United States Nuclear Regulatory Commission - Protecting People and the Environment


ACCESSION #: 9703210143



Donald C. Cook Plant, Units 1 and 2

Docket Numbers 50-315 and 50-316

Operating Licenses DPR-58 and DPR-74



This fax serves as a report of a 10 CFR Part 21 defect, reported under 10

CFR 21.21.d.3-i.



Description of Event



On January 8, 1997, while installing a new torque switch assembly for

motor operated valve 2-MMO-421, it was noted that a spacer appeared to be

missing from the torque switch.  An inspection of all the standard SMB-00

torque switches assemblies remaining in stock determined that they were

all missing a spacer.  These torque switch assemblies were part of a

group of 7 received from Limitorque for general use at DC Cook under ASP

18787.  A condition report was written to investigate if this was a new

design.



On January 12, 1997, 2-WMO-728, West Essential Service Water (ESW) Supply

to the 2CD Emergency Diesel Generator (EDG) Heat Exchanger Shutoff Valve,

failed to fully close during performance of routine surveillance **2 OHP

4030.STP.027CD, "CD Diesel Generator Operability Test".  Investigation of

the failure on January 14, 1997 discovered that the torque switch

assembly installed on the valve was also missing a spacer.  The valve was

declared inoperable, however the valve was still capable of performing

its design basis function of opening, therefore, the operability of the

2CD Diesel Generator was not affected.



On January 14, 1997, in evaluating the failure of 2-WMO-728 and the

effects of the missing spacer on the torque switch assembly, it was

determined that the lack of the spacer allows the torque switch shaft to

rotate slightly along the shaft length.  This shaft rotation allowed the

torque switch contacts to open.  With the closed torque switch contacts

open, the actuator control circuit will not allow the actuator to run in

the closed direction and therefore will not allow the valve to fully

close.  The actuator control circuit uses only the closed set of contacts

and therefore the open operation is not affected.



In the investigation, it was determined that 2-CMO-415, the Component

Cooling Water (CCW) to Miscellaneous Header Shutoff Valve for Train A. 

had received one of the torque switch assemblies from the lot of 7 which





Part 21 Report

DC Cook Plant

Page 2



were missing the spacer, Because the operability of the valve could not

be assured, it was declared Inoperable.  As the defective assembly had

been installed In September of 1996, it was determined that a

10CFR50.72(b)(1)(ii)(B) ENS call for a condition outside the design basis

was appropriate.  The ENS call was made on January 14, 1997 at 1650

hours.



The fourth defective torque switch assembly was found to have been

installed in 1-WMO-754.  With the exceptIon of the 2-CMO-415, all the

valves in which the defective assemblies had been Installed had either an

open" safety function (2-WMO-728 and 1-WMO-724) or were a BOP valve (2-

MMO-421), and thus their operability was not in question.



During the investigation of this event, an operability evaluation was

performed for 2-CMO-415.  The valve was found to have been successfully

tested under dynamic conditions during the September 1996 to January 1997

interval and that the defective torque switch assembly would not have

kept the valve from performing its design basis function of closing. 

Therefore, the valve had never been Inoperable.  The ENS notification was

retracted on February 22, 1997.



Cause of Event



The defective lot of 7 received from Limitorque apparently resulted from

a manufacturing/assembly error at the Limitorque facility.



Effect of Failure on Plant Operations



The double pole torque switch is a standard configuration for American

Electric power and is used extensively at the DC Cook Plant in SMB-00

actuators.  The 7 assemblies supplied under ASP 18787 were placed in open

stock for use In the next valve requiring one.  Therefore, the 3 torque





Part 21 Report

DC Cook Plant

Page 3



switch assemblies In open stock could have been used in any number of

safety related applications with unknown results, The failures in the 4

valves in which they were installed did not result in any safety impact,

however, this could not be guaranteed for all other SMB-00 valve

actuators in the plant due to the large variety of applications for the

assembly.  Because it is not possible to definitively evaluate all

possible applications for significant safety hazard, it was

conservatively decided to submit this event as a Part 21.



Corrective Action



All 4 of the defective assemblies which were installed have been either

replaced, or repaired by addition of a spacer.  All 7 assemblies were

returned to Limitorque for evaluation on March 10, 1997.  Limitorque has

not been able to predict when their evaluation might be complete.





                             Fax Cover Sheet



Date:     March 10, 1997



To:       NRC Operations Center

          301/816-0550

          Fax: 301/816-5151



From:     Mary Both Depuydt

          616/465-5901, x1589

          FAX: 616/406-2905



Total # of Pages: 4, including cover page





POWER REACTOR                           EVENT NUMBER: 31922



FACILITY: COOK           REGION: 3      NOTIFICATION DATE:  03/10/97

UNIT:     [1] [2] [ ]     STATE: MI     NOTIFICATION TIME:  11:25 [ET]

RX TYPE: [1] W-4-LP, [2] W-4-LP         EVENT DATE:         03/10/97

                                        EVENT TIME          00:00 [EST]

NRC NOTIFIED BY: MARY BETH DEPUYDT      LAST UPDATE DATE:   03/10/97

HQ OPS OFFICER:  JOHN MacKINNON

                                                  NOTIFICATIONS

EMERGENCY CLASS: NOT APPLICABLE

10 CFR SECTION

CDEG 21.21(c)(3)(i)      DEFECTS/NONCOMPLIANCE

                                        VERN HODGE, RVIB    NRR



UNIT SCRAM CODE RX CRIT INIT PWR  INIT RX MODE  CURR PWR  CURR RX MODE

1    N              N    0         REFUELING      0         REFUELING

2    N              Y    100       POWER          00        POWER

                                   OPERATION                OPERATION



                               EVENT TEXT



STANDARD SMB-00 TORQUE SWITCHES ASSEMBLIES REMAINING IN STOCK

DETERMINED

THAT THEY WERE ALL MISSING A SPACER.



ON JANUARY 8, 1997, WHILE INSTALLING A NEW TORQUE SWITCH ASSEMBLY

FOR

MOTOR OPERATED VALVE 2-MMO-421, IT WAS NOTED THAT A SPACER APPEARED

TO BE

MISSING FROM THE TORQUE SWITCH.  AN INSPECTION OF ALL STANDARD

SMB-00

TORQUES SWITCHES ASSEMBLIES REMAINING IN STOCK DETERMINED THAT

THEY WERE

ALL MISSING A SPACER.  THESE TORQUE SWITCH ASSEMBLIES WERE PART OF A

GROUP OF 7 RECEIVED FROM LIMITORQUE FOR GENERAL USE AT DC COOK

UNDER ASP

18787.  A CONDITION REPORT WAS WRITTEN TO INVESTIGATE IF THIS WAS A NEW

DESIGN.



THE DEFECTIVE LOT OF 7 RECEIVED FROM LIMITORQUE APPARENTLY RESULTED

FROM

A MANUFACTURING ASSEMBLY ERROR AT THE LIMITORQUE FACILITY.



THE DOUBLE POLE TORQUE SWITCH IS A STANDARD CONFIGURATION FOR

AMERICAN

ELECTRIC POWER AND IS USED EXTENSIVELY AT THE DC COOK PLANT IN SMB-00

ACTUATORS.  THE 7 ASSEMBLIES SUPPLIED UNDER ASP 18787 WERE PLACED IN

OPEN

STOCK FOR USE IN THE NEXT VALVE REQUIRING ONE.  THEREFORE, THE 3

TORQUE

SWITCH ASSEMBLIES IN OPEN STOCK COULD HAVE BEEN USED IN ANY NUMBER

OF

SAFETY RELATED APPLICATIONS WITH UNKNOWN RESULTS.  THE FAILURES IN

THE 4

VALVES IN WHICH THEY WERE INSTALLED DID NOT RESULT IN ANY SAFETY

IMPACT,

HOWEVER, THIS COULD NOT BE GUARANTEED FOR ALL OTHER SMB-00 VALVE

ACTUATORS IN THE PLANT DUE TO THE LARGE VARIETY OF APPLICATIONS FOR

THE

ASSEMBLY.  BECAUSE IT IS FOR SIGNIFICANT SAFETY HAZARD, IT WAS

CONSERVATIVELY DECIDED TO SUBMIT THIS EVENT AS A PART 21.



                        (Continued on next page)





FACILITY COOK                             PAGE # 2 OF EVENT NUMBER: 31922



ALL 4 OF THE DEFECTIVE ASSEMBLIES WHICH WERE INSTALLED HAVE BEEN

EITHER

REPLACED, OR REPAIRED BY ADDITION OF A SPACER, ALL 7 ASSEMBLIES WERE

RETURNED TO LIMITORQUE FOE EVALUATION ON MARCH 10, 1997.  LIMITORQUE

HAS

NOT BEEN ABLE TO PREDICT WHEN THEIR EVALUATION MIGHT BE COMPLETE.



COPY OF PART 21 SENT TO VERN HODGE.





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