ML20151U618

Augmented Insp Team Repts 50-413/88-14 & 50-414/88-14 on 880310-18.Violations Noted.Major Areas Inspected:Events, Equipment Status & Evaluation & Regulatory Requirements

ML20151U618
Person / Time
Site:	Catawba
Issue date:	04/13/1988
From:	Peebles T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
To:
Shared Package
ML20151U552	List: ML20151U549 ML20151U618
References
50-413-88-14, 50-414-88-14, NUDOCS 8805020106
Download: ML20151U618 (50)

See also: IR 05000413/1988014

Text

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UNITED STATES -

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NUCLEAR REGULATORY COMMISSION

REGION 11 -

a4 101 MARIETTA STREET, N.W.

D f ATLANT A, G EORGI A 30323

%,...../

U.S. NUCLEAR REGULATORY COMMISSION

REGION II

AUGMENTED INSPECTION TEAM-

-REPORT NOS. 50-413/88-14 AND 50-414/88-14

Licensee: Duke Power Company

422 South Church Street

Charlotte, NC 28242

Docket Nos.: 50-413 and 50-414

License Nos.: NPF-35 and NPF-52

Facility Name: Catawba Units 1 and 2

Inspection Conducted: March 10-18, 1988

Team Members: B. R. Crowley, Reactor Engineer, RII

K. N. Jabbour, Catawba Project Manager, NRR

P. S. Lam, Chief, Reactor Systems Section, AE00

M. S. Lesser, Resident Inspector, Catawba

W. T. Orders, Senior Resident Inspector, McGuire

.,

Team Leader:

T.

/

A.' Peebles, Chief

b , f-/.7 ,f7

Date Signed

Projects Section 3A

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8805020106 880420

PDR ADOCK 05000413

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TABLE OF CONTENTS

Page

I. Introduction - Formation and Initiation of AIT

A. Background 1

B. Formation of Augmented Inspection Team (AIT) 1

C. AIT Charter - Initiation of Inspection 1

D. Persons Contacted 3

E. Design Descriptions 3

1. Nuclear Service Water (RN) System 3

2. Auxiliary Feedwater (CA) System 7

3. Condensate Storage (CS) System 8

II. Description of Events

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Overview of Event for Catawba Unit 2

1. Event Description 9

2. Detailed Sequence of Events 12

III. Equipment Status and Evaluation

A. Auxiliary Feedwater Suction Swapover to

Nuclear Service Water System 1

1. Control Logic for CS/RN Swapover 14

2. Equipment As Found 16

3. Suction Swapover Event Analysis 19

4. Dynamic Test 22

5. Dynamic Testing Conclusions 24

6. Conclusions 24

7. Corrective Actions 25

B. Investigation of Clam Fouling of RN Supply

1. History of Licensee Programs for RN Fouling 25

2. Flushes and Inspection 28

3. Evaluation of Short Term Corrective Actions 34

4. Long Term Corrective Actions 36

IV. Regulatory Requirements 37

V. Conclusions 39

VI. Exit 40

Attachment 1 - Three (3) Graphs of Dynamic Testing

Attachment 2 - Two (2) Detail figures of CA Flow Control Valve (2CA56)

. Attachment 3 - Three (3) Letters of Concurrence

! Attachment 4 - Three (3) Training Diagrams of CA

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REPORT DETAILS

I. INTRODUCTION - FORMATION AND INITIATION OF AIT

A. Background

Catawba Units 1 'and 2 are four loop Westinghouse Pressurized

Water Reactors rated at 1145 megawatts electric. 'They have ice

condenser containments and are located about 25 miles south of

Unit 1 was licensed January 17,

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Charlotte, North Carolina.

1985, and Unit 2 in May 25, 1986.

On March 9, 1988 at 10:15 PM, the licensee notified the NRC

headquarters duty officer of the following event:

Catawba Unit 2 reactor tripped from 21% power on low-low

steam generator (S/G) level on "B" S/G. This occurred when

the feedwater regulating valve on "B" S/G (2CF37) failed

open (cause unknown and being investigated) when being

placed in auto. This caused a feedwater swing which

resulted in "C" and "D" S/G to be fed up giving a P14

signal (high-high S/G 1evel) on the "0" S/G. On the P14

signal, a feedwater isolation occurred which resulted in

all S/Gs levels decreasing and the "B" S/G reaching the

low-low level giving a reactor trip signal. Both auxiliary

feedwater pumps auto started but for an unknown reason the

"A" auxiliary feedwater (CA) pump suction swapped over to

the nuclear service water (RN) system.

B. Formation of AIT

On the morning of March 10, 1988, the Regional Administrator,

after briefing by regional staff and consultation with senior

NRC management, directed the dispatch of an AIT.

C. AIT and Charter

The charter for the AIT was prepared on March 10, 1988, and the

AIT members began arriving at the Catawba site that morning.

The licensee shutdown the other unit at 10:50 a.m. due to their

concerns of CA operability. An entrance meeting and briefing by

the site staff and plant manager was held with the AIT at

5:00 p.m.

A Confirmation of Action letter (CAL) was issued on March 11,

1988. This CAL documented the understanding between the

licensee and NRC that Region II would be in agreement with

investigation results prior to startup of either unit.

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The charter for the AIT specified that the following tasks be

completed.

1. Develop and validate a detailed sequence of events

associated with the March 9, 1988 Reactor - Trip and

subsequent swapover of the suction to the Auxiliary

Feedwater Pumps to the Nuclear Service Water System and

subsequent degraded auxiliary feedwater flow.

'2. Evaluate the significance of the event with regard to

radiological consequences, safety system performance,

safety significance, and plant proximity to safety limits

as defined in the Technical Specifications.

3. Evaluate the accuracy, timeliness, and effectiveness with

t.hich information on this event was reported to the NRC.

4. For nach equipment malfunction, to the extent practical,

determine:

a. Root cause;

b. If the equipment was known to be deficient prior to

the event;

c. If equipment history would indicate that the equipment

had either been historically unreliable or if

maintenance or modifications had been recently

performed;

l d. Any equipment vendor involvement prior to or after the

event;

e. Pre-event status of surveillance, testing and/or

preventive maintenance; and

f. The extent to which the equipment was covered by

existing corrective action programs and the

irrplication of the failures with respect to program

effectiveness.

5. Evaluate the licensee's action taken to verify equipment

operability on the operating unit.

6. Identify any human factors / procedural deficiencies related

to the event.

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7. Through o'perator and technician interviews, determine if

any of 7the following played a significant role in the

event: plant. material condition; the quality _ of

maintenance; or the responsiveness of engineering to

identified problems.

8. Provide la Preliminary Notification upon initiation of the

-inspection and an update'<on the- conclusion of the

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inspection..

9. Prepare a special inspection report documenting the results

of the above activities within 30 days of the start of the

inspection.

D. Persons. Contacted

Licensee Employees at Exit Meeting

T. B. Owen, Manager, Catawba Nuclear Station (CNS)

C.-L. Hartzell, Compliance Engineer, CNS

M. A. Cote, Licensing Specialist, CNS

C. E. Muse, Unit 2 Coordinator, CNS

R. F. Wardell, Technical Services Superintendent, CNS

W. R. McCollum, Station Services Superintendent, CNS

G. T. Smith, Maintenance Superintendent, CNS

Othe'r Licensee Employees

E. Fritz

M. Carwile

J. Kammer

M. Anderson

J. Caldwell

Z. Taylor

Other licensee employees were contacted.

E. Design Descriptions

1. Nuclear Service Water System (FSAR Section 9.2.1)

The Nuclear Service Water System (RN) provides essential

auxiliary support functions to Engineered Safety Features

of the i.sation. The system is designed to supply cooling

water to various heat loads in both the safety and

non-safety portions of each unit. Provisions are made to

ensure a continuous flow of cooling water to those systems

and components necessary for plant safety during normal

operation and under accident conditions. Sufficient

redundancy of piping and components is provided to ensure

that cooling is maintained to essential loads at all times.

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Functionally, the system consists of four sections which,

when put together in series, serve to assure a supply of

river water to various station heat loads and return the

heated effluent back to its proper heat sink.

In order of flow, these are:

a. Source and intake section

b. RN Pumphouse section

c. Station heat exchanger section

d. Main discharge section

Source and Intake Section

Two bodies of water serve as the ultimate heat sink for the

components cooled by the RN System. Lake Wylie is the

normal source of nuclear service water. A single transport

line conveys water from a Class 1 seismically designed

intake structure at the bottom of the lake to both the A

and B pits of the Nuclear Service Water Pumphouse serving

the RN pumps in operation. Isolation of each line is

assured by two valves in series and fitted with electric

motor operators powered from separate power supplies.

Should Lake Wylie be lost due to a seismic event in excess

of the design of Wylie Dam; the Standby Nuclear Service

Water Pond (SNSWP), formed by the Class 1 seismically

designed SNSWP Dam, contains sufficient water to bring the

station safely to a cold shutdown condition following a

single loss of coolant accident. The SNSWP has an intake

structure designed to Class 1 seismic requirements, with

two Class 1 seismic, redundant lines to transport water

independently to each pit in the RN Pumphouse. Each line

is secured by a single motor operated valve. Automatically

upon loss of Lake Wylie the isolation valves are closed and

the SNSWP valves are opened to both pit A and pit B.

RN Pumphouse Section

The RN Pumphouse is a Class 1 seismically designed

structure that contains two separate pits from which two

independent and redundant channels of RN pumps take

suction. Each pit can be supplied from both the normal

source and also the assured source of water. Either pit is

capable of passing the flow needed for a simultaneous unit

LOCA and unit cooldown. Flow spreaders in front of all the

intake pipe entrances prevent vortices and flow

irregularities while removable lattice screens protect the

RN pumps from solid objects,

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pumps IA and 2A take suction from pit A and discharge

through RN strainers 1A and 2A respectively. The outlet

piping of the 1A and 2A RN strainers then join back

together to form the channel A Supply line to channel -A

components in both units.

RN pumps 18 and 28 are physically separated from RN pumps

IA and 2A by a concrete wall, and take suction from pit B,

discharging through RN strainers 1B and 2B respectively.

The . outlet piping of strainers 18 and 2B join together to

form the channel B supply line to channel B components in

both units.

The supply and return headers are arranged and fitted with

isolation valves such that a critical crack in either

header can be isolated and will not jeopardize the safety

functions of this system or flood out other safety related

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equipment. The operation of any two pumps on either or

both supply lines is sufficient to supply all cooling water

requirements for the two unit plant for unit startup,

cooldown, refueling, or post-accident operation. However

additional pumps are normally started for unit startup and

cooldown and two pumps per unit operate during the

hypothetical combined accident and loss of normal power if

both diesel generators are'in operation. In an accident

the safety injection signal automatically starts both RN

pumps in each unit, thus providing full redundancy.

Heat Exchanger Section

Nuclear Service Water supplied by the RN pumps is used in

both units to supply essential and non-essential water

needs or as an assured source of water for other

safety-related systems.

Essential components are those necessary for safe shutdown

of the unit, and must be redundant to meet single failure

criteria. Nonessential components, are not necessary for

safe shutdown of the unit, and are not redundant. Each

unit has two trains of essential heat exchangers designated

A and B, and one train of nonessential heat exchangers

supplied from either A or B and isolated on Engineered

Safety Features actuation.

The following components or services are supplied by each

essential header of the RN System. Some components are

normally in operation, some are automatically supplied upon

ESF actuation, and others are used when needed.

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a. RN Pump Motor Cooler

b. RN Strainer Backflush

c. RN Pump Bearing Lube Injection Water

d. RN Pump Motor Upper Bearing Oil Cooler

e. Diesel Generator Engine Jacket Water Cooler

f. Diesel Generator Building Essential Fire Water

g. Diesel Generator Engine Starting Air Aftercooler

h. Component Cooling Heat Exchanger

1. Assured Auxiliary Feedwater Supply

j. Assured Fuel Pool Makeup

k. Assured Component Cooling (KC) System Makeup

1. Containment Spray Heat Exchanger

m. The Control Room Area Chiller Condenser (Condensers A

and B are shared between units, so they are fed by

Unit 1 Essential Headers only).

n. Auxiliary Shutdown Panel Air Conditioning Unit.

o. Assured Containment Penetration Valve Injection Water

(RW) System Makeup

From each essential RN header, a six inch branch line

provides the backup water supply for Auxiliary Feedwater.

This six inch line travels for approximately 250 feet

before the first isolation valve. Just upstream of the

isolation valve, a line branches off to supply

approximately 10 GPM continucus flow to each auxiliary

shutdown panel air conditioning unit condenser.

No provision is made for prevention of long-term corrosion

in the RN System. Allowances for such corrosion were made

by increasing the wall thickness of the pump pressure

boundary, piping, and the heat exchanger shells and tubes

in accordance with the applicable codes. Larger pipe sizes

than necessary were used for pump adequacy considering

scaling.

Asiatic clam control is achieved by a series of design

features and operating procedures. Intake structures take

suction elevated off the bottom of the lake and SNSWP and

at a velocity well below that required by the Environmental

Protection Agency for wildlife protection, so large clams

are not drawn into the system. A bar screen with openings

4 in. x 4 in, keeps debris from entering the intake lines

and a lattice screen with 1 in x 1 in, openings separates

the forebay of the RN Pumphouse from the RN pump suction

bay, providing a second level of defense. The water

discharging from each RN pump passes through an RN strainer

with 1/32 inch openings to strain out dirt and sand

particles that could clog control valves with cavitrol trim

located throughout the RN System. These screens and

strainers will prevent all but the smallest clam larvae

from entering tha RN piping.

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It is understood that Asiatic clam larvae do not

permanently attach to pipe walls and grow, but nest in

stagnant places such as valved off pipes and idle heat

exchangers and operating heat exchanger heads in front of

the tube sheet, performance monitoring programs to verify

adequate flow, and visual inspection of the intake piping

and inlet heat exchanger heads during maintenance provide

early detection of any clam infestation of raw water

systems.

2. Auxiliary Feedwater System (FSAR Section 10.4.9)

The Auxiliary Feedwater System (CA) assures . sufficient

feedwater supply to the steam- generators (S/G), in the

event of loss of the Condensate /Feedwater System, to remove

energy stored in the core and primary . coolant. The two

units are provided with separate CA Systems.

The CA System is designed to start automatically in the

event of loss of offsite electrical power, trip of both

main feedwater pumps, safety injection signal, or low-low

S/G water level; any of which may result in, coincide with,

or be caused by a reactor trip. The CA System will supply

sufficient feedwater to maintain the reactor at hot standby

for two hours followed by cooldown of the Reactor Coolant

System (NC) to the temperature at which the Residual Heat

Remocal System (ND) may be operated.

Three CA pumps are provided, powered from separate and

diverse power sources. Two full capacity motor driven

(MDCA) pumps are powered from two separate trains of

emergency on-site electrical power, each normally supplying

feedwater to two steam generators. One full capacity

turbine driven (TDCA) pump, supplying feedwater to two

steam generators, is driven from steam contained in either

of the two steam generators. A minimum of 225,000 gallons

feedwater supply is required for the design basis hot

standby followed by normal cooldown to conditions at which

the ND System may be operated.

Standards for nuclear safety related systems are met for

the CA System except for the condensate quality feedwater

sources.

The normal lineup is for train A MDCA pump 1(2)A to supply

A and B steam generators, for train B MDCA pump 1(2)B to

supply C and D steam generators and for the TDCA pump to

supply B and C steam generators,

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The MDCA pumps will automatically start and provide the

minimum required feedwater flow within one minute following

any of these conditions:

a) Two out of four low-low level alarms in any one of the

i four steam generators,

b) Loss of both main feedwater pumps,

c) Initiation of the safety injection signal.

d) Loss of station normal auxiliary electrical power.

The TDCA pump will automatically start and provide the

minimum required feedwater flow within one minute following

either of these conditions:

a) Two out of four low low level alarms in any two of the

four steam generators.

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b) Loss of station normal auxiliary electric power.

Driving steam for the TDCA pump is provided from either. the

steam generator B or C main steam lines upstream of the

main steam lines containment isolation valves and is

discharged to the atmosphere from the turbine.

3. Condensate Storage System (FSAR 9.2.6) (CS)

The Condensate Storage System provides a readily available

source of deaerated condensate for makeup to the condenser

and is the preferred source of auxiliary feedwater for

makeup to the steam generators. It also serves to collect

and store miscellaneous system drains.

Makeup to the Condensate Storage System is to the upper

surge tank (UST) dome from the Makeup Demineralized Water

System. The upper surge tank dome drains to the two upper

surge tanks. Makeup to the condenser is supplied by

gravity flow from the UST. The UST also provides sealing

water for various equipment, and the supply for the

auxiliary electric boiler feedwater pumps. Overflow from

the UST is returned to the Condensate Storage Tank (CST)

through a 27 foot loop seal which prevents the introduction

of air into the upper surge tanks. Valve ICM363 provides a

means for filling and makeup to the loop seal. The CST

receives the drains from various equipment and holds these

drains until they are transferred to the UST dome by the

two full capacity CST pumps. The CST operates at

atmospheric pressure and is vented to the roof. The

overflow line from the CST has a 3 foot loop seal to

prevent steam from the hot drains discharging into the tank

from entering the building.

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) The preferred source of clean' water supply for the l

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auxiliary feedwater pumps is provided by the main condenser i

hotwell (170,000 gallons) and the two UST (85,000 gallons  ;

total) on each unit and the shared Auxiliary Feedwater  :

Condensate Storage Tank (CACST) (42,500 gallons). Relative j

pressure differentials considering normal vacuum in the

hotwell and UST result in the supply to the CA pumps  !

initially from the CACST -then th9 UST. The hotwell may

then be pumped to the UST or vacuum relieved and supplied

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directly to the CA pumps. The Condensate Storage System ,

i tanks are not safety related, since the. assured source of  ;

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water for the auxiliary feedwater pumps is provided from  !

the Nuclear Service Water System. j

Sufficient instrumentation is provided to monitor system [

performance. Alarms are provided in the control room for  !

high and low UST level, high and low CST level, low hot

well level and low CACST tank level.

All of the preferred sources of condensate quality water-  ;

are normally aligned to the CA pump suctions. The l

condensate reserve for-each unit is maintained among the  ;

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Source Max. Capacity .j

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a. Auxiliary Feedwater 42,500 gallons / station i

1 Condensate Storage Tank (Shared by both units)  !

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b. Upper Surge Tanks 85,000 gallons / unit  !

(two 42,500 gallon tanks  !

per unit) j

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! c. Condenser Hotwell 170,000 gallons / unit l

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II. DESCRIPTION OF EVENT

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Overview of Event for Catawba Unit 2 l

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i 1. Event Description  !

! At 6:25 pm on March 9,1988, Catawba Unit 2 was operating 7

at 20*4 reactor power carrying load of 150 MWE and in the -

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process of starting up from the unit's first refueling. An

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operator was transferring from the feedwater (CF) bypass i

valve to the main feedwater regulating valve (2CF37) on l

! . steam generator (S/G) B. As the valve (2CF37) was placed [

in automatic, it failed full open which caused the  ;

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operating main feedwater pump speed to start oscillating

thus resulting in a major swing in flow throughout the feed

system. Another operator assumed manual control of the

pump and attempted to bring it under control. The operator

on the B main feedwater regulating valve assumed manual

control and closed it down to prevent over feeding S/G B.

Level in S/G's C and 0 meanwhile increased until two of

four channels on S/G 0 reached High/High S/G level. This

resulted in a main turbine trip, a feed water isolatior,

and a main feedwater pump trip.

Both motor driven auxiliary feedwater (MDCA) pumps auto

started immediately upon loss of the main feedwater pump.

An apparent CA pump low suction pressure resulted in the

swap of the A train MDCA pump suction to the RN system

which serves as the safety related assured source (valves

2RN 250A and 2CA 15A opened). Details concerning the swap

to RN are delineated in Section III. A of this report.

Level in S/G's A and B were meanwhile dropping and a

reactor trip occurred due to Low / Low Level in S/G A. The

turbine driven auxiliary feedwater (TOCA) pump was

initiated when S/G B also reached Low / Low level which

satisfied the logic of two of four S/G's at Low / Low level.

The operators secured the TDCA pump approximately one

minute after it auto started and manually throttled CA flow

to stabilize S/G levels.

Approximately 13 minutes into the event, the control room

operators reviewed the panels to determine any abnormal

indications. It was at this time that one operator saw an

annunciator illuminated which indicated that a CA suction

swapover had occurred and another operator detected (on the

control panel) that valve 2RN 250A was open. The operators

immediately closed 2RN 250A, and verified suction flow path

from the UST. It should be noted that neither operator

detected that valve 2CA 15A had opened. (Valve 2RN 250A

and valve 2RN 15A are in series and both must open for RN

to be surplied to MDCA pump 2A.)

Approximately 20 minutes into the event, with auxiliary

feedwater maintaining steam generator levels it was

detected that the level in the 8 generator was starting to

decrease slightly. The operator opened the CA flow control

valve supplying the B S/G (2CA 56) but noticed that the

valve when full open would pass only 100 gpm, instead of

normal flow of 300 gpm. This was the first indicstion of

flow degradation even though the operators at this time

still had not detected that valve 2CA 15A had opened in

response to the apparent low suction pressure signal.

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At approximately 7:00 pm, some 35 minutes into the event, "

during shift turnover, the oncoming shift supervisor

detected. that valve 2CA 15A was open. It was not until- >

this time that the on duty operating shift knew that

2CA 15A- had repositioned. Furthermore, it was not until

this time that the on duty Unit Supervisor and Shif t  :

Supervisor became aware that the unit had experienced a CA  !

suction problem. This is indicative of a communications ,

problem on the part of the on duty operations crew. "

Auxiliary feedwater continued to supply the generators _  !

until about 8:45 pm when the operators were able to restart i

the main feedwater pump, and place the CA system in

standby,

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After it was detected that valve 2CA 15A had opened,

actions were initiated to disassemble and inspect CA flow '

control valves 2CA 56 and 2CA 60, the valves which had

passed RN water to S/G's A and B. By 10:30 am March 10, it

was determined that the valves were clogged with clam

shells.

By 11:50 a.m. March 10, it had also been concluded that .

continued safe operation of unit 1, which was at 100% i

reactor power, could not be assured due to the possibility

of clam fouling of the CA system. At 12:50 p.m. the .l

licensee began shutting unit I down to mode 4. At 4:45  ;

p.m., unit 2 was taken into mode 4. '

The licensee formulated a program of flushes and ,

inspt:ctions to confirm that suspect RN lines supplying [

assured sources of cooling to safety related equipment were  :

clear of fouling. Details of these programs are delineated *

in Section III.B of this report.

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The licensee also initiated a test and inspection program

to verify the correct operation of the instrumentation, j

logic and equipment associated with the CA suction

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swapover, as well as CA pump verification tests and CA ,

system valve function. Details of the testing performed ,

are described in Section III.A. of this report.

Subsequent to the completion of the aforementioned flushes,

and inspections on March 11, 1988, unit I restarted af ter  ;

conferences with the AIT, the Region and NRR. Unit 2 was ,

allowed to restart on March 18, 1988 after resolving the r

issues of fouling and CA suction swapover.

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2. Detailed Sequence of Eveny

The sequence of events was developed from discussions with

operations personnel, review of computer alarm typer data

recorded during the event and review of plant logs and

investigation packages.

March 9, 1988

6:25:00 PM - Unit operating at 21*e power carrying load of

150 4'E.

6:25:37 - Received Turbine Trip. Feedwater isolation

and Feedwater Pump trip on High/High S/G

1evel in the D S/G when main feedwater

regulating valve 2CF37 failed open when

placed in automatic,

6:25:37 -

Both MDCA pumps started on the loss of the

running main feedpump.

6:25:44 -

Low CA pump suction pressure resulted in

swap of suction to Nuclear Service Water,

the assured source.

6:25:49 - Levels in A and B S/G's decreasing; level l

in S/G A reaches low / low level in 2 of 4

channels resulting in reactor trip.

6:26:09 -

Level in 8 S/G reaches low / low level in 2

of 4 channels - results in autostart of TD

CA pump.

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TOCA pump secured.

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Operators throttle CA flow to S/G's to

stabilize cooldown rate.

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Operators isolate RN from CA pump suction by

closing valve 2RN 250A.

6:45 approx. -

It was noticed that CA flow to the A and B

S/G's had degraded over time. Initial flow

was normal (300 gpm/SG) but had decreased to

approximately 100 gpm to the A S/G and 200

gpm to the B S/G. Operator notes that with

valve 2CA 56 (CA flow control valve to the A

S/G) full open, valve will pass only 100

gpm.

10:15 PM Licensee notified NRC Duty Officer of Unit 2

Reactor Trip.

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i

March 10, 1988  !

!

6:00 AM - Licensee disassembles and-inspects CA flow

10:00 AM control valves 2CA56 and 2CA60 which supply

the A & B S/G's. . Upon disassembly, valves i

were found to be clogged with clam shells, j

9:00 AM Licensee discusses event'with Region II. }

---

-

Licensee evaluating cause of CA swap to RN. .

11:50 AM' - Licensee determines continued safe operation  !

of Unit 1 can not be assured due to the '

possibility of clams fouling the CA system, I*

>

should swapover to . RN become necessary.

Unit shutdown began.  !

12:30 PM Licensee notified NRC Outy Officer of the  :

shutdown of both units. i

12:53 PM Licensee notified NRC Duty Officer of  !

Unusual Event declared on Unit 1 as a safety i

system i

(CA) was degraded at power and shutdown of I

both units was commencing. [

11:15 PM Unusual event terminated. Unit 1 in mode 4,

March 11, 1988 .

l

---

- Licensee initiater program to flush stagnant i

portions of RN piping which serve as back up i

supply to safety systems, Flushing program i

includes radiography and boroscopic exami- -i

nations to confirm flush adequacy. [

---

- Licensee initiates testing on both units CA i

- to RN swap logic and equipment to determine  :

if calibrated, operable and cause for swap t

on Unit 2. l

-

CAL Issued f

11:00 PM - All testin0 and flushing complete on Unit 1,  !

unit receives NRC concurrence for restart. I

f

---

-

Unit 2 flushing and testing continuing. l

!

March 13, 1983 I

9:18 PM -

Unit 1 enters Mode 2 i

i

March 12-18, 1988

---

- Flushes, inspections and tests continue, j

l March 18 -

Unit 2 allowed to restart commensurate with

j CAL. Licensee agreed to utilize

compensatory measures relative to CACST l

valve 2CA 6. }

I

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III. EQUIPMENT STATUS AND EVALUATION j

!

- A. Auxiliary Feedwater Suction Swapover to Nuclear Service Water [

System

'

This section discusses the Catawba Unit 2 CA suction swapover l

.

from the normal sources to the safety-related assured source of r

RN. To cover the March 9,1988, event in detail the following .r

sections are included:

. 1. Control icgic '

t

,

2. Equipment as found

3. Conclusion

i

1. Control Logic for CS/RN Swapover [

l f

"

As the CA System serves a vital safety related function r

during all postulated occurrences two trains supplied by a

safety grade, seismically designed water source must be ,

assured at the pump suctions to assure pump operability and l

function. The Standby Nuclear Service Water Pond, with a i

maximum capacity of 2.74 x 10' gallons total for the  !

station, serves as the ultimate long-term safety related I

source of water for the CA System. To maintain steam l

generator water chemistry, especially for events which t

4 require fast response recovery such as; blackout, loss of f

i'

"

normal feedwater, or main steam system malfunction, the CA l

pumps are normally aligned to condensate quality water, i

The sources of condensate quality water exist as non-  ;

seismic grade sources in the Turbine Building. To prevent  :

inadvertent injection of out of chemistry nuclear service [

water to the steam generators a reliable means of detecting l

1 loss of condensate source and automatic transfer of the  !

pump suctions to the nuclear service water sourco is [

t employed. Such detection and transfer controls are  ;

automatic since minimum CA System flow must be established  !

within one minute from the initiating event. The automatic #

detection and transfer controls will detect and transfer .

the pump suctions to nuclear service water upon detection i

i of any of the listed postulated failures of the non-seismic

I condensate supplies:

(a) Deeletion of all condensate sources.

Losa of source due to pipe break.

,

(b)

(c) Partial or complete loss of source due to air leakage

2

into the system from a pipe crack, or failure to t

'

l

isolate a depleted source.

4

(d) Partial loss of source due to steam void formation in j

the suction piping caused by excessive friction loss i

associated with a high flow rate, failure or spurious  !

i operation of a valve causing partial closure, or [

bending or partial obstruction in the pipe. l

l

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. The detection scheme incorporates three trains of three

differential pressure switches located in the Auxiliary

-Building in a vertical leg of the common condensate supply

. pipe to all three CA - ~ pump s . Two trains of pressure

switches . serve the two safety grade RN trains, and the

-remaining train of pressure switches serves 'the condenser

circulating (RC) system supply. RC provides a backup to

RN for further CA suction supply. One of three pressure ,

y switches activating gives a low pressure alarm in the

'~

control room. Upon two out of three indications of low

suction pressure from any train, the transfer logic will be

activated for that train. The instrumentation and controls

for the RN trains meet the standards for nuclear safety

related systems, including requirements for redundancy and

separation. If the station normal auxiliary electrical

power is available during the initiating occurrence, a

maximum 30,000 gallons additional condensate supply is

available from the condensate storage tank. If the two

makeup demineralizers are available, a maximum condensate

supply of 950 GPM is available for the short term or 475

GPM for an indefinite period. Additional condensate . may

also be provided from condensate sources associated with

the other unit, if these sources are available, operable,

and a loss of normal station auxiliary electrical power has

not occurred.

The logic for the automatic swapover of the CA system to

take suction from the nuclear service water (P.N) system is

based upon the following conditions:

1. CA pump running

2. Loss of condensate source (i.e. 2 out of 3 low

suction pressures at pressure switches)

. The Technical Specifications assume an overall

time for swapover to occur of 15 seconds with 10

seconds allowed for valve movement.

Applied to the above logic is a time delay (3-5 seconds)

for the low suction pressure. The purpose of the time

delay relay is to allow for a momentary low suction

pressure during a pump start transient. f-

The automatic switchover to RN takes place only if the CA

system has been initiated by a CA auto start signal and the

CA pump suction pressure is low as sensed by 2/3 pressure

switches. Low pressure in one of three A or B train

pressure switches will alarm the Onerator Aid Computer

(OAC). Either train A or B RN st.ction sources can align to

the turbine driven CA pump if all of the following has

occurred within the proscribed sequence:

(1) The TDCA pump has received an auto start signal.

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(2) The pump turbine steam supply: valve 'SA2 or SAS has .

opened.

(3) The-pump turbine trip and throttle valve is open.

(4) A 3-5 second time delay -times out .pr.ior to providing

the'run indication to the swapover logic of TDCA pump.

This time delay relay is in addition to-the 3-5 second

'

time delay intended to prevent _ swapover on a pump

start transient.

(5) Two out of three low section pressure indications from

the train A or B pressure switches and their 3-5

second time delay relay has timed out.

CA purnp -suction following swapover to RN is through the

following paths:

Train A is from the 24 inch A troin RN header to the ,

6 inch RN line through valve RN 250A then either

through valve CA 15A to the A train MDCA pump or

through valve CA 116A to the TDCA pump.  ;

Train B is from the 24 inch B :cain RN header to the

6 inch RN line through valve . RN 3103 then either

through valve CA 18B to the B traia MDCA pump or

through valve CA 85B to the TOCA pump. ,

The following section lists all the as found setpoints for

. trains 1A, 1B, 2A, and 28,

2. Equipment as found -

(a) pressure Switches

(1) Unit 1 A Train

Required setting: 10.5 .15 psig

.- Pressure Switch As Found Setpoint

1 CAPS 5220 .'.0. 8 p si g

l.

1 CAPS 5221 10.44 psig

1 CAPS 5222 9.92 psig

Technical Specification (TS) trip setpoint

i 3 10.5 psig

l

TS Allowable Value 1 9.5 psig

!

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(2) Unit 1 B Train

e

.Raquired: setting: 6.0 .15 psig

is Pressure Switch- As Found Setpoint~

1 CAPS 5230 5.95 psig-

'

-1 CAPS 5231 .5.90 psig

-1 CAPS 5232 6.10 psig .

TS trip setpoint 6.2 3 psig

,

TS Allowable Value t 5.2 psig

l

(3) Unit 2 A Train

Required setting: 10.St.15 psig

Pressure Switch As Found Setpoint

,

2 CAPS 5220 11.0 psig

2 CAPS 5221 11.2 psig

2 CAPS 5222 10.6 psig

TS trip setpoint 310.5 psig

. TS Allowable Value 1 9.5 psig

(4) Unit 2 B Train

Pressure Switch As Found Setpoint

2 CAPS 5230 6.85 psig

2 CAPS 5231 6.05 psig

2 CAPS 5232 6.05 psig.

l

TS trip setpoint t 6.0 psig

TS Allowable Valve 3 5.0 psig

! It was noted that the licensee interprets the Trip

I

Setpoint, as specified in Table 3.3-4 of TS, as a

nominal value and allows a band of .15 psig. The TS

indicates that the trip setpoint is a minimum value as

opposed to a nominal value, although TS basis

discusses it as a nominal value. The licensee's

interpretation appears to be consistent with the

Westinghouse setpoint methodology. This was confirmed

with R. Giardina of NRR, OTSB.

- .__ - _ _ _ _ - __

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r (b) Time Delay

,

o

i: The Unit 1 A Train time delay was found to be 4.27

b seconds and for Unit 1 B Train it was 4.39 f seconds.

The Unit 2 A Train time delay was found to .tme .4.15

[ ,

L . . seconds and for Unit 2 B Train it was 4.7 seconds.

These values . were found acceptable because they

conform to the manufacturer's recommendations of being

in the range of 3-5 seconds.

(c) Pressure Switch Root Valves

Pressure switches 2 CAPS 5220, 5221, 5222 have common

impulse lines and are isolated by one root valve.

. Pressure switches 2 CAPS 5230, 5231, 5232 have common

impulse lines and are isolated by one root valve. The

root valves on Unit 2 A and 2 B Trains were found to be

partially blocked by magnetite. The blockage may have

contributed to the fact that the alarm in the control

room had a 51 second duration before it cleared.

(d) Valve 2CA6

Valve 2CA6 is the supply of condensate grade water to

the CA pump from the CACST and is powered from the

emergency bus. The valve is normally open and for 3

days af ter the event the licensee believed the valve

had been open. However, after completing their

'

interviews of the operators, the licensee determined

that 2CA6 had been closed at the start of the event.

The same valve on Unit I had been closed at various

times over the past year to prevent drainage of the

CACST through the CA system. The CACST is a common

tank to both units and was receiving makeup from Unit

1 at the time. The licensee had been attempting to

identify the causes for CACST level decreases.

The losses of CACST ievel were not fully understood

by the licensee but were believed to be a result of

check valve backleakage to the hotwell or a design

feature.

The operations r.taff had decided to close 2CA6 on

Unit 2 to prevent migiation of water between Units 1

and 2 and to prevent draining the CACST. The CACST

normally supplies the highest head and thus shutting

2CA6 apparently removed this added margin and

contributed to the low suction pressure event.

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(e).'Swapover Valves

All of the major Unit 2 train A and B Swapover valves-

had been periodically stroke tested and were tested

and found operable following the event.

3. Suction Swapover Event Analysis

Normally all three CA pumps are aligned to non-safety

grade, condensate -quality sources. The safety-related RN

supply-is not normally aligned to the CA pump suction, but.

is automatically aligned when low suction pressure is

detected.

The following evaluation of the March 9,1988 sequence of

events is based on analysis of strip charts, computer

l- alarm printouts, calibration of components and interviews

'

of personnel. This is the AIT evaluation which is

consistent with that of the licensee's evaluation.

Both MDCA pumps 2A and 2B started after the main feedwater

pump trip. The OAC received a low pressure alarm from both

~

the train A and train B pressure switches. Valves 2RN250A

and 2CA15A opened, aligning the RN train A suction source

with MDCA pump 2A. MDCA pump 2B was still aligned to the

normal suction soure.e. MDCA pump 2A was operating while

taking suction fr'm its assured RN source, and

simultaneously pump c3 was operating while taking suction

from the normal non-safety grade sources. About 32 seconds

af ter the MDCA pumps star..ed, valves SA2 and SAS opened,

and the TDCA pump began to ramp up to 3650 rpm and pump

auxiliary feedwater to stear.' generators B and C. The pump

had received a CA pump start signal on detection of low low

level in two of four steam generators. Nineteen seconds

after valves SA2 and SAS opened, the low suction condition

in train A and B cleared.

Based on the actuation sequence of the CA pump suction

pressure switches, it appears that when the CA pumps

started, the suction pressure dropped below the actuation

pressure of the decreasing setpoint on at least two of the

train A pressure switches, (2CAPSS220, 5221, and 5222) and

below the decreasing setpoint of one of the train B

switches, (2 CAPS 5230, 5231, and 5232). No information is

available that indicates condenser circulating water (RC)

pressure switches (2 CAPS 5240, 5241, and 5242) actuated.

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_ _ _ _ _ _ _ _ _ _ _ - _ _ _ _ _ _ _ _ _ _

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20

The pressure appears to have stayed below the reset

pressure of the two train A switches for at least four

seconds, and . initiated swapover. to RN as a source for MDCA

purrp 2A. . After about 51 seconds, the pressure apparently

rose above the reset point of the train B sw:tch and all

the train A switches.

As two of the three train A pressure switches had actuated

and a partial train A swapover to - RN occurred, it was

questioned why valvo 2CA116A did not open during the

March 9 event and Clow RN to supply the TDCA pump.

After the initial s, over occurred, one of the pressure

switches could have reset between five and thirty-two

seconds into the event, aided by the pressure increase from

the RN supply, and prevented valve 2CA116A from opening.

The limit switch indicating valve 2CA116A closed on the

computer was.not functioning, so no positive indication of

valve position was available. However, since: 1) the TDCA

pump auto start signal occurred approximately 32 seconds

af ter the MDCA pump auto start signal; 2) a time delay

occurs in opening 2SA2 or 2SA5; and 3) a 3-5 second time

delay relay times out before the low suction pressure 3-5

second time delay relay starts the 2/3 low suction pressure

logic; the logic could have partially cleared at some

point in this sequence and demand for 2CA116A to open was

never actuated.

The licensee initially suspected that valve 2CA116A had

partially opened because chemistry results of the 2C S/G

indicated high levels of cation conductivity. Several days

later it was determined that these samples were in error.

The sample line from C S/G became clogged af ter the trip

and the chemistry technicians were actually sampling A or B

S/G. The chemistry of steam generators C and D was found

to be actually within specification indicating that valve

2CA116A did not open. Further inspections were conducted

on valve 2CA116A; it passed a stroke test following the

event and it was disassembled and inspected and no problems

were found. Also, the TDCA pump seal water supply from its

discharge was inspected and found clean.

! The swapover of the train A pump to RN system indicates

that at least two of the train A pressure switches

actuated. No swapover occurred on train B which indicates

that apparently only one of the train B switches actuated.

This hypothesis is also supperted by calibration checks

done or the pressure switches, which showed that the three

pressure switches with the highest actuation pressures were

two train A's and one train B. A logic check on both

trains was performed, and no problems were identified.

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The electrical system performed _ as expected. When more

than one of the train A switches sensed pressure below

decreasing setpoint and the timer timed out, swapover,to RN

occurred. The computer alarm listings indicate that after

51 seconds, all switches in both train A and train B had

reset. Because both trains indicated low pressure, it does-

-

- not appear that an electrical failure was responsible for

the swapover. The wiring of the switches was checked to

ensure that there was no crossover between trains.

Calibration checks of the train A and B pressure switches

were performed. Pressure switches are tubed from separate

manifolds. A failure of a single root valve, manifold, or

pressure switch could not prevent actuation of a separate

train. Although the train B- root valve was found to be

partially clogged, that condition would not affect the

operation of train A. Barton 580 series pressure switches,

- the type used for the -CA system swapover logic, have a

deadband of 10%. It is impossible to predict the exact

reset pressure of a given switch within the deadband, and

the reset sequence of a group of switches might not be the

, same as the actuation sequence.

Therefore, it was concluded that all of.the logic for the

swapover of TDCA pump suction was not made up, which was

proper as was confirmed by several means as noted above.

However, whether a low pressure condition actually

occurred and if it did why train B was not actuated was

not yet known.

An investigation of the hydraulic system was performed to

determine if a low pressure condition actually occurred.

Plant personnel verified that the isolation valves from the

hotwell and upper surge tank were open, however, the CA

condensate storage tank isolation valve 2CA6 was closed.

Normally UST level is maintained greater than 80%; however,

during the event the water level in the upper surge tank

was believed to have been approximately 55-65%. This was

not known until a few days after the event. The tank level

per recorder had stuck at the 90% level and the tank makeup

had been isolated that day for maintenance. Under these

conditic,s, when MDCA pumps 2A and 28 started, the steady

state pressure at the instrument taps was calculated to be

12 to 20 psi higher than the low pressure set points.

Explanations for extremely low suction pressure would be

loss of the normal suction sources due to inadvertent

isolation, check valve failure, or depletion of suction

sources. A failure of the common supply suction check

valve CA129 or the upper surge tank supply check valve CA3

resulting in flow blockage, would be the most probable

occurrence. Valve 2CA1, the notwell check valve, might

have had excessive leakage, short circuiting the supply

from the upper surge tank, subsequently limiting flow to

the CA pumps and causing a low pressure condition.

However, effects of rising hotwell level were not observed.

. - _ . --

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22

After the incident occurred, and the check valve failure

investigation begun, the common suction supply check valve

CA129 and the upper surge - tank check valve CA3 were

inspected; the discs were observed to swing freely with no

apparent obstructions-or misalignment. The hot'well supply

check valve 2CA1 was inspected : and had virtually -no

leakage. 2CA3 was also inspected and no problems were

observed.

At this point the licensee could not explain why or if an

actual low pressure condition occurred. A dynamic test was

developed to prove operability of the system and obtain

more data to explain the event.

4. Dynamic Testing

In order to obtain transient data on CA pump suction

pressure during CA pump starts, the CA suction header was

'

instrumented at 5 different points with temporary 0-50 t

O.125 psig pressure transmitters and visicorders- .

TT/2/A/9200/14, CA System Autostart Transient Test, was

written and approved to measure -and record suction header

pressure during various CA pump starts. An attempt would

be made to recreate conditions necessary for swapover to RN

. supply on an extended low suction pressure greater than the

3-5 second time delay. In this test, the pumps would be

manually started. The logic for manual starts of the pumps

requires that if an actual low suction pressure existed

longer than the time delay, the pumps would automatically

trip and swapover to RN would not occur. (Swapover to RN

occurs with an autostart signal and extended low suction

pressure.)

The pressure switches were recalibrated to be within their

required settings prior to dynamic testing.

The following conditions were considered in determining

test prerequisites:

a. All 3 CA pumps starting simultaneously would create

the lowest possible transient suction pressure.

b. A 34 second time delay in starting the TOCA pump would

simulate starting conditions under certain actual

demands.

c. Upper Surge Tank (UST) level would be maintained at

60-80% level, as level was estima'ed to have been at

65% during the March 9 event.

d. Starting the pumps with 2CA 6 open and again with 2CA6

shut would show system response with and without the

additional suction head of the CA CST available.

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23

The test therefore would include 4 manual starts in the

,

following manner:

'

.

(1) Simultaneous start of all 3 CA_ pumps with 2CA6 open.

(2) Simultaneous start of all 3 CA pumps with 2CA6 shut.

(3) Simultaneous start of both MDCA pumps, TDCA pump start

34 seconds later, with 2CA6 open.

(4) Simultaneous start of both MDCA pumps, TDCA pump start

34 seconds later, with 2CA6 shut.

The test was run on March 17 with the unit in Mode 3 and

the following results were observed:

The transients exhibited a characteristic suction pressure

dip of 25-30 psig just after pump start as expected,

lasting 3-4 seconds. (Refer to graph 1.) In each case

where 2CA6 was open, the CA suction pressure never dipped

below the low suction pressure setpoints. When 2CA6 was

shut,- available NPSH was less and pressure was observed to

drop below the low pressure setpoints. This caused control

room annunciators to momentarilyLalarm, but not longer than

the 3-5 second time delay and the CA pump trip did not

occur. In all cases steady state suction pressure was

acceptable.

Af ter the 4 starts with UST level at about 60%, and 2CA6

shut, vacuum on the main feed pump (CF) condenser was

inadvertently lost and the running CF pump tripped. This

caused a CA autostart. Both MDCA pumps started, a swapover

to RN occurred on train A and raw water was again injected

into steam generators A and B. During this event the MDCA

pumps were thought to have started in a staggered manner

1/2 - 1 second apart, which was suspected to have extended

'

the pump start transient past the time delay on train A and

caused swapover. UST level also appeared to be a more

significant parameter than originally believed. Since the

TDCA pump did not start during this event, it was concluded

that it played no role in the swapover scenario.

Evaluation of the results of the initial dynamic testing

and the inadvertant CA start led to the conclusion that the

March 9 low pressure sce..ario was real and therefore could

be duplicated. A further test program was defined and

additional instrumentation installed.

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24

Three (3) starts of the MDCA pumps, staggered by 2 seconds,

were then conducted with 2CA6 shut. UST level varied.from

65-90%. No CA pump trips were observed. On graph 2 one

notes that the transient is indeed extended to about 6

seconds; however, the pressure did not dip below the

.setpoints. The licensee suspected this stagger time to be

too long to cause swapover'and did 3 more starts with pump.

starts staggered at 1/2 - 1 second. In each of these last

3 starts the train A MDCA pump tripped, indicative of an

extended' low pressure. sensed.on train A. The transient is

shown on graph 3. The sequence of starting pump A or B

first did not matter.

UST level was dropped to 55% and the- running CF pump was

tripped to initiate an autostart of the CA pumps. A

swapover to RN occurred ' on train A only. The time

difference between pump starts was measured and concluded

.to be negligible.

1

5. Dynamic Testing Conclusions

As a result of the testing the following conclusions were

reached:

a. With 2CA6 shut and UST level between 55-60%, starting

the MDCA pumps simultaneously or slightly staggered

would cause a swapover to RN on "A" train only because

of 3 reasons.

(1) The suction pressure transient dipped lower and

lasted longer than expected.

(2) The pressure transient as sensed by "A" train

instruments typically lasted 0.3 to 0.4 seconds

longer than "B" train due to the location of the

instruments and the length of impulse lines.

(3) The time delay relay on "A" train (4.15 seconds)

was shorter than "B" train (4.70 seconds).

b. With UST above 90% and 2CA6 shut or with 2CA6 open,

enough NPSH was available during tha trarsient to

pre,ent swapover.

6. Conclusions

Partial swapover of CA to RN on train A occurred because of

the following reasons:

1

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-25

1. 2CA6 was shut by operations- to eliminate water-

migration between Uni.ts 1 and 2 and to prevent loss tf

CACST level.

'

2. UST : level had dropped to 55-65% level 'without'

knowledge of the operators since the pen recorder _had

stuck at 90%.

3. Two pressure. switches of . Train A suction and one on -

Train B were slightly high out of tolerance.

4. The time delay : relay on Train A was shorter than on

Train B and the transient was sensed by Train A for a

slightly longer time; therefore, swapover only

occurred on Train A.

5. The logic for swapover was made up for the MDCA pump

and not for the TDCA pump.

7. Corrective Actions for Short Term

The licensee has committed to operating with valve ICA6

and 2CA6 open until evaluations determine an operating

envelope for proper autostarts of the CA pumps.

B. Investigation of Clam Fouling of RN Supply

1. History of Licensee Program For RN Fouling

a. On September 3, 1980, Arkansas Nuclear One experienced

low service water flow through the containment cooling

' units due to Asiatic clams in the system. As a

result, NRC issued IE Bulletin 81-03 on April 10,

1981. The Bulletin requested, in part, that holders

of construction permits (Catawba at time of Bulletin)

determine if Asiatic clams were present in the

vicinity of the station, determine whether

infestations were present in potentially affected

systems, components, or systems affected, and outline

corrective and preventative actions. The licensee

responded in July 1981 and March and September 1983.

The following summarizes the responses:

(1) 1981 Response Summary

- The Asiatic clam has been present in the

Duke service area since the mid 1960s. In

1978 Duke formed an ad hoc committee to deal

with clam related problems at all Duke

generating facilities.

,

4 y~. ~_ , , , - , ,, ,, . - - .,

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,

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At Catawba, clams are a-potential ' problem in

4~ two systems that have safety-related ,

implications, the Nuclear Service Water (RN)

system and the Fire. Protection Systems (RF

and RY).

-

The. Catawba RN system includes provisions to

~

prevent the introduction of clams into the

'

system .from the lake via . the RN intake

structure by filtering the water discharged

from each RN pump through a strainer with

1/32 inch openings. Provisions have also

been made to allow backflushing the.

redundant heat exchanger trains and piping

to remove any clams in safety-related RN

'

components and piping. -

-

Chlorinated filtered water is used to

provide normal makeup and maintain pressure

in the fire protection system. The main'

fire pumps on the intake structure are

equf pped with basket strainers on the pump

suction which prevent mature clams from

being - pumped into the system. Periodic

operational testing of the main fire pumps '

will detect any blockage of the pump. suction

veri fy acceptable pump

.

screens and

performance.

-

Periodic performance monitoring programs to

verify adequate flow, and visual inspection

of the intake piping and inlet heat

exchanger heads during maintenance will

provide early detection of any clam .

!

Infestation of raw water systems.

(2) 1983 Response Sr nary

-

Clams are a potential problem in the Nuclear

Service Water (RN) and fire protection (RF

and RY) systems.

-

Following turnover of the RN system to the

Nuclear Production Department, the system

will be functionally tested to verify

capability to supply required cooling flows

in accordance with plant safety analysis.

Subsequently two heat exchangers in the RN

system will be monitored on a quarterly

.

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6

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27

basis by setting reproducible flow through

the heat exchanger and recording the inlet

and outlet pressures. The differential

pressure will be checked to determine if

significant fouling has occurred. The heat

exchangers will be a-component cooling water

heat exchanger and the Diesel Generator

Starting Air After Cooler.

-

Preventative actions now being taken consist

of preventive maintenance inspection' of

system components and backflushing of raw

water system piping. The frequency of these

inspections and backflushes is now

determined by what is discovered when

components are examined. System performance

monitoring will also be used to determine

frequency of preventative maintenance once

the plant is operational.

-

The October 17, 1983, final report on the

Corbicula infestation recommends that

flushing of RN lines, especially low flow

lines, be accomplished twice a year.

b. Presently, Catawba has in place several programs and

practices designed to verify adequate Nuclear Service

Water (RN) flow to various systems and components.

This includes the following activities:

-

The RN system is periodically flow balanced to

verify the required RN flow rates are maintained

to the appropriate equipment.

-

Essential heat exchangers serviced by the RN

system are systematically tested to verify their

heat transfer capability, or are cleaned

periodically, based on differential pressure

indications, to prevent fouling. During

cleaning, these heat exchangers and/or any other

raw water system piping are examined for the

presence of clams or unusual fouling conditions.

-

The inspections of the RN system dead leg piping

for clams has consisted of spot radiographic (RT)

inspection. In April 1987, questions concerning

accumulation of clams in the RN system dead legs

resulted in spot RT inspection of three low spots

in each unit's RN to CA lines. In addition, in

March 1988, prior to the Unit 2 CA swapover to

the RN system, two low spots in the Unit 1 RN to

CA dead leg piping were RT inspected. None of

the RT inspections revealed any clams.

.-.

._ . ._- . .. . - . .. --

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2. Flushes and Inspection of Nuclear Service Water (RN) and

Associated Systems

As a . result of the Unit 2 Auxiliary Feedwater (CA) System

Swapover from Condensate (CS) to RN system water and the

subsequent introduction of raw water and clams into the CA

system, the licensee initiated a program of flushes and/or

inspection of dead legs between the RN system and various

. safety-related systems. Since RN water was introduced.into

Train "A" of the Unit 2 CA system, the flushes for Unit 2

included flushing :CS water- through Train "A" CA flow

control valves to steam generators "A" and "B" . The

following summarizes the results of the flushes / inspections

and the NRC's inspection activities:

a. Flushes / Inspections

(1) RN to CA

There is approximately 250 feet of six inch RN

pipe connecting each- train of CA piping to the

main RN Header. This 250 feet of RN pipe as well

as the connecting CA piping contains stagnant RN

water. Each train of both Units 1 and 2 was

flushed at approximately 1500 gpm for greater

than 30 minutes until relatively clean. The

flush path was from the RN header through the

stagnant RN and CA piping to the Condenser

Circulating Water (RC) system. The results were

as follows:

-

Unit 1 - Visual of flush samples taken at

drain valve ICA176 revealed some

small clams (< 1/2 inch diameter)

in train "B" and small clam

fragments in both trains "A" and

"B"

-

Unit 2 - Procedure and sampling identical

to Unit 1: results similar to

Unit 1

After flushing, Unit 2 Train "A" and "B" stagnant

RN piping was spot RT inspected for the presence

of clams. Each train received five spot RTs (17

inches for each spot). The five areas included

the two low spots in each train. No clams were

found.

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In . addition to the flushing and RT inspections,

check valve CA172. was disassembled on both

Units 1 and 2 and the CA piping on either side of

the valve inspected for' clams with<a boroscope

~("Videoprobe"). Results were as follows:

-

Unit 1 - Piping for about three feet on

either side of valve ICA172 was-

inspected. Water contained -some

silt and was fairly cloudy. No

clams were detected.

-

Unit 2 - On the downstream side of valve

2CA172, piping was inspected to

valves 2CA116A and 2CA15A. On the

t upstream side of the valve, piping

was inspected to valve 2RN 250A.

'

The water was fairly clear and the

pipe walls appeared clean. No

clams were detected.

Historically, the only flush these lines have

received has been during the quarterly Inservice

Test (IST) of check valves CA171 and CA172.

These check valves - are partially stroked each

quarter in accordance with PT/1(2)/A/4200/08F, CA

Pump Suction Check Valve Partial Stroke Test.

This test requires that isolation valves RN250A

and RN310B be opened and a small flow be

established through the check valves and out

CA183 and CA184 test drain valves to a sump.

Therefore, only minor flushing occurs and RN

water is introduced to the CA system dead legs,

t

During evaluation of the event the following

Unit 2 valves were disassembled for inspection of

the valves and/or inspection of the piping:

2CA1

2CA3

2CA129

2CA172

2CA116A

2CA175

2CA173

2CA174

2CA48

2CA52

2 CAPS 5230

2CA56

2CA60

. ,_ . . _ _ , ,, _ _ _ _ , _ _ ,

'

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• ~ ,

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. . .

30

No significant problems were identified except

.for valves 2CA56 and 2CA60 which are described

below.

,

(2) Condensate to CA

After flushing RN to CA piping, .the dead legs' in

the CA piping were flushed with condensate ' water

to remove residual RN water from CA lines (both

Units 1 and 2). The flow paths were as follows:

-

CA129 - calla - CA12 - CA15A -Call 6A - CA175

to RC

-

CA129 - CA98 - CA98 - CA18B - CA858 - CA175 ,

to RC

-

CA129 - CA171 - CA858 - CA175 to RC

These flushes were accomplished before the

boroscope inspection described in paragraph (1)

above.

(3) RN to Component Cooling (KC)

RN supplies emergency makeup water to the KC

system. The RN piping between the supply header

and the RN/KC isolation valve is a short section

containing stagnant RN water. The licensee

concluded that clam infestation was likely in

these pipes. RT inspection was performed at

suspect locations (low spots) on both trains of

both units. In addition, A and B trains on

Unit 2 and B train on Unit 1 were flushed. The

flush path was from the RN system through

temporary drains on disassembled valves KC 498

and KC495 to the basement sump. A minimum

pressure of 50 psig was considered adequate to

remove any debris.

The results of the flushes and RT inspections

were as follows:

-

Unit 1 - Train A: RT inspected, no clams,

not flushed.

- Train B: RT inspected before and '

after flush. No clams

before or af ter flush.

Good flow during

flushing.

_ _ _ _ _ -_ - - _ - . . _ - . ._ _ __ ___ __ . _ _ -

_ --___

.

. $. '

s

. .

31

s

-

Unit 2 - Train A: Vertical connection to

RN. -RT before flush

revealed several small

' clams. During flush,

debris could be heard

moving in-pipe - assumed

'

to be clams. RT after

.

flush revealed'no clams.

-1 Flow was good.

- Train B: Horizontal connection to

RN. RT before flush

revealed an object that

appears to be a clam.

The object is still

visible by RT after

flushing. Flow was

good.

(4) RN to Containment Penetration Valve Injection

Water (NW)

RN is the safety related source of water for the

NW system. These stagnant RN lines were flushed

through their normally closed isolation valves to

confirm whether clam . infestation could degrade

their ability to operate. Flow rates were

acceptable with a clean water discharge. Also,

all in-line valves in trains 18 and 2B (NW61B and

RN493) were successfully stroked and checked for

shutoff capability.

(5) RN to Spent Fuel Pool Cooling (KF)

RN supplies emergency makeup water to the KF

system. RN lines to the spent fuel pool are not

restricted by valves with limited flow or

components with narrow passages. Each train has

an unobstructed path to the spent fuel pool.

Therefore, flushing of the stagnant lines was not

considered a high priority or re-start issue.

However, the licensee planned to flush these

stagnant lines shortly after re-start of the

plants. Radiographs taken later did reveal the

presence of some clams and a flush procedure is

being developed.

.

f

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__ ,- . _ _ _ - . _ . , -.

_ ._- _ _ - -

.-

..

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,

. .

32

'

(6) Condensate through CA to Steam Generator (S/G)

(Unit 2, Generator A and B)

During the initial. event (swapover to RN), flow

through CA train A degraded to approximately 100

gpm to S/G A and 200 gpm to S/G B versus a design

flow' rate of- approximately 300 gpm -per S/G.

Af ter plant shutdown, flow control valves 2CA 56

and 2CA60 were disassembled and found to be-

clogged with clam fragments. Approximately 1 1/2

pints of clam fragments were found in each valve.

The valves are Design ET Fisher Controls valves

with anti-cavitation cages which have 1/8 inch to

1/4 inch diameter flow holes. The clam fragments

easily clogged the small holes. TDCA Pump Flow

Control Valves (2CA48 and 2CA52) were

disassembled and inspected. No clams were found.

Later investigacions revealed that only A Train

motor driven CA pump swapped over to RN.

Due to RN water and clams being introduced into A

Train MDCA pump suction and discharge piping, it

was necessary to assure that these lines were

free of clams and clam fragments that would l

degrade flow. The lines had. seen. approximately

20 minutes of degraded flow from condensate after

switch back from RN to condensate. Af ter the

flow control valves (2CA 56 and 2CA 60) were

disassembled and cleaned, the A train MDCA pump

suction and discharge were flushed approximately

10 minutes to each S/G using condensate water.

The flow path was from condensate through the CA

pump to the S/Gs. The flow rate was approxi-

mately 700 gpm, or about twice the design flow

rate. Therefore, the suction piping saw 700 gpm

for approximately 20 minutes. There was no

degradation of flow. The valves (2CA 56 and 2CA

60) were disassembled and inspected for clams a

second time. A few small fragments were found in

each valve. Further investigation indicated

that, based on the location of the small

fragments and the method used to clean the

valves, the fragments most likely had not been

removed during the first cleaning. The licensee

declared the lines clean and reassembled the

valves.

In addition to the above flushes, piping down-

stream of CA pump 2A was inspected for clams at

valves 2CA 27, 2CA 28, and 2CA 29. No clams were

found.

>

, =- ---- - . , . , . , - - - , , , - - , - , , - - - - - --

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Additional flushing . occurred during flow

balancing the CA system. Train "A" was operated

a minimum of 20 minutes at approximately 600 gpm

through the pump- and 300 gpm to each S/G. No

flow degradation occurred.

After all flushes had been completed, the CA

system again swapped over to the RN system during

dynamic testing (see paragraph III.A.4) in mode

3. After switching back to Condensate Water,

flow control valves - 2CA56 and 2CA60 reacted

properly and therefore no further inspection was

required.

b. NRC Inspection Activities

The NRC AIT members reviewed / observed the following

relative to the activities detailed in paragraph a.

above:

(1) The team reviewed flush paths, completed

procedures and results of the flushes described

above. The procedure review specifically

included the following procedures:

TT/1/A/9200/13 - RN to KC Assured Source Piping

Flush

TT/2/A/9200/12 - RN to CA Piping Flush

TT/2/A/9200/18 - RN to KC Assured Source Piping

Flush

TT/2/A/9200/12 - RN to CA Piping Flush

The RN to NW flushes were documented on a

memorandum to file dated March 12, 1988. The

team questioned whether a memorandum was adequate

documentation for this work. The licensee

pointed out that no plant conditions were changed

and that valve manipulations for the flushes were

documented under their Removal and Restoration

(R&R) procedures. The team verified by visual

observations that systems were restored to their

correct alignment after flushing.

(2) For the RN to KC flushes, valves KC495 and KC498

were disassembled. The valve work was covered by

Work Requests 5289MNT, 5290MNT, 5291MNT and

5292MNT. The team reviewed the completed Work

. _ -

_ . , , ,_ _ _ _ .

._.

5 S

.

2..

' 'e .

Requests including associated ' documentation to

insure that valves. and systems were returned to

-

required conditions.

(3) Video tape recordings of the boroscope inspec-

tions performed of CA piping through valve CA172

'were reviewed.

(4) The two trains of Unit 2 stagnant piping (250

feet / train) between the RN header and the CA

system were walked-down to insure that low spots

were identified for RT inspection. RT film for

these sections of pipe were reviewed.

(5) RT film associated with - the KC flushes were

reviewed.

(6) Valve lineup and preparations for Train.1B RN to

KC flush was observed.

(7) Operability evaluations (PIRs 1-C88-0108 and

2-C88-0107) relative to flushes were reviewed.

3. Evaluation of Short Term Corrective Actions

(a) Effectiveness of Short Term Actions

The licensee's short-term corrective actions to eliminate

clams and clam shells from the CA system lines and the RN

system lines by flushing these lines with relatively high

volumeteric flows while obtaining confirmatory indications

that clams and clam shells are absent from these lines was

judged adequate for the restart of Catawba Units 1 and 2  ;

based on fundamental fluid dynamics considerations and

confirmations by visual and radiographic examinations.

However, long term corrective actions are also required to

.

assure the effective control of clams in the RN system

lines as the present configuration of the RN/CA system

interfaces are conducive for clams growth and infestation.

-

A brief discussion of these considerations is given below.

(b) Flushing of CA System Lines

The CA system lines were flushed with a flow rate of

approximately 700 gpm. This corresponds to an average flow

velocity of 17 ft/see to 31 ft/sec in the 4-inch and 3-inch

diameter lines, respectively. The CA pump discharge line

rises from the CA pump elevation to the steam generator

,

d

- . . - - - , , .,. ,v.- , -- -

--. ---- - - . . - . . - - --

.. .

a

>

. .-

35

level. The Reynolds numbers associated with these flow

velocities are of the order of 4x10' to 8x105, well into

the turbulent flow regime. Empirical velocity profiles

indicate that, within a distance of a few hundredths of an

inch from the interior wall of the pipe, the flow velocity

is already close to 60% of the average velocity. Based on

empirical data and drag and lift coefficients, this range

of flow velocities is estimated to create sufficient drag

and lift forces on the clams and clam shells in the CA

system discherge lines to flush them out of the lines.

As to the 10-inch diameter suction line to the CA pump, it

runs vertically down from the RN line. The average

velocity in the line is of the order of 3 ft/sec for a flow

rate of 700 gpm. The flow is still sufficiently turbulent

so that the drag and lif t forces on the clams and clam

shells are estimated to be sufficient to flush them out of

the line.

The .above discussions indicated that the short-term

corrective action of flushing the CA lines with a 700 gpm

flow is judged adequate for the removal of clams and clam

shells from the lines. This judgement, is confirmed by the

observatior. that the number of clam shells and shell debris

collected at the CA flow control valve was practically none

after flushing.

(c) Flushing of RN lines

The RN lines were repeatedly flushed with a flow rate of

1500 gpm. This corresponds to an average velocity of

approximately 17 f t/sec in the 6-inch diameter RN lines.

The Reynolds number associated with this velocity is about

8x105, well into the turbulent flow regime. As indicated

earlier, for turbulent flow inside a pipe, at this Reynolds

number, the velocity at a distance of a few hundredths of

an inch from the interior wall of the pipe is already close

to 60% of the average velocity. Therefore, the turbulent

! flow is estimated to create sufficient drag and lift forces

on the clams and clam shells to flush them out of the NSW

i lines. This co,'clusion is supported by two confirmatory

indications: (1) the results of visual inspections of

selected portions of the RN lines indicating the absence of

I clams and clam shells, and (2) the results of rad'ographic

examinations of selected portions of the RN lines including

all the low points indicating the absence of clams and clam

l shells.

l

l

I

.

L

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a

. .

36

4. Long Term Corrective Actions

The presence of Corbicula sp. organism or shells in the local

environment of Catawba Station (Lake Wylie) was well recognized

by the licensee. In response to NRC IE Bulletin 81-03, "Flow

Blockage of Cooling Water to Safety System Components by

Corbicula SP. (Asiatic clam) and Mytilus SP. (Mussell)," actions

were taken by the licensee to address clam-related problems.

These actions included provisions in the FSAR section 9.2.1.6 to

prevent the introduction of clams into the RN system from the

lake by filtering the water discharged from each RN pump through

a strainer with 1/32 inch openings; provision to allow

backflushing the redundant heat exchanger trains and piping to

remove clams from safety-related components; provisions of flow

elements in the RN system to allow verification of adequate

service water flow to safety-related heat exchangers during

performance monitoring programs; and the visual inspection of

the intake piping and inlet heat exchanger heads during

maintenance for the early detection of clams.

These actions collectively have been effective in controlling

clam-related problems associated with the component cooling

water heat exchangers and diesel generator cooling. However,  :

due to the relatively stagnant conditions in the 250 feet of

6-inch diameter segments of the RN to CA system lines,

additional corrective actions are required to assure that clams

will not grow in these lines.

The 250 feet of 6-inch diameter piping from the RN system to the

CA system is not entirely stagnant, but has a flow of about 10

gpm, and is likely to have temperatures above 65 F. These

conditions provide a favorable environment for the breeding and

growth of the C_oribicula sp. There are several options for the

control of the breeding and growth of the species:

Option 1: Chlorination

Shock chlorination to control mature clams requires a high

concentration of free residual chlorine of 10 to 40 ppm for a

duration of about 54 hours6.25e-4 days <br />0.015 hours <br />8.928571e-5 weeks <br />2.0547e-5 months <br /> to ensure a 90% mortality. To

control shelled larvae of about 200 microns in size, chlorine

residual of 0.3 to 0.4 ppm is required for a duration of about

100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> to ensure a 100% mortality. Since clams grow about

1/4 to 1/2 inch per year depending on the environmental

conditions, to control the size of clams in the system to less

than 1/8 inch would require at least a quarterly treatment. The

effectiveness of the treatment can be enhanced by performing it '

during peak clam spawning periods, and the use of clam traps and

mechanical cleaning, if feasible, during outages. Chlorination

is generally acceptable only in closed systems.

.. _ -

t, ..

4

. .

37

Option 2: Heat Treatment-

Corbicula sp. is more vulnerable ' to heat than to chlorine

treatment. A 2-minute exposure to 120 water would lead to a

99% mortality of mature clams and larvae. Another nuclear power

plant licensee has observed a 100% mortality rate when their

service water system was flushed ~ with 170 F water from the

auxiliary boiler for about 30 minutes. The backflushing of a

system with sufficiently hot water will achieve the dual

objectives of ensuring a 100% mortality of mature clams as well

as larvae, and the removal of clam shells from the system,

Option 3: System Modifications

Potential system modifications may involve the removal of the 10

gpm flow through the relatively stagnant RN line by re-routing

the 2 inch line to another location; relocating the CA/RN

interface valve or adding another isolation valve upstream of

the relatively stagnant RN line; or provide means for

backflushing the relatively stagnant RN line. These system

modifications aim at developing an un-inhabitable condition for

clams or allowing the line to be chlorinated, heat treated, or

backflushed. t

Option 4: Other biocides or Chemical Treatments

On a longer. term, other biocides or chemical treatments may be

developed to inhibit and control clam growth as well as meeting

existing state environmental restrictions. Currently there are

many questions about the feasibility of developing an effective

program, and its testing and verification. Therefore this

I

option appears to be suitable only for a much longer term

application.

IV. REGULATORY REQUIREMENTS

A. Catawba Technical Specification 3.7.1.2 requires that three

independent steam generator auxiliary feedwater pumps and .

'

associated flow paths be operable with:

-

Two motor-driven auxiliary feedwater pumps, each capable of

being powered from separate emergency busses, and

-

One steam turbine-driven auxiliary feedwater pump capable

of being powered from an operable steam supply system when

the unit is in modes 1, 2, or 3.

With one auxiliary feedwater pump inoperable, it is required to

be restored to operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or be in at least

hot standby within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in hot shutdown within

the following 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.

'

_ .

..

g.

' '

38

With two auxiliary feedwater pumps inoperable the unit must be

in at least hot standby within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in hot shutdown

within the following 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.

It is further required that each auxiliary feedwater pump be

demonstrated operable at least once per 31 days on a staggered

test basis by:

-

Verifying that each motor-driven pump develops a total

dynamic head of greater than or equal to 3470 feet at a

flow of greater than or equal to 400 gpm,

-

Verifying that the steam turbine-driven pump develops a

total dynamic head of greater than or equal to 3550 feet at

a flow of greater than or equal to 400 gpm when the

secondary steam supply pressure is greater than 600 psig

and the auxiliary feedwater pump turbine is operating at

less than or equal to 3800 rpm and,

-

Verifying that each non-automatic valve in the flow path

that is not locked, sealed, or otherwise secured in ,

position is in its correct position.

It is further required that at least once per 18 months that the

valve in the suction line of each auxiliary feedwater pump from

the Nuclear Service Water System be tested to verify that it

automatically actuates to its full open position within less

than or equal to 15 seconds on a loss-of-suction test signal.

The conditions of the plant which may have been contrary to the

above requirements are:

1. On March 9, 1988, with the unit operating at 20% power,

three independent steam generator auxiliary feedwater pumps

and associated flow paths were not operable in that;

-

During an actual turbine trip /feedwater isolation

transient and resulting auxiliary feedwater (CA)

initiation, the train A discharge flow control valves,

,

2CA 56 and 2CA 60, became clogged with Asiatic clam

shells and did not properly function af ter MDCA pump

2A suction realigned to the nuclear service water

assured source.

B. 10 CFR Appendix B, Criterion XI, requires that a test program be

established to assure that all testing required to demonstrate ,

that structures, systems, and components will perform

'

satisfactorily in service is identified and performed in

accordance with written tests procedures which incorporate the

requirements and acceptance limits contained in applicable

design documents. The test program shall include, as

i

- -- -

. ,_ , . . . _ . - . _ _ . - . _ _ _ , _ _ _ . , ,_ _ __.-._.. -.___. . - . - -

.

. .

.*

• '

39

appropriate, proof tests prior to installation, pre-operational ,

tests, and operational tests during nuclear power plant

' operation, of structures, systems, and components. Test results

shall be documented and evaluated to assure that test

requirements have been satisfied.

The surveillance program recommended in response to NRC

Bulletin 81-03 stated that flushing of RN lines, especially low

flow lines, twice a year was appropriate. This was documented

in a memo dated October 17, 1983, from J. J. Hall to

R. W. Quellette and was presented to the AIT.as the final report

referred to in the early 1983 Bulletin responses that was to be

available by November 1983. In lieu of flushing, the licensee

performed RT of selected pipes for clam infestation.

This flushing was not being accomplished. Also, the

radiographic inspections that were made were inadequate in that

they did not show clams and clams were present.

V. CONCLUSIONS

A. Reportability Review

The inspector reviewed the telephone reporting of the event to

the NRC. The licensea appropriately reported the Unit 2 Reactor

Trip as required. L;ter that evening, the licensee recognized

the possible significant degradation of the CA system. Although

the 11censee communicated the additional information effectively

to NRC: Regior. II the following morning, it would have been

appropriate to initiate a followup phone call to NRC on the

previous backshift in order to allow a more timely assessment by ,

> the NRC of the event. The licensee indicated that personnel

would be sensitized to make followup calls when bdditional

significant information is discovered relative to events and

that more procedure guidance would be developed in this regard.

The next day, the licensee properly reported the shutdown of

both units and the Unusual Event caused by the degraded systems

during shutdown.

B. Auxiliary Feedwater Suction Swapover to RN

1. CA to RN swapover occurred, during the March 9, 1988 event,

to the A train MDCA pump due to a momentary low pressure

condition caused by the suction lineup being different than

on previous CA pump auto-starts. The CACST was isolated ,

'

and the UST level was lower than normal.

2. A more timely debriefing of the opera + ors involv0d would

4

have expedited the event evaluation,

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13. There were 'no precursors to the event which would have

provided ^ early - warning and no' equipment problems were

repetitive or were ignored.

4. Short: term corrective action is adequate.

C. Auxiliary. F' eedwater Degradation of Flow

1. The' CA flow degradation was due to clam particles clogging -

the flow control valves. The clam particles were induced

when the CA suction swapped to RN supply. The clams in the-

RN supply were there due to inadequate surveillance of the

stagnant lines.

2. Some surveillance for clams in the stagnant lines was

conducted by radiography but was inadequate as clams were

found in the lines after radiography.

3. The licensee took appropriate and timely corrective actions

by evaluating similar conditions on the other units.

Catawba Unit I was shutdown and the stagnant lines flushed

and inspected. Stagnant lines at McGuire Units 1 and 2

were inspected by boroscoping.and they were found clean.

i 4. Flushing of stagnant lines at Catawba was recommended but

not accomplished.

'

l 5. -The short term corrective-actions are adequate.

[ VI. EXIT

.

.

,

The inspection scope and findings were summarized on March 18, 1988,

with those persons indicated in section I.V. The inspector described

the areas inspected and discussed in detail the inspection findings.

No dissenting comments were received from the licensee, but areas of

concern will be addressed at the forthcoming enforcement conference.

[

'

.

The licensee did not identify as proprietary any of the material

i provided to or reviewed by the inspectors during this inspection.

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                                                                            ATTACHMENT 2                                                                                  Page 1 of 2
     0
   o
                                                                       OETAIL FIGURE 1
       ,    . Dgsigns ED, E AD, ET, E AT                                                                                            -
           Installation                                                                           7. Iron easy.e valve bodies are rated at 125 and 250 lb.
                                                                                                 ANSl; steel and alloy steel bodies are rated at 150, 300 and
             1. Before ,nstalling
                         i         an easy-e body, inspect it for any sh,p.       i
                                                                                                 600 lb. ANSI. Do not install the valve in a system where the
           ment damage and for any foreign material that may have                                working pressures exceed those specified in the standards.
           collected during crating and shipment.                                                                                                                                         .
             2. Blow out all pipelines to terrove pipe scale, welding
                                                                                                 Maintenance
           slag, and other foreign materials.
             3. Install the valve so that flow through the body will be                                                       WARNING

I in the direction indicated by the flow direction arrow on

           the body.                                                                                    To avo:J personal injury and damage to the
                                                                                                        process system, i:of t.te the control valve from
             4. Install the valve using accepted piping practices. For                                  the system and release all pressure from the

f flanged bodies, use a suitable gasket between the body and body and actuator before disassembling. '

           pipeline flanges. Before installing welding-end bodies having
           composition seats, remove the trim to avoid damage to elas-
           tomer parts fron: heat generated by welJing.                                          Disassembly
                                                                                                 Part names used in the following steps refer to figure 2
             5. Control valves with an easy e body can be installed in                           except where indicated.
           any position, but the normal method is with the actuator
           vertical above the body.                                                                                             .
                                                                                                   1. Af ter the actuator is disconnected and taken off the
                                                      .
                                                                                                 body, remove the nuts (key 16, figure 7) or cap screws from
             6. If cont;nuous operation .is required during maintenance                          the bonnet flange.
            and inspection, install a conventional three valve bypass
            around the body.                                                                       2. Lift off the bonnet along with '                                      'ug and stem
                                                                                                             $1140                                 ,                                        ,
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             2
                                                                                                                                                                                                l
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                                                                                             . _ _ - _ _
 o'           ' Attach'nent 2                                                                            DETAIL FIGURE 2                              Page 2 of 2
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                                                                                                                                         Designs ED, EAD, ET, EAT
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 [                                                     LINEAR                                                                         WHISPER TRIM 31
                                                                                          Figure 3. Cages for easy-e Bodies
                     3. Loosen the pacWng flange nuts (key 5, figure 12) and                                           6. Lif t out the seat ring and its gasket. For composition
       y           separate the valve plug and stem from the bonnet. If th)                                          seats,lif t out the disc retainer, disc seat and disc.            r
                   stem needs replacing, drive out the groove pin and unscrew
                                                                                                                                                         ,
                   the stem. If the valve plug needs raplacing, always reclace
                   the entire valve plug and stem assembly.                                                          Reassembly
                                                                                                                     Part names used in the following steps are shown in figure 2
                                                                                                                     except where indicated.
                                                                                                                       1. Clean all gasketed surf aces and use all new gaskets for
                           Never use an old stem with a new valve plug.                                              reassembly.
                           The use of an old stem <equires drilling a new
                           groove pin hole through the stem, thereby                                                   2. For restricted trim (figure 8), replace the seat ring
                           weakening the stem.                                                                       adaptor gasket (key 14) and adaptor.
                     4. The internal parts of the bonnet can be disassembled,if                                        3. Install the seat ring gasket and replace the seat ring. If a
                   desired. For packing replacement, instructions are given in                                       composition seat is used, assemble it by inserting the disc
                   the section "Replacing Packing." For bellows seat replace-                                        into the disc retainer and slip this assembly over the disc
  ,
                   ment, follow the section entitled "Replacing Bellows Seal."                                       seat.
                                                                                                                       4. Install the cage on top of the seat ring. Be sure that the
                                             CAUTION

l' cage slips onto the seat ring properly. Any rotational orien- l tation of the cage with repect to the body is acceptable. I

                           The exposed portion of the cage provides a
                           guiding surf ace that must not be damaged dur.                                              5. For full site trim, place cage gasket, spiral wound gas.
                           ing disassembly or maintenance. If the cage is                                            ket, and bonnet gasket on the shouldcr of the cage,
                           stuck in the body, use a rubber mallet to strike

( the exposed portion at several points around 6. For restricted trim, place the cage gasket, spiral wound

                           the circumference.                                                                        gasket, and another cage gasket on the sholder of the cage.
          '
                                                                                                                     For 2" x 1" angle and 11/2" x 1" globe bodies, a body
            3        5. Lif t out the cage and gas,ats. For restricted trim                                          adaptor gasket (key 20, figure 11) is required be* ween the
         "
                   (figure 8), also remove the cage adaptor (key 4) and seat                                         cage adaptor and body. Insert the cage adaptor and place
                   ring adaptor (key 5).                                                                             the bonnet gasket on the adaptor.
                                                                                                                                                                                        1
                                                                 - - - - - - - - - - - - - -                                                                                            )

         '
  .
 * *
     '
                                                  ATTACHMENT 3       _
                                                                                        Page 1 of 3
                                                   UNIT E D ST AT Es
        ,[pMf       'o
                   " ,d
                                        NUCLEAR REGULATORY COMMISSION
       &'                                             REoloN 11
       C'              o                     101 M ARIETTA sTRE ET. N.W.
                       j
             s
       (*                                     ATLAN1 A, GEORGI A 30323

' \ $'

           %                                         3l)3l)Y
               Oocket Nos. 50-413, 50-414
               License Nos. NPF-35, NPF-52
               Duke Power Company
               ATTN: Mr. H. B. Tucker, Vice President
                         Nuclear Production Department
               422 South Church Street
               Charlotte, NC 28242
               Gentlemen:                                                                          .
               SUBJECT:    CONFIRMATION OF CONCURRENCE - STARTUP OF UNIT 2 - DOCKET NO 50-414
               This letter is to confirm our concurrence with your intention to restart Unit 2
               following completion of your short term corrective actions relative to the
               Catawba Unit 2 trip on March 9,1988 and subsequent swap-over of the auxiliary
               feedwater pumps suction supply and degraded auxiliary feedwater system flow.
               We had earlier confirmed with you our understanding of commitments to be
               completed prior to restart of Units 1 and 2 in a letter dated March 11, 1988.
               Af ter a review of your short term corrective actions by the NRC Augmented
               Inspection Team we gave you verbal concurrence to restart Unit 2 on March 18,
               1988 at about 9:00 a.m. Concurrence was given with the understanding that the
               Auxiliary Feedwater (CA) Condensate Storage Tank (CST) isolation valve (CA-6)
               would remain open pending your analysis of CA system transient data. Also, it
               is our understanding that if your short term analysis of CA system transient
               data supports a change in system configuration to assure a supply of quality
               condensate grade water you will keep NRC Region II and the Catawba Resident
               Inspectors informed.
               If your understanding is dif ferent from the above, please inform this office
               promptly.
                                                                 Sincerely,
                                                                         t
                                                                 J. Nelson Grace
                                                                 Regional Administrator
               cc:    J. W. Hampton, Station Manager                                ~
                      Senior Resident Inspector - McGuire
          S S // 4 /1/ p 4 6 / g

p - - - _ _ _ _ .

-

      3
        
               Attachment 3                                                                                                     Page 2 of 3
                                                         UNITE 3) STATES

l /ja ano "

                                               NUCLEAR REGULATORY COMMISSION
  *
    ,         3"                                            REGION il
           **j                                      101 MARIETTA STREET,N.W.
             *               I
                               f                     ATLANTA. GEORGI A 30323
              %.,,,,*/
                 t                                     March 11, 1988
                   Docket Nos. 50-413, 50-414
                   License Nos. NPF-35. NPF-52
                   Duke Power Company
                   ATTN: Mr. H. B. Tucker, Vice President
                             Nuclear Production Department
                   422 South Church Street
                   Charlotte, NC 28242
                   C:'tlemen:
                   SUBJECT: CONFIRMATION OF ACTION LETTER - DOCKET NOS. 50-413 AND 50-414
                   This letter is to confirm our understanding                                    of comitments made during a
                   telephone call between Mr. T. Owen, Catawba Plant Manager, and Mr. T. Peebles
                   of my stati on March 10, 1988. The telephone discussions related to the
                   Catawba Unit 2 reactor trip and subsequent swap-over of the suction to the
                   auxiliary feedwater pumps and degraded auxiliary feedwater flow. Subsequent
                   discussions were held between our staffs to fully understand your actions
                   relative to the Notice of Unusual Event and shutting down of Catawba Unit 1 as
                   follow-up actions to the Unit 2 degraded auxiliary feedwater flow circum-
                   stances.
                   With regard to this situation, it is our understanding that you have comitted
                   to notify the NRC Region II and Senior Resident Inspector, with adequate
                   advance notice in order to obtain the concurrence of the NRC Region II Regional
                   Administrator or his designee prior to startup (Mode 2).
                   If your understanding of this matter differs 'ren that stated above for either
                   unit, contact this office promptly.
                                                                    Sinceirely,
                                                               jG   J. Nelsen Grace
                                                                    Regional Administrator
                                                                                           .       h
                  CAL 50-413-8801
                        50-414-8801
                  cc:    T. B. Owen, Station Manager
                         Senior Resident Inspector - McGuire
           -wp3 f 94WF
                                                  lp
                                                                          - _ - - - - - - - - -                       - - - - -             1

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     .,.
          
             ' Attachment 3                                                                       Page 3 of 3
     .
                      $7.rfou                                UNITED STATES
                                o                  NUCLEAR REGULATORY COMMISSION
       ,a      '           #
                                                                REGION 11
              3
              **
                                  j                     101 MARIETTA STREET. N.W.
                                                         ATLANT A, G EORGI A 30323
                                  t           .
                '+,           ,d
                     .....
                                                             MAR 17 ;553
   ,
                       Docket Nos. 50-413, 50-414
                      License Nos. NPF-35, NPF-52
                      Duke Power Company
                      ATTN: Mr. H. B. Tucker Vice President
                                  Nuclear Production Department
                      422 South Church Street
                      Charlotte, NC 28242
                      Gentlemen:
                      SUBJECT:      CONFIRMATION OF CONCURRENCE - STARTUP OF UNIT 1 - DOCKET NO. 50-413
                      This letter is to confirm our concurrence with your intention to restart Unit 1
                      following completion of your corrective actions relative to declaration of an
                      Unusual Event and shutting down of Unit 1 on March 10, 1988. We had earlier
                      confirmed with you our understanding of commitments to be completed prior to
                      restart of Units 1 and 2 in a letter dated March 11, 1988. After a review of
                      your corrective actions by the NRC Augmented Inspection Team we gave you verbal
                      concurrence to restart Unit 1 on March 11, 1958 at about 11:00 p.m. Also, as
                      stated in our March 11, 1988 letter, you have connitted to obtain NRC Region 11
                      concurrence prior to Unit 2 restart.
                      If your understanding is different from the above, please infonn this office
                      promptly.
                                                                        Sincerely,
                                                                           9
                                                              [ J. Nelson
                                                                        Regional   Grace
                                                                                    Administrator

j

                     cc:     T. B. Owen, Station Manager
                             Senior Resident Inspector - McGuire

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           *
      ..                                                                       ATTACHMENT 4                                            Page 1 of 3
 '*
                        ,                                                     CA FLOW DIAGRAM
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   TITLEe                      NOTESs
                                                                                10 W'     CN-CF-CA-3 l DATE' 3-7-86
    AUXILI ARY FEEDWATER ( CA)  CACST SUPPLY / OVERFLOW NORMAL                  REF.
                                LINEUP                                           D"" 8    LY / CM      l " * *'
                                                                                             TRAINING USE ONLY

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