View source for Information Notice 1996-61, Failure of a Main Steam Safety Valve to Reseat Caused by an Improperly Installed Release Nut

{{Adams
| number = ML031050516
| issue date = 11/20/1996
| title = Failure of a Main Steam Safety Valve to Reseat Caused by an Improperly Installed Release Nut
| author name = Martin T
| author affiliation = NRC/NRR
| addressee name = 
| addressee affiliation = 
| docket = 05000003, 05000010, 05000029, 05000133, 05000155, 05000171, 05000206, 05000213, 05000219, 05000220, 05000237, 05000244, 05000245, 05000247, 05000249, 05000250, 05000251, 05000254, 05000255, 05000259, 05000260, 05000261, 05000263, 05000265, 05000266, 05000267, 05000269, 05000270, 05000271, 05000272, 05000275, 05000277, 05000278, 05000280, 05000281, 05000282, 05000285, 05000286, 05000287, 05000289, 05000293, 05000295, 05000296, 05000298, 05000301, 05000302, 05000304, 05000305, 05000306, 05000309, 05000311, 05000312, 05000313, 05000315, 05000316, 05000317, 05000318, 05000320, 05000321, 05000322, 05000323, 05000324, 05000325, 05000327, 05000328, 05000329, 05000330, 05000331, 05000333, 05000334, 05000335, 05000336, 05000338, 05000339, 05000341, 05000344, 05000346, 05000348, 05000352, 05000353, 05000354, 05000361, 05000362, 05000364, 05000366, 05000368, 05000369, 05000370, 05000373, 05000374, 05000382, 05000387, 05000388, 05000389, 05000390, 05000391, 05000395, 05000397, 05000400, 05000409, 05000410, 05000412, 05000413, 05000414, 05000416, 05000423, 05000424, 05000425, 05000437, 05000438, 05000439, 05000440, 05000441, 05000443, 05000444, 05000445, 05000446, 05000454, 05000455, 05000456, 05000457, 05000458, 05000461, 05000482, 05000483, 05000498, 05000499, 05000508, 05000528, 05000529, 05000530
| license number = 
| contact person = 
| document report number = IN-96-061, NUDOCS 9611140131
| document type = NRC Information Notice
| page count = 10
}}
{{#Wiki_filter:-  /
                                           UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, DC 20555-0001 November 20, 1996 NRC INFORMATION NOTICE 96-61: FAILURE OF A MAIN STEAM SAFETY VALVE TO

RESEAT CAUSED BY AN IMPROPERLY INSTALLED

RELEASE NUT

==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 failure of a main steam safety valve (MSSV) to reseat during a plant

transient as a result of an improperly installed release nut. 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==
At Arkansas Nuclear One, Unit 1 (ANO-1), there are eight MSSVs on each of the A and B

steam generators. On May 19, 1996, the plant experienced a feedwater transient and a

reactor trip. Six of the MSSVs on the B steam header opened as designed, but one of these

failed to close following the secondary overpressure condition. As a result of the stuck-open

MSSV (PSV-2685), the secondary side of the B steam generator was isolated in accordance

with plant emergency procedures and allowed to toil dry. None of the A MSSVs opened

during this event, and the A steam generator remained operable.

The licensee determined that PSV-2685 failed to reseat because a release nut on the valve

spindle had been improperly installed. The release nut is installed to provide a surface

against which a lifting lever can bear to permit opening of the valve manually. The nut is

castellated to provide a slot through which a cotter pin may be aligned with a hole in the

spindle so that, with the cotter pin engaged in the slot and extending through the hole in the

stem, the nut would be prevented from tuming. With the nut held in its fixed position, there

was to be a specified clearance between the bottom of the nut and the top of the lifting lever

beneath to allow for expansion and contraction of the spindle during thermal cycles.

Following the ANO-1 event, the licensee found that the release nut had been threaded onto

the valve spindle at a position too low to be property staked by the cotter pin. Because the

cotter pin could not prevent the rotation of the nut, vibration occurring during the valve

discharge caused the nut to turn and travel down the stem until it rested upon the lifting lever

mechanism. Without any clearance between the bottom of the nut and the top of the lever, the valve was held open.                                                                             x

9611140131         P   AR        t       p tI t                  .O1D\
          ,>gw           6ntll;l8 rt                         e-

K>11 IN 96-61 November 20, 1996 As a result of Ks review of the event, the licensee concluded that a contributing cause of the

problem was an inadequate instruction related to establishing the proper position of the

release nut with respect to the cotter pin hole in the stem. The instruction, derived from

vendor guidance, specified the clearance between the release nut and the lifting lever as

1/16 inch to 1/8 inch. The minimum value of 1/16 inch was necessary to allow enough space

to accommodate thermal effects on clearances, but the maximum value of 1/8 inch was an

unneeded limitation that distracted attention from the need to ensure that the nut was staked

sufficiently with the cotter pin to preclude nut rotation. The licensee changed the

maintenance procedure to eliminate the confusion about the nut-to-lever clearance and

modified the design of the release nut to increase the depth of the slot, thereby providing

greater assurance of proper engagement between the cotter pin and the nut. In subsequent

action, the licensee determined that the manual lifting devices were unnecessary from an

operational standpoint and removed the lever and nut assemblies from all the steam safety

valves.

The licensee also found other MSSVs that had less-than-desirable engagement between the

release nut and the cotter pin. These valves were on the main steam headers from both the

A and the B steam generators. If a transient caused valves on both headers to open and

they failed to reseat, reactor decay heat removal could have been accomplished using main

or emergency feedwater in a "trickle-feed" process specified in the existing emergency

operating procedures.

Discussion

Other operating reactor events have occurred that involved the failure of MSSVs to reseat as

a result of the rotation of release nuts. In February 1984, at St. Lucie Unit 2, an MSSV stuck

partially open following the actuation of the valve. An MSSV at the Davis-Besse Nuclear

Power Station stuck open in March 1984, permitting the steam generator to boil dry. In both

of these events, the release nuts on the MSSVs rotated because the cotter pins had corroded

and failed. The corrective actions consisted of either replacing the cotter pins with stainless

steel pins or removing those parts of the lifting mechanism that the release nut would contact

if the nut were to rotate downward. These events are addressed in NRC Information

Notice 84-33, "Main Steam Safety Valve Failures Caused by Failed Cotter Pins." More

recently, in 1993, an MSSV failed to reseat at Crystal River Unit 3 because the release nut

was not engaged with the cotter pin, just as in the current ANO-1 event. The Crystal River

event is described in Licensee Event Report 93-09, submitted to the NRC by the licensee, Florida Power Corporation, by letter dated October 13, 1993, Docket No. 50-302.

Licensees have also reported situations in which the cotter pins were missing from the

release nuts. A main steam safety valve failed to reseat at ANO-1 in May 1989 because the

cotter pin was missing, as reported in Licensee Event Report 89-018. The Oconee licensee

reported, under the requirements of 10 CFR Part 50.72, that, during inspections of Units 2 and 3 on October 14, and October 24, 1996, respectively, cotter pins were missing

from 4 of 16 main steam safety valves on Unit 2 and from 2 of 16 valves on Unit 3. On

IN 96-61 November 20, 1996 October 31, 1996, the Millstone licensee reported, also under the requirements of 10 CFR

Part 50.72, that inspection of the main steam safety valves on Unit 3 showed that the cotter

pins were missing from 2 of the 20 valves.

The valves at ANO-1, Davis-Besse, Crystal River, and Millstone were manufactured by

Dresser Industries, Inc. The valves at St. Lucie and Oconee were manufactured by Crosby

Valve and Gage company.

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: Charles G. Hammer, NRR

(301) 415-2791 Email: cgh@nrc.gov

Terrence Reis, Region IV

(817) 860-8185 Email: txr@nrc.gov

Robert A. Benedict, NRR

(301) 415-1157 Email: rabl@nrc.gov

Attachments:
1. Steam Safety Valve

2. List of Recently Issued NRC Information Notices

60            Jk/ka

IN 96-61 November 20, 1996 STEAM SAFETY VALVE

COTTER F'IN                SPINDLE

lU T    ....- ::-
TOP LEV 'ER

FRONT                      TOP

......................

*,:

W-oJ

Attachment 2 IN 96-61 November 20, 1996 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information                                       Date of

Notice No.            Subject                     Issuance       Issued to

96-60            Potential Common-Mode Post-      11/14/96      All holders of OLs or

Accident Failure of Residual                     CPs for nuclear power

Heat Removal Heat Exchangers                    reactors

96-59           Potential Degradation of          10/30/96      All holders of OLs or

Post Loss-of-Coolant                            CPs for nuclear power

Recirculation Capability                        reactors

as a Result of Debris

96-58            RCP Seal Replacement with         10/30/96      All holders of OLs or

Pump on Backseat                                CPs for pressurized-water

reactors

96-57            Incident-Reporting Require-       10/29/96      All U.S. Nuclear

ments Involving Intakes,                         Regulatory Commission

During a 24-Hour Period                          licensees

That May Cause a Total

Effective Dose Equivalent

in Excess of 0.05 Sv

(5 rems)
OL = Operating License

CP = Construction Permit

IN 96-61 November 20, 1996 October 31, 1996, the Millstone licensee reported, also under the requirements of 10 CFR

Part 50.72, that inspection of the main steam safety valves on Unit 3 showed that the cotter

pins were missing from 2 of the 20 valves.

The valves at ANO-1, Davis-Besse, Crystal River, and Millstone were manufactured by

Dresser Industries, Inc. The valves at St. Lucie and Oconee were manufactured by Crosby

Valve and Gage company.

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.

original signed by

Thomas T. Martin, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Charles G. Hammer, NRR

(301) 415-2791 Email: cgh@nrc.gov

Terrence Reis, Region IV

(817) 860-8185 Email: btr@nrc.gov

Robert A. Benedict, NRR

(301) 415-1157 Email: rabl@nrc.gov

Attachments:
                1. Steam Safety Valve

2. List of Recently Issued NRC Information Notices

Tech Editor reviewed and concurred on 08/24/96
     *SEE PREVIOUS CONCURRENCES

DOCUMENT NAME: 96-63.IN

To receive a copy of this document. Ihdlcate hI the box: 'C - Copy w/o

attachment/enclosure E' - Copy w/attachmentfenclosure 'N' - No copy

OFFICE          TECH CONTS                 I      C/EMEB:DE          I  C/PECB:DRPM              RPM        [   i

NAME            CHammer*                          RWessman*             AChaffee*            TMa7ti, -
                  TReis                                                   EFG for AEC

RBenedict*_
  DATE            08/27/96                          08/27/96               11/12/96            j, /y1/96
                  11/07/96                                                                                              l

OFFICIAL RECORD COPY

IN 96-xx

November xx, 1996 four of 16 main steam safety valves on Unit 2 and from two of 16 valves on Unit 3. On

October 31, 1996, the Millstone licensee reported, also under the requirements of 10 CFR

Part 50.72, that inspection of the main steam safety valves on Unit 3 showed that the cotter

pins were missing from two of the twenty valves.

The valves at ANO-1, Davis-Besse, Crystal River, and Millstone were manufactured by

Dresser Industries, Inc. The valves at St. Lucie and Oconee were manufactured by Crosby

Valve and Gage company.

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: Charles G. Hammer, NRR

(301) 415-2791 Email: cgh@nrc.gov

Terrence Reis, Region IV

(817) 860-8185 Email: txrenrc.gov

Robert A. Benedict, NRR

(301) 415-1157 Email: rabl@nrc.gov

Attachments:
                1. Steam Safety Valve

2. List of Recently Issued NRC Information Notices

*SEE PREVIOUS CONCURRENCES

DOCUMENT NAME: G:\RAB1\ANONUTIN.REV

To receive a copy of this document, Indicate hi the box: 'C' - Copy w/o

attachment/enclosure E - Copy w/attachmentlenclosure 'N' - No copy

OFFICE           TECH CONTS                I       C/EMEB:DE            C/PECB:DRPM I

NAME            CHamler*                          RWessman*            AChaffee*            TMartin

TReis                                                  EFG for AEC

RBenedict*
  DATE            08/27/96                          08/27/96              11/12/96               / /96
  .11/07/96                                O F_                     RECORD

OFFICIAL RECORD CUPY

IN 96-xx

November xx, 1996 cotter pin was missing, as reported in Licensee Event Report 89-018. The Oconee licensee

reported, under the requirements of 10 CFR Part 50.72, that, during inspections of Units 2 and 3 on October 14, 1996, and October 24, 1996, respectively, cotter pins were missing

from four of 16 main steam safety valves on Unit 2 and from two of 16 valves on Unit                  On

October 31, 1996, the Millstone licensee reported, also under             the requirements  of Il, KFR

Part 50.72, that inspection of the main steam safety valves on Unit 3 showed th - he cotter

pins were missing from two of the twenty valves.

The valves at ANO-1, Davis-Besse, Crystal River, and Millstone were m ufactured by

Dresser Industries, Inc. The valves at St. Lucie and Oconee were m ufactured by Crosby

Valve and Gage company.

This information notice requires no specific action or written re onse. Ifyou have any

questions about the information in this notice, please conta one of the technical contacts

listed below or the appropriate Office of Nuclear Reactor gulation (NRR) project manager.

Thomas T artin, Director

Division Reactor Program Management

Office f Nuclear Reactor Regulation

Technical Contacts:             Charles G. Hammer,          R

(301) 415-2791 Email: cgh@nrc.g

Terrence Reis egion IV

(817) 860-81 Email: txr nrc.gov

Robert     . Benedict, NRR

(301 415-1157 E I: rabi@nrc.gov

Attachments:
               1. Steam Safety V e

2. List of Recentl ssued NRC Information Notices

*SEE PREVIOUS CONG RENCES

DOCUMENT NAME: G:\ B1\ANONUTIN.REV

To mceive a copy of ths docu  tr.kiicate In the box: 'C - Copy w/o

attachmentlenclosurs E -     y w/attachment/ nclosure 'N' - No copy

OFFICE          TECH PONTS                     C/EMEB:DE             C/PECB:DRPM         D/DRPM          I

NAME           CR        r*RWessman*                                AChaffee            TMartin

TR nedict*                                            Eqq7 DATE             8/27/96                      08/27/96                     96              / /96
             /CA 7 /96                                     R/
                   / .                       OFFICIAL RECORD COP

IN 96- October     , 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 man er.

Thomas T. Martin, Director

Division of Reactor Program     nagement

Office of Nuclear Reactor R ulation

Technical Contacts: Charles G. Hammer, NRR

(301) 415-2791 Email: cghenrc.gov

Terrence Reis, Region IV

(817) 860-8185 Email: txr@nrc.gov

Robert A. Benedict, NRR

(301) 415-1157 Email: rabl@nrc.gov

Attachments:
                1. Steam Safety Valve

2. List of Recently Issued NRC Informati                     Notices

*SEE PREVIOUS CONCURRENCES

DOCUMENT NAME: G:\RAB1\ANONUTIN.                              V

To receive a copy of this document. indicate in the box:   - - Copy w/o

attachmentlenclosure 'E' - Copy w/attachment/enclosre N' - No copy                                                            --- - - - I

OFFICE          TECH CONTS                 I       VEMEB:DE               C/PECB:DRPM

NAME            CHalammer*                     ,RWessman*                 AChaffee             TMartin

TReis rvtb-ti'ol

RBenedict*_                                                      _     _     _     __               _   _ _
  DATE            08/27/96               /           08/27/96                   / /96               / /96
                      _/   /96                     r  -TAI      -     rM     U__Il         I

_
                                                UI-1-LIML      KtUKU     CUPT

(--)

K>
                                                                                               IN 96- August    , 1996 Page 3 of

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:                  Charles G. Hammer, NRR

(301) 415-2791 Email: cgh@nrc.gov

Terrence Reis, Region IV

(817) 860-8185 Email: txr@nrc.gov

Robert A. Benedict, NRR

(301) 415-1157 Email: rabl@nrc.gov

Attachment:            List of Recently Issued NRC Information Notices

DOCUMENT NAME:               G:\RAB1\ANONUTIN.REV

To receive a copy of this document, hdlcate hI the box: 'C - Copy w/o

attachment/enclosure 'E'- Copy w/attachmentlenclosure 'N - No cop

OFFICE         TECH CONTS                        C/EMEB:DE            /PECB:DRPM      D/DRPM

NAME           CHammer C00b                      RWessm              AChaffee         TMartin

RBenedict

/'-/6'                           X

DATE        t/1/2-796 U;10                A       l96 /'/96               /9               /96
                         //96                             j= A"A*
                                                             ^ty

---                               OFFICIAL RECORD C MY}}

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