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 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

SHUTDOWN COOLING

NRC INFORMATION NOTICE NO. 90-06: POTENTIAL FOR LOSS OF COOLANT LEVELS

WHILE AT LOW REACTOR

Addressees

nuclear power

All holders of operating licenses or construction permits for

reactors.

Purpose

to a potential problem

This information notice is intended to alert addressees (RHR) system during

affecting the operability of the residual heat removal

is expected that re- operating conditions involving mid-loop operation. It to their facilities

-cipients will review the information for applicability problems. However, and consider actions, as appropriate, to avoid similar constitute NRC

suggestions contained in this information notice do not

response is required.

requirements; therefore, no specific action or written

Description of Circumstances

the residual heat

On July 18, 1989, at Comanche Peak Unit 1, train 'Al ofloading. The air

removal system was in operation prior to initial fuel

being used to

operated RHR heat exchanger flow control valve (FCV) was water level was

maintain system flow below 2000 gpm. The reactor vessel

legs.

being maintained slightly abpve the center line of the hot

FCV failed. The loss

The inverter supplying power to the controller for the to its emergency core

of power to the controller resulted in the FCV failing open valve caused

cooling system (ECCS) position of being fully open. The flow caused

an increase in system flow to 4400 gpm. This sudden, increased

the RHR pipe con- conditions where vortexing was expected at the suction of

nection to the RCS.

to an alternate

The power supply for the controllers was manually transferred

terminating the event.

source and the FCV was throttled, thus

Discussion:

flow through the

The FCV is manually throttled to maintain a desired rate of to control the

RHR heat exchanger. The heat exchanger flow rate is adjusted

to the vessel. Total system flow is

temperature of the water being returned with the

regulated by throttling the heat exchanger bypass valve coincident

adjustment of the FCV.

001230175 Z ((

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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 Issuance Issued te

Notice No. SubJect

90-05 Inter-System Discharge of 1/26/9O All holders of ULs

Reactor Coelant or Ch for nuclear

power reactors.

90-04 Cracking of the Upper Shall- 1/26/90 All holders of OLs

to-Transition Cone Girth or CPs.for Westinghouse.

Melds Is Steam Generators designed and Combustion

Engineering-disigned

nuclear power reactors.

90-03 malfunction of Borg-Varner 1/23/90 All holders of OLs

SBlted Sonnet Check Valves or CPs for uclewr

Causd by Failure of the power reactors.

Swing Arm

90-02 Potential Degradation of 1/29D All holders of OLs

Secondary Contaient or CPs for Slis.

90-01 lIportace of Proper 1/12/90 All holders of NRC

Response to Self-Identifted materials licenses.

Violations by Licensees

89-90 Pressurizer Safety Valv 12/28/84 All holder of OMs

Lift Setpoint Shift or Ch for Pilb.

89-8 Event Notificatton 12/26/89 All holders of CLs

Workshents or en for nuclear

powerreactors.

89-88 Recent XRC-Sponsored 12/26189 All holders of Ots

Testing of motor-Operated or CPsfor nutlear

Valves poer reactors.

8647 Disablilg of Emergency 12/19189 All helders of OLs

Diesel Generators by or CVs for nuclear

Their Neutral Ground-Fault power reactors.

Protection Circuitry

8945. etalclad. Lou-Voltage 12/IS/19 All holders of OLs

Supp. 2 Power Circuit Dreakars or CPsfor nuclear

Refurbished with power reactors.

Substandard Parts

OL*OpitunceS - _

CV s Construction Permit

UNITED STATES

IPOSTAGE & FEES PAOID

NUCLEAR REGULATORY COMMISSION ISNiRC 1 WASHINGTON, D.C. 20555 OFFICIAL BUSINESS

PENALTY FOR PRIVATE USE. 8300

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 TECH:EDITOR EAB:NRR C:EAB:NRR C:OGCB:NRR NRR:SRXB

• NFields: db *BCalure *DCFischer *CJHaughney *CHBerlinger *RJones

1/12/90 1/13/90 1/16/90 1/16/90 1/17/90 1/23/90

1/Z3'90

K)j V%2IN 90-

January , 1990 No specific action or written response is required by this information notice.

If you have any questions about this matter, please contact one of the technical

contacts 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

Attachment: List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCE

EAB:NRR TECH:EDITOR EAB:NRR C:EAB:NRR C:OGCB:NRR N R B

• DCFischer *CJHaughney* *CHBerlinger RJV es

• NFields:db *BCalure

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D:DOEA:NRR

CERossi

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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

Attachment: List of Recently Issued NRC Information Notices

C0Wvtn Au t

AJF VIU46x1 4fhire0rAtU rAI CV

EAB:NRR TECH:EDITOR EAB:NRR C:EAB:NRR C:OGCB:NRR D:DOEA:NRR

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