Information Notice 1994-48, Snubber Lubricant Degradation in High-Temperature Environments

Snubber Lubricant Degradation in High-Temperature Environments

ML031060631
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:	06/30/1994
From:	Grimes B Office of Nuclear Reactor Regulation
To:
References
IN-94-048, NUDOCS 9406240045
Download: ML031060631 (20)

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 June 30, 1994 NRC INFORMATION NOTICE 94-48: SNUBBER LUBRICANT DEGRADATION

IN HIGH-TEMPERATURE ENVIRONMENTS

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 the possible degradation of the lubricant used

in mechanical snubbers manufactured by Pacific Scientific (PSA) when the

snubber is used in a high-temperature environment. 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.

DescriDtion of Circumstances

During the ninth refueling outage at the Joseph M. Farley Nuclear Plant, Unit 2 at the end of 1993, the Southern Nuclear Operating Company (the

licensee) functionally tested a number of safety-related snubbers as

prescribed by its technical specification surveillance requirements. From an

original test sample of 88 mechanical snubbers, the licensee identified

8 failures. Two of these failures, a PSA-1/4 on a steam generator blowdown

line and a PSA-10 on a pressurizer safety valve, led to the discovery of four

additional snubbers that failed their functional tests for common causes

(three more PSA-1/4s on steam generator blowdown lines and another PSA-10 on

the pressurizer).

The licensee concluded that high environmental temperatures (ranging from 38 to 93 *C [100 to 220 'F]) for extended periods had degraded the internal

lubricants used in these PSA snubbers. The licensee determined that the

failure mechanism of the PSA-1/4s was a loss of lubricant, and for the PSA-10s

it was a breakdown of lubricant viscosity. Elevated temperatures caused the

PSA-1/4 snubber grease to bake and dry up, resulting in complete lockup when

these snubbers were tested. For the PSA-10 snubbers, the high temperatures

caused the grease to lose almost all viscosity,iresulting in insufficient drag

resistance during testing.

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'~ IN 94-48 June 30, 1994 The licensee subsequently replaced all failed snubbers, and conducted physical

inspections and engineering evaluations to ascertain if any structural damage

had occurred. No support damage or system operability concerns were

identified by the licensee.

Discussion

The licensee does not have the capability to overhaul mechanical snubbers.

Consequently, unlike their hydraulic counterparts, mechanical snubbers are not

part of any routine preventive maintenance program. PSA mechanical snubbers

are purchased and installed with the expectation that they are maintenance

free for the duration of their life in the plant. The physical conditions of

all snubbers are examined by visual inspections which, depending on the number

of unacceptable snubbers identified in the previous inspection interval, could

be performed once in every 36 months. Although the operability of some

snubbers is verified by functional testing each refueling outage, only a small

sample of the snubber population is exercised and tested. Past industry

experience with snubber failures has demonstrated that the failure modes of

mechanical snubbers are not readily discernible by visual inspection or even

physical str.'ing. Only functional testing under actual load conditions

appears to confirm their operability. For example, of all the functionally

tested mechanical PSA snubber failures identified by the licensee for both

units since commercial operation, only one was discovered by visual

inspection.

Depending on the size and distribution of the snubber population, sample

selection techniques and failure rates, it may take decades before all plant

snubbers are actually tested. In the case of Farley Unit 2, none of the

failed PSA snubbers had been tested since the unit began commercial operation

in 1981. The subject PSA-1/4 and PSA-10 snubbers were installed during

original construction and were about 15 years old.

The licensee concluded that the failure of PSA snubbers as the result of

lubricant degradation after extended exposure to high temperatures is a new

issue. The Snubber Utility Group (SNUG), of which the licensee is a member, and PSA are aware of the issue. In December of 1993, PSA sent letters to all

users of its snubbers, including Farley Unit 2, informing them of these

grease-related problems. Although PSA snubbers are lubricated with a

radiation-resistant grease (i.e., NRRG-159), recent test results from PSA and

the industry also indicate there could be an adverse impact on the service

life of snubbers in environments with elevated temperatures. PSA and the SNUG

Lubrication Working Group have requested users to inspect and evaluate all PSA

snubbers removed from service because of preventive maintenance or functional

failure for possible lubrication degradation. SNUG also requested utilities

to forward any relevant information using a standard data sheet.

~- IN 94-48 June 30, 1994 PSA and SNUG are establishing a database to analyze and develop criteria based

on time and temperature for a service life program to be used by all

utilities. The NRC staff is following the above industry activities and will

evaluate whether additional NRC actions are necessary.

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.

nanK. Grimes, Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts: Floyd S. Cantrell, RII

(404) 331-5534 Arnold J. H. Lee, NRR

(301) 504-2758 Attachment:

List of Recently Issued NRC Information Notices

Attaachment

IN 94-48 June 30, 1994 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

94-13, Unanticipated and Unin- 06/28/94 All holders of OLs or CPs

Supp. 1 tended Movement of Fuel for nuclear power reactors.

Assemblies and other

Components due to Improper

Operation of Refueling

Equipment

94-47 Accuracy of Information 06/21/94 All U.S. Nuclear Regulatory

Provided to NRC during Commission Material

the Licensing Process Licensees.

94-46 NonConservative Reactor 06/20/94 All holders of OLs or CPs

Coolant System Leakage for nuclear power reactors.

Calculation

94-45 Potential Common-Mode 06/17/94 All holders of OLs or CPs

Failure Mechanism for for nuclear power reactors.

Large Vertical Pumps

94-44 Main Steam Isolation 06/16/94 All holders of OLs or CPs

Valve Failure to Close for nuclear power reactors.

on Demand because of

Inadequate Maintenance

and Testing

94-43 Determination of Primary- 06/10/94 All holders of OLs or CPs

to-Secondary Steam for pressurized water

Generator Leak Rate reactors.

94-42 Cracking in the Lower 06/07/94 All holders of OLs or CPs

Region of the Core for boiling-water reactors

Shroud in Boiling-Water (BWRs).

Reactors

94-41 Problems with General 06/07/94 All holders of OLs or CPs

Electric Type CR124 for nuclear power reactors.

Overload Relay Ambient

Compensation

OL = Operating License

CP = Construction Permit

IN 94-48 June 30, 1994 PSA and SNUG are establishing a database to analyze and develop criteria based

on time and temperature for a service life program to be used by all

utilities. The NRC staff is following the above industry activities and will

evaluate whether additional NRC actions are necessary.

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.

riginal gned by

8rian K. Grimes

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts: Floyd S. Cantrell, RII

(404) 331-5534 Arnold J. H. Lee, NRR

(301) 504-2758 Attachment:

List of Recently Issued NRC Information Notices

• forwarded by JRJohnson memorandum to BKGrimes dated 3/8/94 see previous concurrence

OFFICE *Region II *Region II *Region II *OGCB/NRR

NAME FSCantrell DMVerrelli JRJohnson RJKiessel

[ DATE 3/ 8/94 3/ 8/94 3/ 8/94 4/19/94 OFFICE *Tech Editor *EMEB/NRR *EMEB/NRR *DE/NRR

NAME MFMejac AJHLee JANorberg BWSheron

DATE 4/19/94 4/21/94, 4/22/94 5/17/94 OFFICE OGCB/NRR =

NAME AJKugler* i s I

DATE 5/25/94 06/Zf(/94 Document Name: 94-48.IN

IN 94-xx

May xx, 1994 PSA and SNUG are establishing a database to analyze and develop criteria based

on time and temperature for a service life program to be used by all

utilities. Both of these organizations recognize that high temperatures seem

to be the leading cause of lubrication breakdown in snubbers. The NRC staff

is following the above industry activities closely and will take appropriate

regulatory actions deemed necessary.

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, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts: Floyd S. Cantrell, Region II

(404) 331-5534 Arnold J. H. Lee, NRR

(301) 504-2758 Attachment: List of Recently Issued NRC Information Notices

• forwarded by JRJohnson memorandum to BKGrimes dated 3/8/94 see previous concurrence

OFFICE *Region II *Region II *Region II *OGCB/NRR

NAME FSCantrell DMVerrelli JRJohnson RJKiessel

DATE 3/ 8/94 3/ 8/94 3/ 8/94 4/19/94 OFFICE *Tech Editor *EMEB/NRR *EMEB/NRR *DE/NRR

NAME MFMejac AJHLee JANorberg BWSheron

DATE 4/19/94 4/21/94 4/22/94 5/17/94 OFFICE OGCB/NRR DORS/NRR l l

NAME AJKugler BKGrimes

DATE 5/2 794 5/ /94 _

Document name: b:\KJK\NKLNb\NKL1N.441

IN 94-xx

April xx, 1994 utilities. Both of these organizations recognize that high temperatures seem

to be the leading cause of lubrication breakdown in snubbers.

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, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts: Floyd S. Cantrell, Region II

(404) 331-5534 Arnold J. H. Lee, NRR

(301) 504-2758 Attachment: List of Recently Issued NRC Information Notices

• forwarded by JRJohnson memorandum to BKGrimes dated 3/8/94 see previous concurrence

OFFICE l*Region II l*Region II l*Region II l*OGCB/NRR

NAME FSCantrell DMVerrelli JRJohnson RJKiessel

DATE 3/ 8/94 3/ 8/94 3/ 8/94 4/19/94 VIU

OFFICE *Tech Editor EMEERRR k AE/ N

NAME MFMejac A ee r erg BWShero

DATE 4/19/94 4N-/94 4

4/t-94 4/ %94\

OFFICE OGCB/NRR DORS/NRR a___

NAME AJKugler BKGrimes

DATE 4/ /94 4/ /94 Document Name: b:\KJK\NKL1Nb\NKL1N.441

• forwarded by JRJohnson memorandum to BKGrimes dated 3/8/94 see previous concurrence

OFFICE *Region II *Region II *Region II OGCB/NRR A AA

NAME FSCantrell DMVerrelli JRJohnson RJKiessel

DATE 3/ 8/94 3/ 8/94 3/ 8/94 4//M/94 OFFICE Tech Editor EMEB/NRR [ EMEB/NRR l DE/NRR

NAME d A Jo+ JHL & JANorberg BWSheron

DATE 4/k?/94 4/'1/94 4/ /94 4/ /94 OFFICE OGCB/NRR DORS/NRR _

NAME AJKugler BKGrimes

DATE 4/ /94 4/ /94 Document Name: G:\RJK\NRCINS\NRCIN.441