Information Notice 1996-58, RCP Seal Replacement with Pump on Backseat

RCP Seal Replacement with Pump on Backseat
	ML031050560
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, 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, Crane
Issue date:	10/30/1996
From:	Martin T; Office of Nuclear Reactor Regulation
To:	;
References
	IN-96-058, NUDOCS 9610250137
	Download: ML031050560 (7)
	v • d • e

I

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555-0001

October 30, 1996

NRC INFORMATION NOTICE 96-58: RCP SEAL REPLACEMENT WITH PUMP ON

BACKSEAT

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 a potential problem during replacement of reactor coolant pump (RCP) seal

packages. 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

On March 1, 1996, Sequoyah Unit I had a forced outage (Mode 5) to replace an RCP seal

package that had been leaking. The licensee elected to perform this maintenance activity

with the reactor coolant sy.sem (RCS) depressurized and the RCS level within the normal

pressurizer (PZR) level band. With RCS level in the PZR, the RCS maintenance boundary

for the seal replacement activity was provided by the weight of the pump impeller/shaft

assembly (approximately 6000 pounds) which had been placed on its backseat. To achieve

backseating, the RCP motor coupling bolts were loosened; this lowered the pump on its

backseat above the RCP thermal barrier housing.

Preceding the outage, site Engineering had determined that an upward pressure of

approximately 15 psig would lift the pump assembly off its backseat resulting in RCS leakage.

This information was never given to the operators. In addition, the operators were not given

specific guidance regarding the maximum PZR level or a PZR level operating range which

should be maintained to ensure that the static pressure of the RCS was less than the

pressure required to lift the impeller/shaft assembly off its backseat. Operators questioned

the lack of guidance and were subsequently given specific information regarding acceptable

PZR level.

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9610250137

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i~1 IN 96-58

October 30, 1996 Discussion

The Sequoyah RCPs (Westinghouse model Al 93S) were designed with a backseat that

provides an RCS pressure boundary to permit replacement of the seal package. The weight

of the impeller/shaft assembly provides pressure boundary control for this maintenance

activity. However, excessive RCS static head (high pressurizer level) could lift the assembly

off its backseat, resulting in RCS leakage into the maintenance area.

The staff recognizes that by replacing the RCP seal with level in the pressurizer the licensee

avoids risks associated with reduced inventory or midloop operation. However, problems

associated with this operation also exist. Therefore, licensees may wish to consider

(1) determining a maximum pressurizer level to preclude unseating the pump, (2) providing

operators with control data that can be used with available instrumentation (e.g., pressurizer

level limits) to ensure that RCS pressure does not cause the impeller/shaft assembly to lift off

its seat, and (3) providing operators with cautions to prevent unwarranted safety injection into

the RCS which could increase the probability of lifting the pump intemals.

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: Robert D. Starkey, RII

(423) 842-8001 E-mail: drs@nrc.gov

William F. Burton, NRR

(301) 415-2853 E-mail: wfb@nrc.gov

Attachment:

List of Recently Issued NRC Information Notices

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Attachment

IN 96-58

October 30, 1996 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information

Date of

Notice No.

Subject

Issuance

Issued to

96-57

96-56

96-55

96-54

96-53

95-04, Supp. 1 Incident-Reporting Require- ments Invohring Intakes, During a 24-Hour Period

That May Cause a Total

Effective Dose Equivalent

in Excess of 0.05 Sv

(5 rems)

Problems Associated with

Testing, Tuning, or Reset- ting of Digital Control

Systems While at Power

Inadequate Net Positive

Suction Head of Emergency

Core Cooling and Contain- ment Heat Removal Pumps

Under Design Basis Accident

Conditions

Vulnerability of Stainless

Steel to Corrosion When

Sensitized

Retrofit to Amersham 660

Posilock Radiography

Camera to Correct Incon- sistency in 10 CFR Part 34

Compatibility

Excessive Cooldown

and Depressurization

of the Reactor Coolant

System Following Loss

of Offsite Power

10/29/96

10/22/96

10/17/96

10/15/96

10/11/96

All U.S. Nuclear

Regulatory Commission

licensees

All holders of OLs or

CPs for nuclear power

reactors

All holders of OLs or

CPs for nuclear power

reactors

All materials licensees

All industrial radio- graphy licensees

All holders of OLs or CPs

and vendors for nuclear

power reactors

OL = Operating License

CP = Construction Permit

.

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IN 96-58

October30, 1996 Discussion