NRC-85-3034, Informs of Status of Investigations Into Repts by Two Plants of Resistance Temp Detector Calibr Anomalies in Detectors Manufactured by Rdf Co

Informs of Status of Investigations Into Repts by Two Plants of Resistance Temp Detector Calibr Anomalies in Detectors Manufactured by Rdf Co

ML20129A271
Person / Time
Site:	Wolf Creek
Issue date:	05/06/1985
From:	Rahe E WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
To:	Thomas C Office of Nuclear Reactor Regulation
Shared Package
ML19344B955	List: ML20129A223 ML20129A255 ML20129A289 NRC-85-3034, Informs of Status of Investigations Into Repts by Two Plants of Resistance Temp Detector Calibr Anomalies in Detectors Manufactured by Rdf Co
References
NS-NRC-85-3034, TAC-57896, NUDOCS 8506040516
Download: ML20129A271 (4)

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XEROX TELECOPIER 495 ;31- 5-85: 8:42AM *

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• Attachment to KMLNRC 85-130

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May 6,1985

. '-eem NS-NRC-85-3034 Mr. Cecil D. Tiiomas, Chief i Division of Licensing

. U. S. Nuclear Regulatory Comission s  ! 2920 Norfolk Avenue Washington, D. C. 20555 i

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Dear Mr. Th mas:

RCS Rdf RTD CAf TBRATION FRRORS This letter is to infonn you of the status of the Westinghouse investigations into rep)rts by two plants of Resistance Temperature Detector (RID) calibration anomalies in Westinghouse supplied RTDs manufactured by the RdF Company. The issue concerns the potential for RTD calibration errors to be in excess of the Reactor Coolant System RTD error allowance identified in the RTD Equipnent Specification and used in the rarety analysis.

The increavd RTD calibratinn inacentraries were disenvered when the caletilated resistance versus temperature curves were compared to an actual calibration point which was not used in the calculation. The Westinghouse review indicated that the calibration methods used could lead to Reactor Coolant System RTD errors in excess of that currently assmed in the FSAR. Westinghouse has initiated activities to evaluate this effect and has formally notified the utilities whose plants are affected by this issue. Based on safety evaluations perfonned to date, it is our judgenent that the potential increases in the RTD r, arrow and wide range and reference junction box errors do not represent a significant adverse effect on plant safety, therefore we believe that there is sufficient justification to support continued operation.

l Increased narrow range RTD errors would primarily affcot DNS reloted transients l presented in the FSAR involving the following control and protection system pararneters: Overtemperature Delta-T Reactor Trip, Overpower Delta-T Reactor l Trip, Low Reactor Coolant Flcw Reactor Trip, RCS average temperature measurements used for control board indication and the rod control system, and the calculated value of the RCS flow measurement tocertainty.: For some l Westinghouse plants, the increased indicated inaccuracy of the wide range RTDs may affect the total accuracy of the Post Accident Monitorir.g System, the Cold Overpressure Hitigation System and the, Reactor Vessel Level Instrunentation System. The increased indicated inaccuracy of the reference junction box RTDs

may affect the total accuracy of the thermocouple system.

8506040516 850531 PDR ADOCK 05000482 P PDR l

XEROX TELECOPIER 495 131- 5-85; 8:44AM  : 412 374 4693m 316261678638 2

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l l Westinghouse has initiated activities to evaluate this effect and to identify corrective measures on a plant-by-plant basis. Westinghouse has formally notified the utilities whose plants are affected by this issue. Attachment 1 l

provides a list of the affested plant,6.

In the inter.im,, pending resolution on a permanent basis, safety margin assessments are being perfonned by Westinghouse for the operating plants to evaluate the potential effects of increased narrow and wide range and reference jmetion box RTD errors on the existing safety analysis, the total accuracy of the affected monitoring and indication systems, and the plant technical specifications. These safety evaluations are based on what we believe to be a conservative estimate of the potential plant specific RTD calibration errors which were derived from RdF calibration data.

[ Based on safety evaluations perfonned to date, DNB would not be expected to occur for the transients presented in the FSAR When the effects of the

• conservatively derived narrow range RTD errors are included. Further, a more a saliably elUswn!s wssavs yaLivc walysas 01 Ene .1Imiting UND T,ranslent iMod Withdrawal at Power) including the effects of increased RTD errors indicates that the DNB design basis would still be met with considerable margin.

Preliminary results of plant specific safety evaluations perrenned to date confins that the conservatively. derived RTD errors can be acco:,nodated on an interim basis through the reallocation of plant specific margins although some deviations from the existing technical specifications may result.

The increased sensor calibration ts) certainties for the wide range and reference junction box RTDs manufactured by the RdF Company are expected to have a negligible safety impact since no changes to the total accuracy of the affected monitoring or indication systems are expected. Therefore it is our judgement w4eu was paarn,2mA 2rcreases an tne nau narrow ana w1oe r$nge anc reterence jtziction box errors do not represent a significant adverse effect on plant safety.

I In addition, Westinghouse is working with several operating plant utilities to l ' assist them in quantifying the in-plant RTD calibration errors. Westinghouse has recently provided draft revised calibration data for the installed RTDs '

based'en a composite of the RTD vendor laboratory measurements and plant startup (cross-calibration) test results along with reconnendations for

, verification tests. Subject to utility review and verification, Westinghouse l expects that the new calibrations will be accurate to within 0 5 F. This, in l conjunction with parallel Westinghouse generic activities to define the b t ubb y w . F 1 the safety analysis. In the interim, it is our judgement that there is s ed in

!. sufficient justification to support continued operation. -

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3 XEROX TELECOPIER 495 31- 5-85: 8:45AM  : 412 374 46935 3162616786:0 3

.FROM f ( F R I )0 5. 31. ' 8 5 10 42 NO.1 PAGE 3

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I'. Mr. C. Thomas NS-NRC 85-3034

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! wrresponoence wim respecc to mis issue snou.tc De cirectec to Ms. P. A.

!  !.cftus, of any staff at 412/374-4901.

/ Very truly yours, WESTINGHOUSE ELECTRIC CORPORATION s  % %A = *=--

P . P. Rahe, Jr.

Nuclear Safety Department l

PAUds/1sv l

Attactanent i

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XEROX TELECOPIER 495 131- 5-85; 8:45AM  : 412 374 4G935 3162616786:0 4

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 ; ATTACHE.NT 1 .

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RCS RID CALIBRATION ERRORS

POTENTIALLY AITECTED PLANTS

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. Doerating Plants Non Orwrating Plants l

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. Wolf Creek Byron 2 8mn1 PrNef99d 1 e i Virgil C. Simner Shearon Harris Indian Point 2 Catawba 2 Indian Point 3 South Texas 1 & 2 Callaway Beaver Valley 2 Catawba 1 Alvin W. Vogtle 1 & 2 D. C. Cook 1 & 2 Seabrook 1 & 2 Diablo Canyon 1 Comanche Peak 1 & 2

Watts Bar 1 & 2 Millstone 3 Diablo Canyon 2

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