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, Three Mile Island, 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
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

power

All holders of operating licenses or construction permits for-nuclear

reactors.

PurDose

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

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

safety-related raw water sources. It is expected that recipients will actions, this information for applicability to their facilities and consider

in

as appropriate, to avoid similar problems. However, suggestions contained

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 safety

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

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

raw

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

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

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

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

two

The auxiliary feedwater system at McGuire Nuclear Station consists of

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 tank, grade source of water for auxiliary feedwater is either the upper surge

the condenser hotwell, or the condensate storage tanks. The safety grade, water

seismic category I source of auxiliary feedwater is the-nuclear service

from the nuclear service water system, system. When aligned to take suction the

train "Al and "B" of the auxiliary feedwater system take suction from 1). The

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

"A"

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

or "B" of the nuclear service water system. In addition to the train

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

suction of the auxiliary feedwater system through a supply line controlled used to

from the standby shutdown facility. (The standby shutdown facility is

mitigate certain fire and security events.)

9302040248 -' D

Th/L C-

IN 93-12 February 11, 1993 The licensee discovered two different sources of

water system that could have potentially affected air in the nuclear service

auxiliary feedwater system. On March 27, McGuire the operability of the

a high point in the Unit 1 standby shutdown system personnel discovered air at

isolation valves that separate the nuclear service line upstream of the

feedwater systems (Valves ICA161C and ICA162C, Figurewater and the auxiliary

repeatedly vented this line over the following days, 2). McGuire personnel

produced at the high point. After thoroughly searching but air continued to be

performing a detailed engineering and chemical evaluationfor air inleakage and

McGuire staff concluded that the air was produced of the system, raw lake water. As a result of this discovery, the by off-gassing of the heated

found the second source of air at high points in licensee searched for and

service water discharge header (Detail A-A, Figurethe NA" train of the nuclear

operating conditions, these additional sources of 2). Under certain

air could have affected the

"A" auxiliary feedwater pumps and the turbine-driven

on both units. auxiliary feedwater pumps

The auxiliary feedwater line from the "A' train on

the discharge line of the emergency diesel cooling each unit is attached to

point where this line discharges into the main "A" heat exchanger, near the

discharge header. The cooling water from the diesel train service water

flows at the rate of 900 gpm. With the diesel running generator heat exchanger

feedwater pump drawing water from the diesel line, and only one auxiliary

sufficient

would be supplied to the feedwater pump suction without diesel coolant

main NA" train discharge line. However, if the "A" drawing water from the

diesel

is lost, or if both a motor-driven and a turbine-driven generator cooling

pump are operated simultaneously, water could be auxiliary feedwater

drawn from the high point on

the main 'A' train discharge line along with any

in this discharge line. The "B" train on each unitair that might have collected

it had a different piping configuration. was not affected because

Discussion

The events discussed in this information notice highlight

off-gassing ft auxiliary feedwater system raw water the potential for

Henry's law, the solubility of a gas in water at sources. According to

approximately proportional to the partial pressurea constant temperature is

at a constant pressure, however, generally decreasesof the gas. The solubility

with increasing

temperature. The solubility of air in water at atmospheric

example, is reduced from 29 milliliter per liter pressure, for

at OC (320F) to

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

with air in the outside environment is not likely that has become saturated

water system supply piping because the pressure ofto emit gas in the service

increased by pumping while the temperature of the the water has been

water remains near its

original value. As this water is heated by the various

the pressure of the water decreases to near atmospheric plant systems, and as

discharge piping, some of the air can be expected levels in the

to

collect above any elevated, slow moving water volumes evolve from the water and

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

5e 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 (t

W ,

'0

D

-A I

Figure 1

MCGUIRE NUCLEAR STATION

NUCLEAR SERVICE WATER SYSTEM

1AJ0

PROBLEM DESCRIPTION

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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 Single Failure Vulner- 02/04/93 All holders of OLs or CPs

ability of Engineered for nuclear power reactors.

Safety Features

Actuation Systems

93-10 Dose Calibrator Quality 02/02/93 All Nuclear Regulatory Com- Control mission medical licensees.

93-09 Failure of Undervoltage 02/02/93 All holders of OLs or CPs

Trip Attachment on for nuclear power reactors.

Westinghouse Model DB-50

Reactor Trip Breaker

93-08 Failure of Residual 02/01/93 All holders of OLs or CPs

Heat Removal Pump for nuclear power reactors.

Bearings due to High

Thrust Loading

93-07 Classification of Trans- 02/01/93 All Licensees required to

portation Emergencies have an emergency plan.

93-06 Potential Bypass Leak- 01/22/93 All holders of OLs or CPs

age Paths Around Filters for nuclear power reactors.

Installed in Ventilation

Systems

93-05 Locking of Radiography 01/14/93 All Nuclear Regulatory

Exposure Devices Commission industrial

radiography licensees.

93-04 Investigation and Re- 01/07/93 All U.S. Nuclear Regulatory

porting of Misadministra- Commission medical

tions by the Radiation licensees.

Safety Officer

93-03 Recent Revision to 01/05/93 All byproduct, source, and

10 CFR Part 20 and special nuclear material

Change of Implementa- licensees.

tion Date to

January 1, 1994 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