leads to

printed c card failures which crate spurious

alarms and Instrument readings. Temps. 88.90P

outside cabinets.

Chiller tripped on low refrigerant tomp.

McGuire ¶82

North Anna I

7/14/86 Cold Shutdown Chiller tripped again on low refrigerant temp.

5s8 95% Containment temp. exceeds tech spes llmitL

0

North Anni I

North Anna I

North Anna I

North Anna I

Perry 1

River end I

River Bend I

U/7

8/1 8/78

4&5181

atel

619

11/85

2/0

3&4190

Hot Standby Containment temp. exceeds tech specs limit.

95% AbsorptIon chiller not functioning, caused

containment temp. Hmit to be exceeded p>1059).

Sackup chiller brought temp. back down.

100% Containment temp. exooods tech specs limI*

100% Containment tomp. excoeds tech specs limit.

100% Chiller A outet temp. and refrigerant pressure

readings were high.

5% Containment chillers tripped and temperature

inraosed In containment.

100% Four chillers were inoperable. LCO entered end

plant shutdown initiatedf t'

100% Chiller C tripped.

High temperatures in control cabinets cause cards to

create spurious indications.

Recently cleaned oondonsor tubes had high hoat

transfer, which caused low temp ,outout switch to trip.

Loose flange on oompreasor *uction elde caused

refrigerant leak. Also controller needed calibration. May

have also contributed to WI4N88 event.

Absorption chiller steam nozzles and etrainore clogged.

gasket leak.

Absorption chiller tubes fouled.

Incorrect valve Hne-up dumped an condensate from the

chiller condenser.

Absorption chiller operating Improperly and mechanical

chll t of sewvice.

Switch problem from absorption to mechanical chiller. s

Guldevane linkage had slipped on the shet to the

guldevanes. All S chillers needed modification to prevent

set sorew sippage.

Voltage transient caused trip and operator failed to

resore cooling water to containment ooeors in timely

manner.

Chler 1A failed to start due to inadequate chilled water

flow becmese of low building temp. and valve control

problem. Chiller ID breaker needed resetting due to

unknown Interlock and over-current trip. Flow bypass

and valve control procedure was needed.

The motor current limiter was oet too low.

I)

River Bend I
I

0

Nuclear Power Experience (NPE) Database on Chillers

-

0

*0~

Pk"

San Onodto 2

8an Onofr 2

8Gn Onroe 2

San Onoke 2

San Onoke 2

San Onoie. 2

San Onolt. 2

SGn Oriol 2&30

San Onalre 2&3

San Onrl. 2&3

San Onotre 2&3

San Oniole 2&3

San Onotte 283

Sequoyah1

Summer

Summer

Surly I

Strry 1

Dais

7/11/82

7/16/82

7/19/82

1AWe

Power Level

Hot Shutdown

HO Stadby

Hot Standby

50%

12(18182 COld ShUkdown

3JV/83

4/22/87

4-10183

4/29183

6/1/83

821183

100/183

5/84

i680

3/17183

3/2683

9/9/83

W88/

Col SD

Cold SD

Varuoua

s0 & 100%

100%

Shutdown

50%

Cold Shutdown

100%

Cold Shutdown

Dewlpleon

Both eseential chillers inoperalle.

Unit compresaor fewd to tA

Both esntial chillers Ioprable.

Both e Wni chillers inoperabb..W

Both essential chillers Inoperable.

Chiller A failed to start

Chiter stagled during testing.

SerIes of electrical problems to both chillers.

Chll start failure.

Chiler Inoperable.

Chiller failed to staL

Chiller tripped twie.

Jumper installation error caused chiller to start and

ten trip. As a result, two Iwertois were Inopetable

and LCO was InvokeLU)

Invrtlor loom temperature hlgh.

Train A chillet Inoperable.

Train B chiller Inoperable.

Two of 3 chillers Inoptable. One down for main

tenance and other had control panel catch on tire.

All essential chillers inoperable.

-

Cause

Trip telay cover Improperly Islld and faulty

temlperaw mtodule.

Defoie mpele displacsment swih

Faulty high temperature bearing alarm In one unit.

One unit o of service and otha uni Na faulty high

temp. motor windig FirD.

One uni out of service and other tripped on high bearing

temperawe.

Chilled waler flow control switch Inadvertently valved out

Valve closed on compression tank surge line.

Caused LCO problems due to lt inverters and loss of

air cooling for LOSP. TotS and Si events.

Supply breaker misalignment.

Control circuitry and Weaker problems.

Fuse failure.

Spurious alarms for low CCW flow.

Restat failed du to stuck micoawitch In program timer.

Chiller thmota out of calibration

Cam/nulcroxwlloh miaignment

Faulty isotation valve control switch.

Blown condenser zic plug caused motor starter

contractors to shot

Lack of service water cooling, inadequate CCW HX-f lilling

procedure.
Nuclear Power Experience (NPE) Database on Chillers

Plant Dote Power Level Desciption Cause

Su"y 1

Suny 2

Turkey Point 3&4

Turkey Point 3&4

81 f8

8181

7/26186

12/19186

Hot Shutdown All ewntll chillers ioperble.

100% Two of 3 chem Inoperable.

Lock of SW cooling due to inadequate chiller

stertingfttopping procedure.

SW stralne was co ed on one Unit

100%

100%

Potential Ion of 3 ompreeors and air handler In Transfer switch stuck duiag safeguard. test

CRVS. Loee of power at MCC's a concerm. Circuits

jumpered temporari.

:.a MCC transfer switch feiled. Concern for

subsequent failure of chiller compressors to be

operable.

Transfer switch cover plate was improperly designed.

(1)

(2)

Situations where el easential chillers ate inoperatbl. Often oauses LCO event. Sometim plant shutdown.

Comp" situation With two plants sh Common Power supple", etc.
Appendix E

IPRDS Database Maintenance Report Summary for Nuclear Power Plant A
Appendix E

Appendix E

IPRDS Database Maintenance Report Summary for Nuclear Power Plant A

This appendix contains a summary of chiller maintenance record data from a single NPP (Plant A). The information is

from the IPRDS database at the Oak Ridge National Laboratory. The plant and chiller identification are confidentiaL

1- El ~~~~~~NUREGICR-
Appendix E

Chiller Maintenance Records for Plant A, Chiller IA

Date Description of Problem

10/18/82 Gasket blown.

10/18/82 Need to install a press gauge on the high press top of FS.

10/082 Anti-recycle timer has loose internals; contacts sometimes makeup.

03)03/83 Chiller high discharge pressure safety switch shutting down chiller.

03/03/83 Condenser oil cooler tubes are getting plugged up, chiller can't make 100%.

08/12/83 Oil temperature sensing element should be located on oil line down stream of

oil pump.

08/28/83 Chiller condenser tubes plugged.

1130/83 Cannot read delta on lube oil filter. Replace oil filter.

03/27/84 Chillers been tripping lately, with safety switches light on and 2TR relay.

03t30/84 Cannot get chiller loaded, oil pump breaker keeps tripping off

05/11/84 Control building chiller tripped on oil pressure failure.

05/15184 Suspect that the heat exchangers are becoming fouled again.

05/29/84 Chiller when in 'auto' tripped on low oil pressure. Slide VLV went T

05/29/84 Chiller has oil leak on discharge pipe from oil pump.

06/14/84 Won't start Not enough oil pressure hot gas B/P doesn't open.

07/22/84 Chiller tripped on low oil press. The alarm would not reset.

08A01/84 Lube oil filter dP is 22#. Limit is 8-12.

10131/84 The 'A7 chiller trips with no associated alarms for indication of trip.

12A06/84 Several oil leaks including mechanical seal and oil drain plug.

02/23/85 Chilled water temperature too high.

03/16/85 While removing fire barrier from tray section IL-3A cable 1B-305A nicked.

03/16/85 Cable lB-305A given temperature fix on MAR 061346 due to being nicked and

then shorting out.

03/26/85 Leaking oil, appears to be leaking at compressor seal near coupling.

06/17/85 Condenser on this chiller needs to be cleaned.

06124/85 0A7 chiller safety switch will not allow starting of IV-CH-lA.

06/24/85 Hot gas B/P solenoid does not open.

06/24/85 1C0261B5 alarm; *A' chiller trouble in solenoid. There is no apparent problem.

NUREG/CR-6043E. E.2
Appendix E

Chiller Maintenance Records for Plant A, Chiller IA

Date Description of Problem

06/24/85 'A chiller will not start due to safety switch activation.

07/06/85 On a startup sequence the oil pump comes on but will not clear/reset low.

07121/85 A7 chiller shows characteristics of being very low on freon. Low suction

pressure.

07)21/85 Oil plus discharge pressure gauge missing.

08/08/85 "A chiller trips off on low temperature (oil sump) even when oil temperature

shows OK.

08i08/85 "A" chiller slide valve operation is sporadic

01/06/86 Plug and seal top panel openings of chiller starter cabinet.

04/23/86 Oil pumps do not develop a discharge pressure. Chiller tripped on low oil

pressure.

04/26/86 Oil leak of I drop/lO seconds from the southern most compressor load/unload

solenoid.

04/28/86 100%1o current limit setting is 180 amps while motor nameplate is 230A.

05/19/86 It tripped on low oil sump temperature when sump temperature was 1250F and

switch was set at 90. Switch and/or gauge needs checked.

06/01/86 Chiller fails to start due to low oil pressure; low oil leveL

08/03/86 Liquid line sight glass 12 full As per IP200 it should be full and clear.

08/14/86 Anti-recycle timer not set at 15 minutes per vendor manual.

10/20/86 Temperature load controller not holding chilled water temperature steady.

lbmperature keeps dropping for a given setting.

11/11/86 Condenser head gasket is leaking (east end).

11/13/86 Relays and relay block terminal boards need to be replaced due to sloppiness in

pin connection board. Switching relays and blocks: 1SR, 2SR, 3SR, and 4SR.

11122/86 Oil leak on connection on the southern most unloader assembly solenoid valve.

The leak is on upper connection between the solenoid operator and the valve

body.

11122/86 Oil leak on load solenoid valve.

12/886 Small freon leak on stem of load solenoid valve. This leak persisted after

installing solenoid valve repair kit.

12114/86 Oil and refrig leaking from suction flange of compressor and manual isolation

unloading valve at the compressor near suction flange (leak is very small).

E3 NUREG/CR-6043
Appendix E

Chiller Maintenance Records for Plant A, Chiller 1A

Date Description of Problem

04/03/87 Does not dump hot gas at low load (<20%).

04126)87 The 'low 0.7 temperature alarm light socket broke and shorted out. The chiller

will run without it, but we have no low temperative' indication.

0428/87 The WA' chiller has tripped three times today. No alarm conditions were

indicated by the time the second ASST got up there Readjust oil pickup valves,

adjust TCU for the water.

05101/87 A chiller waterbox gasket is blown out.

05/16/87 Has an excessive oil leak as evidenced by lowering oil pressures and increasing

leak-off bottle level. This bottle level is increasing.

06(22/87 Chiller is getting low on oil. Oil addition required unit to be shut down about

one hour.

07/20/87 Chiller condenser needs cleaning.

07(21/87 Check oil cooler tubes for cleanliness.

08/11/87 Mechanical seal of compressor still leaking.

08/18/87 Chiller tripping on oil press failure.

09/0 9/87 Insufficient cooling in condenser. Believe tubes need to be cleaned.

NUREG/CR-6043 EA4
Appendix E

Chiller Maintenance Records for Plant A Chiller 1B

Date Description of Problem

0216/81 Chiller was not operating correctly.

05)04/81 Low oil pressure. }

05/19/82 Chiller has low oil pressure after 2 days of running.

07120/82 Gasket rupture on well WTR/FSW piping between condensate and cond outlet

07/A4/82 Gasket leak on chiller condenser, west side of condenser between end beL

08/03/82 Control building chiller will not control load in auto. It always drifts.

10/18/82 Gasket ruptured.

10/18/82 Need to install a press gauge on the high press top of FS.

10/19/82 Copper line from sniffers to compressor suction line has crack and is leaking.

O27/83 Condenser and oil cooler tubes are getting plugged.

03/10/83 TLC load signal causing load solenoid to chatter.

03/15/83 Chiller circuit power on local panel keeps tripping; chiller must be C.

07/13/83 Cannot read delta on lube oil filter.

07/17/83 Oil sump has low oil level; no level is visible with chiller on.

08130/83 Chiller condenser tubes plugged.

11,08/83 Will not start

11/09/83 Timing for anti-cycle does not work.

04/03/84 Miming for anti-cycle does not work.

04/16/84 Motor termination box for 200 HP chiller motor has a hole burned in it.

05/17/84 Chiller tripped.

06/14/84 Control building chiller cycles continuously between loading and unloading.

07/09/84 Leaks oil from oil regulator that control slide valve.

12/17/84 Vertical run on oil pickup line has a crack in it.

04/30/85 Condenser refrigerant service valve leaks by seal.

05/07/85 Install temperature DP indicators across two-flow switches.

05/19/85 Three-way well water inlet valve to chiller condenser stuck closed.

05120/85 Gaskets on both ends of chiller condenser are bad. Gaskets blown.

05127/85 Oil leaks on unload solenoid throttle and load indicator housing.

E5 E.5 ~~~~~NUREG/C
Appendix E

Chiller Maintenance Records for Plant A, Chiller 1B

Date Description of Problem

05129185 Anti-recycle timer times out in 7 minutes.

06101/85 While performing PMAR on chiller, found contacts carboned over and badly

arched; needs replacement.

06103185 Load solenoid chatters at near temperature set point

06/23/85 "B" chiller unloaded and stopped for STP. When restarted, would not load.

06125185 'B" chiller loading solenoid valve is chattering due to chiller loading and

unloading.

06/25/85 Circuit power button trips off. No safety switch trips on chiller.

09124/85 Chiller will not load beyond 50% (loading solenoid is energized).

01106/86 Plug and seal top panel openings of chiller control panel.

08104/86 Anti-recycle timer times out in 4 minutes.

08127/86 The east end of chiller has a lagged pipe that connects the chiller, and the

compressor has an oil leak. Oil is leaking from under the lagging.

09/01/86 Uppermost oil pickup line has a cracked flare fitting.

09108/86 Oil pressure is low reading 33#'s instead of the normal 60#.

09126/86 Load control unit was found to be rapidly blinking the load and unload lights on

and off causing loading solenoid valves to chatter continuously.

10/05/86 Chiller cycles (loads) on and off. This MAR can be referenced to what was

worked on 10/1/86, and problem still existed after sign off.

11/13/86 Relays and relay block terminal boards need to be replaced due to sloppiness in

pin connection board. Switching relays and blocks 1SR, 2SR, 3SR, and 4SR.

02/13/87 Install new ejector valve and oil jet pump.

02121/87 Chiller tripped twice and was running with low suction press (45#) high oil

temperature. See attached readings, chiller will not run now. 'hips on low

suction. Leak needs repair.

06/23/87 'B" chiller needs to have freon added to it.

08124/87 Temperature load control current limiter does not allow motor to go to full load

amps, thereby reducing full load capacity of chiller. Resistor needs to be

adjusted.

NUREG/CR-6043 E.6

I
Appendix F

Chiller Work Request Summary for Nuclear Power Plant B
Appendix F

Appendix F

Chiller Work Request Summary for Nuclear Power Plant B

This appendix contains a summary of the Nuclear Power Plant B chiller maintenance, work-request database. The

information was provided by a cooperating utility from their maintenance database. These two chillers are non-safety,

and they are relatively new.

P.I. F.1 ~~~~~NUREG/CR
Appendix F

Work Request Summary for Plant B, Chiller IA

Date Work Request Description

01/0888 Verified S/D oil level, ran unit and monitored oil level for 4 hours. Oil less than

1/2 sight glass, no draining required.

011)8/88 Voided level normal per vendor operating procedures.

03/30/88 Removed test gauges from chiller, capped test gauges and sensing lines.

04/27/88 Drained evaporator and purged with N2.

1Z/04/90 Completed flushing unit.

12/05190 Removed chiller float assembly, placed on storage racks. Removed condenser

and evaporator water heads, cleaned inner surfaces. Fabed flush fixtures, covers,

blind flanges, etc for flushing cond/evap shell.

12/27/90 Cut pipe on elbow socket, tightened nipple into float chamber nozle, rewelded

socket.

01/17/91 Fabricated magnetic liquid level indicator, piping hanger and installed.

Performed hydro test on level indicator. Repainted new hanger, installed

insulation on level indicator piping.

02i01191 Repaired plug welds as required in Section M plan, appeared to be solid and

sound when finished.

01/21/91 Installed two 12 pt. screws.

02/27191 All electrical components on the chiller skid and in the control panel cleaned,

inspected, and tested. Various terminal UGS and electrical components were

replaced per MWR instructions. Startup of the chiller was per specifications.

06/10/91 Fabricated cover and gasket.

09t26/91 Replaced cover.

12103/91 Applied adequate heat and sufficient leverage to free shaft from bull gear.

Cleaned threads and shaft surface.

llf22191 Thirteen access holes were cut, plates were stamped and bagged, and tubes from

condenser and evaporator were removed. Cleaned purge unit. Cleaned inside

shell, wire brushed and sand blasted. Removed debris from shelL

01/29192 Cut service water supply piping to condenser, then cut off chilled water supply

piping to evaporator, reinstalled and hydrotested SW and CCH piping IAW

Section XI plan.

02/07192 Obtained spare jet pump solenoid from warehouse, removed solenoid and

installed it on this chiller, installed new terminal board and replaced flex

conduit.

03)04192 Performed calibration as required.

NUREG/CR-6043F2 F.2
Appendix F

Work Request Summary for Plant B, Chiller LA

Date Work Request Description

04f0Q/92 Painted chiller.

03104/92 Prepped, reinstalled and welded access cut-out plates back onto shell IAW

MWR and Section XI plan. Performed pneumatic testing on shell per test

requirements.

O3/04/92 Installed new evaporator tubes per MWR and Section XI plan number 2-0667

instructions, installed new mist eliminator and reinstalled expanded metal,

Installed and welded plugs in damaged tube sheet holes per change notice #1 of

Section XI plan.

06130192 Added oil.

F.3 F.3 ~~~~~~NUREG/C
Appendix F

Work Request Summary for Plant B, Chiller [B

Date Work Request Description

01/05/87 Void; no work required. Unit has held its charge since 11109/86 without any loss

of pressure.

O0122/87 Removed freon charge from A/B units, removed float chamber cover. Removed

wire tie down from float assembly, evacuated, purged with N2. Evacuated

second time, checked for leaks. Charged with 650# freon 11. Started and ran

both units. Set hotgas bypass linkage. ¶Ibrqued bolts to 80#.

04/02/87 Removed and replaced oil pump from vendor, changed pump discharge tube

fitting. Run pump, checked rotation. Checked for leaks, found none.

Rebuilding of pump will be done.

01/11/88 Started unit, monitored oil level for 4 hours, drew 12 gallon of oil to keep level

< 1/2 upper sight glass.

04/25/88 Lack of run capability caused by a bad valve lineup.

07,06/88 Replaced oil filter.

04/27/88 Simulated all alarm sensor actuations, all operate fine.

06/29/88 Void; no work required.

07/0788 Void; no work required.

08/17/88 Added about 2 1/2 gallons of oil.

05/25190 Added approximately 625 lb freon R-11.

09/19/91 Installed liquid level indicator on expansion piping at chiller.

11/14/91 Replaced refrigerant filter, leak checked, repaired leaks, serviced with R-11.

12113/91 Removed jet pump solenoid valve and rotated 1800 and reinstalled. Charged

system with oil and R-11, test ran machine.

1216191 Changed oil filter and replaced with new oil. Solenoid valve coil needed

replacement, also removed bottom of jet pump for inspection and reassembly,

continued trouble-shooting steps.

01/16192 Installed test equipment for degraded voltage test. Performed preventive

maintenance. Disconnected test equipment for degraded voltage test.

NUREG/CR-6043 F.4

',
;: s . .e

Appendix G

ANS Paper Comparing Safety and Non-Safety Chillers

:.~
Appendix G

Appendix G

ANS Paper Comparing Safety and Non-Safety Chillers

This appendix contains a transactions summary of a

paper that compares safety- and non-safety-related

chiller failure experience at the River Bend NPP. Te

paper was presented at the American Nuclear Society

(ANS) 1992 Annual Meeting in Boston, Massachusetts,

June 7-12,1992. This summary is fromANS Tramacdons, Volume 65, June 1992, Pages 303-305 (courtesy

of the American Nuclear Society).

G.1 G.1 ~~~~~~NUREG/C
Appendix G

4. Impact of Safety Requirements on Component

Availability, Bob Chuistie (RAPA), Wendell

McDougald (Gulf States UMgl St. Franciivile)

The purpose of this work was to show the impact of

safety requirements on the availability of similar components. It is generally believed that "safety-related"

equipment is more reliable than non-safety-related

equipment This is not always the case- This work documents the negative impact that safety requirements can

have on component availability.

As part of the System Reliability Program at the River

Bend Nuclear Station, component availabilities were

calculated and trended for the control building chillers

(safety related) and for the turbine building chillers

(non-safety related). There are four control building

chillers (A and C in Division I; B and D in Division l)

with only one chiller running at a time. There are three

turbine building chillers (A, B, C) with two running at a

time.

The chillers are very similar in design. All the chillers

have been cooled by the same normal service water and

powered by essentially the same electric power sources.

The major differences in the chillers are as follows:

1. Control Building Chillers

Manufacturer Carrier Model MFA 443

Size: 189 t

Loading: Mostly throttled

2. Turbine Building chillers

Manufacturer: TBane Model NOX-T52-WV2

Size: 1250 t

Loading: Generally fully loaded.

The availabilities of the non-safety-related turbine

building chillers have been generally above the availabilities of the safety-related control building chillers.

Tables I and II show the run hours, fail hours, availability, number of failures, mean-time-to-failure, and

mean-time-to-repair of the respective chillers. The key

difference is the mean-time-to-failure of the average

turbine building chiller versus the mean-time-to-failure

of the average control building chiller. The safetyrelated control building chillers fail approximately three

times as often.

The safety-related control building chillers fail approximately three times as often as the non-safety-related turbine building chillers because of the stringent control

requirements imposed on the control building chillers.

The control building chillers must meet the single-failure criterion and must respond automatically to a wide

variety of changing parameters following any perturbation in the control building chilled water system. This

added complexity in the control building chillers has

resulted in a significantly lower availability and a significantly higher maintenance and operation burden on

plant personnel.

The control building chillers are included in the technical specifications for the plant because of their safety

classification. Because of the lower availabilities of the

control building chillers, the conditions that place the

system in a limiting condition for operation (LCO) are

frequently entered. Operations and maintenance personnel have been able to avoid plant derating due to exceeding the LCO (time) in the period covered in

Tables I and H. However, the plant was derated twice in

1987 because of problems with the control building

chillers

While the final numbers have not yet been compiled for

calendar year 1991, the same pattern is continuing. The

non-safety-related turbine building chillers have

achieved an availability of >99% while the availability

of the safety-related control building chillers dipped

below 80% in 1991.

NUREGICR-6043G2 G.2
Appendix G

Reliability and Risk Assessment

Table I Turbine Building Chillers

1988 1989 1990 TOTAL

HVN-CHL1A Run Hours 6379 4480

Fail Hours 20 0

Availability 99.7 100

Failures 3 0

MiTI 2126 --

MmTR 6.7 --

HVN-CHL1B Run Hours 4627 4863

Fail Hours 187 30

Availability 96.1 99.

3750

0

100

0

5403

387

4 933

Failures 4 2 4

MITF 1157 2432 1350

MmIR 46.8 15 97

HVN-CHL1C Run Hours 6387 3365 4693

Fail Hours 665 29 76

Availability 90.6 99.1 98.4

Failures 4 2 2

Ml 1597 1680 2350

MITR 166 14.5 38

ALL Run Hours 17393 12708 13846

Fail Hours 872 59 463

Availability 95.2 99.5 96.8

14609

20

99.9

3

4870

6.7

14893

604

96.1

10

1490

60

14445

770

94.9

8

1810

96

43947

1394

96.9

21

2090

66

Failures

MTrF

MTrR

11 4 6

1581 3177 2308

793 14.8 77.2

G.3 G3 ~~~~~~NUTREGI
Appendix G

Reliability and Risk Assessment

TAble II Control Building Chillers (Paper 4)

IiV*cHLI

A

HVK*CHL1

B

HVK*CHL1

C

HVK*CHLI

D

ALL

Run Hours

Fail Hours

Availability

Failures

MTR

Run Hours

Fail Hours

Availability

Failures

M7rF

MI'R

Run Hours

Fail Hours

Availability

Failures

M=TF

M1TR

Run Hours

Fail Hours

Availability

Failures

MNrr

M1TR

Run Hours

Fail Hours

Availability

Failures

MTN

M1TR

1988

3654

96

97.4

6

609

16

2102

46

97.9

3

350

7.7

1292

82

94.0

4

323

20.5

1739

8

99.5

3

580

2.7

8787

232

97.4

19

460

12.2

1989

1650

2

99.9

2

825

1

2723

2

99.9

6

1360

1

1516

5

99.7

2

758

2.5

615

775

44.2

2

310

390

6504

784

89.2

8

813

98

1990

2356

2

99.9

2

1150

1

1588

820

66.0

2

794

410

1101

S

99.6

1

1101

5

2130

254

89.4

3

710

85

7175

1081

86.9

8

897

135

ALL

7660

100

98.7

20

766

10

6413

868

8&1

10

641

86.8

3909

92-

97.7

7

558

13.1

4484

1037

81.2

8

561

130

22466

2097

91.5

35

642

60

-

NUREG/CR-6043G4 G.4
NUREG/CR-6043

PNL,8614

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Technical Report Files (5)

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Distr.2
NRC FORM 335 U.S. NUCLEAR REGULATORY COMMISSION 1. REPORT NUMBER

(2-89) RAaudlgd by NRCr Add Vol., Supp., Rev.

NRCM 1102NW ad Adendum Nunfers If any.

3201,3202 BIBLIOGRAPHIC DATA SHEET N[JREG/CR-6043

(See Insrnictiors on the Jverse) PNL-8614

2. TITLE AND SUBTITLE Vol. 1

Aging Assessment of Essential HVAC Chillers Used

in Nuclear Power Plants I YEA MONTH | YEAR

Phase I September 1993

4. FIN OR GRANT NUMBER

__________________________________________________ B2911

5. AUTHOR(S) 6. TYPE OF REPORT

D. E. Blahnik, R. F. Klein Technical 7. PERIOD COVERED finclusive Dates)

&*PERFORMING ORGANIZATION -NAME AND ADDR ESS OfNR~C provide Division, Offie or Revon, U.S. Nuclea ResutawtrvrCommiaiOOn, nd;ling gddes, f entacorprvtdc

n&"*andnidn paddresj

Pacific Northwest Laboratory

Richland, WA 99352

9. SPONSORING ORGANIZATION - NAME AND ADDRESS (ii NRC. nw Same as aiJow'if contractor. provide NRC Division. Df fice or Region. U.S NwiearReilaeoyCommiuion

9. SPONSOR ING ORGAN IZATION -NAM EAND ADDR ESS OfNARC. Urn So wss ovfea~ntrctot.pax iNRC Dyivon Ofriceor Rebn, U5 Nucar RvulvbtoCommbshi,

andmailf addreL.

Division of Engineering

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Washington, DC 20555-0001

10. SUPPLEMENTARY NOTES

11. ABSTRACT r200 wond ors

The Pacific Northwest Laboratory conducted a Phase I aging assessment of chillers used

in the essential safety air-conditioning systems of nuclear power plants. Centrifugal

chillers in the 75- to 750-ton refrigeration capacity range are the predominant type

used. The chillers used, and air-conditioning systems served, vary in design from

plant-to:plant. It is crucial to keep chiller internals very clean and to prevent the

leakage of water, air, and other contaminants into the refrigerant containment system'.

Periodic operation on a weekly or monthly basis is necessary to remove moisture and noncondensable gases that gradually build up inside the chiller. This is especially

desirable if a chiller is required to operate only as an emergency standby unit.

The primary stressors and aging mechanisms that affect chillers include vibration,

excessive temperatures and pressures, thermal cycling, chemical attack, and poor quality

cooling water. Aging is accelerated by moisture, non-condensable gases (e.g., air),

dirt, and other contamination within the refrigerant containment system, excessive

start/stop cycling, and operating below the rated capacity. Aging is also accelerated

by corrosion and fouling of the condenser and evaporator tubes. The principal cause

of chiller failures is lack of adequate monitoring. Lack of performing scheduled

maintenance and human errors also contribute to failures.

12 KEY WORDS/DESCRIPTORS (List an ,locad me 13. AVAILASIUTY STATEMENT

aging UJnl imited

Centrifugal chillers l. SECURITY CLASSIFICATION

chiller aging Imihk

chillers Unclassified

failures (This Report)

NPAR Unclassified

nuclear power plants 15. NUMBER OF PAGES

operating experience

safety-related chillers 6. PRICE

NRC FORM 335 (249)
Federal Recycling Program
NUREG/CR-6043

Vol. 1

AGING ASSESSMENT OF ESSENTIAL HVAC CHILLERS USED IN NUCLEAR POWER PLANTS SEPTEMBER 1993

UNITED STATES

NUCLEAR REGULATORY COMMISSION

WASHINGTON, D.C. 20555-0001

SPECIAL FOURTH-CLASS RATE

POSTAGE AND FEES PAID

USNRC

PERMIT NO. 0-67 1

OFFICIAL BUSINESS

PENALTY FOR PRIVATE USE, $300