ML20205C037

Part 21 Rept Re Stationary Sleeve on Atwood & Morrill Co,Inc MSIV Thrust Bearings Extending Past Rotating Face.Stationary Sleeve Machined to Provide .02 Inch Clearance Below Rotating Face

ML20205C037
Person / Time
Site:	Trojan File:Portland General Electric icon.png
Issue date:	07/25/1986
From:	Withers B PORTLAND GENERAL ELECTRIC CO.
To:	Martin J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
References
REF-PT21-86, REF-PT21-86-264-000 86-23-PO, PT21-86-264, PT21-86-264-000, NUDOCS 8608120233
Download: ML20205C037 (6)

Text

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% a t.t th sc,-z 2,- f'o C g:j M d ia Ebrt D. Wahers Vce Presx*w l G OMly 25,1986 Trojan Nuclear Plant Docket 50-244 License NPF-1 Mr. John B. Martin Regional Administrator, P.egion V U.S. Nuclear Regulatory Commission 1450 Maria Lane, Suite 210 Walnut Creek CA 94596-5368

Dear Sir:

TROJAN NUCLEAR PLANT 10 CFR 21 Defect Report Main Steam Isolation Valve - Thrust Bearing The attached 10 CFR 21 Defect Report identifies a defect which we have evaluated to be reportable in accordance with 10 CFR 21 requirements. The defect results from the failure to inspect or identify a deviation in the quality of the thrust bearings that were used for modification of the main steam isolation valves (MSIVs) at Trojan. The supplier of the MSIV modifi-cation parts has been contacted and has been made aware of the results of our 10 CFR 21 evaluation.

Please direct any questions you may have regarding the technical issues to the Manager, Nuclear Plant Engineering, R. L. Steele.

Sincerely,

_e #

Bart D. Withers Vice President Nuclear Attachment c: Director, Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington DC 20555 Mr. Lynn Frank, Director State of Oregon Department of Energy 8608120233 860725 PDR ADOCK 05000344 S PDR 121 S W Satrnon Street. Port:and, Oregon 97204

e 10 CFR 21 DEFECT REPORT Portland General Electric Company Report Number: 86-02 121 SW Salmon Street Report Date: July 25, 1986 Portland, Oregon 97204 TROJAN NUCLEAR PLANT Responsible Officer: Mr. B. D. Withers, Vice President Nuclear Date Responsible Officer Received Information: July 25, 1986 Basic Component or Activity: Main Steam Isolation Valve Thrust Bearing, Part #37M PGE Drawing 6478-NQ-00777-13-1 PGE Purchase Order NQ-00777 Firm Supplyinz Basic Component: Atwood & Morrill Company, Inc.

285 Canal Street Salem, Massachusetts 01970 Description of Defect and Substantial Safety Hazard That Could be Caused:

During the 1986 refueling outage, a modification was made to the Main Steam Isolation Valves (MSIVs) in accordance with an approved Plant design change (RDC 83-029-02). The MSIVs were changed by modifying the packing gland on the non-operator end of the valve shaft with a support sleeve, thrust bearing, and closure cap. The modification eliminates the need for packing and, consequently, the packing-inducad fricti:- !..ces on the non-operator end of the valve shaft. The reduced friction load on the shaf t improves the conditions for proper closure upon receipt of a main steam isolation signal. The MSIV is a reverse seating check valve that is held open, against a spring closing force, by an air cylinder.

Upon receipt of a closure signal, the air cylinder is vented and the valve is closed by the spring and forward flow of the steam itself.

During the installation of modification components, the stationary sleeve on three of the four thrust bearings was found to extend past the rotating face. This condition was determined to be unacceptable for this applica-tion. The extension of the sleeve beyond the rotating surface of the thrust bearing was sufficient to permit contact between the stationary sleeve and the split-bearing surface on the MSIV shaft. This condition, if not corrected, could have led to a galled surface and the creation of a high rotating frictional torque. Attachments to this report have been provided to illustrate the above configuration.

The potential binding condition between the thrust bearing stationary sleeve and the MSIV shaft split-bearing surface could have prevented proper closure of the valve. The failure of the MSIVs to close during a main steam line break accident would cause the reactor to exceed the

Page 2 analyzed conditions described in Section 15.1 of the Trojan Updated Final Safety Analysis Report. This was determined to be a substantial safety hazard.

Number and Location of Such Components in Use at the Trojan Nuclear Plant:

The four MSIVs are located in the Main Steam Support Structure between the Containment Building and the Turbine Building. No other components at Trojan use the thrust bearing configuration which is unique to the MSIV design modification.

Corrective Action:

The stationary sleeve on each of the thrust bearings was machined to provide a 0.020 inch clearance below the rotating face of the thrust bearing. The modified MSIVs were satisfactorily tested prior to the resumption of power operation.

Other Pertinent Information:

The circumstances and corrective action regarding the stationary sleeve height have been discussed with representatives of Atwood & Morrill. The actual deviation related to thrust bearing was initially identified by the Atwood & Morrill Field Service Supervisor at the Trojan Nuclear Plant. However, there was no specific quality control inspection in either the vendor's or PGE's modification procedures to measure and verify the dimensional tolerances of the thrust bearing. Subsequently, PGE representatives recommended that the vendor's receipt inspection process for these bearings should include a functional check to ensure that the stationary sleeve height does not interfere with the free rotation of the bearing face. The sleeve height dimension may not be critical in most applications of the thrust bearing. However, in the unique configuration for the MSIV, the dimension of this commercial grade item is critical. The recommended inspection by the vendor prior to actual assembly and installation should preclude this condition from recurring at other facilities where this modification may be installed.

This report represents both the initial and final written notification to the NRC of the 10 CFR 21 defect.

MHM/kal 1031W.786

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