United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 88-84: Defective Motor Shaft Keys in Limitorque Motor Actuators

                                  UNITED STATES
                          NUCLEAR REGULATORY COMMISSION
                      OFFICE OF NUCLEAR REACTOR REGULATION
                             WASHINGTON, D.C.  20555

                                October 20, 1988


Information Notice No. 88-84:  DEFECTIVE MOTOR SHAFT KEYS IN LIMITORQUE
                                   MOTOR ACTUATORS


Addressees: 

All holders of operating licenses or construction permits for nuclear power 
reactors. 

Purpose: 

This information notice is being provided to alert recipients to potential 
problems from defective motor shaft keys installed in certain Limitorque 
actuators.  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 do not constitute NRC requirements; therefore, no specific action or 
written response is required. 

Description of Circumstances: 

On October 15, 1987, the NRC received a report from Houston Lighting and Power
Company concerning sheared motor shaft-to-pinion keys found in a Limitorque 
actuator at its South Texas Project, Unit 2, nuclear plant.  A similar key 
failure also occurred in April 1987.  The sheared key from one of the valves 
was sent to a metallurgical laboratory which found that the properties of the 
material were not consistent with those of American Iron and Steel Institute 
(AISI) type 1018 steel.  AISI type 1018 steel is the material designated by 
Limitorque for these particular keys as specified in Limitorque design 
documents. 

In August 1987, three additional keys had been removed from similar actuators 
and sent to the laboratory for analysis.  One of the removed keys was split 
and the other two showed signs of deformation.  Laboratory analysis of these 
keys revealed that the properties of the key material were not consistent with
those of AISI type 1018 steel.  The metallurgical analysis revealed that the 
keys had failed longitudinally along manganese sulfide inclusions and that the
key material was probably an AISI type 1118 or 1119 resulphurized steel.  
Addi-tionally, on March 16, 1983, Westinghouse had submitted a 10 CFR Part 21 
report to the NRC concerning its discovery of sheared keys on six actuators.  
These keys were also analyzed and found to be made of other than AISI type 
1018 steel.

Discussion: 

During an NRC inspection at Limitorque in May 1988, inspectors found that at 
the time of the manufacture of the South Texas actuators, keys were purchased 

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                                                            October 20, 1988 
                                                            Page 2 of 2 


from a commercial vendor without certificates of conformance for the material 
type or properties.  No checks were performed at Limitorque to verify that the
proper key material was received.  Keys purchased today are still bought as 
commercial grade; however, certified material test reports (CMTRs) are 
received from the vendor.  Limitorque also performs hardness and dimensional 
checks of the keys upon receipt from the vendor. 

In a letter to the NRC dated May 19, 1988, Limitorque provided additional in-
formation on this issue.  Limitorque stated that the current material control 
procedures for key procurement were fully implemented in September 1983.  At 
that time, the existing key inventory was scrapped and completely replaced 
with keys purchased under the new controls.  It is estimated that all 
actuators from serial number 362735 onward were supplied with keys procured 
under the upgraded material controls.  Additionally, Limitorque determined 
that only the following actuator-motor combinations could potentially 
experience similar key failures due to improper material. 

          Unit Size                               Motor Size

          SMB-000                                 None

          SMB-00                                  25-ft.lb   1800 rpm 

          SMB-0                                   25-ft.lb   1800 rpm 
                                                  25-ft.lb   3600 rpm 
                                                  40-ft.lb   1800 rpm 

          SMB-1                                   60-ft.lb   1800 rpm 
                                                  60-ft.lb   3600 rpm 

          SMB-2                                   80-ft.lb   3600 rpm 

No specific action or written response is required by this information notice.
If you have any questions about this matter, please contact the technical 
contact listed below or the Regional Administrator of the appropriate regional
office.




                                   Charles E. Rossi, Director
                                   Division of Operational Events Assessment
                                   Office of Nuclear Reactor Regulation


Technical Contact:  Jeffrey B. Jacobson, NRR
                    (301) 492-0996

Attachment:  List of Recently Issued NRC Information Notice
.                                                            Attachment 
                                                            IN 88-84 
                                                            October 20, 1988 
                                                            Page 1 of 1

                             LIST OF RECENTLY ISSUED
                             NRC INFORMATION NOTICES
_____________________________________________________________________________
Information                                  Date of 
Notice No._____Subject_______________________Issuance_______Issued to________

88-83          Inadequate Testing of Relay   10/19/88       All holders of OLs
               Contacts in Safety-Related                   or CPs for nuclear
               Logic Systems                                power reactors. 

88-82          Torus Shells with Corrosion   10/14/88       All holders of OLs
               and Degraded Coatings in                     or CPs for BWRs. 
               BWR Containments 

88-81          Failure of Amp Window         10/7/88        All holders of OLs
               Indent Kynar Splices                         or CPs for nuclear
               and Thomas and Betts                         power, test, and 
               Nylon Wire Caps During                       research reactors.
               Environmental Quali-
               fication Testing 

88-80          Unexpected Piping Movement    10/7/88        All holders of OLs
               Attributed to Thermal                        or CPs for PWRs. 
               Stratification 

88-79          Misuse of Flashing Lights     l0/7/88        All holders of OLs
               for High Radiation Area                      or CPs for nuclear
               Controls                                     power reactors. 

88-69, Supp 1  Movable Contact Finger        9/29/88        All holders of OLs
               Binding in HFA Relays                        or CPs for nuclear
               Manufactured by General                      power reactors. 
               Electric (GE) 

88-78          Implementation of Revised     9/22/88        All holders of OLs
               NRC-Administered Requali-                    or CPs for nuclear
               fication Examinations                        power reactors. 

88-77          Inadvertent Reactor           9/22/88        All holders of OLs
               Vessel Overfill                              or CPs for BWRs. 

88-76          Recent Discovery of a         9/19/88        All holders of OLs
               Phenomenon not Previously                    or CPs for nuclear
               Considered in the Design                     power reactors. 
               of Secondary Containment 
               Pressure Control 
_____________________________________________________________________________
OL = Operating License
CP = Construction Permit 
Page Last Reviewed/Updated Tuesday, November 12, 2013