ML20087A376
| ML20087A376 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 12/31/1991 |
| From: | Scace S NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| RTR-REGGD-01.012, RTR-REGGD-1.012 MP-91-1080, NUDOCS 9201090078 | |
| Download: ML20087A376 (2) | |
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ww, ao3 m s.so30 liec etnber 31 1991 MP-91-1080 Do;Let No. 50-423 Re: 10CFR$0 73 U.S. Nuclear Regulatory Commi% ion Document Control Desk Washington, D.C. 20$$$
Refeiences: (1) Regulatory Guide 1.12. Instrumentation For Earthquakes C) ANS!/ANS-2.2-19?S. Earthquake instrumentation Criteria for Nuclear Power Plants (3) ANSPANS-2.10-1t 7S, Guidelines for Retrieval. Review Processing, and Evaluation of Records Obtained From Seismic Instrumentation (4) Special Report (Letter) h1P-91 756 dated September 25.1991, from Stephen E. Scace/ John S. keenan to US NRC, entitled "htillstone Nuclear Poner Station, Unit No. 3. In@uahle Sehmic_h10All.eljnt instrumentatiori Gentlemen:
hiillstone Nuclear Power Station. Unit No. 3 lnemahl _. Seismic blonitortrit_untrumentatis f
This Special Report is being submitted to provide update information for Special Report Letter h!P 91-756 listed as Reference No. 4. Special Report (Letter) hlP-91-756 was submitted pursuant to the requirements of plant Technical 5,ecifications 3.3.3.3.a:
SEISh11C INSTRUh1ENTATION, and 6.9.2: SPEC'AL 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 hiode 5 (Cold Shutdown), at 95 degrees Fahrenheit and atmospherie pressure. the passive Triaxial (Recording) Peat Accelerograph 3ERS-PAS 28 which is insta' led on the Charging Pumps Cooling Surre Tank, was remosed from service to perform its refueling channel calibration. While per' cming the surveillance, an instrumentation & Controls Department technician raised coneerns that the surveillance acceptance criteria tolerance was not repeatable gis en the field conditions and the design of the pauis e devices, in addition, the reliability of all three passive Triaxial Peak accelerographs installed in the plant was questioned, based on the inconsistency of the magnetic trace data obtained as part nf the operability verification / channel calibration The subseque nt investipation concluded that the s endor stmed tolerance of 4-59 (full scale) could not be consistently verified with confidence when applied to devices installed in the field and new devices being bench tested prior to replacement installation.
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, *.As stated in the referenced Special Report, hiillstone 3 plants to pursue replacement of L
the subject passive accelerographs with a more reliable model which complies with the requirements of Regulatory Guide 1.12. In the interim, the triaxial pcal accelerographs will remain installed but will not meet the requireC.t 59 of full scale acceptance l
criteria. As corrective action to restore the existing devices to operable status, testing j
has been performed on the subject desices io establish instrument repeatability and j
accuracy. An engineering evaluation of the data is ongoing to establish an acceptance
- i criteria which can be interpreted using the existing surveillance equipment provided by the vendor. The eneinectmp esaluation will reconcile any inconsistencies between the Final Sefety Ana1 sis Report design basis for the triasial peak accelerographs and the 3
requirements of Regulator Guide 1.12.
The remaining S actise' passive seismic
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instruments listed on Technical Specification Table 4.3-4 are in compliance with
. Regulator) Ouide 1.12. These instruments will provide sufficient data for evaluation of the response of the structures und equipment to any seismic motion.
A Final Safety Analysis Report (FSAR) change is being processed to reconcile the acce 3tance criteria tolerance, the FSAR design basis for the triaxial pral acce erographs, and the requirements of Regulatory Guide 1.12.
Since complete resolution of the inoperable triasial accelerographs has not been accomplished, another update will be provided by July 31, 1992, to discuss resolution details.
The licensee contact for this Special Report is Vere Joseph, who may be contacted at (203)444-f 571.
I Very truly yours, NORlHEAST NUCLEAR ENERGY COh1PANY
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/ Stephe E. Scace Director, h1illstone Station SESNRJ:tp ec:
T. T. h1artin, Region 1 Administrator W. J. Raymond Seninr Resident inspector, hlillstone Unit Nos.1,2 and 3 j
V L. Rooney, NRC Project hianager, Atillstone Unit No. 3 b
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