Fuels beyond natural uranium, modelled core by core.

Uranium nitride in CANDU

With Janne Wallenius of KTH Royal Institute of Technology he studied uranium nitride as a fuel for CANDU reactors (PHYSOR 2018). Nitride fuel is denser in uranium than the standard oxide. Made from natural uranium with nitrogen-15, it lengthened the average residence time of a fuel bundle in the core from 210 to 360 days compared with UO₂. The trade-offs were quantified too: coolant void worth rose by 20 %, and the total power coefficient was halved.

Thorium for small modular reactors

In late 2023 he held a senior research fellowship at the Royal Military College of Canada on thorium-based fuel for small modular reactors, looking at fuel sustainability and waste management through better fuel utilisation. A paper from that work is in preparation. Small modular reactors are also a stated research interest of his fellowship with INTI International University.

Burning actinides

His doctoral thesis designed the Multispectrum CANDU Reactor: a helium-cooled fast-neutron core set inside a CANDU thermal core, so that surplus weapons-grade uranium or plutonium can be destroyed while the thermal core makes power from natural uranium. Neither core is critical on its own, so disturbing either one shuts the reactor down.

He built six full-core models in Serpent, fuelled with 19.9 % enriched uranium or with plutonium, and followed excess reactivity, regeneration factor, burnup and actinide inventories in each. The best uranium model destroyed 10.7 % of its fissile isotopes over 1000 days without refuelling. The best plutonium model destroyed 15.3 % over 2600 days. An earlier stage of the design, with 37-element bundles in both cores and core sizes and enrichment set for criticality safety, was presented at the 2015 International Conference on Modelling and Simulation in Nuclear Science and Engineering in Ottawa.

Depletion as the common thread

Every one of these studies turns on depletion: how a fuel’s composition, reactivity and power shape change as it burns. His work with the University of West Bohemia benchmarked the fast depletion code UWB1 on the CANDU bundle, so that absorber additives to the fuel can be screened in seconds per depletion step before the slower reference codes confirm them.