Blanket performance and radioactive waste of fusion reactors : a neutronics approach

Colling, Bethany and Joyce, Malcolm (2019) Blanket performance and radioactive waste of fusion reactors : a neutronics approach. PhD thesis, Lancaster University.

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Abstract

Fusion energy for use in power plants is a continually developing area and many of the related parameters are not yet fixed. The investigation of fusion neutronics and development of computational approaches for assessment is imperative in the road to commercial realisation of fusion power. This research has explored blanket performance, including tritium breeding and the shielding requirements, and assessed radioactive waste, utilising the 3-D Monte Carlo transport code MCNP, and the activation inventory code FISPACT. The performance of some solid and liquid breeder materials has been compared with regards to tritium breeding, energy production and shielding. In the case of novel spherical tokamak concepts, that make use of high temperature superconducting magnets and have no inboard blanket, scoping studies have been performed to investigate the impact of shielding requirements on how small the tokamak can be. Fusion power plants will not produce high level waste, as seen in nuclear fission plants, however the components and structures will become active as a result of interactions with high energy neutrons. A suitable radioactive waste management plan will be required in order to deal with this material appropriately, with an aim to recycle or clear from regulatory control all materials 100 years after shutdown. The study indicates that through suitable material selection and the use of component dismantling the requirement could potentially be satisfied. In terms of computational methods, the neutron flux averaging has been assessed throughout the work and has shown in neutronics estimates to produce some substantial differences. The recently developed unstructured mesh approach to neutronics modelling has been explored and the potential use for more accurate radioactive waste inventory calculations. Although the analysis and comparison shows promising results, it still requires significant development and improvement in the work flow to create a robust neutronic analysis method.