Information Notice 1996-60, Potential Common-Mode Post-Accident Failure of Residual Heat Removal Heat Exchangers

Potential Common-Mode Post-Accident Failure of Residual Heat Removal Heat Exchangers

ML031050550
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:	11/14/1996
From:	Martin T Office of Nuclear Reactor Regulation
To:
References
IN-96-060, NUDOCS 9611070081
Download: ML031050550 (7)

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UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, DC 20555-0001 November 14, 1996 NRC INFORMATION NOTICE 96-60: POTENTIAL COMMON-MODE POST-ACCIDENT

FAILURE OF RESIDUAL HEAT REMOVAL HEAT

EXCHANGERS

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 to alert

addressees to a potential common-mode post-accident failure of boiling water reactor

(BWR) residual heat removal (RHR) heat exchangers. 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 are not NRC requirements; therefore, no specific action or written response is

required.

Background

The NRC staff issued Information Notice 96-45, 'Potential Common-Mode Post-Accident

Failure of Containment Coolers," on August 28, 1996, to alert licensees to a potential

failure mechanism of containment coolers during a design-basis loss-of-coolant accident

(LOCA) with a concurrent loss of offsite power or with a delayed sequencing of safety- related equipment. Specifically, if the containment coolers are exposed to forced

convection in a post-LOCA environment without cooling water flow, boiling may occur on

the stagnant cooling water side of the containment coolers. When cooling water flow is

subsequently reinitiated, the steam voids will collapse and may create significant

hydrodynamic loads (waterhammer). The waterhammer may threaten the integrity of the

containment cooler or the associated cooling water piping. Generic Letter 96-06,

"Assurance of Equipment Operability and Containment Integrity During Design-Basis

Accident Conditions," issued on September 30, 1996, also addressed this issue.

Description of Circumstances

A potential waterhammer scenario in the service water side of the RHR heat exchanger

was identified at the LaSalle Nuclear Station. The postulated phenomenon is analogous

to that identified for containment coolers in Information Notice 96-45 and Generic

Letter 96-06.

9611070081

96110460 7008 t04do aa{\

IN 96-60

November 14, 1996 At LaSalle, a BWR 5 plant, the top of the vertical RHR heat exchanger is the high point of

the RHR service water system and is at an elevation that is higher than that of the ultimate

heat sink by approximately 9 meters (30 feet) for normal lake levels. The resultant

pressure in the heat exchanger tubes in a standby condition is estimated to be between

7000 and 21,000 pascals (1 and 3 psia), with associated saturation temperatures between

430 and 600 C (1100 and 1400 F). Boiling will occur in these tubes if these temperatures

are exceeded. Under low lake levels, the licensee found that voiding would occur in the

top of the tubes regardless of temperature.

At LaSalle, the RHR system is lined up so that flow will go through both the RHR heat

exchanger and a bypass valve whenever the RHR system is initiated in its safety injection

(low pressure coolant injection) mode. The RHR service water flow to the tube side of the

RHR heat exchangers does not start automatically on a safety injection signal. Emergency

operating procedures direct that the RHR service water pumps be started manually within

the first 10 minutes of an accident.

It is postulated that during a LOCA, water from the suppression pool, which could start

from the technical specification allowable 41 0 C (1050 F), could quickly be heated to

88OC (1900 F). When the relatively hot suppression pool fluid would be pumped through

the RHR heat exchanger, it would boil the stagnant low pressure service water. When

RHR service water flow would subsequently be manually initiated, the steam voids would

collapse and might create significant hydrodynamic loads. The hydrodynamic loads might

impair the integrity of the heat exchangers or the associated service water piping. This

scenario does not occur during normal operation of the RHR system in the shutdown

cooling mode because the RHR service water system is started first to ensure that cooling

flow is established before h~ot fluid is introduced into the heat exchangers.

Both units at the LaSalle Nuclear Station are currently shut down. The licensee continues

to assess this issue and will ensure operability of the RHR heat exchangers before restart.

The licensee is considering the installation of a keep-fill system on the RHR service water

system to keep the heat exchangers pressurized.

Discussion

The RHR heat exchangers provide an important safety function for long term heat removal.

The postulated failure scenario could cause a common failure of the RHR heat exchangers, thereby potentially challenging this function. In addition, a structural failure of the RHR

heat exchangers could create a containment bypass release path and divert low pressure

coolant injection flow. An individual plant vulnerability to these postulated failures

depends on a number of factors. The physical configuration of the RHR service water

system and RHR heat exchanger, the operational alignment of the heat exchanger isolation

valves, the sequencing of the RHR service water pumps, and other site-specific parameters

have an effect on facility vulnerability to this potential failure mode.

IN 96-60

November 14, 1996 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.

I Thomas T. Martin, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: V. Patricia Lougheed, Region IlIl

(630) 829-9760

E-mail: vpl@nrc.gov

James Tatum, NRR

(301) 415-2805 E-mail: jetl @nrc.gov

John Tappert, NRR

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

Attachment: List of Recently Issued NRC Information Notices

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Attachment

IN 96-60

November 14, 1996 -

LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

96-59 Potential Degradation of 10/30196 All holders of OLs or

Post Loss-of-Coolant CPs for nuclear power

Recirculation Capability reactors

as a Result of Debris

96-58 RCP Seal Replacement with 10/30/96 All holders of OLs or

Pump on Backseat CPs for pressurized-water

reactors

96-57 Incident-Reporting Require- 10/29/96 All U.S. Nuclear

ments Involving Intakes, Regulatory Commission

During a 24-Hour Period licensees

That May Cause a Total

Effective Dose Equivalent

in Excess of 0.05 Sv

(5 rems)

96-56 Problems Associated with 10/22/96 All holders of OLs or

Testing, Tuning, or Reset- CPs for nuclear power

ting of Digital Control reactors

Systems While at Power

OL = Operating License

CP = Construction Permit

N;

IN 96-60

November 14, 1996 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.

original signed by D. B. Matthews

homas T. Martin, Director

/ Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: V. Patricia Lougheed, Region III

1630) 829-9760

E-mail: vpl@nrc.gov

James Tatum, NRR

(301) 415-2805 E-mail: jetl @nrc.gov

John Tappert, NRR

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

Attachment: List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCE

Tech Editor reviewed 10/29 DOCUMENT NAME: 96-62.IN

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NAME PLougheed TMarsh AChaffee Ma

JTatum

JTappert _ _ _t -

DATE 10/30/96 11/04/96 11/06/96 11/1/96 Official Record Copy

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one of the technical contacts listed below or the appropriate Office of /

Nuclear Reactor Regul ation (NRR) project manager.

Thomas T. Martin, Dire r

Division of Reactor rogram Management

Office of Nucle eactor Regulation

Technical Contacts: V. Patricia Lougheed. Re n III

(630) 829-9760

E-mailt: vpl@nrc. v

James Tatum. R

(301) 415g20

E-mail: jetl@nrc.gov

Jo zTap ert. NRR

301) 415-1167 E-mail: jrt@nrc.gov

Attachment:

1. List of Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCE

Tech Editor reviewed 10/29 ,24t nrij% I 4r

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NAME: G:\JRT\LSALRHR.IN

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OFFICE Contacts* C/SPLB:DSSA* C/PECB:DRPM D/DRPM

NAME PLougheed TMarsh AChaffee Thartin

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DATE 10/30/96 11/04/96 11/L& /96 11/ /96 UTTIClal Kecr'u LUpy

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IN 96-xx

November xx. 1996 This information notice requires no specific action or written response. If

you have any questions about the information in this notice. please conta

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

Thomas T. Martin, Dir dor

Division of Reactor rogram Management

Office of Nuclear eactor Regulation

Technical Contacts: V. Patricia Lougheed. Region i

(630) 829-9760

Internet: vpl@nrc.gov

James Tatum, NRR

(301) 415-2805 Internet: jetl@nrc.go

John Tappert. NRR

(301) 415-1167 Internet: jrt@nr gov

Attachment:

1. List of Recently Issued NRC I ormation Notices

Tech Editor re ewed 10/29 DOCUMENT NAME G:\JRT\LSALRHR.IN

OFFICE C9tacts C/SPLB:DSSA C/PECB:DRPM D/DRPM

l ME Loughee TMarsh AChaffee TMartin

JTatum

DATE 10/30/96 11/ 4/96 11/ /96 11/ /96 Official Record Copy

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