Information Notice 1991-12, Potential Loss of Net Positive Suction Head (NPSH) of Standby Liquid Control System Pumps

Potential Loss of Net Positive Suction Head (NPSH) of Standby Liquid Control System Pumps

ML031190605
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:	02/15/1991
From:	Rossi C Office of Nuclear Reactor Regulation
To:
References
IN-91-012, NUDOCS 9102190010
Download: ML031190605 (5)

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C.

20555

February 15, 1991

NRC INFORMATION NOTICE NO. 91-12: POTENTIAL LOSS OF NET POSITIVE SUCTION

HEAD (NPSH) OF STANDBY LIQUID CONTROL

Addressees

All holders of operating licenses or construction permits for boiling water

reactors (BWRs).

Purpose

This information notice is intended to alert licensees to potential problems

with the adequacy of Net Positive Suction Head (NPSH) for Standby Liquid

Control System (SLCS) pumps. 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 do not constitute NRC requirements; therefore, no specific action or written response is required.

Description of Circumstances

On February 11, 1991, a special test of the Standby Liquid Control System was

performed at Quad Cities Unit 1, to determine if NPSH would be maintained with

the conditions of minimum SLCS tank level and maximum sodium pentaborate solution

temperature in the tank. The test was terminated after about 20 minutes following

indications of pump cavitation due to loss of NPSH.

Following the test, the

licensee determined that with the flow rate achieved during the test, the amount

of sodium pentaborate necessary to bring the plant to cold shutdown would not be

pumped to the reactor vessel with one or both SLCS pumps within the 20 minute

period. In light of the test results at Quad Cities, the licensee declared the

SLCS at Quad Cities Unit 2, and the operating sister units, Drvesden Units 2 and 3, inoperable. Following further evaluation of the test results and engineering

analysis, the licensee increased the administratively controlled limit on SLCS

tank level and reduced the administratively controlled limit on solution

temperature in the SLCS tank at Quad Cities to ensure sufficient NPSH for the

SLCS pumps; verified that current limits at Dresden allowed for sufficient NPSH;

and declared the pumps at the Quad Cities and Dresden units operable.

The SLCS system is required to provide liquid poison in the event that control

rod insertion is inadequate to achieve and maintain a cold shutdown condition.

For low probability Anticipated Transient Without Scram (ATWS) events, SLCS

pump fai ure to inject a sufficient amount of solution to shutdown the reactor

902

/0

IN 91-12 W

February 15, 1991. could result in a serious threat to containment integrity. The total volume of

poison solution required to assure subcriticality at cold, xenon free conditions

in most plants results in a near depletion of the poison storage tank. During

the course of poison injection, the tank level decreases resulting in a decrease

of available NPSH. Insufficient NPSH can lead to reduced pumping capability or

pump failure. While lesser amounts of poison can still maintain the reactor

shutdown at hot conditions, there is a poison level below which the reactor

would still be producing power. Under such conditions containment integrity

can be threatened in the short term.

The basic SLCS design is common to all BWRs and nearly all use similar positive

displacement pumps. Consequently, there is a question as to whether adequate

testing has been performed at other BWRs to assure that throughout the required

range of operating conditions the SLCS pumps will have sufficient NPSH to

perform their intended function.

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

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

the technical contact listed below or the appropriate NRR project manager.

es.Rossi, Director

Div-iision of OperatriilaT Eve-nlts Assessmeni

Mark A. Caruso, NRR

(301) 492-3235 Attachment: List of Recently Issued NRC Information Notices

Attachment 1

IN 91-12

February 15, 1991 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information

Date of

Notice No.

Subject

Issuance

Issued to

91-11

86-99, Supp. 1

89-32, Supp. 1

Inadequate Physical Separation

and Electrical Isolation of

Non-safety-related Circuits

from Reactor Protection System

Circuits

Degradation of Steel Con- tainments

Surveillance Testing of Low- Temperature Overpressure-

Protection Systems

02/20/91

All holders of OLs

or CPs for W-designed

nuclear power reactors.

02/14/91

All holders of OLs or

CPs for nuclear power

reactors.

02/12/91

All holders of OLs or

CPs for nuclear power

reactors.

91-10

Summary of Semiannual Program

P - 1Performance -Reports-on-Fltness--

for-Duty (FFD)

in the Nuclear

Industry

02/12/91

All holders of OLs or

--

CPs for nuclear power

reactors.

91-.09

91-08

90-77, Supp. 1

91-07

Counterfeiting of Crane Valves

Medical Examinations for

Licensed Operators

Inadvertent Removal of Fuel

Assemblies from the Reactor Core

Maintenance Deficiency Assoc- iated with General Electric

Horizontal Custom 8000

Induction Motors

02/05/91

All holders of OLs or

CPs for nuclear power

reactors.

02/05/91

All holders of OLs or

CPs for nuclear power, test and research

reactors.

02/04/91

All holders of OLs or

CPs for pressurized- water reactors (PWRs).

02/04/91

All holders of OLs or

CPs for nuclear power

reactors.

OL = Operating License

CP = Construction Permit

STATES

NUCLEAR KauULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C.

20555

February 15, 1991

NRC INFORMATION NOTICE NO. 91-12: POTENTIAL LOSS OF NET POSITIVE SUCTION

HEAD (NPSH) OF STANDBY LIQUID CONTROL

Addressees

All holders of operating licenses or construction permits for boiling water

reactors (BWRs).

Purpose

This information notice is intended to alert licensees to potential problems

with the adequacy of Net Positive Suction Head (NPSH) for Standby Liquid

Control System (SLCS) pumps. 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 do not constitute NRC requirements; therefore, no specific action or written response is required.

Description of Circumstances

On February 11, 1991, a special test of the Standby Liquid Control System was

performed at Quad Cities Unit 1, to determine if NPSH would be maintained with

the conditions of minimum SLCS tank level and maximum sodium pentaborate solution

temperature in the tank. The test was terminated after about 20 minutes following

indications of pump cavitation due to loss of NPSH.

Following the test, the

licensee determined that with the flow rate achieved during the test, the amount

of sodium pentaborate necessary to bring the plant to cold shutdown would not be

pumped to the reactor vessel with one or both SLCS pumps within the 20 minute

period. In light of the test results at Quad Cities, the licensee declared the

SLCS at Quad Cities Unit 2, and the operating sister units, Dresden Units 2 and 3, inoperable.

Following further evaluation of the test results and engineering

analysis, the licensee increased the administratively controlled limit on SLCS

tank level and reduced the administratively controlled limit on solution

temperature in the SLCS tank at Quad Cities to ensure sufficient NPSH for the

SLCS pumps; verified that current limits at Dresden allowed for sufficient NPSH;

and declared the pumps at the Quad Cities and Dresden units operable.

The SLCS system is required to provide liquid poison in the event that control

rod insertion is inadequate to achieve and maintain a cold shutdown condition.

For low probability Anticipated Transient Without Scram (ATWS) events, SLCS

pump failure to inject a sufficient amount of solution to shutdown the reactor

9102190010

K)

1"O

IN 91-12 February 15, 1991 could result in a serious threat to containment integrity. The total volume of

poison solution required to assure subcriticality at cold, xenon free conditions

in most plants results in a near depletion of the poison storage tank. During

the course of poison injection, the tank level decreases resulting in a decrease

of available NPSH. Insufficient NPSH can lead to reduced pumping capability or

pump failure. While lesser amounts of poison can still maintain the reactor

shutdown at hot conditions, there is a poison level below which the reactor

would still be producing power.

Under such conditions containment integrity

can be threatened in the short term.

The basic SLCS design is common to all BWRs and nearly all use similar positive

displacement pumps.

Consequently, there is a question as to whether adequate

testing has been performed at other BWRs to assure that throughout the required

range of operating conditions the SLCS pumps will have sufficient NPSH to

perform their intended function.

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

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

the technical contact listed below or the appropriate NRR project manager.

rfglinal Signed by

thades E Rossi

Charles E. Rossi, Director

Division of Operational Events Assessment

Mark A. Caruso, NRR

(301) 492-3235 Attachment:

List of Recently Issued NRC Information Notices

OFC :DST:R

.

NRR

.L

DOEA:NRR :

--

-

--

-

--

-

-

--

-

-

--

-

-

-

-

-

--

-

-

NAME :MCarusf4G Holahan

DATE :2/1?0/91

2/1 /92

2//

191

OFFICIAL RECORD COPY

Document Name: IN 9142