United States Nuclear Regulatory Commission - Protecting People and the Environment

ACCESSION #: 9704150068

Indiana Michigan

Power Company

500 Circle Drive

Buchanan, MI 49107-1395





April 9, 1997                                     AEP:NRC:0971H

                                                       10 CFR 21

Docket Nos.:   50-315


U. S. Nuclear Regulatory Commission

ATTN: Document Control Desk

Washington, D. C.  20555


               Donald C. Cook Nuclear Plant Units 1 and 2


In accordance with 10 CFR 21.21(c)(4), Indiana Michigan Power provides

notification of defective torque switch assemblies received from

Limitorque Corporation.

Initial notification of this matter was provided by facsimile to the NRC

Operations Center in accordance with 10 CFR 21.21(c)(3) on March 10,


The information required by 10 CFR 21 is provided in attachment 1 to this



E. E. Fitzpatrick

Vice President


THIS   DAY OF   , 1997

     Notary Public

My Commission Expires



c:   A. A. Blind

     A. B. Beach

     MDEQ - DW & RPD

     NRC Resident Inspector

     J. R. Padgett

                       ATTACHMENT TO AEP:NRC:0971H

Attachment to AEP:NRC:0971H                                        Page 1

(i)       Name and address of the individual informing the Commission:

          E. E. Fitzpatrick

          Vice President

          Indiana Michigan Power Company

          500 Circle Drive

          Buchanan, MI 49107

(ii)      Identification of the facility which fails to comply or

          contains a defect:

          Donald C. Cook Nuclear Plant, Unit 2

          Indiana Michigan Power

(iii)     Identification of the firm constructing the facility or

          supplying the basic components which contain a defect:

          Limitorque Corporation

          5114 Woodall Road

          Lynchburg, VA 24506

(iv)      Nature of the defect and the safety hazard which is created or

          could be created by such defect:

          The double pole torque switch assembly used in SMB-00 valve

          actuators was missing a spacer.  The missing spacer allowed 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 would not allow the actuator to run in the

          closed direction, and therefore would not allow the valve to

          fully close.  The actuator control circuit used only the closed

          set of contacts and therefore the open operation is not


          The seven assemblies supplied by Limitorque were placed in open

          stock, available for use in the next valve requiring

          replacement.  Therefore, the three torque switch assemblies in

          open stock could have been used in any number of safety related

          applications with unknown results.  The failures in the four

          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.

(v)       The date on which the information of such defect was obtained:

          March 10, 1997

Attachment to AEP:NRC:0971H                                        Page 2

(vi)      In the case of a basic component which contains a defect, the

          number and location of all such components in use at the

          facility subject to the regulations in this part:

          The double pole torque switch is a standard configuration for

          Indiana Michigan Power and is used extensively at the Cook

          Nuclear Plant in SMB-00 actuators.

          Seven defective torque switch assemblies were received from the

          manufacturer, only four of which were installed.  These

          assemblies were installed in valves 2-WMO-728, 1-WMO-724, 2-

          MMO-421, and 2-CMO-415.

          With the exception of 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 balance of

          plant valve (2-MMO-421), and thus their operability was not in


          2-CMO-415 was originally declared inoperable when the problem

          with the torque switch assembly was discovered and an ENS

          notification made.  During the investigation of that 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 1966 to January 1997 interval

          and it was determined 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 for 2-CMO-415 was retracted

          on February 22, 1997.

(vii)     The corrective action which has been, is being, or will be

          taken; the name of the individual or organization responsible

          for the action; and the length of time that has been or will be

          taken to complete the action:

          All four of the defective assemblies that were installed have

          either been replaced or repaired by addition of a spacer.

          The three defective assemblies that were never installed were

          returned to Limitorque on March 10, 1997.  These assemblies

          will be evaluated by Limitorque to determine the cause of the

          defect.  Limitorque has stated that they will also be

          performing failure mode analysis on the defective assemblies.

(viii)    Any advice related to the defect that has been, is being, or

          will be given to purchasers or licensees:



Page Last Reviewed/Updated Monday, March 30, 2020