ML19309B641

Part 21 Rept Re Potential for Control Rod Guide Tube Support Pins Breaking Due to Stress Corrosion Cracking.Results of Support Pin Insp Program & Ongoing Matls Test Program Will Determine Corrective Actions

ML19309B641
Person / Time
Site:	North Anna
Issue date:	03/18/1980
From:	Stallings C VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
References
REF-PT21-80-204-000 NUDOCS 8004070019
Download: ML19309B641 (3)

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VI:;orwxA Er.ncrRIC AND Powxit COMPANY Rrcrotown,Vrmor: era 23261 March 18, 1980

._.26 f-COO Mr.~ James P. O'Reilly, Director Serial No. 237 Office of Inspection and Enforcement P0/FHT:baw

, U. S. Nuclear Regulatory Commission Docket No. 50-339 Region II - Permit No. CPPR-78 101 Marietta Street, Suite 3100 Atlanta, Georgia 30303

Dear Mr. O'Reilly:

Under the provisions of .10CFR21, NRC Region II was notified on March 14, 1980, of a potential for control rod guide tube support pins breaking due to stress corrosion cracking. This problem was also reported to the Commission in Westing-house letter NS-TMA-2214 dated March 14, 1980.

In accordance with the reporting requirements of 10CFR21, the following information is submitted:

A.~ Name and address of reporting individual:

Mr. E. A. Baum, Executive Manager Licensing and Quality Assurance Virginia Electric and Power Company P. O. Box 26666 ,

Richmond, Virginia 23261 B. Facility, activity, and/or component affected:

North Anna Power Station Unit 2-Control Rod Guide Tube Support Pins.

C. Name of firm constructing the facility or supplying the component, activity or service:

-Westinghouse Water Reactor Division Box 355 Pittsburgh, Pennsylvania 15230 D. Description of defect, deficiency, or failure to comply-Recent support pin inspections at a foreign plant revealed stress c_orrosion cracking in Westinghouse supplied support pins which had been solution heat treated at 1625*F. The support pins prevent lateral movement of the guide tubes and if broken, could result in misalignment of the guide tubes with possible restriction of control rod. movement.

The Westinghouse safety evaluation concluded that control rod operation is not jeopardized by a broken pin for non-Upper Head Injection' plants (i.e. , North Anna Power Station)

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due to the small gap between the non-UHI guide tube and the core plate.

E. Date of determination of reportability: .

March 13,1980 F.. Similar components, activities, or services:

North Anna Unit 1, Surry Units 1 and 2 ,

G. Corrective action which has been, is being or will be taken, the individual responsible and the length of time to complete the action:

Laboratory testing conducted by Westinghouse indicates that susceptability. to stress corrosion cracking decreases with increasing solution heat treatment temperatures. In the n'e ar future, Westinghouse will conduct ultrasonic inspections lat two operating domestic plants of guide tube support pins having solution heat treatment temperatures less than 1800*F.

The results of the support pin inspection program as well as the on-going materials test program will determine Vhat further corrective actions, if cny, are required. We will replace the pins with pins having higher heat treatment temperatures,

._ in North Anna Unit No. 2, as a conservative measure. The pin replacement will be completed before' the upper internals are installed in the reactor vessel.

H. Other information:

None. -

Any information not available at this time will be submitted in a Licensee Event Report or in a 10CFR50.55(e) 30 day report.

Should you require further information regarding this matter, please contact this office.

Very truly yours, d 2)?.J?a.y C. M. Stallings Vice President-Power Supply and Production Operations cc:- Director, Office of_ Inspection  ;

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