United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. NO 86-02: Failure of Valve Operator Motor During Environmental Qualification Testing

                                                            SSINS No: 6835 
                                                            IN 86-02       

                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                    OFFICE OF INSPECTION AND ENFORCEMENT
                           WASHINGTON, DC 20555

                               January 6, 1986

Information Notice No. NO 86-02:   FAILURE OF VALVE OPERATOR MOTOR DURING 
                                   ENVIRONMENTAL QUALIFICATION TESTING 

Addressees: 

All nuclear power reactor facilities holding an operating license (OL) or a 
construction permit (CP) 

Purpose: 

This notice is to alert recipients of a potentially significant problem 
involving the failure of Reliance Motor Corporation magnesium motors during 
environmental qualification (EQ) testing of Limitorque valve operators for 
River Bend and Nine Mile Point 2 nuclear power stations It is expected that
recipients will review this information for applicability to their 
facilities and consider actions, if appropriate, to preclude a similar 
problem 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 August 30, 1985, the General Electric Company (GE) reported to the NRC 
that they had experienced test anomalies of the Reliance, class RH, ac 
motors during EQ testing of a Limitorque fast-acting SMB-3-150 valve motor 
operator for its Gulf States Utilities (River Bend) and Niagara Mohawk (Nine 
Mile Point 2) BWR customers These motors have magnesium rotors Magnesium 
rotor motors have previously undergone EQ testing by Limitorque (PWR 
Qualification - Project 600456A) without failures However, during the 
current testing, three motors failed during the 100-day design-basis-event 
(DBE) test The first motor had been subjected to the 40-year qualification 
series of radiation, thermal, mechanical, and dynamic aging before the 
loss-of-coolant-accident (LOCA) testing This motor had been exposed for 7 
days to a steam environment with temperatures as high as 355F when the 
rotor bar at the interface with the end ring had corroded, causing 
separation of the end ring from the conducting bars A second (unaged) motor 
was then substituted into the test; after 14 days in the steam environment, 
with a maximum temperature of 245F, it experienced the same failure as 
the first motor A third (unaged) motor experienced the same failure 
following 43 days with a maximum temperature of 223F 



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                                                            IN 86-02       
                                                            January 6, 1986 
                                                            Page 2 of 2    

Discussion: 

Limitorque Corporation has used Reliance medium and large (180 frame and 
larger) ac motors, with magnesium alloy as a standard rotor material, in its
operators for many years Although all specific applications and affected 
power plants could not be identified, Limitorque has concluded that all 
domestic nuclear power facilities, using Limitorque actuators, would have 
several motors in 180-frame size and larger containing magnesium alloy 
rotors The magnesium alloy rotors have been primarily used where high 
torque, high horsepower, fast-acting motors are required Reliance Motor 
Corporation has stated that, while they are reviewing possible design 
changes to prevent corrosion of the rotor in high temperature steam 
environments, there are no existing rotors available to replace the 
magnesium alloy components and retain the same motor characteristics 

General Electric has reviewed the BWR applications and has provided 
recommended action via Service Information Letter No 425 (July 17, 1985) 
In summary, GE recommends that licensees determine the plant-specific 
applications of magnesium motors subject to harsh environment, the adequacy 
of long-term cooling could be evaluated assuming failure of the magnesium 
rotor MOVs a few days after the DBE Some systems may allow for the operator
to position the valve to its safety position immediately following the DBE 
instead of waiting for automatic actuation, while other systems may require 
realignment to a standby mode after initial core cooling In addition to 
operator training, it may be prudent to disconnect some of the valve 
actuation logic following safety positioning to prevent valve realignment 
without operator initiation Other corrective actions may be appropriate for
specific applications 

PWR owners may wish to review their Limitorque MOV qualification packages in
light of this new information If the review determines that the equipment 
may not be qualified for its intended use then they may wish to consider 
taking action, as recommended by GE for BWRs and as described above, to 
mitigate the potential for long-term core cooling problems caused by 
motor-operated valve (MOV) failures in the days following a DBE 

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



                                   Edward L Jordan Director 
                                   Division of Emergency Preparedness 
                                     and Engineering Response 
                                   Office of Inspection and Enforcement 

Technical Contact:  James E Stewart
                    (301) 492-9061

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