Comparison of U-Pu and Th-U Cycles in MSR - Jiri Krepel @ ThEC2018

Objective comparison of the U-Pu & Th-U from a purely neutronic perspective.

When fuel cycle parameters: power, reprocessing scheme, feed composition, etc. are fixed, reactor will converge to equilibrium state / fuel composition. The composition depends on feed type 238U or 232Th and on the reactor spectrum.

The spectrum is determined by scattering materials. Equilibrium composition and spectrum determine the multiplication factor. Equilibrium is inherent core state (composition, spectrum, reactivity). Equilibrium reactivity indicates neutron efficiency of the core and its capability for breeding in closed fuel cycle.

Better performance: Th-U in thermal and U-Pu in fast spectra. Graphite moderated MSR only in Th-U. Fluorides fast MSFR possible in both cycles (equal performance). Chlorides fast MSR maximum reactivity in both cycles. B&B possible for U-Pu.

Parasitic captures strongly differ between reactors.
- 20% in fast & up to 40 % in thermal Th-U cycle.
- 30% in fast & up to 120 % in thermal U-Pu cycle.
- Reactivity loss in Th-U is much lower (1/3 in thermal, 2/3 in fast case).

Th-U: lower ν and lower parasitic capture of 233U, breeding also in thermal spectrum.
U-Pu: higher ν and higher parasitic capture of 239Pu, better performance in fast spectra.
Th-U high efficiency.
U-Pu high economy.

Jiri Krepel | Advanced Nuclear System Group | Paul Scherrer Institute

This talk was captured at Thorium Energy Conference 2018 (ThEC2018) in Brussels, Belgium. The footage may be recycled by https://ThoriumRemix.com/ for narrative purposes. Thorium Energy (World) conferences can be found here: http://www.thoriumenergyworld.com/

ThEC2018 videos are collected in this ThEC2018 Playlist: https://www.youtube.com/playlist?list=PLKfir74hxWhPll2rp9pJO2oiCceFccHls

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