Information Notice 1995-03, Loss of Reactor Coolant Inventory and Potential Loss of Emergency Mitigation Functions While in a Shutdown Condition

Loss of Reactor Coolant Inventory and Potential Loss of Emergency Mitigation Functions While in a Shutdown Condition

ML031060404
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:	01/18/1995
From:	Grimes B Office of Nuclear Reactor Regulation
To:
References
IN-95-003, NUDOCS 9501110412
Download: ML031060404 (10)

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555-0001 January 18, 1995 NRC INFORMATION NOTICE 95-03: LOSS OF REACTOR COOLANT INVENTORY AND POTENTIAL

LOSS OF EMERGENCY MITIGATION FUNCTIONS WHILE IN

A SHUTDOWN CONDITION

Addressees

All holders of operating licenses or construction permits for nuclear power

reactors.

Purpose

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

notice (IN)to alert addressees to a recent incident involving a loss of

reactor coolant inventory while in a shutdown condition at a Westinghouse

pressurized-water reactor. The incident is unique because the initiating

event has the potential to create an accident and cause a loss of accident

mitigation capability. It is expected that recipients will review the

information for applicability to their facilities and consider actions, as

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

this notice do not constitute NRC requirements; therefore, no specific action

or written response is required.

Background

NRC has issued a number of generic communications describing events at reactor

facilities involving inadvertent loss of reactor coolant inventory while the

facility was in a shutdown condition. In Generic Letter 88-17, "Loss of Decay

Heat Removal (DHR)," the staff requested several actions to address loss of

DHR events that occurred while the reactor was in a shutdown condition. In

two information notices (IN90-55, "Recent Operating Experience on Loss of

Reactor Coolant Inventory While in a Shutdown Condition," and IN 91-42, "Plant

Outage Events Involving Poor Coordination Between Operations and Maintenance

Personnel During Valve Testing and Manipulations"), the staff discussed

inadvertent loss of inventory events. A document issued by the NRC Office for

Analysis and Evaluation of Operational Data (AEOD/E704), "Discharge of Primary

Coolant Outside of Containment at PWRs While on RHR Cooling," reported six

additional events having similar characteristics.

This IN deals with the Wolf Creek draindown event of September 17, 1994. A

similar event occurred at Braidwood in 1990. Both events involved operators

inadvertently transferring more than 9000 gallons of reactor coolant system

(RCS) inventory to the refueling water storage tank (RWST) while preparing to

shift operation of the residual heat removal (RHR) trains. However, the Wolf

Creek event occurred when the RCS was pressurized to 340 psi at a temperature

9501110412 t1.0(4 5-il

v

IN 95-XX

January xx, 1995 The Wolf Creek draindown event has been classified (November 22, 1994) by the

Office for Analysis and Evaluation of Operational Data and the Office of

Nuclear Reactor Regulation as a "Significant Event for the Performance

Indicator Program."

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 Project Support

Office of Nuclear Reactor Regulation

Technical contacts: J. Frederick Ringwald, RIV

(316) 364-8653 John Kauffman, AEOD

(301) 415-6830

Attachment:

List of Recently Issued NRC Information Notices

DOCUMENT NAME: G:\JRT\INDRAFT.WC

______ v,'c C7L= & 7&-eh EJali-r on l ___A __ _

OFFICE OECB:DOPS SC/OECB:DOPS SRXB:DSSA l C/SRXB:DSSA

NAME lJTappert EGoodwin l _LLois l RJones

DATE l______ /9/ / 12 / /

lOFFICE TA/OECB:DOPS C/OECB:DOPS D/DOPS l _ _

NAME RKiessel AChaffee BGrimes - _

l DATE I I/

OFFICIAL RECORD COPY

IN 95-03 January 18, 1995 of 300 OF. As a result, more than 9000 gallons of RCS inventory was drained

from the RCS to the RWST in about 1 minute.

The Wolf Creek design incorporates a 24 inch header pipe from the RWST from

which the RHR pumps, the charging pumps, the high-head injection pumps, and

the containment spray pumps take suction. If an RCS to RWST fluid transfer

filled the 24 inch header with steam and pump operation were attempted, the

pump could have been severely damaged and lost as a means of supplying RCS

makeup and core cooling. In addition, such steam would create conditions

favoring water hammer, which could be destructive to involved components.

Description of Circumstances

On September 17, 1994, the Wolf Creek Generating Station experienced a loss of

reactor coolant inventory while in a shutdown condition when operators

performed two incompatible activities concurrently. Preceding the event, operators were controlling the reactor coolant system in Mode 4 (hot shutdown)

at approximately 300 OF and 340 psig. Operations personnel found that during

the latter part of the cycle leaking check valves had diluted the boron

concentration in the RHR train B piping. Licensee procedures require that the

water in the piping be reborated before the RHR B train is put into operation

in this circumstance. This was routinely done by recirculating the RHR piping

water through the RWST using a containment spray pump.

Maintenance personnel were repairing a packing leak and performing valve

motor-operator diagnostic testing on the train A RHR discharge crossover

isolation valve. The shift supervisor decided that it would be acceptable to

stroke the train A discharge crossover isolation valve provided that the RHR

train B discharge crossover isolation valve and the RHR crossover return to

the RWST manual isolation valve remained shut. To continue the cooldown to

Mode 5, operators began preparations to start RHR train B so that reactor

coolant pumps could be secured. While personnel continued the repair and

valve motor-operator diagnostics on the train A crossover isolation valve, an

auxiliary operator opened the RHR crossover return to the RWST manual

isolation valve for the reboration. When both valves were opened, the reactor

coolant system had a draindown flowpath through RHR train A into the 24-inch

pipe that leads from the RWST. After approximately 1 minute, operators

recognized an unintended flowpath and shut the train A discharge crossover

isolation valve to terminate the draindown. The event transferred

approximately 9200 gallons of RCS water to the RWST, depressurized the RCS to

approximately 225 psig, and allowed the RCS temperature to increase by

approximately 7 *F.

Discussion

The Office for Analysis and Evaluation of Operational Data (AEOD) reviewed

this event at the Wolf Creek site from November 7 through 10, 1994, and plans

to issue a report. The following discussion is, in part, based on the AEOD

review and, in part, on the Office of Nuclear Reactor Regulation (NRR) and

regional staff view of the potential safety implications.

IN 95-03 January 18, 1995 Two incompatible activities were performed concurrently, causing this event:

(1) alignment of the RHR train B crossover isolation valve (to adjust the

boron concentration) required the valve to be opened and (2) motor-operator

diagnostic testing required the train A RHR discharge crossover isolation

valve to be stroked open and closed. These two activities inadvertently

created the flow path for the draindown. The failure of several individuals, including the reactor operator, supervising operator, and shift supervisor, to

recognize that these activities were incompatible resulted in a loss of

control of plant configuration and directly caused the draindown event.

The shift supervisor initially recognized the potential for diverting RHR flow

from the RCS to the RWST; however, the shift supervisor failed to establish a

positive barrier, such as tagging or padlocking, to ensure that the manual

crossover return to the RWST manual isolation valve remained shut. Repair and

diagnostic testing of the train A discharge crossover isolation valve

represented work on the only available train of a safety system. These

decisions permitted work on a safety system required for safe operation of the

plant without proper controls in place to prevent an inappropriate system

configuration.

In recognition of additional challenges to plant operators during outage

conditions, the licensee had established an outage emergent work process to

evaluate unscheduled work. This process was intended to relieve some of the

additional burden that might distract the operators from properly monitoring

the safe condition of the plant. It was also intended to provide additional

assurance that potential adverse impacts on plant operation were fully

considered. However, this emergent work process was not used to evaluate the

motor-operated valve work on RHR train A.

The presence of the deborated water in the RHR train B piping, the attempt to

reborate, and the concurrent repair and testing of the RHR train A crossover

isolation valve raises the following concerns:

1. There is a possibility of introducing hot RCS water into the common

24-inch suction header supplied from the RWST. The RHR pumps, the

charging pumps, the high-head injection pumps, and the containment spray

pumps take suction from this header. Introducing hot RCS water into this

header could create steam conditions and interfere with RHR pump

operation. If the RHR pump were lost, alignment of the other pumps to

this header as a response to the loss of RHR cooling could have also

interfered with the operation of these other pumps.

2. There is the potential that if the draindown continued, the RHR piping

could become filled with steam. This would create conditions favoring

water hammer, which could damage valves, pumps, piping, or pipe supports.

The RWST supply to the ECCS and containment spray could be jeopardized.

IN 95-03 January 18, 1995 3. There was the possibility for inadvertent injection of relatively cold, lightly borated water from the RHR train B piping into the RCS. In the

hot shutdown condition (Mode 4), where the reactor is being borated as it

cools down, introduction of cold, lightly borated water reduces the

margin to criticality. The licensee determined that the injection of the

water from the RHR train B piping into the RCS would not have brought the

reactor to a critical state. However, the potential for criticality may

exist at other facilities under similar conditions.

The Wolf Creek draindown event has been classified by the NRC staff as a

significant event for the NRC Performance Indicator Program.

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 project manager.

Brian K. Grimes, Director

Division of Project Support

Office of Nuclear Reactor Regulation

Technical contacts: J. Frederick Ringwald, RIV

(316) 364-8653 Lambros Lois, NRR

(301) 504-3233 Attachment:

List of Recently Issued NRC Information Notices

Attachment

IN 95-03 January 18, 1995 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

95-02 Problems with General 01/17/95 All holders of OLs or CPs

Electric CR2940 Contact for nuclear power reactors.

Blocks in Medium-Voltage

Circuit Breakers

95-01 DOT Safety Advisory: 01/04/95 All U.S. Nuclear Regulatory

High Pressure Aluminum Commission licensees.

Seamless and Aluminum

Composite Hoop-Wrapped

Cylinders

94-90 Transient Resulting in a 12/30/94 All holders of OLs or CPs

Reactor Trip and Multiple for nuclear power reactors.

Safety Injection System

Actuations at Salem

94-89 Equipment Failures at 12/28/94 All U.S. Nuclear Regulatory

Irradiator Facilities Commission irradiator

licensees.

94-88 Inservice Inspection 12/23/94 All holders of OLs or CPs

Deficiencies Result in for pressurized water

Severely Degraded Steam reactors.

Generator Tubes

94-87 Unanticipated Crack in a 12/22/94 All holders of OLs or CPs

Particular Heat of for nuclear power reactors.

Alloy 600 Used for

Westinghouse Mechanical

Plugs for Steam Generator

Tubes

94-86 Legal Actions Against 12/22/94 All holders of OLs or CPs

Thermal Science, Inc., for nuclear power reactors.

Manufacturer of Thermo-Lag

94-85 Problems with the 12/21/94 All holders of OLs or CPs

Latching Mechanism for nuclear power reactors.

in Potter and Brumfield

R1O-E3286-2 Relays

OL = Operating License

CP = Construction Permit

K>

IN 95-03 January 18, 1995 '

3. There was the possibility for inadvertent injection of relatively cold, lightly borated water from the RHR train B piping into the RCS. In the

hot shutdown condition (Mode 4), where the reactor is being borated as it

cools down, introduction of cold, lightly borated water reduces the

margin to criticality. The licensee determined that the injection of the

water from the RHR train B piping into the RCS would not have brought the

reactor to a critical state. However, the potential for criticality may

exist at other facilities under similar conditions.

The Wolf Creek draindown event has been classified by the NRC staff as a

significant event for the NRC Performance Indicator Program.

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 project manager.

Brian 'K>Grim s, uirec or

Division of Project Support

Office of Nuclear Reactor Regulation

Technical contacts: J. Frederick Ringwald, RIV

(316) 364-8653 Lambros Lois, NRR

(301) 504-3233 Attachment:

List of Recently Issued NRC Information Notices

DOCUMENT NAME: 95-03.IN

• See previous concurrence

Reviewed by Technical Editor via QTE on 12/28/94 Reviewed via e-mail on 12/29/94: J. Frederick Ringwald, RIV

Dwight Chamberlain, RIV

John Kauffman, AEOD

OFFICE OECB:DOPS SC/OECB:DOPS SRXB:DSSA C/SRXB:DSSA

NAME .JTappert* EGoodwin* LLois* RJones*

DATE 112/29/94 12/29/94 12/29/9£, ,- /29/94 OFFICE _TA/OECB:DOPS C/OECB:DOPS S--_______

NAME RKiessel AChaffee* f__5______

Z________

DATE 01/ /95 12/30/94 l 01/ It95 _ _ _

OFFICIAL RECORD COPY

v>

IN 95-03 January 18, 1995 3. There was the possibility for inadvertent injection of relatively cold, lightly borated water from the RHR train B piping into the RCS. In the

hot shutdown condition (Mode 4), where the reactor is being borated as it

cools down, introduction of cold, lightly borated water reduces the

margin to criticality. The licensee determined that the injection of the

water from the RHR train B piping into the RCS would not have brought the

reactor to a critical state. However, the potential for criticality may

exist at other facilities under similar conditions.

The Wolf Creek draindown event has been classified by the NRC staff as a

significant event for the NRC Performance Indicator Program.

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 project manager.

Division of Project Support

Office of Nuclear Reactor Regulation

Technical contacts: J. Frederick Ringwald, RIV

(316) 364-8653 Lambros Lois, NRR

(301) 504-3233 Attachment:

List of Recently Issued NRC Information Notices

DOCUMENT NAME: 95-03. IN

• See previous concurrence

Reviewed by Technical Editor via QTE on 12/28/94 Reviewed via e-mail on 12/29/94: J. Frederick Ringwald, RIV

Dwight Chamberlain, RIV

John Kauffman, AEOD

OFFICE OECB:DOPS SC/OECB:DOPS SRXB:DSSA C/SRXB:DSSA

NAME jJTappert* EGoodwin* LLois* RJones*

DATE 12/29/94 1 2_29_94_12/29__A129/94 OFFICE TA/OECB:DOPS C/OECB:DOPS l ____________

NAME RKiessel AChaffee* dI ___________

DATE 01/ /95 12/30/94_01/_ _95 OFFICIAL RECORD COPY

IN 95-,W'o

January , 1995 3. There was the possibility for inadvertent injection of relatively cold, lightly borated water from the RHR train B piping into the RCS. In the

hot shutdown condition (Mode 4), where the reactor is being borated as it

cools down, introduction of cold, lightly borated water reduces the

margin to criticality. The licensee determined that the injection of the

water from the RHR train B piping into the RCS would not have brought the

reactor to a critical state. However, the potential for criticality may

exist at other facilities under similar conditions.

The Wolf Creek draindown event was classified by the Office for Analysis and

Evaluation of Operational Data and the Office of Nuclear Reactor Regulation as

a "Significant Event for the Performance Indicator Program" on

November 22, 1994.

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 project manager.

Brian K. Grimes, Director

Division of Project Support

Office of Nuclear Reactor Regulation

Technical contacts: J. Frederick Ringwald, RIV

(316) 364-8653 Lambros Lois, NRR

(301) 504-3233 Attachment:

List of Recently Issued NRC Information Notices

DOCUMENT NAME: G:\JRT\INDRAFT.WC

• See previous concurrence

Reviewed by Technical Editor via QTE on 12/28/94 Reviewed via e-mail on 12/29/94: J. Frederick Ringwald, RIV

Dwight Chamberlain, RIV

John Kauffman, AEOD

OFFICE OECB:DOPS SC/OECB:DOPS SRXB:DSSA C/SRXB:DSSA

NAME JTappert* EGoodwin* LLois* RJones*

DATE 12/29/94 12/29/94 12/29/94 12/29/94 OFFICE TA/OECB:DOPS C/OECB:DOP5i D/DOPS

NAME RKiessel AChaffee ( 7BGrimes

DATE / / IQ I / /

OFFICIAL RECORD COPY

IN 95-XX

January xx, 1995 3. Finally, there is the potential that if the event continued, the RHR

piping could become filled with steam. This would create conditions

favoring water hammer, which could damage valves, pumps, piping, or pipe

supports. The RWST supply to the ECCS and containment spray could be

Jeopardized.

The Wolf Creek draindown event was classified by the Office for Analysis and

Evaluation of Operational Data and the Office of Nuclear Reactor Regulation as

a "Significant Event for the Performance Indicator Program" on

November 22, 1994.

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 project manager.

Brian K. Grimes, Director

Division of Project Support

Office of Nuclear Reactor Regulation

Technical contacts: J. Frederick Ringwald, RIV

(316) 364-8653 Lambros Lois, NRR

(301) 504-3233 Attachment:

List of Recently Issued NRC Information Notices

DOCUMENT NAME: G:\JRT\INDRAFT.WC

• See previous concurrence

Reviewed by Technical Editor via QTE on 12/28/94 Reviewed via e-mail on 12/29/94: J. Frederick Ringwald, RIV

Dwight Chamberlain, RIV

John Kauffman, AEOD

OFFICE OECB:DOPS SC/OECB:DOPS SRXB:DSSA C/SRXB:DSS~l

NAME JTappert* EGoodwin I LLois* RJones a

DATE 12/29/94 }'L_/ )$ii 9 112/29/94 /

114 f/ Af

OFFICE TA/OECB:DOPS C/OECB:DOPS D/DOPS _

NAME RKiessel AChaffee BGrimes

DATE J I frfr

OFFICIAL RECORD COPY