Impact limits of partitioning and transmutation scenarios on the radiotoxicity of actinides in radioactive waste

Abstract

The used fuel discharged from nuclear power plants constitutes the main contribution to nuclear waste in countries which do not undertake reprocessing. As such, its disposal requires isolation from the biosphere in stable deep geological formations for long periods of time (some hundred thousand years) until its radioactivity decreases through the process of radioactive decay. Ways for significantly reducing the volumes and radiotoxicities of the waste and to shorten the very long times for which the waste must be stored safely are being investigated. This is the motivation behind the partitioning and transmutation (P&T) activities worldwide. This paper addresses the potential impact of P&T on the long-term disposal of nuclear waste. In particular, it evaluates how realistic P&T scenarios can lead to a reduction in the time required for the waste to be stored safely. The calculations have been done independently by three research groups: ITU and FZK in Germany, and by the CEA in France.

Highly Efficient Separation of Actinides from Lanthanides by a Phenanthroline-Derived Bis-triazine Ligand

“…One strategy for reducing the radiotoxicity of the waste involves partitioning and transmutation of the long-lived minor actinides into shorter-lived or stable elements by neutron fission. 3 However, it is first necessary to separate the actinides from the bulk of the lanthanides and other fission and corrosion products that are also present in the acidic PUREX waste streams because the lanthanides have high neutron capture cross-sections. 4 The separation of the radioactive minor actinides from the lanthanides is therefore one of the principal current challenges in nuclear waste reprocessing.…”

Influence of diluent alkyl substitution on the extraction of Am(III) and Eu(III) by a 6,6´-bis(1,2,4-triazin-3-yl)-2,2´-bipyridine ligand dissolved in alkylated cyclohexanone diluents

“…Thus no significant extraction of either metal ion was observed by the neat diluents themselves, in contrast to cyclohexanone [28]. The extraction of Am(III) and Eu(III) from 4 M HNO 3 by solutions of CyMe 4 -BTBP 1 in the various diluents is shown in Fig. 5.…”

“…Currently, the PUREX process is used worldwide [1,2] to remove plutonium and uranium but the remaining waste also contains the minor actinides americium, curium and neptunium which are highly radiotoxic. Once removed, these elements can be fissioned or transmuted into shorterlived radionuclides by neutron bombardment in fast reactors or dedicated transmuters, enabling safer geological disposal of the remaining waste [3,4]. A highly selective solvent extraction process (SANEX process) has been 2 (10) proposed for the future reprocessing of waste solutions produced in the PUREX process, involving the selective separation of the minor actinides from the lanthanides and fission products which make up the bulk of the waste [5,6].…”

Adsorption Characteristics of Trivalent Rare Earths and Chemical Stability of a Silica-Based Macroporous TODGA Adsorbent in HNO3Solution

“…The remaining radiotoxic nuclides in the waste may decay to the level of natural uranium within a few centuries unlike in the untreated case (more than 100,000 y). 1,2) To realize the partitioning and transmutation in the development of the new nuclear energy system, separating the long-lived trivalent minor actinides (MAs) such as Am(III) and Cm(III) from spent fuels is one of the challenging tasks in the partitioning process. 3,4) For this purpose, a number of partitioning processes by means of liquid-liquid extraction technology using various conventional and newly developed extractants such as CMPO (octyl(phenyl)-N,Ndiisobutylcarbamoylmethylphosphine oxide), TRPO (trialkylphosphine oxide), and Cyanex301 (bis(2,4,4-trimethylpentyl) dithiophosphinic acid) have been developed.…”