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Curium in Metallic Alloys

#3991


Study of Curium Thermodynamics in Metallic Alloys

Tech Area / Field

  • ENV-RWT/Radioactive Waste Treatment/Environment

Status
3 Approved without Funding

Registration date
15.09.2009

Leading Institute
NIIAR (Atomic Reactors), Russia, Ulianovsk reg., Dimitrovgrad

Collaborators

  • CEA, France, Paris

Project summary

Curium isotopes presented in spent nuclear fuel have high specific energy release and a long half-life. Therefore, they should be separated from high-level wastes (HLW) and transmuted. The objective of the proposed investigation is to obtain data on thermodynamics of formation of curium compounds in metallic alloys. These fundamental data can be subsequently used for feasibility assessment of the curium separation processes in the “chloride melt/metallic alloy” system.

Molten chlorides and liquid/solid metal alloys have more high radiation resistance than aqueous and organic media, that is important because of the high specific activity of curium. Data on curium behaviour in molten chlorides were obtained by RIAR during execution of ISTC project#3231 “Curium in Chlorides”. Data on curium behaviour in metallic alloys for partitioning and transmutation purposes are scanty and refer to its conventional standard potential in the zinc alloy and to the distribution coefficient between the salt phase and cadmium. Data are lacking on curium thermodynamics in the wide range of metal alloys, which are currently urgent for partitioning of minor actinides. Acquisition of these data will provide the fundamental basis for development of curium partitioning processes in the “molten salt/metallic alloy” system.

RIAR has carried out investigations into the properties of curium compounds in various metal alloys both for purposes of sources production and partitioning/transmutation over a long period of time. The applied physical (SEM/EPMA) and electrochemical (EMF, CV, chronopotentiometry) methods make it possible to obtain data on alloy formation thermodynamics, the conventional standard electrode potentials and curium activity coefficients in alloys, curium solubility and composition of formed intermetallic compounds.

The proposed project would contribute to integration of Russian weapon scientists into the international scientific community.

It is anticipated that the proposed project will provide the fundamental data on curium behaviour, which can be used for feasibility assessment of the curium separation processes in molten chlorides on metallic alloys.

It is supposed that RIAR will carry out the following investigations:

  • Task 1: Thermodynamics of curium alloys with liquid metals.
RIAR will carry out experiments in the “melt (3LiCl-2KCl or NaCl-KCl) / liquid metal (Al, Ga, Cd, Bi)” system at several temperatures (in the range of 450 – 850оС) using EMF, cyclic voltammetry and chronopotentiometry. It is supposed to obtain data on the temperature dependence of the conventional standard potential and thermodynamics of formation of curium alloys with fusible metals (∆Gexcess., ∆Hexcess., ∆Sexcess.), curium activity coefficients in alloys, its solubility and composition of the formed intermetallic compounds. Dependencies of these parameters on the reverse effective radius of the metal cation will be used for calculation of similar thermodynamical data for other liquid metals.
  • Task 2: Thermodynamics of curium recovery on solid aluminium
RIAR will carry out experiments in the “the molten 3LiCl-2KCl / solid Al” system using EMF, cyclic voltammetry and chronopotentiometry and potentiostatic electrolysis at 450оС. The experiments will provide data on thermodynamics and composition of the formed intermetallic compounds during recovery of curium on the solid aluminium and distribution of curium and aluminium over the area and along the selected line at a 2μm minimum interval using SEM/EPMA. The local quantitative analysis of the mass curium and aluminium fraction in the selected points will be made.
  • Task 3: Modeling of curium behavior in metal alloys.
Based on the data obtained from tasks 1 and 2, the mathematical model of curium behaviour in metal alloys will be built.


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