Information Notice 1989-71, Diversion of the Residual Heat Removal Pump Seal Cooling Water Flow During Recirculation Operation Following a Loss-Of-Coolant Accident

Diversion of the Residual Heat Removal Pump Seal Cooling Water Flow During Recirculation Operation Following a Loss-Of-Coolant Accident
	ML031190081
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, Zimmer, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	10/19/1989
From:	Rossi C; Office of Nuclear Reactor Regulation
To:	;
References
	IN-89-071, NUDOCS 8910130014
	Download: ML031190081 (8)
	v • d • e

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 October 19, 1989 NRC INFORMATION NOTICE NO. 89-71: DIVERSION OF THE RESIDUAL HEAT REMOVAL

PUMP SEAL COOLING WATER FLOW DURING

RECIRCULATION OPERATION FOLLOWING A

LOSS-OF-COOLANT ACCIDENT

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

resulting from a design deficiency that may affect the operability of the

residual heat removal (RHR) pumps during recirculation operation following

a loss-of-coolant accident (LOCA). The problem, which can occur as a result

of a single failure can cause a diversion of the cooling water flow from the

RHR pump seal coolers, resulting in inadequate seal cooling and the potential

for ultimate failure of the RHR pumps. 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 information notice do not constitute NRC requirements;

therefore, no specific action or written response is required.

Description of Circumstances

During a probabilistic risk assessment (PRA) study of the emergency core

cooling system at Haddam Neck, the licensee discovered that a single failure

in response to a LOCA could disable both RHR pumps. The single failure would

cause the diversion of the cooling water flow from the RHR pump seal coolers

resulting in inadequate seal cooling and possible pump failure.

As indicated in Attachment 1, cooling water for the RHR pump seal coolers comes

from the cooling water Inlet lines to each RHR heat exchanger. During normal

operation, the component cooling water system provides cooling to the RHR heat

exchangers and pump seal coolers. However, during a LOCA condition, component

cooling water is isolated, and service water is used to provide cooling to the

RHR components. Because the RHR pump seal cooler water supply line is cross- connected to both the component cooling and service water systems, a failure

of one of the service water motor-operated valves to open following a LOCA

would result in only one branch of service water being available to provide

cooling to both RHR heat exchangers and the seal water coolers.

891013001,

- low

IN 89-71 October 19, 1989 Under these conditions, the RHR seal water coolers would receive inadequate

flow, with the potential for ultimately causing the failure of both RHR pumps.

The licensee corrected this problem by installing check valves in the seal

water cooling piping (shown in Attachment 2) to preclude one branch of service

water from feeding two RHR heat exchangers.

Discussion of Safety Significance:

The design deficiency described above was identified in a plant that switches

cooling water systems during a LOCA. However, the problem could occur in any

auxiliary cooling water system that provides sizably different cooling needs

for different redundant components such as RHR heat exchangers and seal coolers.

The important feature in the system is the interconnecting piping between the

auxiliary cooling water system branches and the piping to the individual components.

In the situation described in this notice, a single failure of a valve to open

would cause one branch of auxiliary cooling water to service multiple redundant

components, thereby reducing flow below design requirements. Licensees may wish

to review their auxiliary cooling water system designs for similar deficiencies.

Several other flow design problems that affect operation while in the recircu- lation mode following a LOCA have been previously identified in IN 87-63,

"Inadequate Net Positive Suction Head in Low Pressure Safety Systems," and

IN 88-74, "Potentially Inadequate Performance-of ECCS in PWRs During Recircu- lation Operation Following a LOCA." It is important to note that a flow balance

analysis would determine the impact of asymmetric flow balances caused by single

failures in these systems. A simple review of piping diagrams may be sufficient

to identify systems with potential flow problems, but hydraulic analyses are

necessary to confirm suspected problems.

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: S. Israel, AEOD

(301) 492-4437

0. Prochnow, NRR

(301) 492-1166 Attachments:

1. Diagram of Haddam Neck's Original RHR Cooling Water System

2. Diagram of Haddam Neck's Modified RHR Cooling Water System

3. List of Recently Issued NRC Information Notices

'me/ S Attachment I

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Diagram of .addam Neck's Modified RHR Cooling Water System

Attachment 3 IN 89-71 October 19, 1989 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

89-70 Possible Indications of 10/11/89 All holders of OLs

Misrepresented Vendor or CPs for nuclear

Products power reactors.

89-69 Loss of Thermal Margin 9/29/89 All holders of OLs

Caused by Channel Box or CPs for BWRS.

Bow

89-68 Evaluation of Instrument 9/25/89 All holders of OLs

Setpoints During or CPs for nuclear

Modifications power reactors.

89-67 Loss of Residual Heat 9/13/89 All holders of OLs

Removal Caused by or CPs for PWRs.

Accumulator Nitrogen

Injection

89-66 Qualification Life of 9/11/89 All holders of OLs

Solenoid Valves or CPs for nuclear

power reactors.

88-46, Licensee Report of 9/11/89 All holders of OLs

Supp. 4 Defective Refurbished or CPs for nuclear

Circuit Breakers power reactors.

89-65 Potential for Stress 9/8/89 All holders of OLs

Corrosion Cracking in or CPs for PWRs.

Steam Generator Tube

Plugs Supplied by

Babcock and Wilcox

89-64 Electrical Bus Bar Failures 9/7/89 All holders of OLs

or CPs for nuclear

power reactors.

89-63 Possible Submergence of 9/5/89 All holders of OLs

Electrical Circuits Located or CPs for nuclear

Above the Flood Level Because power reactors.

of Water Intrusion and Lack

of Drainage

OL = Operating License

CP - Construction Permit