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Pyrometallurgical processing research programme

Objective

The proposed research programme rallies five major European research organisations, often associated with universities or specialized laboratories as contractors, around the theme of pyrometallurgical processing processes. Two Non-EU laboratories with concrete experience in this field, NRI in Czech Republic and CRIEPI from Japan (on a self-financing basis), will be associated with the programme. The planned work including extensive experimental work and documentary concept evaluation studies, will focus on segregation processes by means of electrolysis and/or metal/salt exchange in chloride or fluoride media. This comprehensive R & D program should yield sufficient basic data to establish and assess pyrometallurgical processing flow sheets suitable for use with advanced fuel cycles designed to minimize the radiological impact from nuclear waste. This joint effort will consolidate and revive European expertise in this field.
In order to avoid work duplication the investigation field has been shared between the partner according to their possibilities and national programme interests. In the contract, five partners (BNFL, ITU, CRIEPI, CIEMAT and ENEA) are working on the basis of the process developed in Argone DOE laboratories i.e an electrorefining in LiCl-KCl, and the last two partners focus on fluoride medium, separation by electrolysis for NRI and separation by reductive salt/metal extraction for CEA. CRIEPI associated with JRC ITU carry out in Karlsruhe experiments on a small-scale installation for the demonstration of pyrometallurgical reprocessing. This year electrorefining experiments have been carried out using the individual metals (uranium and plutonium) as anode but recently also using a uranium, plutonium, zirconium alloy. Other experiments are focussed on the difficult separation of MA from Ln´s, by means of electrolysis. Before Am studies, inactive experiments in molten LiCl-KCl eutectic have been conducted. For lanthanum, neodynium and americium elements a combination of transient electrochemical techniques (cyclic voltammetry, chronopotentiometry and square wave voltammetry) have been applied in order to investigate valency and reduction mechanisms with the aim of optimising the conditions for an efficient separation of Am by electrolysis. These investigations have been followed by, electrodeposition tests of La, Nd and Am on solid and liquid Cd cathodes.

BNFL associated with AEA-T is working on the same process and focused on the controling parameters of the electrorefining, they have already performed U transport and deposit onto solid and liquid cathode. ENEA which have less experience in this field than the other laboratories started designing and building an experimental electrorefiner with the final objective to study thorium behaviour in the electrochimical process. At the end of the first year project, some adjustments of the project schedule due to a internal reorganisation of the ENEA pyrochemical team have been necessary. To day the main parts of the apparatus are on building and they will be fitted together and the apparatus checked from the outset of 2002. CIEMAT associated with UVA carried out experiments aimed at analyse and predict the kinetic behaviour of lanthanide elements, which are the most difficult fission products to separate from actinides due to their similar chemical properties in LiCl-KCl. Studies were carried out to determine La, Ce, Pr, Y and Nd thermodynamic properties and to obtain the electrochemical deposition mechanisms of La, Ce and Nd. In parallel CIEMAT also focused on determining the stability of the compounds formed and the reaction rates when direct chlorination from the oxide form is performed. Fundamental data acquisition in the eutectic LiCl-KCl at 4500C is one of the main aims of this study. In this way, chemical stability of rare earth (i.e. La, Ce, Y,) trichlorides, and their oxide compounds in the eutectic LiCl-KCl at 4500C has been determined. Studies on chemical stability of praseodymium and neodymium chlorides and their oxide compounds are in progress.

Preliminary experiments on UO2 chlorination were performed by several chlorinating gaseous mixtures (HCl, Cl2, Cl2+C tube and powder) in order to establish the experimental conditions of SIMFUEL matrix chlorination. NRI works also on separation by electrorefining but in fluoride salt medium which is one of the possible selected candidate for molten salt fuel reactors. The first year of the contract has been dedicated to the construction and tests of electrolyser prototypes and first electrolysis with uranium. Carrying out these experiments needed for NRI to examine some subsidiary steps like carrier melt selection (two melt composition were particularly studied LiF/NaF and LiF/NaF/KF), and material and equipment selection. Concerning the last work package, ENEA associated with CEA focus on the study of one possible candidate matrix for the contaminated used LiCl/KCl salt. As glass currently used in reprocessing is not adapted to high contain chloride wastes, sodalite( Na8[(Al6Si6O24)] Cl2) in which some Na atoms could be exchanged by other alkaline atoms has been proposed. The aims of this study is for ENEA, to synthesise sodalite, assess exchange capability of Na atoms with other fission products atoms and for CEA carried out some standard leaching tests in order to estimate this matrix performance. The paper studies are supposed to start only during the second part of the contract so only preliminary studies have already be carried out. Mainly, the methodology of the joint system study (CEA/ENEA/NRI) aimed to assess the industrial implementation of the pyrochemical processes have been settled.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

COMMISSARIAT A L'ENERGIE ATOMIQUE
Address
Centre De La Vallee Du Rhone
30207 Bagnols-sur-ceze
France

Participants (6)

BRITISH NUCLEAR FUELS PLC
United Kingdom
Address
Sellafield B170
CA20 1PG Seascale
CENTRAL RESEARCH INSTITUTE OF ELECTRIC POWER INDUSTRY
Japan
Address
Iwato Kita 11-1, Chome Komae-shi 2
201 Komae, Tokyo
CENTRO DE INVESTIGACIONES ENERGETICAS, MEDIAMBIENTALES Y TECNOLOGICAS
Spain
Address
Avenida Complutense 22
Madrid
COMMISSION OF THE EUROPEAN COMMUNITIES
Germany
Address
Hermann-von-helmholtz Platz 1
76125 Karlsruhe
ITALIAN AGENCY FOR NEW TECHNOLOGY, ENERGY AND THE ENVIRONMENT
Italy
Address
Via Martiri Di Monte Sole 4
40129 Bologna
NUCLEAR RESEARCH INSTITUTE REZ A.S.
Czechia
Address
Rez 130
250 68 Rez - Praha