ポリブタジエンの光化学的トリチウム化

概要

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An organic polymer is used as a conventional standard material for tritium beta-ray sources. It is, present study, cis-1, polybutadiene (CPB) was examined to be tritiated photochemically under UV irradiation. This method is expected to produce no tritiated byproduct, in contrast with conventional chemical syntheses from monomers having been applied to prepare standard tritium beta-ray sources and to immobilize tritium in the form of organic polymers. It was found that the UV irradiation on CPB in the presence of HT could cause CPB tritiated with producing no detectable tritiated byproduct. In addition, it was also observed that CPB was isomerized to its trans-isomer. There was a linear relation between the tritiation and the isomerization of CPB. A [－CH2－CH=CH－CH－] radical mechanism was proposed for the tritiation and the isomerization. The extent of the tritiation was rather low in the present study as 432MBq/g for 10 hour UV irradiation from a low pressure mercury lamp (5W) at 30 Torr of HT. The specific activity, however, was comparable to conventional beta-ray sources and hence this method is promising to prepare standard tritium beta-ray sources without producing tritiated byproducts. The low tritiation yield appeared to be due to the fact that HT molecules do not react readily with the radicals. This method, however, could be improved for immobilization of waste tritium by making tritium radicals in suitable ways.
富山大学の論文