SILICON ISOTOPE ENRICHMENT FOR LOW-ACTIVATION

Silicon isotope separation from hexafluorodisilane (Si2F6) has been ex amined using a CO2 pulsed laser. Si2F6 containing certain isotopes was preferentially decomposed to SiF4 depending on the wavenumber (k) of the laser. Si-29 and Si-30 were concentrated in the SiF4 produced at k = 945-955 cm(-1), and in the residual Si2F6 at k = 970-980 cm(-1). Th e SiF4 containing Si-30 of about 43.3% and Si-29 at a maximum of 12.3% was continuously produced with a yield of 4.4% at k = 951.203 cm(-1) and 9.6% at 956.205 cm(-1), respectively. The decomposition reaction o f Si2F6 by the infrared laser irradiation could be explained as Si2F6( gas) + nhv --> SiF4(gas) + SiF2(solid), calculated from a mass balance analysis of the experimental results. A Si-30 concentration higher th an 90% was estimated to be achievable by repeating the irradiation of the residual Si2F6 at around k = 975 cm(-1) and finally decomposing th e Si2F6 to SiF4 at k = 951.203 cm(-1). SiC enriched with Si-29 and Si- 30 was predicted to show an excellent low activation behavior in fusio n neutron environments. (C) 1998 Elsevier Science S.A. All rights rese rved.