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Information Notice No. 87-08: Degraded Motor Leads in Limitorque DC Motor Operators
SSINS No.: 6835 IN 87-08 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C. 20555 February 4, 1987 Information Notice No. 87-08: DEGRADED MOTOR LEADS IN LIMITORQUE DC MOTOR OPERATORS Addressees: All nuclear power reactor facilities holding an operating license (OL) or a construction permit (CP). Purpose: This notice is provided to alert recipients of potentially defective dc motors installed in Limitorque motor operators. The motors in question were manufactured at H. K. Porter (now Peerless-Winsmith) between December 1984 and December 1985. The motors are fitted with Nomex-Kapton insulated leads that are susceptible to insulation degradation and subsequent short circuit failure. The Nomex-Kapton leads are different than the leads which were tested and reported in Limitorque Qualification Report B-0009 dated April 30, 1976. Valves with these Nomex-Kapton leads have recently failed to actuate on demand at two nuclear plant sites. It is expected that recipients will review this information for applicability to their facilities and consider actions, if appropriate, to preclude a similar problem from occurring at their facilities. However, suggestions contained in this notice do not constitute NRC requirements; therefore, no specific action or written response is required. Description of Circumstances: On May 6, 1986 the NRC received from Portland General Electric Company a 10 CFR 21 report concerning a motor failure which occurred at its Trojan Nuclear Power Plant. The failure involved shorting of the motor leads inside a Limitorque motor operator connected to an auxiliary feedwater flow control valve. Upon inspection it was determined that the failure was the result of insulation degradation of the motor leads that had allowed two leads to short together. Further, inspection at Trojan revealed three similar motors that also had experienced insulation degradation. Recently, the NRC has also learned of a failure at the Turkey Point Nuclear Power Plant in which the steam supply valve for the auxiliary feedwater turbine failed to operate after a Limitorque motor operator experienced a similar motor lead short circuit. The Trojan and the Turkey Point Limitorque operators were found to contain motors manufactured with Nomex-Kapton insulated leads. 8702020135 . IN 87-08 February 4, 1987 Page 2 of 3 On January 12-14, 1987, the NRC conducted an inspection at Peerless-Winsmith, Inc., manufacturer of dc motors for Limitorque Co. During this inspection it was determined that the failed Nomex-Kapton leads were different than the leads which were fitted to the motors, tested, and documented in Limitorque Qualification Report B-0009 for dc motor operators. The leads attached to the tested motors were insulated with Nomex plus an epoxy impregnated braided fiberglass sleeve. The NRC knows of no analysis or testing that has been performed to show the Nomex-Kapton leads are acceptable for use in an application requiring environmental qualification. Further, it should be noted that the failures cited above occurred under normal operating conditions, not under the harsh conditions which could occur in areas where environmental qualification is required. On December 19, 1986, Limitorque notified 30 plant sites (Attachment 1) that had received affected motors and recommended the sleeving of existing Nomex-Kapton motor leads. The sleeving system is still under development and Limitorque expects to have this system tested for environmental qualification by the third quarter of 1987. Discussion: The Peerless-Winsmith motors were manufactured between December 1984 and December 1985 and can be identified by the first two letters of the serial number data code on the motors. Motor serial numbers beginning with the letters ZM, NN, PN, QN, RN, SN, TN, UN, VN, WN, XN, YN, and ZN likely contain the Nomex-Kapton leads. The lead insulation consists of one layer of 50 percent overlapped 0.003 inch Nomex plus a 50 percent overlapped layer of 0.0012 inch F616 Kapton/FEP. This insulation system is about one-sixth the thickness of the leads which were part of the Limitorque qualified motor. Peerless-Winsmith has since switched to a third type of insulated lead similar to the ones used originally. No failures with this type of lead have been reported; however, qualification of this type wire also needs to be ensured. Previous, unrelated problems involving wiring installed in Limitorque motor actuators have been identified in Information Notices 83-72, 86-03 and 86-71. Although no written response to this notice is required, it is expected that holders of OLs or CPs will review the information in this notice for applicability at their facilities. Because of the failures such as those discussed above and the lack of demonstrated environmental qualification, NRC's evaluation of this problem is continuing. Depending on the result of the evaluation, specific actions may be requested. If you have any questions regarding this . IN 87-08 February 4, 1987 Page 3 of 3 matter, please contact the Regional Administrator of the appropriate NRC Regional Office, or this office. Edward L. Jordan Director Division of Emergency Preparedness and Engineering Response Office of Inspection and Enforcement Technical Contact: J. Jacobson, IE (301) 492-8845 Attachments: 1. List of Affected Plants 2. List of Recently Issued IE Information Notices .
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