ML20062E585

Submits Response to Item 5 of IE Bulletin 82-02, Degradation of Threaded Fasteners in RCPB of PWR Plants. Boric Acid Wastage Found on Bonnet Studs of RCPB Valves

ML20062E585
Person / Time
Site:	Kewaunee
Issue date:	08/02/1982
From:	Giesler C WISCONSIN PUBLIC SERVICE CORP.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
CON-NRC-82-131, REF-SSINS-6820 IEB-82-02, IEB-82-2, NUDOCS 8208100159
Download: ML20062E585 (5)

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, NRC-82-131 WISCONSIN P U B LI C S ERVICE CO RPORATIO N P.O. Box 1200, Green Bay, Wisconsin 54305 August 2, 1982 Mr. J. G. Keppler, Regional Director Office of Inspection & Enforcement Region III U.S. Nuclear Regulatory Ccmmission 799 Roosevelt Road Glen Ellyn, IL 60137

Dear Mr. Keppler:

Docket 50-305 Operating License DPR-43 Kewaunee Nuclear Power Plant IE Bulletin No. 82-02: Degradation of Threaded Fasteners in the Reactor Coolant Pressure Boundary of PWR Plants This report is submitted in response to Item 5 of IE Bulletin 82-02. In accordance with the requirements of IE Bulletin No. 82-02, Degradation of Threaded Fasteners in the Reactor Coolant Pressure Boundary of PWR Plants, a record search was performed to provide the information requested by action Iter 3. The pressure boundary connections included in the scope of this investigation are listed in Tables 1 and 2. It was not necessary to include the pressurizer heater connections, since the heater elements are provided with a welded construction. The control rod drive (CRD) connections were not considered in this report since Kewaunee does not have flanged CRD joints. However, the part-length CRD capped connections (part-length rods have been removed) and the instrument port sealed connections have been included in the investigation.

The bolted closures in the reactor coolant pressure boundary which have exhibited Icakage are the pressurizer manway, steam generator 1B primary manway, and the valve bonnet on SI-13B (safety injection to cold leg check valve). The pressurizer manway leakage was found to occur in July 1974 and again in September 1975. In both cases the cause was attributed to diaphragm (gasket) failure. The corrective action in both cases was the installation of a new gasket. In the 1974 occurrence, four studs were also replaced after they had been damaged by steam leakage. No evidence of stud corrosion was observed in either instance. Steam generator IB primary manway leakage was observed in May 1980. This leakage resulted in boric acid corrosion / wastage of the hot leg manway. A repair groove was ground into the primary manway base material to remove the corrosion products and to relieve stress concentrations. A new manway gasket was installed upon assembly. The manway studs did not exhibit any evidence of corrosion. Check valve SI-13B exhibited body-to -bonnet leakage in April 1982. During leak repair, two of the 8208100159 820802 PDR ADOCK 05000305 4UG 6g a PDR j

Mr. J. G. Keppler August 2, 1982 Fage 2 twelve bonnet studs were found to be significantly damaged by boric acid induced corrosion. The leak, which was caused by gasket failure, was terminated by installing a new gasket, replacing the corroded studs as well as two opposing studs, and seal welding the valve body to bonnet.

The discovery of the corroded studs on SI-13B prompted an inspection for bonnet stud corrosion on 23 other valves that were subjected to boric acid environments.

This included a visual inspection as well as a verification that all studs satisfy the manufacturer's torque specifications. As a result of the bolt inspection, corroded bonnet studs were found on two additional valves (these valves are not addressed under the scope of this bulletin). The studs were subsequently replaced.

Based on a review by members of the plant staff, four lubricants have been approved for use on fasteners associated with the closures and connections listed in Tables 1 and 2. These lubricants are Fel-Pro C5A, Fel-Pro N-1000, Fel 'ro N-5000 and Neolube.

A brief description of the composition of the lubricants is given below:

Lubricant Composition Fel-Pro CSA Copper graphite paste, no certification of impurities.

Fel-Pro N-1000 Similar to CSA, has certification of impurities.

Fel-Pro N-5000 Nickel graphite paste, has certification if impurities.

Neolube Colloidal suspension of graphite in alcohol.

Kewaunee does not use injection sealant compounds on primary-side components; their use is solely restricted to secondary-side valves and components. In the past, Furmanite sealant has been used for temporary leak repair of steam generator secondary manways and various secondary-side valves. These components are disassembled and properly re-scaled when the plant comes off-line for maintenance (i.e.; during refueling).

There has been no evidence of stress-corrosion cracking at the Kewaunee Plant.

However, as stated earlier, boric acid corrosion wastage has been found on bonnet studs of reactor coolant pressure boundary valves. This problem is currently being investigated through the Design Change Program.

We are continuing our work with respect to the other action items of Bulletin 82-02.

Preparation of this report required approximately 60 man-hours. To the best of my knowledge the information presented here-in is

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Very truly yourc,.

A G, Carl W. Giesler Subscribed and Sworn to Before Me This 2nd Day Vice President - Nuclear Power of August 1982 js , - ? e//

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• Notary Public, Sta[e of Wisconsin cc - Mr. Robert Nelson, NRC Sr Resident Inspector Director, Office of Inspection & Enforcement My Commission Expires:

March 24, 1985 i

TABLE 1. Reactor Coolant Pressure Boundary Valves Included 's .

In The Scope of IE Bulletin No. 82-02 Valve Manufacturer Size / Type Bonnet Stud Material Leakage RHR-1A Velan 8" Cate (16) 1 3/8"-8UN-2A x 8 1/2"LG.

ASTM A193 Gr. B7 None RHR-1B Velan 8" Gate (16) 1 3/8"-8UN-2A x 8 1/2"LC.

ASTM A193 Cr. B7 - None RHR-2A Velan 8" Cate (16) 1 3/8"-8UN-2A x 8 1/2"LG.

ASTM A193 Gr. B7 None RHR-2B Velan 8" Cate (16) 1 3/8"-8UN-2A x 8 1/2"LG.

ASTM A193 Gr. B7 None RHR-11 Darling 10"x8"x10" Cate (16) 1 7/8"-6UN-2A ASTM A193 Gr. B7 None SI-13A Velan 6" Check (12) 1 1/4"-8UN x 6 1/2"LG.

ASTM A193 Gr. B7 hone SI-13B Velan 6" Check (12) 1 1/4"-8UN x 6 1/2"LC.

ASTM A193 Gr. B7 Yes SI-21A Darling 12" Check (16) .1 3/4"-8UN-2A ASTM A193 Gr. B7 None

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S I-2'1B Darling 12" Check (16) 1 3/4"-8UN-2A ASTM A193 Gr. B7 None SI-22A Darling 12" Check (16) 1 3/4"-8HN-2A ASTM A193 Gr. B7 None SI-22B Darling 12" Check (16) 1 3/4"-8UN-2A ASTM A193 Gr. B7 None SI-303A Velen 6" Check (12) 1 1/4"-8UN x 6 1/2"LG.

ASTN A193 Gr. B7 None SI-303B Velan 6" Check (12) 1 1/4"-8UN x 6 1/2"LG.

ASTM A193 Gr. B7 None J

TABLE 1. - Page 2 s s .

Valve Manufacturcr Size /7ype Bonnet Stud Material Leakage ,

SI-304A Velan 6" Check (12) 1 1/4"-8UN x 6 1/2"LC. '

ASTM A193 Gr. B7 None SI-304B Velan 6" Check (12) I 1/4"-8UN x 6 1/2"LG.

ASTM A193 Gr. B7 Neue PR-3A Crosby 6" Relief N/A ASTM A193 Gr. B7 ' None PR-3B Crosby 6" Relief N/A ASTM A193 Gr. 37 None 9

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TABLE 2< Remaining Reactor Coolant Pressure Boundary '. ' .

Connections Addressed in.IE. Bulletin..No..82-02.

RCPB Connection Lubricant Leakage S/G 1A primary manways ' Fel-Pro N5000 None S/G IB primary manways Fel-Pro N5000 Yes

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Pressurizer manway Fel-Pro C5A .

Yes RCP 1A main flange .Fel-Pro N}000 None RCP IB main flange Fel-Pro N1000 None Reactor vessel head Neolube None Instrument port conoscals Neolube None Part-length CRD conoscals Neolube None h-

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