Information Notice 1996-07, Slow Five Percent Scram Insertion Times Caused by Viton Diaphragms in Scram Solenoid Pilot Valves

Slow Five Percent Scram Insertion Times Caused by Viton Diaphragms in Scram Solenoid Pilot Valves

ML031210497
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:	01/26/1996
From:	Crutchfield D Office of Nuclear Reactor Regulation
To:
References
IN-96-007, NUDOCS 9601260139
Download: ML031210497 (7)

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555-0001 January 26, 1996 NRC INFORMATION NOTICE 96-07: SLOW FIVE PERCENT SCRAM INSERTION TIMES CAUSED

BY VITON DIAPHRAGMS IN SCRAM SOLENOID PILOT

VALVES

Addressees

All holders of operating licenses or construction permits for boiling water

reactors (BWRs).

Purpose

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

notice to alert addressees to slow five percent scram insertion times

associated with fluoroelastomeric (Viton) diaphragms used in scram solenoid

pilot valves. 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 December 8, 1995, after a scram due to feedwater oscillations at Vermont

Yankee, a licensee review of scram time data for 77 control rods revealed that

the core-wide average to notch 46 (5 percent insertion) was trending slower

(in the 30-40 msec range) than the previous test results taken at the

beginning of the fuel cycle in April 1995. The technical specification limits

were not exceeded.

On January 20, 1996, during scram time testing of a 10 percent sample of

control rods at Brunswick Unit 1, 12 of the 14 rods in the sample exceeded the

technical specification core-wide average limit (0.358 sec) for insertion to

notch 46 by about 0.043 seconds. Previous scram time data showing a core-wide

average of about 0.304 seconds had been recorded during a scram on

September 30, 1995. On January 21, 1996, 6 rods were fully inserted into the

core (4 of the 12 slow rods and 2 rods that were not slow). Special

diagnostic test equipment was used to test the scram solenoid pilot valves

(SSPVs) from one of the slow rods and one of the satisfactory rods. The slow

SSPV was found to take longer (in the range of 55-120 msec) than normal to

exhaust air when the solenoids were deenergized. On January 22, 1996, 14 more

rods were tested and were also found to be trending slower than their previous

scram times. The licensee decided to shut down the unit after finding the

9601260139 Id A Ioll3 l

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IN 96-07 January 26, 1996 first 5 rods in the second group with increased scram times. On January 23,

1996, the reactor was manually scrammed from 28 percent power. Data taken

from 79 additional control rods during the scram showed that the core-wide

average 5 percent insertion time was about 0.380 seconds, which exceeded the

technical specification limit for insertion to notch 46.

Discussion

Investigation by General Electric (GE), Automatic Switch Company (ASCO - the

SSPV manufacturer), and the licensee for Vermont Yankee determined that the

slow times resulted from adherence of the Viton diaphragm to the brass valve

seat. The Viton diaphragms were installed as a design change in the SSPVs

(GE Part Number 107E6022P001) supplied by ASCO in response to problems with

Buna-N rubber diaphragms becoming brittle and cracking, which was seen at some

BWRs in the early 1990's. Most of the American BWR-2, BWR-3, BWR-4, and some

BWR-5 plants have replaced the Buna-N diaphragms with Viton in the past year

or so. Some BWR-5 and all BWR-6 plants use a different model (T-type) of

scram solenoid pilot valve that appear not to be susceptible to this problem.

Several BWR plants have noted the trend toward slower scram insertion times to

notch 46, but except for the Brunswick event discussed above, these slower

times were 20 to 30 milliseconds after about 6 months in service. The

Brunswick event is the first case where a plant actually exceeded the

technical specification core-wide average limit for 5 percent insertion. This

deterioration occurred between two successive surveillances even though the

licensee performed surveillance testing at the 120 day interval required by

their technical specifications.

The staff is continuing to follow this issue and will consider whether further

generic communications are warranted.

Related Generic Communications

NRC Information Notice 94-71, "Degradation of Scram Solenoid Pilot Valve

Pressure and Exhaust Diaphragms," was issued on October 4, 1994, to alert

licensees to embrittlement and cracking of Buna-N diaphragms used in SSPVs.

IN 96-07 January 26, 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.

fr' Dennis M. Crutchfield, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Jerome Blake, R11

(404) 331-5539 Internet:jjbl@nrc .gov

David Skeen, NRR

(301) 415-1174 Internet:dls@nrc.gov

Attachment: List of Recently Issued NRC Information Notices

'f e - X(;/ a_ , on ke

IN 96-07 January 26, 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.

,mtathned by arn K.Grimes

Dennis M. Crutchfield, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Jerome Blake, RII

(404) 331-5539 Internet:jjbl@nrc.gov

David Skeen, NRR

(301) 415-1174 Internet:dls@nrc.gov

Attachment: List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCES

OFC PECB:DRPM* R-II:DRS* C/SRXB:DSSA* C/PECB:DRPM*

NAME D. Skeen H. Christensen R. Jones A. Chaffee

DATE 01/25/96 4 01/25/96 01/26/96 01/26/96 .

lOFC .l D/_

NAEC-ulc- i. d

Cel

l D~y/01/ )S96

[OFFICIAL RECORD COPY]

DOCUMENT NAME: 96-07.IN

IN 96-07 January 26, 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.

Dennis M. Crutchfield, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Jerome Blake, RII

(404) 331-5539 Internet:jjbl@nrc.gov

David Skeen, NRR

(301) 415-1174 Internet:dls@nrc.gov

Attachment: List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCES

OFC PECB:DRPM* R-II:DRS* C/SRXB:DSSA C/PECB:DRPM

NAME D. Skeen H. Christensen R. Jone eA. C

DATE 01/25/96 01/25/96 O1/9,4/96 I0121/96 OFC D/DRPM

NAME D. Crutchfield

DAT 01/ /96

[OFFICIAL RECORD COPY]

DOCUMENT NAME: 96-07.IN

IN 96-07 January 26, 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.

Dennis M. Crutchfield, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Jerome Blake, R1I

(404) 331-5539 Internet:jjbl@nrc.gov

David Skeen, NRR

(301) 415-1174 Internet:dls@nrc.gov

Attachment: List of Recently Issued NRC Information Notices

OFC l PECB:DR R-II: DRS ..

> /SRXB:DSSA C/PECB:DRPM

NAME D. Skeen~lr H. Christensen R. Jones A. Chaffee

DATE 011/595 01/a"s95 01/ /95 01/ /95 OFC D/DRPM

NAME D. Crutchfield

DATE 01/ /95

[OFFICIAL RECORD COPY]

DOCUMENT NAME: 96-07.IN

Attachment

IN 96-07 January 26, 1996 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

96-06 Design and Testing 01/25/96 All holders of OLs or CPs

Deficiencies of Tornado for nuclear power reactors

Dampers at Nuclear Power

Plants

96-05 Partial Bypass of Shutdown 01/18/96 All holders of OLs or CPs

Cooling Flow from the for boiling water reactors

Reactor Vessel

96-04 Incident Reporting Require- 01/10/96 All radiography licensees

ments for Radiography and manufacturers of radio- Licensees graphy equipment

96-03 Main Steam Safety Valve 01/05/96 All holders of OLs or CPs

Setpoint Variation as a for nuclear power reactors

Result of Thermal Effects

96-02 Inoperability of Power- 01/05/96 All holders of OLs or CPs

Operated Relief Valves for PWRs

Masked by Downstream

Indications During Testing

96-01 Potential for High Post- 01/03/96 All holders of OLs or CPs

Accident Closed-Cycle for PWRs

Cooling Water Temperatures

to Disable Equipment

Important to Safety

95-58 10 CFR 34.20; Final 12/18/95 Industrial Radiography

Effective Date Licensees

OL = Operating License

CP = Construction Permit