Information Notice 1996-31, Cross-Tied Safety Injection Accumulators

Cross-Tied Safety Injection Accumulators
	ML031060062
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:	05/22/1996
From:	Grimes B; Office of Nuclear Reactor Regulation
To:	;
References
	IN-96-031, NUDOCS 9605170288
	Download: ML031060062 (7)
	v • d • e

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555-0001 May 22, 1996 NRC INFORMATION NOTICE 96-31: CROSS-TIED SAFETY INJECTION ACCUMULATORS

Addressees

All holders of operating licenses or construction permits for pressurized

water reactors (PWRs).

Purpose

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

notice to alert addressees to the potential for operation in an unanalyzed

condition with safety injection (SI) accumulators cross-tied. 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 in this information notice are not NRC requirements;

therefore, no specific action or written response is required.

DescriDtion of Circumstances

On March 8, 1996, the licensee for Indian Point Nuclear Generating Unit No. 3 (IP3) reported that the plant may have operated outside its design basis

because the safety injection accumulators had periodically been cross-tied for

short periods of time. The IP3 technical specifications require the cross- connection of the safety injection accumulators once every shift to perform a

channel check when an accumulator second pressure or level instrument channel

is inoperable. The licensee had also cross-tied safety injection accumulators

together to sluice water or nitrogen from one accumulator to another to ensure

adequate water or nitrogen. An evaluation by the licensee engineering staff

(confirmed by Westinghouse) shows that the plant may not be protected if

accumulators are cross-tied during some loss-of-coolant accidents because

nitrogen pressure is postulated to bleed off through the faulted loop to the

containment.

Since the IP3 licensee report, several other licensees have reported that

their plant procedures also allow cross-connection of safety injection

accumulators, in some cases, all of the accumulators in order to equalize

pressure. No other licensee has reported a requirement to perform this

operation. The IP3 licensee has submitted an application to amend its

technical specification to remove the cross-connection requirement. Other

licensees have taken administrative action to prohibit cross-connection of the

accumulators.

Discussion

The safety injections accumulators are pressure vessels filled with borated

water and pressurized with nitrogen gas. The accumulators are isolated from

72 or) pA D - C ok

PDR ZC-E sorCte96o -631 %60S-22 I

IN 96-31 May 22, 1996 the reactor coolant system cold legs by two check valves in series. Should

reactor coolant system pressure fall below the accumulator pressure, the check

valves would open and borated water would be injected into the reactor coolant

system. The accumulators function as passive engineered safety features and

perform a critical function in mitigating a loss-of-coolant accident. As

stated in the IP3 final safety analysis report, the design capacity of the

accumulators is based on the assumption that flow from one of the accumulators

will spill onto the containment floor through the ruptured loop. The flow

from the three remaining accumulators will provide water to reflood the core.

If two or more safety injection accumulators are cross-connected during a

postulated large-break loss-of-coolant accident, the nitrogen gas pressure of

the cross-connected accumulators on non-faulted loops will decrease because of

gas escaping through cross-connected lines to the accumulator in the broken

loop, through the ruptured pipe, and into the containment. Licensee

calculations showed that the pressure of cross-connected accumulators on non- faulted loops would decrease below the value assumed in the safety analysis

report. The IP3 licensee, with confirmation from Westinghouse, infers that

the peak cladding temperature would exceed 1204 'C [2200 *F] using the design- basis model, but calculations were not performed because fewer than three

accumulators injecting were not considered in their licensing-basis analyses.

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, Acting Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Frank Orr, NRR

(301) 415-1815 Internet:fro@nrc.gov

John Tappert, NRR

(301)415-1167 Internet: jrt@nrc.gov

Attachment: List of Recently Issued NRC Information Notices

I -I

Attachment

IN 96-31 May 22, 1996 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

96-30 Inaccuracy of Diagnostic 05/21/96 All holders of OLs or CPs

Equipment for Motor- for nuclear power reactors

Operated Butterfly Valves

96-29 Requirements in 10 CFR 05/20/96 All holders of OLs or CPs

Part 21 for Reporting and for nuclear power reactors

Evaluating Software Errors

96-28 Suggested Guidance Relating 05/01/96 All material and fuel cycle

to Development and Imple- licensees

mentation of Corrective

Action

96-27 Potential Clogging of High 05/01/96 All holders of OLs or CPs

Pressure Safety Injection for pressurized water

Throttle Valves During reactors

Recirculation

96-26 Recent Problems with Over- 04/30/96 All holders of OLs or CPs

head Cranes for nuclear power reactors

96-25 Transversing In-Core Probe 04/30/96 All holders of OLs or CPs

Overwithdrawn at LaSalle for nuclear power reactors

County Station, Unit 1

96-24 Preconditioning of Molded- 04/25/96 All holders of OLs or CPs

Case Circuit Breakers for nuclear power reactors

Before Surveillance Testing

96-23 Fires in Emergency Diesel 04/22/96 All holders of OLs or CPs

Generator Exciters During for nuclear power reactors

Operation Following Unde- tected Fuse Blowing

96-22 Improper Equipment Set- 04/11/96 All holders of OLs or CPs

tings Due to the Use of for nuclear power reactors

Nontemperature-Compensated

Test Equipment

OL - Operating License

CP = Construction Permit