Spatial heterogeneity of W transmutation in a fusion device

TL;DR

This paper investigates how spatial heterogeneity in a fusion device affects tungsten transmutation, revealing that local neutron environment variations significantly influence rhenium production, with temperature effects being comparatively minor.

Contribution

It introduces a spatially detailed simulation approach to assess tungsten transmutation, highlighting the importance of local environment effects in fusion materials.

Findings

Re production is highly sensitive to local neutron moderation.

Structural steel and water significantly increase Re production.

Temperature effects on transmutation rates are relatively minor.

Abstract

Accurately quantifying the transmutation rate of tungsten (W) under neutron irradiation is a necessary requirement in the assessment of its performance as an armour material in a fusion power plant. The usual approach of calculating average responses, assuming large, homogenised material volumes, is insufficient to capture the full complexity of the transmutation picture in the context of a realistic fusion power plant design, particularly for rhenium (Re) production from W. Combined neutron transport and inventory simulations for representative {\it spatially heterogeneous} models of a fusion power plant show that the production rate of Re is strongly influenced by the local spatial environment. Localised variation in neutron moderation (slowing down) due to structural steel and coolant, particularly water, can dramatically increase Re production because of the huge cross sections of giant resolved resonances in the neutron-capture reaction of \(^{186}\)W at low neutron energies. Calculations using cross section data corrected for temperature (Doppler) effects suggest that temperature may have a relatively lesser influence on transmutation rates.