ML20236T362
| ML20236T362 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 11/27/1987 |
| From: | Heitner K NRC |
| To: | NRC |
| References | |
| NUDOCS 8712010179 | |
| Download: ML20236T362 (2) | |
Text
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. QUESTIONS RELATED TO THE USE'0F A k6 AND
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INCONEL X-750 FASTENER MATERIALS IN j
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..F_0RT/ST. VRAIh! HELIUM CIRCULAT0_R REPAIR
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1.
The preload' stress a i
during assembly is an essential factor in 1
theavoidanceof1 tress' corr'bstoncracking(SCC);alsotheminimum preload. stress should exceed the value where fastener loosenino might'
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occur. What art the prtiAcad stressen that you intend to use on the A-286 'I and X-750 materials, compared to the specified yield and ultimate tensile strengths?
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T 2.
The accuracy of preload stress depends on the tightening metMd chosen; turn of nut and mechanical torque wrench methods have low accuracies, 1
while the precision torque wrench and stretch measurements have http:er
<l accuracies. What method will be 'uset' in the repair of C219'L helium circulator?
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3.
What heat-treatmentsf are to be. specified for eact o/ @e fastener I
materials; what is' thg specified hartfdQ4 after t r( heat-treatment?
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Manufacturincy, chemicals used for coolants during cutting opepted coc4 either initiate'or cause SCC if there is no thermally stable frAibitor(h or if the. coolants do not have compositional limits on sul h r, chlorine etc.
Is this considered to be an issue in the manufuture of the i..
fastener materials for the Fort St. Vrain circulator Yepair?-
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5.
The Mo S or_ Molykqte is known as a detrimental. bolting ifNicant because Mp s
2 it may decompose 1above 100*C and react.withyater (steam) to form hydrogen sulfide corrodant~to cause SCC. What' expe a ental data are available to j
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?
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What quality assurance procedures will be used to inspect the fasteners during manufacture in order to ensure a high quality 1dstener and avoid 7
manufacturing defects?
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The A-236 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 /> f
<% circulator operation.
In addition, these bolts are to be installed in captive location with respect to the rotating compopnts. Total bolt k
efeilure would/ result' only in loss of secondary intersppce pressurization.
Provide a description of the inservice.irppecQon/ p*/cgtam and/or procedures to be implemented to assure'contindmslbt;tgity of the fastener materials.
8.
Describe the process that will be used during refurbishing the 7
circulators to clean the bolt holes in which the new fasteners will be i placed.
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9.
The circulators may be driven by reheat steam, plant water, and/or fire water. Provide the specification that will be implemented for eadh of the drive materials.
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