Information Notice 1993-12, Off-Gassing in Auxiliary Feedwater System Raw Water Sources

Off-Gassing in Auxiliary Feedwater System Raw Water Sources
	ML031080158
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant, Crane
Issue date:	02/11/1993
From:	Grimes B; Office of Nuclear Reactor Regulation
To:	;
References
	IN-93-012, NUDOCS 9302040248
	Download: ML031080158 (12)
	v • d • e

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C.

20555

February 11, 1993

NRC INFORMATION NOTICE 93-12: OFF-GASSING IN AUXILIARY FEEDWATER

SYSTEM RAW WATER SOURCES

Addressees

All holders of operating licenses or construction permits for-nuclear power

reactors.

PurDose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information

notice to alert addressees to problems that could result from off-gassing in

safety-related raw water sources. It is expected that recipients will review

this information for applicability to their facilities and consider actions, as appropriate, to avoid similar problems. However, suggestions contained in

this information notice are not NRC requirements; therefore, no specific

action or written response is required.

Description of Circumstances

7- In March and April 1992, personnel at the McGuire Nuclear Station discovered

air pockets in the nuclear service water discharge piping supplying the safety

grade auxiliary feedwater for both Units 1 and 2. Duke Power Company (the

licensee) determined the source of this air to be the off-gassing of the raw

lake water caused by the warming of the water by the components cooled by the

nuclear service water system. The air intrusion is a safety concern because

it could cause air binding or damage to the auxiliary feedwater pumps.

The auxiliary feedwater system at McGuire Nuclear Station consists of two

450 gallon per minute (gpm) motor-driven pumps and one 900 gpm turbine-driven

pump that take suction from either of two sources. The normal, condensate

grade source of water for auxiliary feedwater is either the upper surge tank, the condenser hotwell, or the condensate storage tanks.

The safety grade, seismic category I source of auxiliary feedwater is the-nuclear service water

system. When aligned to take suction from the nuclear service water system, train "Al and "B" of the auxiliary feedwater system take suction from the

corresponding nuclear service water system train "A" and "B" (Figure 1).

The

turbine driven auxiliary feedwater pump can take suction from either train "A"

or "B" of the nuclear service water system.

In addition to the train "A" and

"B" nuclear service water, nuclear service water can be supplied to the

suction of the auxiliary feedwater system through a supply line controlled

from the standby shutdown facility.

(The standby shutdown facility is used to

mitigate certain fire and security events.)

9302040248 -'

D

Th/L

C-

IN 93-12 February 11, 1993 The licensee discovered two different sources of air in the nuclear service

water system that could have potentially affected the operability of the

auxiliary feedwater system. On March 27, McGuire personnel discovered air at

a high point in the Unit 1 standby shutdown system line upstream of the

isolation valves that separate the nuclear service water and the auxiliary

feedwater systems (Valves ICA161C and ICA162C, Figure 2).

McGuire personnel

repeatedly vented this line over the following days, but air continued to be

produced at the high point. After thoroughly searching for air inleakage and

performing a detailed engineering and chemical evaluation of the system, McGuire staff concluded that the air was produced by off-gassing of the heated

raw lake water. As a result of this discovery, the licensee searched for and

found the second source of air at high points in the NA" train of the nuclear

service water discharge header (Detail A-A, Figure 2).

Under certain

operating conditions, these additional sources of air could have affected the

"A" auxiliary feedwater pumps and the turbine-driven auxiliary feedwater pumps

on both units.

The auxiliary feedwater line from the "A' train on each unit is attached to

the discharge line of the emergency diesel cooling heat exchanger, near the

point where this line discharges into the main "A" train service water

discharge header.

The cooling water from the diesel generator heat exchanger

flows at the rate of 900 gpm.

With the diesel running and only one auxiliary

feedwater pump drawing water from the diesel line, sufficient diesel coolant

would be supplied to the feedwater pump suction without drawing water from the

main NA" train discharge line. However, if the "A" diesel generator cooling

is lost, or if both a motor-driven and a turbine-driven auxiliary feedwater

pump are operated simultaneously, water could be drawn from the high point on

the main 'A' train discharge line along with any air that might have collected

in this discharge line.

The "B" train on each unit was not affected because

it had a different piping configuration.

Discussion

The events discussed in this information notice highlight the potential for

off-gassing ft auxiliary feedwater system raw water sources.

According to

Henry's law, the solubility of a gas in water at a constant temperature is

approximately proportional to the partial pressure of the gas.

The solubility

at a constant pressure, however, generally decreases with increasing

temperature. The solubility of air in water at atmospheric pressure, for

example, is reduced from 29 milliliter per liter at OC (320F) to

16 milliliter per liter at 30*C (860F).

Raw water that has become saturated

with air in the outside environment is not likely to emit gas in the service

water system supply piping because the pressure of the water has been

increased by pumping while the temperature of the water remains near its

original value. As this water is heated by the various plant systems, and as

the pressure of the water decreases to near atmospheric levels in the

discharge piping, some of the air can be expected to evolve from the water and

collect above any elevated, slow moving water volumes in the discharge piping.

IN 93-12 February 11,

1993 Upon discovering air in the auxiliary feedwater supply line for the Unit 1 standby shutdown system, the licensee declared all three of the auxiliary feed

water pumps to be inoperable. The licensee concluded that these pumps had

technically been inoperable since initial plant operation.

The licensee

isolated the auxiliary feedwater line by closing one of the isolation valves

in this line and removing the power supply to this valve. Although this

action made the standby shutdown line inoperable, the action was initially

considered to be sufficient to return the rest of.the auxiliary feedwater

system to operability. However, after discovering the second source of air in

the high points of the "A" nuclear service water train discharge lines of both

units, the licensee isolated the turbine-driven pumps of both units from the

"A" service water lines and declared the turbine-driven pumps to be

inoperable. This action returned the "A" motor driven pumps to operability, because these pumps alone could not draw sufficient water to ingest air from

the main nuclear service water discharge lines.

The licensee considered several options to correct the problem permanently.

One possible solution was to reroute the safety-grade auxiliary feedwater

lines to take suction from the nuclear service water supply piping. A second

possible solution was to reroute the suction of the auxiliary feedwater lines

to sections of the nuclear service water discharge piping that were not

susceptible to the formation of air pockets. However, the licensee chose a

third alternative, which was to install permanent vent valves at the high

points where air was accumulating (Valves IRN1060, 1RN835 and 2RN815, Figure 2). The licensee piped these vent valves to drains and throttled the

valves to provide a continuous drainage flow that was sufficient to vent any

air that might accumulate in the emergency feedwater supply.

This information notice requires no specific action or written response. If

you have any questions about the information in this notice, please contact

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts: P. Kim Vandoorn, RII

(704) 875-1681

Don Kirkpatrick, NRR

(301) 504-1849 Attachments:

1. Figure 1

2. Figure 2

3. List of Recently Issued NRC Information Notices

5 e L

laLW

MCGUIRE NUCLEAR STATION

AUXILIARY FEEDWATER SYSTEM

UNIT I

MOP IA AND TOP I SUCTION SUPPLY

FROM NUCLEAR SERVICE WATER (RN)

DISCHAROE HEADER IA

C

FOW 10 ND TOP I SUCTION SUPPLY

FROM NUCLEAR SERVICE WATER IRNI

DISCWJR=E HEADER I1 oQ

to c

W

,

D

-A

I

'0

(t

Figure 1

MCGUIRE NUCLEAR STATION

NUCLEAR SERVICE WATER SYSTEM

PROBLEM DESCRIPTION

1AJ0

V ~

AW- SqUA~Ca

lPTAlL 'A-A"

' em,

(

An.

LE

-

e ^eospo^ SV.Hk4%E-

Nof

,C=l

.a

4AfWTP I (

SkyIN j

1oAFW IP^p

SRwTlow HeA~pevy *-45

-fo Co"C1SEpE

ell!eLA-riklo wlk-rEa___

Isr Ad.%

sourcL

-

OW~ll

toB

SPUCTIO.

lltx-or-l

(

I 0'0A~4 P16.SEL

. Aw WkNLk

WEA-ob

ft

t !

,

0

I '

rt

Y-

i%.

f' 0

w

0

IDI

v)

"

loo 4L'AAf SEACE

ARIVA fb#p

Figure 2

v)

Attachment 3

IN 93-12 February 11,

1993 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information

Date of

Notice No.

Subject

Issuance

Issued to

93-11

93-10

93-09

93-08

93-07 Single Failure Vulner- ability of Engineered

Safety Features

Actuation Systems

Dose Calibrator Quality

Control

Failure of Undervoltage

Trip Attachment on

Westinghouse Model DB-50

Reactor Trip Breaker

Failure of Residual

Heat Removal Pump

Bearings due to High

Thrust Loading

Classification of Trans- portation Emergencies

Potential Bypass Leak- age Paths Around Filters

Installed in Ventilation

Systems

Locking of Radiography

Exposure Devices

Investigation and Re- porting of Misadministra- tions by the Radiation

Safety Officer

Recent Revision to

10 CFR Part 20 and

Change of Implementa- tion Date to

January 1, 1994

02/04/93

02/02/93

02/01/93

01/22/93

01/14/93

01/07/93

01/05/93

All holders of OLs or CPs

for nuclear power reactors.

All Nuclear Regulatory Com- mission medical licensees.

All holders of OLs or CPs

for nuclear power reactors.

All holders of OLs or CPs

for nuclear power reactors.

All Licensees required to

have an emergency plan.

All holders of OLs or CPs

for nuclear power reactors.

All Nuclear Regulatory

Commission industrial

radiography licensees.

All U.S. Nuclear Regulatory

Commission medical

licensees.

All byproduct, source, and

special nuclear material

licensees.

93-06

93-05

93-04

93-03 OL = Operating License

CP - Construction Permit

IN 93-XX

January xx, 1993 Upon discovering air in the auxiliary feedwater supply line for the Unit 1 standby shutdown system, the licensee declared all three of the auxiliary feed

water pumps to be inoperable. The licensee concluded that these pumps had

technically been inoperable since initial plant operation. The licensee

isolated the auxiliary feedwater line by closing one of the isolation valves

in this line and removing the power supply to this valve. Although this

action made the standby shutdown line inoperable, the action was initially

considered to be sufficient to return the rest of the auxiliary feedwater