Masaki Ozawa

Trivalent minor actinides/lanthanides separation, using organophosphinic acids

Abstract The present paper compares the abilities of purified Cyanex 301, Cyanex 302 and Cyanex 272 acids to extract and separate 241 Am from 152 Eu. Very high separation factors were observed when using Cyanex 301 acid after its purification through the precipitation of its ammonium salt in benzene. Some studies on synergistic mixtures, containing both purified Cyanex 301 acid and tri- n -butylphosphate (TBP), are also described. The stoichiometry of the adducts extracted in the organic phase was estimated through slopes analyses: unexpectedly, different results were observed for 241 Am(III) and for 152 Eu(III).

Separation of actinides and fission products in high-level liquid wastes by the improved TRUEX process

Abstract With the aim of establishing an advanced fuel cycle enabling us to utilize all actinides in the spent fuels, separation of minor actinides in high-level liquid wastes (HLLW) has been studied using a CMPO/TBP mixture extractant. A novel flowsheet is being developed, by counter-current experiments using real HLLW from PUREX experiments, characterized by employing acidification for enhancing extraction of actinides with increasing RuNO 3+ decontamination, and a few mild salt-free reagents for fractional stripping and solvent clean-up steps. The flowsheet can give α- and salt-free HLLW providing a D F Am ≥10 3 . In the counter-current experiments for SETFICS a flowsheet has been developed to separate An(III) and Ln using DTPA, Am and Cm was recovered without light lanthanide, and the applicability of hydroxylamine nitrate as a salting-out reagent was confirmed.

CMPO-TRUEX Process and its Application in the Separation of Actinides from High-Level Liquid Wastes

Abstract Basic studies have been carried out on the high active PUREX raffinate to determine the distribution characteristics of actinides in different extraction systems. The data have been utilised in conducting a series of counter-current extraction experiments, which have led to the establishment of a viable flow-sheet based on a unique PNC salt-free process, that has great potential in minimizing secondary radioactive waste generation. The process was successfully applied to the present purex system, and a decontamination factor DFαof > 103 has been achieved resulting in the formation of a much less toxic HLLW. NMR studies carried out on the Ln Complex extracts have yielded valuable data on their thernio chemical and activation parameters. Consideration on the mechanism of degradation/regeneration/decomposition of TRUEX Solvents are also included.

An approach for evaluating equilibrium and rate constants for the reaction of Np(V) with nitric acid in the Purex process using process data

A new approach for evaluating the apparent equilibrium and rate constants for the reaction of Np(v) with nitric acid by using the process data of multistage countercurrent solvent extraction experiments is proposed. The numerical simulation of neptunium extraction in the co-decontamination process of the Purex process is carried out on the assumption of the rate equation. The apparent equilibrium and rate constants are determined by the nonlinear least-squares method with experimental data for multistage countercurrent solvent extraction with a numerical simulation code. The determined apparent equilibrium and rate constants are 1.25 to 1.97 {times} 10{sup {minus}2} min {sup {minus}1} and 6.04 to 11.5 {times} 10{sup {minus}4} ({ell}/mol){sup 3/2}, respectively. These values are consistent with those obtained in other kinetic studies.

Corrosion behavior of Ti and Zr in dissolution process for spent nuclear fuel reprocessing

Etude, par mesure de perte de poids, des resistances a la corrosion de Ti et Zr dans les conditions de dissolution de combustible nucleaire irradie et de leur comportement a la corrosion par mesure potentiostatique