ML20127C325
| ML20127C325 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 04/27/1990 |
| From: | Baird R NATIONAL ELECTRICAL MANUFACTURERS ASSOCIATION |
| To: | Brach W Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20127C255 | List: |
| References | |
| FOIA-92-212 NUDOCS 9301140134 | |
| Download: ML20127C325 (3) | |
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...______.___--_--.--._-_._______-_-___.m t
flational Electrical Manuf acturers Association i
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(L*ggi Wastungton. O C-200371581 r202) 457 8400 l
101 L Street. fLW. Suite 300 3
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Telex 904077 NEMA WSH April 27, 1990 i
Mr. William Drach Chief, Vendor Inspection Branch Division of Reactor Inspection and Safeguards U.S. Nuclear Hegulatory commission Washington, D.C.
20555 I
SUBJECT liRC Inspection of MCCD Adjustment Procedures at Susquehanna steam Electric Station -
NRC Docket No. 50-387/388 File No. RI-89-A-0072 Dear Mr. Bracht Following discussions between NRC Staff, NUMARC Staff, and.
myself on behalf of The NEMA Molded Case Breaker Section on April lo, 1989, NRC Staff conducted an investigation of Susquehanna Steam Electric Station's procedures related to the inspection and recalibration of molded case circuit breakers. NRC Staff's findings, as a result,f that investigation (Detailed in the subject NRC files) an chat:
"the licensee does perform disassembly and' adjustment of molded case circuit breakers. However, the licensee is performing this task under their Quality-Assurance Program and-in a controlled condition as required by applicable requirements. No safety deficiencies or-violations were identified. This allegation has been closed."
NEMA's Molded Case Breaker Section takes strong exception to this finding. Rebuilding molded case circuit breakers beyond the point specified in manufacturer's literature is inherently unsafe.
Molded case circuit breakers have-factory cslibrated and-sealed trip units. Since they are generally intended to be factory assembled and then not reopened, manufadturers have not issued specific repair kits, assembly drawings, or repair instructions for molded case-circuit breakers. In those exceptional cases where UL-listing permits the-use of field installable components, the use of such. components must be accomplished according to specific directions provided, by the manufacturer, with the components.
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i In that regard, we suggest that Susquehanna's Program be reviewed as to
- 1) What procedures and experience were used in establishing the adjustment procedures in the first place? To our knowledge, neither circuit breaker manufacturers nor any nationally known standards making body have published such procedures.
- 2) What assembly drawings were used to ensure proper reassembly?
- 3) How was a determination made, for example, that it is proper to use a soldering gun or pencil to heat and unlock breaker internal adjustment screws? How was it determined that such heating will not have deluterious effects on the breaker. How was it determined that Lock-tite would not adversely af fect the plastic housing?
- 4) How were Susquehanna's calibration procedure and equipment established?
As we have previously advised NRC, the Section's concern is not related to a question of utility personnel training. It is a question that there are no published instructions or retrofit kits'for rebuilding circuit breakers. There is no non-destructive, completely comprehensive, test program to reverify all aspects of a molded case circuit breaker's performance af ter-reassembly and/or recalibration, nor does the section believe that it would be possibic to develop such a program. It is a-question that field calibrations are not conducted in the same laboratory environments - to the same curves - as are original breaker calibrations. It involves the question that certain parameters can only be checked via destructive tests. Only
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destructive testing, for example, would establish that an interphase barrier had been-inadvertently misplaced _or omitted; or that important lubricants had been removed during the cleaning process.
We hope that the NRC will reconsider'its finding at Susquehanna and determine that rebuilding and/or-recalibrating molded case circuit breakers are not acceptable practices even when conducted under a utility's quality assurance program, i
sincerely, W&
cc: Rebuilt Breakers T/F Robert W. Baird Evan Cox Division Operations Director filetnrccalib.423 R 2
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