WP 2: Improved thermo-chemical data and modelling for nuclear design
Background
The use of chemical-thermodynamic modelling to predict the equilibrium behaviour of materials systems is important in understanding high temperature processes and is well suited to environments where experimental measurements are very difficult. These techniques have become well established in developing an understanding of the behaviour of nuclear materials during normal or abnormal fuel conditions, the effect of any interaction between a fuel and coolant and for modelling reprocessing of the fuel.
State of the art
As a result of international collaboration, critically assessed thermodynamic data have been developed for a number of binary, ternary and multi-component systems of importance to understanding the behaviour of materials in use in current generation nuclear reactors. Much of this work has been concerned with data for oxide fuels and coverage in terms of data for alloys, carbides, nitrides and salts is far less. Furthermore there are hardly any thermodynamic data for minor actinides for all of these types of system. Third and fourth generation nuclear plants are likely to require new types of fuel depending on the design of the reactor, to have the potential to absorb minor actinide decay products and have facilities for on-site reprocessing.
Aims of the work package
There is a need to extend the scope of the pool of critically assessed thermodynamic data to cover materials likely to be used in third and fourth generation nuclear plants to take into account the increased retention of minor actinides, the potential use of non-oxide fuels and new coolants. This work aims to develop and parameterise thermodynamic models for a range of major and minor actinide containing systems, relevant to fuel both in-reactor and during reprocessing that will allow predictions of materials chemistry to be made. These predictions will include phase transformation temperatures and other related properties related to the equilibrium thermodynamics and phase equilibria of the fuel materials and their near environment. The thermodynamic database(s) arising from this work will be compatible with the major software packages used to calculate phase equilibria from thermodynamic data.
Major facilities/equipment
This WP makes use of thermodynamic software developed at NPL (MTDATA) supplemented by use of ab initio quantum mechanics (ABINIT, VASP and NWChem). No large computational facilities are required, however NPL may make use of a recently commissioned High Performance Computing Facility, if appropriate.
Scientific tasks
2.1 Define fuels, coolants and reprocessing technology to be covered (JRC (ITU), NPL)
2.2 Develop models and thermodynamic data (NPL, JRC (ITU))
2.3 Validate prediction of phase equilibria (JRC (ITU), NPL)