Information Notice 1996-59, Potential Degradation of Post Loss-of-Coolant Recirculation Capability as a Result of Debris

Potential Degradation of Post Loss-of-Coolant Recirculation Capability as a Result of Debris

ML031050557
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:	10/30/1996
From:	Martin T Office of Nuclear Reactor Regulation
To:
References
IN-96-059, NUDOCS 9610280088
Download: ML031050557 (6)

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555-0001 October 30, 1996 NRC INFORMATION NOTICE 96-59: POTENTIAL DEGRADATION OF POST LOSS-OF-

COOLANT RECIRCULATION CAPABILITY AS A

RESULT OF DEBRIS

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 that the suppression pool and associated components of two boiling-water

reactors (BWRs) have been found to contain foreign objects that could have impaired

successful operation of emergency safety systems using water from the suppression pool. 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.

Description of Circumstances

Niagara Mohawk Power Corporation, the licensee for Nine Mile Point Unit 2, reported on

October 17, 1996, that a significant amount of debris was found during inspection of the

drywell-to-suppression chamber downcomers. Most downcomers were clean or contained

minimal debris. However, 17 downcomers contained debris, and 7 of the 8 downcomers

located directly under the reactor vessel had cleanliness covers installed over the downcomer

opening. Some debris was floating on the water inside the downcomers and consisted of

foam rubber cleanliness covers, plastic bags, Tygon tubing, hard hats, and so on. The

suppression pool had been cleaned during the previous refueling outage.

Commonwealth Edison Company reported on October 16, 1996, that during the first thorough

cleaning of the LaSalle Unit 2 suppression pool, a significant amount of foreign material had

been found under a layer of sludge. Sludge is a generic term for rust particles from the

carbon steel piping connected to the suppression pool. Foreign material was also found in

several downcomers. The foreign material included a rubber mat, a sheet of gasket material, a nylon bag, and a substantial amount of sludge. The licensee concluded that sufficient

material was present to challenge the clogging limit for multiple emergency core cooling

system (ECCS) strainers. The Unit 2 pool had been inspected previously to remove visible

debris, and the strainers had been cleaned.

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9610280088 cae nl~ll ( ~t/

IN 96-59 October 30, 1996 Discussion

Section 50.46 of Title 10 of the Code of Federal Regulations (10 CFR 50.46)

requires that licensees design their ECCSs so that the calculated cooling performance

following a loss-of-coolant accident (LOCA) meets five criteria, one of which is to provide

long-term cooling capability of sufficient duration following a successful system initiation so

that the core temperature shall be maintained at an acceptably low value and decay heat

shall be removed for the extended period required by the long-lived radioactivity remaining in

the core.

On October 17, 1995, the NRC issued Bulletin 95-02, "Unexpected Clogging of a Residual

Heat Removal (RHR) Pump Strainer While Operating in Suppression Pool Cooling Mode,"

which requested BWR licensees to review the operability of their ECCS and other pumps that

draw suction from the suppression pool while performing their safety function. The

addressees' evaluations were to be based on suppression pool cleanliness, suction strainer

cleanliness, and the effectiveness of their foreign material exclusion practices. In addition, licensees were to implement appropriate procedural modifications and other actions (e.g.,

suppression pool cleaning), as necessary, to minimize foreign material in the suppression

pool, the drywell, and systems that interface with the suppression pool. Licensees were to

verify their operability evaluation through appropriate testing and inspection.

The actions of both licensees were a consequence of the requested actions of Bulletin 95-02.

The LaSalle Unit 2 suppression pool was being thoroughly deaned as requested by the

bulletin, and the Nine Mile Point Unit 2 suppression pool was being reinspected as part of the

enhanced surveillance requested by the bulletin.

The NRC has issued a number of generic communications to describe aspects of the

potential for loss of recirculation capability as a result of strainer clogging and debris

blockage. While the past generic communications contain examples that focus on specific

considerations that are most applicable to either pressurized-water reactors (PWRs) or

BWRs, the basic safety concern applies to both BWRs and PWRs. These events as well as

those in previous generic communications demonstrate the need for a thorough cleaning of

all areas of PWRs and BWRs that may contain materials which could adversely affect LOCA

recirculation. Visual inspection and spot cleaning cannot ensure that all undesirable and

unanticipated foreign material will be eliminated.

Related Generic Communications

Recent instances of problems with strainer clogging are described in the

following generic communications:

NRC Generic Letter 85-22: "Potential for Loss of Post LOCA Recirculation Capability

Due to Insulation Debris Blockage," dated November 22, 1985.

NRC Information Notice 89-77: "Debris in Containment Emergency Sumps and

Incorrect Screen Configuration," dated November 21, 1989.

j

IN 96-59 October 30, 1996 * NRC Information Notice 92-71: "Partial Plugging of Suppression Pool

Strainers at a Foreign BWR," dated September 30, 1992.

• NRC Information Notice 92-85: "Potential Failures of Emergency Core

Cooling Systems Caused by Foreign Material Blockage," dated December 23, 1992.

• NRC Bulletin 93-02 and Supplement 1: "Debris Plugging of Emergency Core

Cooling Suction Strainers," dated May 11, 1993 and February 18, 1994.

• NRC Information Notice 93-34 and Supplement 1: "Potential for Loss of

Emergency Core Cooling Function Due to a Combination of Operational and

Post-LOCA Debris in Containment," dated April 26, 1993 and May 6, 1993.

NRC Information Notice 95-06: "Potential Blockage of Safety-Related

Strainers by Material Brought Inside Containment," dated January 25, 1995.

NRC Information Notice 95-47: "Unexpected Opening of a SafetylRelief

Valve and Complications Involving Suppression Pool Cooling Strainer

Blockage," dated October 4, 1995.

NRC Bulletin 95-02: "Unexpected Clogging of a Residual Heat Removal (RHR) Pump

Strainer While Operating in Suppression Pool Cooling Mode, dated October 13, 1995.

NRC Bulletin 96-03: "Potential Plugging of Emergency Core Cooling Suction

Strainers By Debris in Boiling-Water Reactors," dated May 6, 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.

Thomas T. Martin, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Richard Lobel, NRR

(301) 415-2865 Email: rml@nrc.gov

Jerry Carter, NRR

(301) 415-1153 Email: tjcenrc.gov

Attachment: List of Recently Issued NRC Information Notices

IN 96-59 October 30, 1996 * NRC Information Notice 92-71: "Partial Plugging of Suppression Pool

Strainers at a Foreign BWR," dated September 30, 1992.

• NRC Information Notice 92-85: "Potential Failures of Emergency Core

Cooling Systems Caused by Foreign Material Blockage," dated December 23, 1992.

• NRC Bulletin 93-02 and Supplement 1: "Debris Plugging of Emergency Core

Cooling Suction Strainers," dated May 11, 1993 and February 18, 1994.

• NRC Information Notice 93-34 and Supplement 1: "Potential for Loss of

Emergency Core Cooling Function Due to a Combination of Operational and

Post-LOCA Debris in Containment," dated April 26, 1993 and May 6, 1993.

NRC Information Notice 95-06: "Potential Blockage of Safety-Related

Strainers by Material Brought Inside Containment," dated January 25, 1995.

NRC Information Notice 95-47: "Unexpected Opening of a Safety/Relief

Valve and Complications Involving Suppression Pool Cooling Strainer

Blockage," dated October 4, 1995.

NRC Bulletin 95-02: "Unexpected Clogging of a Residual Heat Removal (RHR) Pump

Strainer While Operating in Suppression Pool Cooling Mode, dated October 13, 1995.

NRC Bulletin 96-03: "Potential Plugging of Emergency Core Cooling Suction

Strainers By Debris in Boiling-Water Reactors," dated May 6, 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

Thomas T. Martin, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Richard Lobel, NRR Jerry Carter, NRR

(301) 415-2865 (301) 415-1153 Email: rmlenrc.gov Email: tjcenrc.gov

Attachment: List of Recently Issued NRC Information Notices

Tech Editor has reviewed and concurred on 10/24/96 *SEE PREVIOUS CONCURRENCES

DOCUMENT NAME: 96-59.IN

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IN 96- October , 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.

Thomas T. Martin. Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Richard Lobel, NRR

(301) 415-2865 Email: rml@nrc.gov

Jerry Carter, NRR

(310 415-1153 Email: tjc@nrc.gov

Attachment:

List of Recently Issued NRC Information Notices

DOCUMENT NAME: G:\TJC\31172_IN.FIN

To receive a copy of this document, indicate in the box C-Copy w/o attachment/enclosure E-Copy with

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Attachment

IN 96-59 October 30, 1996 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

96-58 RCP Seal Replacement with 10130/96 All holders of OLs or

Pump on Backseat CPs for pressurized-water

reactors

96-57 Incident-Reporting Require- 10/30/96 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

96-55 Inadequate Net Positive 10/22/96 All holders of OLs or

Suction Head of Emergency CPs for nuclear power

Core Cooling and Contain- reactors

ment Heat Removal Pumps

Under Design Basis Accident

Conditions

96-54 Vulnerability of Stainless 10/17/96 All materials licensees

Steel to Corrosion When

Sensitized

96-53 Retrofit to Amersham 660 10/15/96 All industrial radio- Posilock Radiography graphy licensees

Camera to Correct Incon- sistency in 10 CFR Part 34 Compatibility

OL = Operating License

CP = Construction Permit