ML20030B105
| ML20030B105 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 06/15/1981 |
| From: | Anderson T WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| To: | Reinmuth G NRC OFFICE OF INSPECTION & ENFORCEMENT (IE) |
| Shared Package | |
| ML20030B104 | List: |
| References | |
| NS-TMA-2457, NUDOCS 8108050443 | |
| Download: ML20030B105 (2) | |
Text
.,
Westinghouse Water Reactor vedoxnNe Electric Corporation Divisions m33 F mwwer.rar.na ttm NS-TMA-2157 i
June 15,1981 G. W. Reinmuth, Chief Vendor and Special Projects Branch Division of Residence and Regional Reactor inspection Office of Inspection and Enforcement 7920 Norfolk Avenue Washington, D.C.
20015
Dear Sir:
The following summa-i:es the status to date with regard to the Limitorque Motor Opsrators.
We have reviewed the Failure Analysis Reports of the Unit 1 and Unit 2 motor failures and witnessed disassembly and ' inspection of the third unaged motor subjected to HELB testing. The third motor failure tends to isolate the significant effects causing failure to the HELB test. In all cases two (2) failure modes are in evidence: a) bearing sel:ure and b) insulation abrasion. The insulation abrasion was verified by the third motor test which was terminated prior to failure. The insulation was locally abraded / degraded on the stator winding directly above the inboard motor drain / vent hole only; which is consistent with the Unit 1 and 2 failure locations. Yet again, the bearing operation was rough. A forms.l report from Reliance on the third motor is Tcheduled for Jur.e 18, 1981. General electrical characteristics of the insulation system ard dimensional / material properties of the bearings have been verified and are in accordance with the Limitorque motor design specification. We have also received a certification through Limitorque from Reliance that the motor design and manufacturing has not changed since 1972.
Since problems of this nature have never been encountered in earlier saturated steam tests and the failure analyses indicate the bearings and insulation system meet specification, we have been investigating diff.erences between the two Limitorque test chambers. Lt.mitorque has used their irge saturated test chamber successfully since 1970. The super-heat chamber employed for the Westinghouse series of tests was originally constructed as a pilot project to gain experience with the new techniques required for future tests and to identify mod:fications that needed to be included in a future planned facility. The experimental super-heat 8108050443 810727 PDR ADOCK 05000289 P
chamber is a factor of ten (10) smaller than the saturated steam chamber and can barely accommodate an SMB-00 operator. Use of the experimental super-heat chamber for the current tests was a mutual Westinghouse and Limitorque decision in on effort to meet Westinghouse schedular commitments.
The significant differences between this smaller super-heat chamber and the one used in earlier tests by Limitorque are 1) si:e,2) location of the spray no::les directly below the steam inlet, 3) high steam flow in excess of 2000 lb/hr, and 4) the absence of steam baffles. All of these factors have added to the severity of the test as compared to the previously employed larger chamber and have resulted in conditions which are clearly more severe than any postulated accident condition.
We have concluded that the current motor design will not pass the conditions specified by Westinghouse for the HELB qualification test in the present Limitorque
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super-heat chamber. Consequently we are considering the availability of other test facilities that do not have the same chamber geometry /st:e limitations and can simulate the Westinghouse specified conditions more realistically. In addition, we are considering possible motor modifications that would increase the operators capability to meet the Westinghouse requirements. In the near future we anticipate further testing to verify the effectiveness of some minor modifications being considered to the motor.
We continue to believe that the earlier Limitorque tests, performed in accordance with IEEE Std 382-72 and ecrlier requirements, continue to be valid references for Westinghouse plants responding to IE Bulletin 79-01B and NUREG 0588. We will keep you informed of further Westinghouse efforts to obtain a successful test of the Limitorque operators to our specified test conditions.
If you have any questions concerning this information, please contact Ale.i Ball (412-373-5628) or George Butterworth (412-373-5761) of my staff.
Y ery truly yours, i
/f n
l i
T. M. Anderson, Manager Nuclear Safety Department l
GB/ABtkeg