ML20062D795

Forwards Loose Thermal Sleeve Safety Evaluation, Results of Ultrasonic Testing & Radiographic Testing & Description of Surveillance Program for Loose Parts in RCS & Supplemental Loose Parts Monitoring Sys

ML20062D795
Person / Time
Site:	North Anna
Issue date:	08/04/1982
From:	Leasburg R VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	Clark R, Harold Denton Office of Nuclear Reactor Regulation
Shared Package
ML20062D798	List: ML20062D795 ML20062D811
References
460, NUDOCS 8208060220
Download: ML20062D795 (8)

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• i VinOINIA EImcTaIC AND Powna ComeAwy Rucnxown,VimonarA nonst August 4, 1982 Vice Pomasomar NoctuAa Ormaarsome i Mr. Harold R. Denton, Director Serial No. 460 Office of Nuclear Reactor Regulation N0/JHL,DWL:acm Attn: Mr. Robert A. Clark, Chief Docket No. 50-339 Operating Reactors Branch No. 3 License No. NPF-7 Division of Licensing U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Gentlemen:

VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA-POWER STATION UNIT No. 2 EVALUATION OF RCS PIPING THERMAL SLEEVES The purpose of this letter is to provide the details of the examinations and evaluations performed by Vepco, Westinghouse Electric Corporation, and Stone and Webster Engineering Corporation regarding thermal sleeve problems that were identified in the North Anna Unit No. 2 Reactor Coolant System (RCS) piping. Attachment 1 provides a description of the thermal sleeve problem at North Anna Unit No. 2 and the detailed evaluation of .the safety aspects of operation with the affected thermal sleeves. Attachment 2 provides the inspection results of the Ultrasonic Testing (UT) and Radiographic Testing (RT) which was conducted to verify the status of the North Anna Unit No. 2 thermal sleeves of the suspect design (including three additional thermal sleeves not suspected to be a problem).

Vepco will remove the four af fected thermal sleeves, that were indicated in Attachment 2, prior to heatup on Unit 2, which is currently scheduled for-August 9, 1982 with the unit scheduled on-line by August 12, 1982.

Since North Anna Unit 2 plans to continue power operation with four _ thermal sleeves of similar design still in-place, Vepco will initiate a program of increased operator training and awareness as well as a program of increased surveillance to address the potential concerns of ' loose parts in the RCS.

Attachment 3 provides a description of these programs and a description of a temporary, supplemental Loose Parts Monitoring System to be installed to monitor the remaining four thermal sleeve locations until the removal of the thermal sleeves.

As indicated in the attached Westinghouse safety evaluation (Attachment 1),

the possibility exists for the 14. inch thermal sleeve on the loop end of the pressurizer surge line to damage the Resistance Temperature Detector (RTD) scoops and the RTD thermowell in the loop C hot leg if it becomes loose.

Shearing of the hot leg RTD-thermowell would create a leak (catogorized as a l large leak, Condition II event)in the RCS. This occurrence would not j significantly degrade the RCS pressure boundary. Attachment 4 provides the safety evaluation regarding the potential for missile generation and jet im-pingement resulting from the loss of the hot leg RTD thermovell. Vepco does 8208060220 820804 DR ADDCK 05000339 PDR

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Vinoix4 Es.zernic ano Powem Couraxv to Harold R. Denton not intend to remove the intact 14 inch surge line thermal sleeve at this time since the UT and RT inspection results indicate the sleeve is intact. In addition, the removal would require a full core off-load due to the particular configuration of the loop C hot leg and surge line connection. Operator awareness and the LPMS will monitor this thermal sleeve location.

If you have any questions regarding the details of the examinations and evaluations provided by this letter or on the schedule for removing the loose thermal sleeves and plant startup, please contact us at your earliest convenience.

Very truly yours, 3

R. H. Leasburg cc: Mr. James P. O'Reilly Regional Administrator Region II

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1 ATTACHMENT 2 NORTH ANNA UNIT NO. 2 4

THERMAL SLEEVE UT AND RT INSPECTION RESULTS i

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• 4 THERMAL SLEEVE UT AND RT INSPECTION RESULTS NORTH ANNA POWER STATION UNIT NO. 2 N0ZZLE LOOP UT RESULTS RT RESULTS r

2" Loopfill* A None intact 2" Loopfill* B None intact 2" Loopfill*- C None intact 3" Charging lB sleeve in-place Welds cracked /40' rotation 6" Safety Injection A sleeve in-place intact 6" Safety Injection B sleeve in-place intact

6" Safety Injection C sleeve in-place Welds cracked /5' rotation 12" Accumulator Discharge A sleeve in-place intact 12" Accumulator Discharge B sleeve out-of-place Welds cracked / Sleeve dropped 4 1/2" 12" Accumulator Discharge C sleeve in-place Welds cracked / Sleeve dropped 1/8" 14" Pressurizer Surge Line** C sleeve in-place intact i

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• The 2" nozzles were later identified as having a different design.

• • Loop end of pressurizer surge line.

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• ATTACHMENT 3 NORTil ANNA UNIT NO. 2 LOOSE PART SURVEILLANCE PROGRAM

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OPERATOR GUIDANCE The control room operators for North Anna Unit No. 2 will be instructed prior to and during plant startup of the potential for loose parts in the RCS resulting from whole or fragmented thermal sleeves. Use of the Loose Parts Monitoring System (LPMS) will be reviewed as well as the existing and additional loose parts surveillance activities. Specific instruction will be provided by Westinghouse in the use of the supplemental LPMS which is being installed to specifically monitor the remaining thermal sleeve locations.

SURVEILLANCE The LPMS will be functionally tested at least once every 31 days. Audible checks of the LPMS are being performed by the Shif t Technical Advisors on a daily basis. This is a new surveillance.

Control rod exercises will be performed on a weekly basis to verify the free movement of the control rod assemblies. Technical Specifications require this activity on a monthly basis.

Reactor coolant activity will be monitored at least once per 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to detect any potential clad damage due to fretting by loose part fragments.

Technical Specifications require this activity on a bi-monthly basis.

Incore instrumentation thimbles will be verified as operable by traversing the movable incore detectors in the lower vessel region on a weekly basis. This should identify any potential damage or deformation of the instrument thimbles by a loose part in the vessel lower internals area. This is a new surveil-lance.

SUPPLEMENTAL LPMS Vepco is installing a temporary supplemental Loose Parts Monitoring System (LPMS) on North Anna Unit 2 to monitor thermal sleeves remaining in the reactor coolant system. This supplemented LPMS will remain in service until such time that removal of all suspect thermal sleeves is accomplished.

The supplemental LPMS for Unit 2 consists of installing accelerometers to be located on Loops A and B cold leg between the 12-inch accumalator discharge line and the reactor vessel. It will not be necessary to install a LPMS on Loop C cold leg since all thermal sleeves of concern have been taken out.

Another accelerometer is to be located on the Loop C hot leg between the 14-inch surge line and the loop isolation valve.

Associated with each accelerometer is a preamplifier which is located as close to the accelerometer as possible in order to obtain the best signal response.

Vepco plans to install all accelerometers one to two feet down-stream from the thermal sleeves to be monitored in order to obtain the best signal response.

The location of these accelerometers was recommended by Westinghouse.

In the control room, a Westinghouse control cabinet will provide continuous alarm monitoring. This supplemented LPMS for the thermal sleeves is similar to the existing LPMS at North Anna.

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ATTACHMENT 4 SAFETY EVALUATION FOR POTENTIAL MISSLES AND JET IMPINGEMENT NORTH ANNA UNIT NO. 2 The investigation of the possible effects of jet impingement and missile impact due to a break at the temperature element (TE-2433) _in the Reactor Coolant "C" loop hot leg has been analyzed. The potential targets in the-vicinity of this instrument, as established by requirements in Standard Review Plan 3.6.2, are the steam generator insulation blanket and the north wall of the "C" cubicle. A field investigation has indicated that there are no safety related equipment, pipes or cables located in the area which would be affected by jet impingement or missile' impact due to.the temperature element connection failure. Therefore, the jet impingement load and missile impact due to'the break at the temperature element connection will not debilitate -equipment required for the safe shutdown of the plant.

ATTACllMENT 1 NORTIl ANNA UNIT NO. 2 LOOSE TIIERMAL SLEEVE SAFETY EVALUATION i

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