A Study of the Production of Transuranium Elements and its Application to the Solution Chemistry in Tohoku University

Abstract

About 2.8 g of UO₂ were irradiated with neutrons(about 1.6 × 10²⁰ nvt) at the Japan Material Testing Reactor(JMTR). After 140 days cooling, the irradiated sample was processed chemically. The isotopic ratios of U and Pu were determined by a-ray spectrometry and mass spectrometry. A small amount of ²⁴²Am(<100 μg) was also irradiated in JMTR. Am and Cm were purified mainly by ion-exchange chromatography. We have tried to estimate the irradiation conditions in JMTR. The thermal neutron flux(Ф) and the epithermal ratio (the ratio of the epithermal to the pure thermal neutron density)(f) were chosen as adjustable variables for the calculation of the isotopic ratios of U, Pu, Am, and Cm. Then, the most reasonable values of Ф and f were obtained which explained the values of the isotopie ratios obtained experimentally. Short-lived Bk tracers, ^243–246Bk were produced by the ²⁴¹Am + α and ²⁴³Am + α reactions using the A.V.F. cyclotron at the Cyclotron and Radioisotope Center, Tohoku University. A compressed aluminium powder disk, in which Am was suspended, was used as the target. Bk tracers were isolated from Am and fission products by HDEHP or TTA extraction of Bk(IV). Stability constants(β₁ and β₂) of the chloro and bromo complexes of trivalent Sm, Eu, Gd, Tb, Ac, Am, Cm, Bk, and Cf were determined by a solvent extraction method using HDEHP with an ionic strength and acidity of 3.0 M and 0.15 M, respectively. Stability constants could be roughly estimated by assuming inner sphere complex formation.