ML20237A815

Forwards List of Questions Re New Bolting Matls for Helium Circulator C2101,per 871118 Telcon.One of Key Issues Was Util Decision to Use A286 Spec Bolts to Fasten circulator- Steam Scroll to Bearing Housing

ML20237A815
Person / Time
Site:	Fort Saint Vrain
Issue date:	12/08/1987
From:	Heitner K Office of Nuclear Reactor Regulation
To:	Robert Williams PUBLIC SERVICE CO. OF COLORADO
References
TAC-65992, NUDOCS 8712150282
Download: ML20237A815 (3)

Text

i December 8,1987 Docket No. 50-267 l Mr. R. O. Williams, Jr. 1 Vice President, Nuclear Operations Public Service Company of Colorado P. 0. Box 840 Denver, Colorado 80201-0840 i

SUBJECT:

FASTNER MATERIAL SELECTION FOR REPAIR OF HELIUM CIRCULATOR C2101 (TAC N0. 65992)

)

We have held preliminary discussions by telephone with your staff concerning your choice of new bolting materials for helium circulator C2101. These discussions were held by telephone November 18, 1987. One of the key issues was your decision to use A286 specification bolts to fasten the circulator-steam scroll to the bearing housing.

l l We have prepared a list of questions related to these issues, which are l enclosed. We request you provide a response to these questions within 45 days l of the date of this letter.

The information requested in this letter affects fewer than 10 respondents; therefore OMB clearance is not required under P.L.96-511.

Sincerely,

/s/

l Kenneth L. Heitner, Project Manager l Project Directorate - IV Division of Reactor Projects - III, IV, V and Special Projects

Enclosure:

As stated cc w/ enclosure:

See next page DISTRIBUTION Docket File: NRC PDR Local PDR PD4 Reading DR4A/ Collins J. Calvo P. Noonan K. Heitner 0GC-Bethesda E. Jordan J. Partlow ACRS (10)

PD4 Diant File PD4/L. .. PD4/PM N PD4/D /770 PNoon KHeitner: sr JCalvo l 11/ / /87 12/ 7 /87 11/(/87 l

87121502B2 871200 PDR P ADOCK 05000267 PDR

9 I Mr. R. O. Williams, Jr.

Public Service Company of Colorado Fort St. Vrain cc:

Mr. D. W. Warembourg, Manager Albert J. Hazle, Director Nuclear Engineering Division Radiation Control Division Public Service Company Department of Health of Colorado 4210 East lith Avenue P. O. Box 840 Denver, Colorado 80220 Denver, Colorado 80201-0840 Mr. David Alberstein, 14/159A Mr. R. O. Williams, Jr., Acting Manager GA Technologies, Inc. Nuclear Production Division Post Office Box 85608 Public Service Company of Colorado San Diego, California 92138 16805 Weld County Road 19-1/2 Platteville, Colorado 80651 Mr. H. L. Brey, Manager Nuclear Licensing and Fuel Division Mr. P. F. Tomlinson, Manager Public Service Company of Colorado Quality Assurance Division-P. O. Box 840 Public Service Company of Colorado Denver, Colorado 80201-0840 16805 Weld County Road 19-1/2 Platteville, Colorado 80651 Senior Resident Inspector U.S. Nuclear Regulatory Commission Mr. R. F. Walker P. O. Box 640 Public Service Company of Colorado Platteville, Colorado 80651 Post Office Box 840 Denver, Colorado 80201-0840 Kelley, Stansfield & 0'Donnell Public Service Company Building Commitment Control Program Room 900 Coordinator 550 15th Street Public Service Company of Colorado Denver, Colorado 80202 2420 W. 26th Ave. Suite 100-D Denver, Colorado 80211 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 1000 Arlington, Texas 76011 Chairman, Board of County Commissioners of Weld County, Colorado Greeley, Colorado 80631 Regional Representative Radiation Programs Environmental Protection Agency 1 Denver Place 999 18th Street, Suite 1300 Denver, Colorado 80202-2413

Enclosure 5,

QUESTIONS RELATED TO THE USE OF A-286 AND INCONEL X-750 FASTENER MATERIALS IN F_0RT ST. VRAIN HElllM CIRCULATOR REPAIR

1. The preload stress applied during assembly is an essential factor in l the avoidance of stress corrosion cracking (SCC); also the minimum preload stress should exceed the value where fastener loosening might occur. What are the preload stresses that you intend to use on the A-286 and X-750 materials, compared to the specified yield and ultimate tensile strengths?

2. The accuracy of preload stress depends on the tightening method chosen; j turn of nut and mechanical torque wrench methods have low accuracies, -

I while the precision torque wrench and stretch measurements have higher accuracies. What method will be used in the repair of C2101 helium circulator?

3. What heat-treatments are to be specified for each of the fastener materials; what is the specified hardness after the heat-treatment?

4 Manufacturing cherricals used for coolants during cutting operation could either initiate or cause SCC if there is no thermally stable inhibitor or if the coolants do not have compositional limits on sulfur, chlorine, 4 I

etc. Is this considered to be an issue in the manufacture of the fastener materials for the Fort St. Vrain circulator repair?

5. The Mo s or Molykote is known as a detrimental bolting lubricant because it may 2decompose above 100*C and react with water (steam) to fore hydrogen sulfide corrodant to cause SCC. What experimental data are available to indicate that silicone-molykote (the lubricant specified for use in the Fort St. Vrain circulator repair) will be stable and compatible with the environment under circulator operation? )

6. What quality assurance procedures will be used to inspect the fasteners during manufacture in order to ensure a high quality fastener and avoid manufacturing defects?

7. The A-286 bolts are projected to have a service life equivalent to the initially installed bolts, which failed by SCC after 60,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> circulator operation. In addition, these bolts are to be installed in captive location with respect to the rotating components. Total bolt l failure would result only in loss of secondary interspace pressurization. i Provide a description of the inservice inspection program and/or procedures to be implemented to assure continuous integrity of the fastener materials.

8. Describe the process that will be used during refurbishing the circulators to clean the bolt holes in which the new fasteners will be placed.

9. The circulators may be driven by reheat steam, plant condensate water, and/or fire water. Provide the specification that will be implemented for each of the drive materials.