ML20209H474

Forwards Response to 860731 Request for Addl Info Re 850318 & 26 Chloride Repts.Items Susceptible to Stress Corrosion Identified & Results of Metallographic Exam of Bolts Discussed

ML20209H474
Person / Time
Site:	Fort Saint Vrain
Issue date:	09/08/1986
From:	Warembourg D PUBLIC SERVICE CO. OF COLORADO
To:	Berkow H Office of Nuclear Reactor Regulation
References
P-86542, TAC-57248, NUDOCS 8609150262
Download: ML20209H474 (4)

Text

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O Public Service ~ e~e s.,*.

Company of Colorado 2420 W. 26th Avenue, Suite 100D, Denver, Colorado 80211 September 8, 1986 Fort St. Vrain Unit No. 1 P-86542 Director of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Attention: Mr. H.N. Berkow, Director Standardization and Special Projects Directorate Docket No. 50-267

SUBJECT:

Chloride Reports

REFERENCES:

1) PSC Letter, Warembourg to Johnson, dated March 18, 1985 (P-85092)

2) PSC Letter, Warembourg to Johnson, dated March 26, 1985 (P-85104)

3) NRC Letter, Heitner to Walker, dated May 7, 1986 (G-86245) i 4) PSC Letter, Warembourg to Heitner dated l June 20, 1986 (P-86419) l 5) NRC Letter, Heitner to l

Williams dated July 31, 1986 i (G-86415) l

Dear Mr. Berkow:

l We have reviewed the three supplemental questions (Reference 5) that i define additional information the staff is requesting to be able to complete their review of the subject chloride reports submitted as reference 1 and 2.

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8609150262 860908 Y i\

PDR ADOCK 05000267 P PDR

1 P-86542 Page 2.

Septembsr 8, 1986 Attachment I to this letter reiterates your question and the associated PSC response.

If you have any questions, please contact Mr. M. H. Holmes at (303)480-6960.

Very truly yours, b.lt d w d r D. W. Warembourg, M ger .

Nuclear Engineering Division DWW/JRR:pa Attachment 9

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V Attachment to P-86542 NRC QUESTION 1 Identify the "certain other elements of the cable assembly that may be susceptible to stress corrosion cracking," mentioned in the GA Technologies Inc., Report 907875, para. 4.6.2.1. Indicate the materials that these "certain other elements" were originally fabricated from, and if the materials were changed, identify the new materials.

,PSC RESPONSE A total of six (6) parts in the control rods and control rod drive mechanisms were identified to be susceptible to stress corrosion cracking and have been changed. The following is a listing of these parts, the materials that the parts were originally fabricated from, and the new material that they were changed to.

Part Dwg. No. Changed From Changed To Anchor Cable SLR D1201-252 Stainless Steel 304 Stainless Steel 416 (AISI) (AISI)

Rod End SLR D1201-263 Stainless Steel 304 Inconel 625 (AMS 5639) (SB 446)

Cable SLR D1201-251 Stainless Steel Inconel 625 AISI 347 ASTM B-446 Spring SLR-1201-1097 Music Wire Inconel X750 AMS 5698 Screw SLR D1201-250 Stainless Steel Alloy Steel Items 11 & 14 AISI 304 Retaining Ring SLR D12-1-250 CARBON STEEL STAINLESS STEEL ITEMS 12 & 20 SAE 1060 - 1090 P.H. 15-7 M0 NRC QUESTION 2 Was a failure analysis

• and metallographic examination conducted

! on the H-11 (AMS 6487) primary closure bolts and the A-286 stator hold down bolts? If so, please provide a copy of the failure analysis.

\, l Attachment to P-86542

• The Failure Analysis should include the following documents:

a. Certificates of Compliance for Materials

b. Inspection Records

c. Procurement Documents

d. Design Requirements and Specifications PSC RESPONSE A failure analysis as defined by the question was not performed since the failure of the H-11 primary closure bolts and the A-286 stator hold down bolts were determined to be primarily the result of stress corrosion cracking as opposed to material or manufacturing defects.

Metallographic examination on randomly selected bolts from all five Fort St. Vrain circulators was conducted. The bolts were sectioned and examined macroscopically and microscopically. It was concluded from these examinations that some cracking was definitely caused by stress corrosion. Randomly selected bolting leached in demineralized water confirmed the presence of chloride which would be a cause of the stress corrosion.

NRC QUESTION 3 Identify the suppliers of the H-11, A-286 and Inconel 718 bolts, and the methods used to form the threads on these bolts.

PSC RESPONSE The original H-11 primary closure bolts and the A-286 stator hold down bolts were purchased from Obscoa who in turn bought them from SPS Technologies. The threads in both cases were formed by rolling. The replacement Inconel 718 primary closure bolts were again supplied by SPS Technologies and the threads were formed by rolling. The replacement Inconel 718 stator hold down bolts were supplied by Lenox Corporation and the threads were formed by grinding.

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