ML20113J115
| ML20113J115 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 07/31/1992 |
| From: | Dacimo F, Scace S NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| MP-91-1080, MP-92-812, NUDOCS 9208070054 | |
| Download: ML20113J115 (3) | |
Text
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NORTHEAST UTILmES o*-S o"= san s"*' S*"n c="a=
3 Ne*s aYsacNSNeIc coEE P O. Box 270
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'J' N e'as N N es*s*e Spany HARTFORD, CONNECTICUT 00141-0270 Nonneast Nocea Energy comcany (203)S65-5000 Docket No. 50-423 Re: 10CFR50.36 July 31, 1992 MP-92-812 U. S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555
References:
(1) Regulatory Guide 1.12, Instrumentation for Earthquakes (2) ANSI /ANS--2.2-1978, Earthquake Instrumentation Criteria For Nuclear Power Plants (3) ANSI /ANS-2.10-1979, Guidelines For Retrieval, Review, Processing and Evaluation of Records Obtained From Seismic Instrumentauon (4) Special Report (Letter) MP-91-756 dated September 25, 1991.
From John S. Keenan/ Stephen E. Scace to US NRC, entitled
" Millstone Nuclear Power Station. Unit No. 3. Inonerable Seismic Monitoring Instrumentation" (5) Special Report (Letter) MP-91-1080 dated December 31, 1991, From Stephen E. Scace to US NRC, enutled " Millstone Nuclear Power Station. Unit No.
3.
Inonerable Seismic Monitoring Instrumentation Gentlemen:
Millstone Nuclear Power Station, Unit No. 3 Inonerable Seismic Monitoring Instrumentation This Special Report is being submitted to provide update information for Special Report MP-91-1080 listed as Reference No. 5.
Special Report MP-91-1080 was submitted in accordance with Special Report MP-91-756 (Reference No. 4) and pursuant to the requirements of plant Technical Specifications 3.3.3.3.a: SEISMIC INSTRUMENTATION, and 6.9.2: SPECIAL REPORTS to report seismic monitoring instruments being inoperable for more than 30 days.
On August 16,1991, at 1253 hours0.0145 days <br />0.348 hours <br />0.00207 weeks <br />4.767665e-4 months <br />, with the plant in Mode 5 (Cold Shutdown), at 95 degrees Fahrenheit and atmospheric pressure, the pass.ve Triaxial (Recording) Perk Accelerograph, 3ERS-PAS 28, which is installed on the Charging Pump Cooling Surge Tank, was removed from service to perform its refueling.hannel calibration. While performing the surveillance, an Instrument & Controls Department technician raised g
concerns that the surveillance acceptance criteria tolerance was not repeatable given the field conditions and the design of the passive devices. In addition, the reliability of all
/{O three passive Triaxial Peak accelerographs installed in the plant was questioned because
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of the inconsistency of the magnetic trace data obtained as part of the operability verification / channel calibration.
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'The subsequent investigation concluded that the vendor stated +/ 5% of full scale -
tolerance (which is also the tolerance specified for the passive devices in' Regulatory Guide 1.12: Instrumentation for Earthquakes) could not be consistently verified 'with confidence when applied to devices installed in the field and new devices beine bench tested prior to replacement installation. Using the field measurement device supplied, and the calibration technique specified by_ the vendor, consistent or repeatable data-interpretation could not be assured - especially: with the +/-2g units.
As resolution', the routine surveillance procedure acceptance criteria has been changed to a tolerance of +/-12% (or +/-0.3mm) for the +/-1g unit and 249 (or +/-0.3mm) for the +/-2g unit. These tolerances bound the repeatability span using the calibration technique and field measurement devices supplied by the accelerograph manufacturer and would provide indication of gross degradation in performance of the accelerographs.
Millstone 3 considers the relaxation of the acceptance criteria tolerance justified given the intended us,e of the accelerographs,. The T,riaxial Peak recording accelerographs are used to provide-qualitative seismic motion data to compare against analog instrumentation post-event. The peak recording accelerographs would still be available to provide representative local peak acceleration levels durine a seismic event. Also; the historical surveillance data would be made available to ' allow a' detailed scientific evaluation of the data post-event-with more precise equipment than used in the field.
Per ANSl/ANS 2.10-1978, the peak recording accelerographs are considered the least reliable when compared with the time-history accelerographs and the response spectrum -
recorders (per Reference No. 3) and are evaluated accordingly.
An engineering evaluation has reconciled the inconsistencies-between.the revised -
acceptance criteria, the licensing basis for the Triaxial Peak accelerographs included in the - Final Safety Analysis Report. (FSAR) and. the requirements of - Regulatory Guide 1.12. A FSAR chance has been initiated to document the reconciliation of the -
acceptance - criteria tolerance, the FSAR licensing basis for the Triaxial Peak accelerographs,- and the - requirements - of Regulatory Guide 1.12.
As previously discussed in Reference Noc4 (Special Report), the remaining 8 active / passive seismic-instruments listed on Technical Specification Table 4.3-4 are in compliance with 3
Regulatory Guide 1.12..These instruments will provide sufficient data for evaluation of the response of the structures and equipment to-any seismic event.
Replacement of the subject _ passive accelerographs with a more reliable model was, considered but determined to be inappropriate for this application. Based on the information available, the most practical approach-is to retain the-Triaxial Peak-
- recording accelerographs and-implement-the newl acceptance criteria. There is no practical benefit for changing accelerographs in the +/-2g range gi_ven the intended use -
of - the devices.
The amended surveillance program ~ assures functionality L (i.e.Jmeasurability and repeatability)_of the existing passive accelerographs and meets the design intent.' The Triaxial Peak recording accelerographs in use at Millstone 3 are Model PRA-103 (+/-1g and +/-2g units) manufactured by Terra Technology.
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'No further Special Report updates are planned on the subject accelerographs. The i
licensee contact for this Special Report is Vere Joseph, who may be contacted at j
-(203) 444-5571.
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l-Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY l
FOR:. Stephen E. Scace Vice President - Millstone Station i
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Fred R. Dacimo j
Millstone Site Services Director i
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T. T. Manin, Recion 1 Administrator -
j-P. D; Swetland.- Senior Resident Inspector, Millstone Unit Nos.1, 2 and 3
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V. L Rooney, NRC Project Manager, Millstone Unit-No. 3 i
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