ML20079D968

Special Rept:On 910816,discovered That Surveillance Acceptance Criteria Tolerance Not Repeatable on Passive Triaxial Peak Accelerograph.Caused by Faulty Vendor Stated Tolerances.Replacement of Accelerographs Under Review

ML20079D968
Person / Time
Site:	Millstone
Issue date:	09/25/1991
From:	Keenan J, Scace S NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
MP-91-756, NUDOCS 9110040262
Download: ML20079D968 (2)

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78.'nI$tINN[oNas HARTFORD. CONNECTICVT 06141-0:70 M w ent w w tw p amr,W 1203lHs-s000 Docket No. 50-423 Re: 10CFR50.36 September 25, 1991 MP-91-756 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555

References:

(1) Regulatorv Guide 1.12. Instruretation For Earthquakes (2) ANSl%NS-2.2-19'E. Earthquale Instrumentation Criteria for Nuclear Power Plants (3) ANSl'ANS-2.10-1975. Guidelines for Retrieva!, Review, Processing, and Evaluation of Records Obtained From Seismic Instrumentauon Gentlemen:

Millstone Nuclear Power Station. Unit No. 3 InoneraNe Seismie hionitoring inctrumentation This Special Report is being submitted pursuant to the requirements of plant Technical Specifications 3.3.3.3.a: SEISMIC INSTRUMENTATION, and 6.9.2: SPECIAL REPORTS. If one or more of the seismic monitorinc instruments remains inoperable for more than 30 days. plant Technical Specification 3.l?.3.a requires that a Special Report be submitted to the NRC within the next 10 davs. outlininc the cause of the malfunction and the plans for restoring the instruments to OPERABLE status.

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 passive Triaxial (Recording) Peak Accelerograph. 3ERS-PAS 28, which is installed on the Charging Pumps Cooline Surce Tank, was removed from service to perform its refueling channel calibration. While performing the surveillance, an Inst;umentation 6: Controls Department technician identified that the surseillance acceptance criteria tolerance was not repeatable. The reliability of all three passive Triaxia' Peek accelerographs install:d in the plant was questioned, based on the inconsistency of the macnetic trace data obtained as part of the operability s erification/ channel calibration. The im estigation concluded that the vendor stated tolerances could not be consistently satisfied with confidence when a? plied to devices installed in the field and new devices being bench tested prior to rep acement installation.

Because of the problematic nature of the triaxial peak accelerographs. Millstone 3 will pmsue ceplacement of the subject passive accelerographs with a more reliable model which complies with the requirements of Regulatory Guide 1.12. In the interim, the triaxial peak accelerographs will remain installed but will not meet the required : 50 of full scale acceptance criteria. As corrective action to restore the existmg devices to operable status, testing will be performed on the subject devices to establish instrument repeatability and accuracy. Based on the test data. an engineering evaluation will be performed w establish a satisfactory acceptance criteria, which is consistent with the requirements of 10CFR100 - Reactor Site Criteria. The engineering etaluation will reconcile any inconsistencies between the Final Safety Anal) sis Repart design basis for the triasial peak accelerocraphs and the requirements of Regulator) Guide 1.11 i c

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y The remaining 6 active:pastive seismic instruments listed on Technical Specification Table 4.3-4 are in compliance with Regulatory Guide 1.12. These instruments will provide sufficient data for evaluation of the response of the structures and equipment to any seismic motion Since the mformation contained in this Special Report ma) be of importance to the industry, a discutsion of the event will be submitted on the INPO Notepad. A Special Repon update will be forwarded te the Staff providing corrective action resolution on the issue of the inoperable tria. sial peak acceleropraphs. This update will be submitted by December 31. 1991.

The licensee contact for this Special Report is Vere Joseph. who may be contacted at (203)444-55'1.

Very truly yours.

NORTHEAST NLCLE AR ENFRGY COh1PANY FOR: Stephen E. Scace Director, hiillstone Station J

I f b ll Ult (N- Q BY: _ John S. Neenan hiillstone Unit : Director SES YRJ:tp cc: T. T. h1artin, Region 1 Administrator W. J. Raymond, Senior Resident Inspector. hlillstone 1. nit Nos 1. : and 3 D. H. Jaff e, NRC Project N1anager, N1illstone Unit Nos.1 and 3

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