Baseline and Lifetime Assessments for DC745U Elastomeric Components

Maxwell, R S ; Chinn, S C ; Herberg, J ; Harvey, C ; Alviso, C ; Vance, A ; Cohenour, R ; Wilson, M ; Solyom, D

Lawrence Livermore National Laboratory

关键词: Aging;    36 Materials Science;    75 Condensed Matter Physics, Superconductivity And Superfluidity;    37 Inorganic, Organic, Physical And Analytical Chemistry;    Chemical Composition;   

DOI  :  10.2172/15014570
RP-ID  :  UCRL-TR-208929
RP-ID  :  W-7405-ENG-48
RP-ID  :  15014570

美国|英语

来源: UNT Digital Library

【 摘 要 】

The silicone elastomer Dow Corning DC 745U is used in two major components in the W80. We have investigated a number of issues concerning this material. Our studies have accomplished a baseline study of the chemical composition of DC745 and LLNL now has a good understanding of the chemical composition of this material. DC745 crystallizes within the system STS. Two potential means identified to mitigate the risk associated with this phenomenon are to (1) change material formulation and (2) predose the parts to {approx} 25 MRad {gamma}-radiation. A candidate material identified by Gordon Spellman has been studied for composition and the lack of crystallization within the STS has been verified. A sensitivity study of the effects of relevant aging mechanisms also has been performed. The extent of aging due to radiation exposure or elevated temperatures is minimal over the expected course of the LEP. In addition, since the DC745 parts are expected to be replaced at rebuild, the aging clock is essentially being reset. No significant aging issues seem likely to develop for these parts. DC745 parts are also subject to permanent deformation in service. Our studies have shown that the deformation is likely due to incomplete mixing of the raw gum stock and the curing agent at production. This results in areas of low crosslink density that are subject to a higher degree of compression set in service. We have identified two production diagnostic tools based on Nuclear Magnetic Resonance spectroscopy to prescreen the parts at production at KCP. These studies are concluded with specific recommendation for changes to core surveillance for this part based on the chemical knowledge we have gained from this study.