Information Notice 1990-06, Potential for Loss of Shutdown Cooling While at Low Reactor Coolant Levels

Potential for Loss of Shutdown Cooling While at Low Reactor Coolant Levels

ML031130325
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, 05000000, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	01/29/1990
From:	Rossi C E Office of Nuclear Reactor Regulation
To:
References
IN-90-006, NUDOCS 9001230175
Download: ML031130325 (7)

UNITED STATES NUCLEAR REGULATORY

COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 January 29, 1990 NRC INFORMATION

NOTICE NO. 90-06: POTENTIAL

FOR LOSS OF SHUTDOWN COOLING WHILE AT LOW REACTOR COOLANT LEVELS

Addressees

All holders of operating

licenses or construction

permits for nuclear power reactors.

Purpose

This information

notice is intended to alert addressees

to a potential

problem affecting

the operability

of the residual heat removal (RHR) system during operating

conditions

involving

mid-loop operation.

It is expected that re--cipients

will review the 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 July 18, 1989, at Comanche Peak Unit 1, train 'Al of the residual heat removal system was in operation

prior to initial fuel loading. The air operated RHR heat exchanger

flow control valve (FCV) was being used to maintain system flow below 2000 gpm. The reactor vessel water level was being maintained

slightly abpve the center line of the hot legs.The inverter supplying

power to the controller

for the FCV failed. The loss of power to the controller

resulted in the FCV failing to its emergency

core cooling system (ECCS) position of being fully open. The open valve caused an increase in system flow to 4400 gpm. This sudden, increased

flow caused conditions

where vortexing

was expected at the suction of the RHR pipe con-nection to the RCS.The power supply for the controllers

was manually transferred

to an alternate source and the FCV was throttled, thus terminating

the event.Discussion:

The FCV is manually throttled

to maintain a desired rate of flow through the RHR heat exchanger.

The heat exchanger

flow rate is adjusted to control the temperature

of the water being returned to the vessel. Total system flow is regulated

by throttling

the heat exchanger

bypass valve coincident

with the adjustment

of the FCV.001230175 Z ( (' D*1 IC, eo uachr

IN 90-06 January 29, 1990 During this event, there were no indications

of pump air ingestion.

However, the increased

system flow corresponded

to the rate at which vortexing

had been calculated

to occur based on the existing RCS level. The licensee had previously

determined

maximum permitted

flow rates for various reduced levels of the RCS to prevent the possibility

of vortexing

and air entrainment

into the RHR pump.Although RHR pump operation

was never actually impaired, the potential

existed for air to be introduced

to the pump's suction. This concern is exacerbated

by* the fact that the heat exchanger

FCVs for both trains of RHR are powered from the same inverter.

Since the FCVs open fully on a loss of power, both trains of RHR could become inoperable

on a loss of power during mid-loop operation.(A loss of instrument

air would also cause the FCVs to fail to the full open position and could also result in the loss of both trains of the RHR system).During most modes of operation, having the FCVs go -fully open on loss of power or instrument

air is not a safety concern because having the valves fully open does not normally prevent the system from performing

its safety function.

However, having the valves go fully open while at mid-loop could result in the loss of decay heat removal capability.

This loss could persist until electrical

power or instrument

air is restored and air is vented from the RHR system.The licensee has revised procedures

for mid-loop operation

to require manually positioning

the cold leg injection

isolation

valves to limit the maximum flow through the system, even with the FCVs fully open. This lineup will be used whenever the unit is at mid-loop and protects against the consequences

of failure of either electrical

power or instrument

air.Several generic communications

have been issued informing

licensees

of the consequences

of the loss of residual (decay) heat removal and the operating conditions

under which the probability

of a loss increases;

i.e., reduced inventory

conditions.

The most recent publications

include Generic Letter (GL) No. 87-12, "Loss of Decay Heat Removal While the Reactor Coolant System is Partially

Filled;" GL No. 88-17, *Loss of Decay Heat Removal;" NRC In-formation

Notice (IN) 87-23, "Loss of Decay Heat Removal During Low Reactor Coolant Level Operation;" IN 88-36, 'Possible

Sudden Loss of RCS Inventory During Low Coolant Level Operation;" and IN 89-67, "Loss of Residual Heat Removal Caused by Accumulator

Nitrogen Injection." The event described above introduces

a subtle failure scenario which licensees

may not have considered.

IN 90-06 January 29, 1990 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

NRR project manager.Charles E. Rossi, irector Division of Operational

Events Assessment

Office of Nuclear Reactor Regulation

Technical

Contacts:

Nick Fields, NRR (301) 492-1173 Steve Bitter, RIV (817) 897-1500 Attachment:

List of Recently Issued NRC Information

Notices

I IN 90-06 January 29, 1990 During this event, there were no indications

of pump air ingestion

However the increased

system flow enrraenan~nA

n~ -~ neto. Hwvr Attachment

~q ) sx 90-06 Jasmary 2§ 1990 Page I of I LIST OF RECEITLT ISSUED NIR INFORtAT1011 OTICES JCW --lnfonation

Notice No.90-05 90-04 SubJect Inter-System

Discharge

of Reactor Coelant Issuance 1/26/9O Cracking of the Upper Shall- 1/26/90 to-Transition

Cone Girth Melds Is Steam Generators

Issued te All holders of ULs or Ch for nuclear power reactors.All holders of OLs or CPs.for Westinghouse.

designed and Combustion

Engineering-disigned

nuclear power reactors.All holders of OLs or CPs for uclewr power reactors.All holders of OLs or CPs for Slis.All holders of NRC materials

licenses.90-03 malfunction

of Borg-Varner

SBlted Sonnet Check Valves Causd by Failure of the Swing Arm 90-02 Potential

Degradation

of Secondary

Contaient 90-01 lIportace

of Proper Response to Self-Identifted

Violations

by Licensees 89-90 Pressurizer

Safety Valv Lift Setpoint Shift 89-8 Event Notificatton

Workshents

89-88 Recent XRC-Sponsored

Testing of motor-Operated

Valves 8647 Disablilg

of Emergency Diesel Generators

by Their Neutral Ground-Fault

Protection

Circuitry 8945. etalclad.

Lou-Voltage

Supp. 2 Power Circuit Dreakars Refurbished

with Substandard

Parts 1/23/90 1/29D 1/12/90 12/28/84 All holder of OMs or Ch for Pilb.12/26/89 All holders of CLs or en for nuclear power reactors.12/26189 All holders of Ots or CPs for nutlear poer reactors.12/19189 All helders of OLs or CVs for nuclear power reactors.12/IS/1 9 All holders of OLs or CPs for nuclear power reactors.OL*OpitunceS

-_CV s Construction

Permit UNITED STATES NUCLEAR REGULATORY

COMMISSION

WASHINGTON, D.C. 20555 OFFICIAL BUSINESS PENALTY FOR PRIVATE USE. 8300 IPOSTAGE & FEES PAOID ISNiRC 1 IN 90-06 January 29, 1990 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

NRR project manager.Charles E. Rossi, Director Division of Operational

Events Assessment

Office of Nuclear Reactor Regulation

Technical

Contacts: Nick Fields, NRR (301) 492-1173 Steve Bitter, RIV (817) 897-1500 Attachment:

List of Recently Issued NRC Information

Notices*SEE PREVIOUS CONCURRENCE

EAB:NRR*NFields:

db 1/12/90 TECH:EDITOR

• BCalure 1/13/90 EAB:NRR C:EAB:NRR*DCFischer

• CJHaughney

1/16/90 1/16/90 C:OGCB:NRR

• CHBerlinger

1/17/90 NRR:SRXB*RJones 1/23/90 1 /Z3'90

K)j V%2IN 90-January , 1990 No specific action or written response is required by this information

If you have any questions

about this matter, please contact one of the contacts listed below or the Regional Administrator

of the appropriate

office.notice.technical regional Charles E. Rossi, Director Division of Operational

Events Assessment

Office of Nuclear Reactor Regulation

Technical

Contacts: Nick Fields (301) 492-1173 Steve Bitter (817) 897-1500 Attachment:

List of Recently Issued NRC Information

Notices*SEE PREVIOUS CONCURRENCE

EAB:NRR*NFields:db

/ /90 D:DOEA:NRR

CERossi/ /90 TECH:EDITOR

• BCalure/ /90 EAB:NRR*DCFischer

/ /90 C:EAB:NRR*CJHaughney*

/ /90 C:OGCB:NRR

• CHBerlinger

/ /90 N R B RJV es I j:/90

IN 90-January , 1990%...Z'age

3 of 3 No specific action or written response is required by this infornation

notice. If you have any questions

about this matter, please contact the technical

contact listed below or the Regional Administrator

of the appropriate

regional office.Charles E. Rossi, Director Division of Operational

Events Assessment

Office of Nuclear Reactor Regulation

Technical

Contacts: Nick Fields (301) 492-1173 Steve Bitter (817) 897-1500 List of Recently Issued NRC Information

Notices Attachment:

AJF EAB:NRR NFields:db

Jr //,/90 C0Wvtn Au t VIU46x1 4fhire0rAtU

rAI TECH:EDITOR

EAB:NRR DCFischer I /11/SQ , /14/90 C:EAB:NRR CJHaughney

I /14/90 CV C:OGCB:NRR

CHBerlinger

/ 117/90 D:DOEA:NRR

CERossi/ /90