Information Notice 1992-60, Valve Stem Failure Caused by Embrittlement

Valve Stem Failure Caused by Embrittlement

ML031200041
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:	08/20/1992
From:	Rossi C Office of Nuclear Reactor Regulation
To:
References
IN-92-060, NUDOCS 9208140032
Download: ML031200041 (8)

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UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C.

20555

August 20, 1992

NRC INFORMATION NOTICE 92-60:

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 problems in which valve stems manufactured from

American Society of Mechanical Engineers (ASME) SA 564, Type 630, H900 through

H1150 age treatment condition (17-4 PH) stainless steel could become brittle

and fail if used in environments that exceed 600 'F. It is expected that

recipients will review this 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.

Backqround

Power-operated relief valves (PORVs) connected to the pressurizer are designed

for the valve stems to operate at saturated steam temperatures.

The valve

stem thermal history is affected by thermal conduction through the valve disk

and by direct contact to the fluid discharge as a result of valve actuation.

The normal operating saturation temperature in a PWR is approximately 650 'F.

The maximum design temperatures are higher.

Data obtained by the Duke Power Company from testing on 17-4 PH material in

the age treated condition indicate that this material will, after several

thousand hours at 600 'F, exhibit an increase in tensile strength with an

accompanying large decrease in ductility (secondary aging).

The secondary

aging mechanisms are the continued precipitation of the intermetallic

compounds and the precipitation of chromium in ferrite (885 'F embrittlement).

After secondary aging occurs, the material with low ductility will have an

increased susceptibility for fracture, especially when subjected to high

torque from a power actuator.

Description of Circumstances

On December 9, 1991, the Catawba Nuclear Station, Unit 2, was in Mode 5 (hot

shutdown) in the final stages of a refueling outage.

The pressure in the

reactor coolant system was approximately 177 psig.

f9208140032) Z

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III

IN 92-60

--/August 20, 1992 Operations personnel had noted some unexpected perturbations in the

pressurizer relief tank earlier during the normal reactor coolant system fill- and-vent process which led them to suspect that either pressurizer PORV

2NC-32B or its associated block valve 2NC-31B may not be opening properly.

Both valves appeared to stroke when observed locally.

To verify that the

valves were functioning properly, operations personnel attempted to

depressurize the reactor coolant system by opening the PORV from the control

room.

When the PORV was opened, and the block valve 2NC-31B indicated an open

condition, the reactor coolant system pressure remained stable.

Operations

personnel suspected that the PORV block valve was stuck in the closed

position.

The PORV block valve is a motor operated 3-inch Rockwell International (now

Edward Valve Company) Equiwedge gate valve.

The licensee reviewed the data

on a test performed on the block valve actuator on November 25, 1991, which

suggested that the stem of the valve had separated from the gate assembly

because the stem pullout force was much lower than normal.

The licensee

replaced the PORV block valve and verified that the stem had failed.

The

failure occurred in an area where the valve stem attached to the gate

assembly.

The licensee replaced the valve with a different type of valve, and

radiographically tested the other PORV block valves on both units to verify

that they were intact and open.

Discussion

____The licensee performed_a metallurgical analysis of the fractured stem and

found that the material had lost ductility at the point of fracture.

Apparently, the stem end attached to the disk was exposed to pressurizer

temperatures above 600 OF for several thousand hours.

The high torque applied

by the power operator was sufficient to shear the stem.

The Edward Valve Company indicated that valve stems made of this material, ASME SA 564, Type 630 (17-4 PH, with an aging treatment of H1100), can become

embrittled in as little as 5,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> when exposed to temperatures greater

than 600 'F. Preliminary information indicates that this material is widely

used in the stems of PORVs and PORV block valves.

It is important to note that a valve with a severed stem may pass a

surveillance test.

For example, if the safety function of the valve is to

close, and the valve is tested in the closed direction, an acceptable closing

force can be obtained even with a severed stem.

This was, in fact, the case

with the 2NC-31B valve.

Determining the valve disk position is an operability

concern for those systems with valves that are normally opened during

operations but are closed during accident conditions.

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IN 92-60

August 20, 19921 I

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 project manager

in the Office of Nuclear Reactor Regulation (NRR).

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical contacts:

William Orders

(803) 831-2963

Donald Naujock

(301)

504-2767 Attachment:

List of Recently Issued NRC Information Notices

Attachment

IN 92-60

August 20, 1992

Page I of 1

LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information

Date of

Notice No.

Subject

Issuance

Issued to

92-59 Horizontally-Installed

08/18/92

All holders of OLs or CPs

Motor-Operated Gate

for nuclear power reactors.

Valves

92-58 Uranium Hexafluoride

08/12/92 All Fuel Cycle Licensees.

Cylinders - Deviations

in Coupling Welds

92-57 Radial Cracking of

08/11/92

All holders of OLs or CPs

Shroud Support Access

for boiling water reactors

Hole Cover Welds

(BWRs).

92-56 Counterfeit Valves in

08/06/92

All holders of OLs or CPs

the Commercial Grade

for nuclear power reactors.

Supply System

92-55 Current Fire Endurance

07/27/92

All holders of OLs or CPs

Test Results for

for nuclear power reactors.

Thermo-Lag Fire Barrier

Material

92-54 Level Instrumentation

07/24/92

All holders of OLs or CPs

Inaccuracies Caused by

for nuclear power reactors.

Rapid Depressurization

92-53 Potential Failure of

07/29/92

All holders of OLs or CPs

Emergency Diesel Gen- for nuclear power reactors.

erators due to Ex- cessive Rate of Loading

91-52, Nonconservative Errors

07/16/92

All holders of OLs or CPs

Supp. I

in Overtemperature Delta- for Westinghouse (W)-

Temperature (OTAT) Set- designed nuclear power

point Caused by Improper

reactors.

Gain Settings

92-52 Barriers and Seals

07/15/92

All holders of OLs or CPs

Between Mild and

for nuclear power reactors.

Harsh Environments

OL - Operating License

CP -

Construction Permit

3/4 This informa ion notice requires no specific action or written respon

If

you have any uestions about the information in this notice, please ontact

one of the tec nical contacts listed below or the appropriate pro .ct manager

in the Office o Nuclear Reactor Regulation (NRR).

Charles E. Rossi, Director

Division of Operational Ey nts Assessment

Office of Nuclear React

Regulation

Technical contacts:

William Orders

803) 831-2963

Do ald Naujock

(30 ) 504-2767 Attachment:

List of Recentl

Issued NRC nformation Notices

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DISTRIBUTION:

Central Files

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IN 92-60

August 20, 1992 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 project manager

in the Office of Nuclear Reactor Regulation (NRR).

Original Signfd by

Charles E. Roti

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical contacts:

William Orders

(803) 831-2963

Donald Naujock

(301) 504-2767 Attachment:

List of Recently Issued NRC Information Notices

Document Name: 92-60.IN

• See previous concurrence

• OGCB:DOEA:NRR

AJKugler

08/03/92

• C/OGCB:DOEA:NRR

GHMarcus

08/05/92 O8//~49

• EMCB:DET:NRR

DGNaujock

07/13/92

• EMCB:DET:NRR

RAHermann

07/13/92

• AC/EMCB:DET:NRR

• RPB:ADM

WBateman

JMain

07/17/92

07/13/92

• D/DET:NRR

JERichardson

07/21/92

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IN 92-XX

August XX, 1992 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 project manager

in the Office of Nuclear Reactor Regulation (NRR).

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical contacts:

William Orders

(803) 831-2963

Donald Naujock

(301) 504-2767 Attachment:

List of Recently Issued NRC Information Notices

• See previous concurrence

OGCB:DOEA:NRR C/OG

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KRR

AJKugler g K

CHBerl

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08/ 3 /92

08/3/92 D/DOEA:NOD

CERossi '

08/ /92

• EMCB:DET:NRR

DGNaujock

07/13/92

• EMCB:DET:NRR

RAHermann

07/13/92

• AC/EMCB:DET:NRR

WBateman

07/17/92

• RPB:ADM

JMain

07/13/92

• D/DET:NRR

JERichardson

07/21/92

- 3 -

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 project manager

in the Office of Nuclear Reactor Regulation (NRR).

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical contacts:

William Orders

(803) 831-2963

Donald Naujock

(301) 504-2767 Attachment:

List of Recently Issued NRC Information Notices

DISTRIBUTION:

Central Files

RAHermann

DET RF

CBerlinger

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DGNaujock

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• See previous concurrence

• DET:EMCB

• DET:EMCB

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• AC:EMCB

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07/17/92

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07/13/92 DOEA: D

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OFFICIAL RECORD COPY

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This information notice requires no specific action or writter/

response.

If you have any questions about the information iy

this notice, please contact one of the technical contacts Tasted

below

the appropriate project manager in the Office of uclear

Reactor egulation (NRR).

Charles E. Rossi, Director

Division of Operational Even s Assessment

Office of Nuclear Reactor

gulation

Technical contact\\: William Orders

(803) 831-2963 onald Naujock

( 1 504-2767 Attachment:

List of Rece

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DISTRIBUTION:

Central Files

DET RF

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