Information Notice 1996-08, Thermally Induced Pressure Locking of a High Pressure Coolant Injection Gate Valve

Thermally Induced Pressure Locking of a High Pressure Coolant Injection Gate Valve

ML031060281
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:	02/05/1996
From:	Crutchfield D Office of Nuclear Reactor Regulation
To:
References
IN-96-008, NUDOCS 9601300092
Download: ML031060281 (9)

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555-0001 February 5, 1996 NRC INFORMATION NOTICE 96-08: THERMALLY INDUCED PRESSURE LOCKING OF A HIGH

PRESSURE COOLANT INJECTION GATE VALVE

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 loss of operational capability and the

recently discovered damage to the internal components of a safety-related

power-operated gate valve, both apparently caused by thermally induced

pressure locking. It is expected that recipients will review the informationto

for applicability to their facilities and consider actions, as appropriate, 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 November 11, 1995, Susquehanna Steam Electric Station (SSES), Unit 1, was

shut down to repair the main generator. During this forced outage, Pennsylvania Power and Light Co, the licensee for SSES Units 1 and 2, discovered a bent retaining ring in the Unit 1 high pressure coolant injection

(HPCI) valve while performing a modification to eliminate susceptibility to

pressure locking. This Anchor Darling 14-inch flexible-wedge motor-operated

pressure seal gate valve is installed in the discharge line from the HPCI to

pump. The valve is located about three pipe diameters from the connection of heat

the feedwater system piping, which the licensee believes is the source ring.

that caused thermally induced pressure locking and the bent retaining

Discussion

On August 17, 1995, the NRC issued Generic Letter (GL) 95-07, "Pressure to

Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves,"

request that licensees take actions to ensure that safety-related power- operated gate valves that are susceptible to pressure locking or thermal

binding are capable of performing their safety functions within the current

licensing bases of the facility. As stated in GL 95-07, pressure locking

occurs in flexible-wedge and double-disk gate valves when fluid becomes

pressurized within the valve bonnet and the actuator is not capable of

overcoming the additional thrust required because of the differential pressure

created across both valve disks.

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IN 96-08 February 5, 1996 Various plant operating conditions can introduce pressure locking. Pressure

in the valve bonnet might be higher than anticipated when (1) the gate valve

is in a line connected to a high-pressure system or (2) the temperature of the

fluid in the valve bonnet increases causing thermal expansion. Temperature in

the valve bonnet might increase in response to heatup during plant operation, a rise in ambient air temperature caused by leaking components or postulated

pipe breaks, or thermal conduction or convection through connected piping.

Over time, bonnet pressure could decrease by leakage past the seating surfaces

or stem packing. However, during the time to depressurize, the valve may

remain pressure locked, and the system may not be able to perform its safety

function. Also, valve actuator operation at locked rotor conditions could

degrade the motor torque capability of a motor-operated gate valve.

While evaluating the operational configurations of safety-related power- operated gate valves in response to the requested actions of GL 95-07, the

licensee found that the HPCI valve, as well as the reactor core isolation

cooling (RCIC) system injection valve, was susceptible to thermally induced

pressure locking. The HPCI valve is normally closed and is installed about

three pipe diameters from the feedwater system, and the intervening piping is

insulated. On the basis of its evaluation, the licensee concluded that, during plant operation, heat transferred from the feedwater line could cause

bonnet heatup of the HPCI injection valve. This valve had previously been

eliminated from consideration of thermally induced pressure locking because of

a perceived absence of a heat source.

While Unit 1 was shut down to repair the main generator, the licensee

initiated and completed modifications of the HPCI and RCIC valves to eliminate

susceptibility to pressure locking by drilling pressure relief holes in the

downstream disk of each valve of Unit 1. During disassembly of the HPCI

valve, the pressure seal spacer and pressure seal segmented retaining ring

were found to be damaged. The inner edge of the retaining ring was bent

approximately 3.4 mm [0.135 inch]. The retaining ring consists of four

segments and has an outer diameter of about 39.6 cm [15.6 inches], an inner

diameter of 34.5 cm [13.6 inches], and a thickness of 22.2 mm [0.875 inch].

The retaining ring serves as a support for the valve bonnet pressure seal and

transfers loads from the valve bonnet to the valve body. This bending

indicates that the retaining ring had experienced a significant force and

supports the licensee's earlier conclusion that this valve was susceptible to

thermally induced pressure locking. A calculation by the valve vendor shows

that a load of approximately 4.4 Meganewtons [1 million pounds] could cause

the identified bending of the retaining ring and corresponds to an internal

pressure of approximately 21 to 48 Megapascals [3000 to 7000 psi]. The

licensee considers these pressures to be threshold values for physical damage

to the valve. The licensee's engineering analysis shows that the heatup of

fluid trapped in the valve bonnet could be sufficient to cause a pressure of

this magnitude.

IN 96-08 February 5, 1996 The licensee's analysis revealed that the actuator for the HPCI valve did not

have sufficient thrust capability to open the valve if this high differential

pressure were created across both valve disks. Therefore, the licensee

reported that for an indeterminate period of time between April 1992 (when the

valve was previously disassembled) and November 11, 1995, the HPCI valve was

inoperable, rendering the HPCI system incapable of performing its safety

function. No inservice testing of this valve was performed during power

operation because the licensee had a cold shutdown justification for this

valve that supported operational testing only when shut down. However, the

valve was operated numerous times while the reactor was shut down, such as to

repair the main generator. The licensee believes that the residual mechanical

damage found in the HPCI valve by itself did not affect valve operability.

GL 95-07 does not specifically request that licensees inspect valve internal

components for damage caused by past pressure locking or thermal binding.

Since pressure locking and thermal binding can occur in varying degrees, licensees should be aware of the potential for valve damage when there is a

strong indication of past pressure locking or thermal binding. Licensees

should also be aware that the operational configurations associated with this

event may occur in pressurized water reactor designs as well. In addition, this event appears to indicate that sufficient heat transfer can occur through

a static length of fluid-filled piping to cause thermally induced pressure

locking.

Related Generic Communications

• NRC Generic Letter 95-07, "Pressure Locking and Thermal Binding of

Safety-Related Power-Operated Gate Valves," dated August 17, 1995

• NRC Information Notice 95-30, "Susceptibility of Low-Pressure Coolant

Injection and Core Spray Injection Valves to Pressure Locking," dated

August 3, 1995

• NRC Information Notice 95-18, "Potential Pressure Locking of Safety- Related Power-Operated Gate Valves," dated March 15, 1995 and

Supplement 1, dated March 31, 1995

• NRC Information Notice 95-14, "Susceptibility of Containment Sump

Recirculation Gate Valves to Pressure Locking," dated February 28, 1995

• NRC Information Notice 92-26, "Pressure Locking of Motor-Operated

Flexible Wedge Gate Valves," dated April 2, 1992

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IN 96-08 February 5, 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 project manager.

Dennifg't. Crutchfield,/,9ii

Division of Reactor Pfogr;

Office of Nuclear Reactor

Technical contacts: Thomas G. Scarbrough, NRR

(301) 415-2794 Internet:tgs@nrc.gov

Howard J. Rathbun, NRR

(301) 415-2787 Internet:hJrl@nrc.gov

Jerry Carter, NRR

(301) 415-1153 Internet:tjc@nrc.gov

Attachment: List of Recently Issued NRC nformation Notices

7  ?

K>

Attachment

IN 96-08 February 5, 1996 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

96-07 Slow Five Percent Scram 01/26/96 All holders of OLs or CPs

Insertion Times Caused for boiling water reactors

By Viton Diaphragms in

Scram Solenoid Pilot

Valves

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 griphy 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

I-

OL - Operating License

CP = Construction Permit

IN 96-08 February 5, 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 project manager.

original signed by

Dennis M. Crutchfield, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Thomas G. Scarbrough, NRR

(301) 415-2794 Internet:tgs@nrc.gov

Howard J. Rathbun, NRR

(301) 415-2787 Internet:hjrl@nrc.gov

Jerry Carter, NRR

(301) 415-1153 Internet:tjc@nrc.gov

Attachment: List of Recently Issued NRC Information Notices

Tech Editor reviewed 12/26/95 DOCUMENT NAME: 96-08.IN

• SEE PREVIOUS CONCURRENCE

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OFFICE PECB* I BC:EMEB* l BC:PECB* I D I

NAME JCarter:jkd RWessman RLD for/AEChaffee D field

DATE 1/17/96 I/t96 1/17/96R C1OPY796 OFFICIAL RECDORD COPY

IN 96-XX

January , 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 project manager.

Dennis M. Crutchfield, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Thomas G. Scarbrough

(301) 415-2794 Internet: tgs@nrc.gov

Howard J. Rathbun

(301) 415-2787 Internet: hjrlnrc.gv

Jerry Carter

(301) 415-1153 Internet: tjc~nrc.gov

Attachment: List of Recently Issued NRC Information Notices

DOCUMENT NAME: A:\29659IN1

• SEE PREVIOUS CONCURRENCE N

• No copy

To receive a copy of this document, indicate In the box C-Copy W/o attachment/enctosure EuCopy with attachment/enclosure

OFFICE lPECB* l lIBC:EMEB* I BC:PECB* l I D:DRPMiI

NAME JCarter:jkd RWessman RLD for/AEChaffee DMCrutchfield

DATE l9/11/96 71/17/96 1/ /96 J

urFILIIML KLUUKU iuvri AntA1/2-'

IN 96-XX

January , 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 project manager.

Dennis M. Crutchfield, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Thomas G. Scarbrough

(301) 415-2794 Internet: tgs@nrc.gov

Howard J. Rathbun

(301) 415-2787 Internet: hjrl@nrc.gov

Jerry Carter

(301) 415-1153 Internet: tjc~nrc.gov

Attachment:

List of Recently Issued NRC Information Notices

DOCUMENT NAME: A:\29659IN1

• SEE PREVIOUS CONCURRENCE N

• No copy

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

OFFICE PEC f BC:EMEB*

RWessman

IC M PECB

AEChiee

al I D:DRPM

jDMCrutchfield

NAME Cfarter:jkd

DATE 1/J7/96 )9 6 1/11/96 iII? 1/ /96 Drr n~n rinV I /

urrIL IAL KECuKu %,uri

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IN 96-XX

January 1996 Page 4 p1 This information notice requires no specific action or written esponse.

you have any questions about the information in this notice, Jhease contacl

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

Nuclear Reactor Regulation project manager.

Dennis M. Cru hfield, Director

Division of eactor Program Management

Office of clear Reactor Regulation

Technical contacts: Thomas G. Scarbrough

(301) 415-2794 Howard J. Rathbun

(301) 415-2787 Jerry Carter

(301) 415-115 Attachment:

List of Recently Issued NRC In ormation Notices

DOCUMENT NAME: A:\296591 To receive a copy of this document, indica in the box CsCopy w/o attachment/enclosure EsCopy with attachment/encLiDsure N a No copy

OFFICE lCB I C:EMEB ) I c lBC: PECB I D: DRPM I

NAME alarter:kd RWessman AEChafee DMCrutchfield

DATE 1/ /96 I 1/il /96 1 I/ /96 1/ /96

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