LRS Contribution to NES/BFE Yearly Report 2015
Molten Salt Reactor - revolutionary safety and fuel cycle features
The Molten Salt Reactor (MSR) is one of the innovative concepts studied in the frame of the
Generation IV International Forum (GIF). Switzerland joined the GIF MSR project on 20 November
2015. MSR has a potential for high resources utilization, low waste production, and risk reduction
with the exclusion of severe accidents. The Nuclear Energy and Safety (NES) department at PSI is
involved in several national and international project related to MSR: the Horizon 2020 project
“Safety Assessment of the MOlten salt FAst Reactor” (SAMOFAR), two Swiss National Science
Foundation (SNF) PhD studies, the EU FP7 project “Safety of ACtinide SEparation processes”
(SACSESS), and the project “Feasibility and plausibility of innovative reactor concepts in an European
electricity supply environment” co-financed by the organization of Swiss electricity producers
swisselectric.
In the frame of the SNF PhD study “Small Modular Molten Salt Reactor Designing for Low Waste
Production” several fuel cycle options are assessed. The study is focusing on achieving excellent
neutron economy, which should enable both breeding of fissile fuel from fertile nuclides (232Th or
238
U) and reduction of both legacy and own waste volume. The pivotal tool for related simulations is
the PSI in-house equilibrium closed cycle routine EQL0D [1, 2]. It is a MATLAB script coupled with the
Monte-Carlo code SERPENT capable to simulate continuous reprocessing, e.g. removal of gaseous
fission products (FPs) from the MSR core.
The performance of fast spectrum MSR was evaluated for several selected carrier salt compositions
including both fluoride and chloride salts: 7LiF-BeF2, 7LiF, 7LiF-NaF, NaF-BeF2, NaF-KF, NanatCl, and
Na37Cl. The 7Li and 37Cl were isotopically enriched. These carrier salts were mixed with the fuel salt to
form an eutectic mixture with low melting point. Both U-Pu and Th-U fuel cycles were evaluated by
means of the equilibrium cycle excess reactivity ρ for infinite medium. To provide further insight
major contributors to the parasitic neutron capture were identified. The highest reactivity excess and
so the best performance in both fuel cycles was provided by Na37Cl carrier salt; the tremendous
reactivity excess in the U-Pu cycle can even enable the use of a breed-and-burn fuel strategy [3]. Best
performance from the fluoride carrier salts has 7LiF, the reference carrier salt of the SAMOFAR
project. It was used for several fuel cycle studies. A parametric spectral study at equilibrium cycle and
at full core level was accomplished with an ERANOS-based EQL3D procedure [4]. A hybrid spectrum
MSR core was evaluated [5], the simplified reprocessing scheme assessed [6], and the continuous
and batch-wise reprocessing schemes compared in [7].
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Reactivity (PCM)
Hypoth. ρ
233U
(ν-2)/ν*1e5
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234U
235-238U
237Np
All Pu
Other Ac
Salt + FPs
Excess ρ
U-Pu cycle
Hypoth. ρ
239Pu
(ν-2)/ν*1e5
239Pu
240Pu
241-244Pu
241-242Am
243Am
Other Ac
Salt + FPs
Excess ρ
Reactivity (PCM)
Th-U cycle
Carrier salts
Carrier salts
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Figure 1: Excess reactivity in infinite media for Th-U (left) and U-Pu (right) fuel cycles and selected
carrier salts. The difference between excess and hypothetical reactivity (for zero parasitic
capture) is isotope-wise break-down into actual parasitic capture components.
[1] Hombourger. B. et al., 2016. THE EQL0D PROCEDURE FOR FUEL CYCLE STUDIES IN MOLTEN SALT
REACTORS. ICAPP 2016. April 17-20, San Francisco, USA.
[2] Hombourger, B. et al., 2015. FUEL CYCLE ANALYSIS OF A MOLTEN SALT REACTOR FOR BREEDAND-BURN MODE. ICAPP 2015. May 03-06, Nice, France.
[3] Křepel, J. et al., 2013. Fuel Cycle Advantages and Dynamics Features of Liquid Fueled MSR. Annals
of Nuclear Energy. vol. 64, pp. 380–397.
[4] Křepel, J. et al., 2014. HYBRID SPECTRUM MOLTEN SALT REACTOR. PHYSOR 2014. Kyoto, Japan,
September 28 – October 3.
[5] Křepel, J. et al., 2014. MOLTEN SALT REACTOR WITH SIMPLIFIED FUEL RECYCLING AND DELAYED
CARRIER SALT CLEANING. ICONE 22. July 7-11, 2014, Prague, Czech Republic.
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