Thorium breeder and burner fuel cycles in reduced-moderation LWRs compared to fast reactors

Lindley, Ben; Fiorina, Carlo; Franceschini, Fausto; Lahoda, E.J.; Parks, Geoffrey T.

doi:10.1016/j.pnucene.2014.06.010

Cited by 15 publications

(12 citation statements)

References 16 publications

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“…The RBWR operating with a burner fuel cycle utilises a heterogeneous assembly with Th-Pu-(MA) and Th-(Pa)-U3 pins in different areas of the fuel assembly as this greatly improves the neutronic performance ( Fig. 3) (Lindley et al, , 2014b.…”

Section: Scenario Modellingmentioning

confidence: 99%

“…This leads to a TRU incineration rate of~13% and 17% per pass respectively, corresponding to~130 kg/GWthyr with MAs and~158 kg/GWthyr without MAs. The incineration rate is limited by the need to keep the void coefficient negative, and is therefore lower than in the SFR (Lindley et al, 2014b). Over the scenario, RBWRs with a break-even fuel cycle are loaded with 16.4% and 16% U3þTRU with and without MAs respectively.…”

Section: Scenario Modellingmentioning

confidence: 99%

“…RBWRs have also been recently considered for a Th break-even fuel cycle (Ganda et al, 2011). The radiotoxicity of Th break-even and burner fuel cycles at equilibrium for SFRs and RBWRs is comparable (Lindley et al, 2014b). However, higher specific power reactors have a more rapid transition to equilibrium (Hesketh and Thomas, 2013), and RBWRs have a relatively low power density compared to SFRs, which is therefore expected to slow their transition to equilibrium.…”

Section: Introductionmentioning

confidence: 99%

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The effectiveness of full actinide recycle as a nuclear waste management strategy when implemented over a limited timeframe – Part II: Thorium fuel cycle

Lindley

Fiorina

Gregg

et al. 2016

Progress in Nuclear Energy

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a b s t r a c tFull recycling of transuranic (TRU) isotopes can in theory lead to a reduction in repository radiotoxicity to reference levels in as little as~500 years provided reprocessing and fuel fabrication losses are limited. However, over a limited timeframe, the radiotoxicity of the 'final' core can dominate over reprocessing losses, leading to a much lower reduction in radiotoxicity compared to that achievable at equilibrium. In Part I of this paper, TRU recycle over up to 5 generations of light water reactors (LWRs) or sodium-cooled fast reactors (SFRs) is considered for uranium (U) fuel cycles. With full actinide recycling, at least 6 generations of SFRs are required in a gradual phase-out of nuclear power to achieve transmutation performance approaching the theoretical equilibrium performance. U-fuelled SFRs operating a breakeven fuel cycle are not particularly effective at reducing repository radiotoxicity as the final core load dominates over a very long timeframe. In this paper, the analysis is extended to the thorium (Th) fuel cycle. Closed Th-based fuel cycles are well known to have lower equilibrium radiotoxicity than U-based fuel cycles but the time taken to reach equilibrium is generally very long. Th burner fuel cycles with SFRs are found to result in very similar radiotoxicity to U burner fuel cycles with SFRs for one less generation of reactors, provided that protactinium (Pa) is recycled. Th-fuelled reduced-moderation boiling water reactors (RBWRs) are also considered, but for burner fuel cycles their performance is substantially worse, with the waste taking~3e5 times longer to decay to the reference level than for Th-fuelled SFRs with the same number of generations. Th break-even fuel cycles require~3 generations of operation before their waste radiotoxicity benefits result in decay to the reference level in~1000 years. While this is a very long timeframe, it is roughly half that required for waste from the Th or U burner fuel cycle to decay to the reference level, and less than a tenth that required for the U break-even fuel cycle. The improved performance over burner fuel cycles is due to a more substantial contribution of energy generated by 233 U leading to lower radiotoxicity per unit energy generation. To some extent this an argument based on how the radiotoxicity is normalised: operating a break-even fuel cycle rather than phasing out nuclear power using a burner fuel cycle results in higher repository radiotoxicity in absolute terms. The advantage of Th break-even fuel cycles is also contingent on recycling Pa, and reprocessing losses are significant also for a small number of generations due to the need to effectively burn down the TRU. The integrated decay heat over the scenario timeframe is almost twice as high for a break-even Th fuel cycle than a break-even U fuel cycle when using SFRs, as a result of much higher 90 Sr production, which subsequently decays into 90 Y. The peak decay heat is comparable. As decay heat at vitrification and repository decay heat affect repository s...

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Section: Scenario Modellingmentioning

confidence: 99%

Section: Scenario Modellingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The effectiveness of full actinide recycle as a nuclear waste management strategy when implemented over a limited timeframe – Part II: Thorium fuel cycle

Lindley

Fiorina

Gregg

et al. 2016

Progress in Nuclear Energy

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“…Studies have noted that at epithermal and fast energy ranges, the effect of increasing neutron energy on the fission-to-capture ratio is smallest when using a thorium-based fuel cycle. 11,[23][24][25] The main disadvantage of the thorium cycle is the lack of 233 U in nature, which necessitates preparation of 233 U in thorium-based reactors or accelerators. In addition, thorium is more abundant than rival elements, and thorium dioxide has greater thermal conductivity and a higher melting point than uranium dioxide.…”

Section: Introductionmentioning

confidence: 99%

Conceptual design of an innovative reduced moderation thorium‐fueled small modular reactor with heavy‐water coolant

et al. 2019

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Summary This paper presents an innovative conceptual design for small modular reactors, the reduced‐moderation small modular reactor (RMSMR), for the sustainable use of nuclear resources. The concept is established by a modification of the well‐understood pressurized water reactor technology. A reduced‐moderation lattice and heavy‐water coolant are used to yield an epithermal‐to‐fast neutron spectrum, which is beneficial for attaining a large conversion ratio and reducing the burnup reactivity swing throughout the core lifetime. Two‐dimensional pin cell and three‐dimensional core burnup calculations are performed to systematically analyze the neutronics influences of important parameters, such as the coolant type, moderator‐to‐fuel ratio, and fuel type. The RMSMR adopts a three‐zone uranium‐thorium dioxide fuel configuration to flatten the power distribution and ensure a negative void coefficient. The radial and axial blanket regions are found to enhance the breeding effect. The proposed RMSMR can sustain power generation of 100 MWe for 7 years without refueling and achieve a conversion ratio of 0.85 at the end of the cycle. Numerical simulations indicate that the proposed concept has satisfactory shutdown margins and reactivity coefficients and conservative thermal‐hydraulic safety. The RMSMR may be a promising candidate to fill the gap between light‐water reactors and fast breeder reactors.

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“…Due to the high effective number of neutrons for each 233 U fission in a thermal and epithermal neutron spectrum, thorium breeding is feasible in most existing and prospective reactor designs (including LWRs [2,3], HWRs [4][5][6][7][8], HTGRs [9] and molten salt reactors [10][11][12]), and it can provide the negative void reactivity coefficient due to the softer neutron spectrum than that of fast reactor. However, the thorium breeding gain in these reactors is far lower than fast reactor's.…”

Section: Introductionmentioning

confidence: 99%

Sustainability of thorium-uranium in pebble-bed fluoride salt-cooled high temperature reactor

Zhu

Zou

2016

EPJ Nuclear Sci. Technol.

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Abstract. Sustainability of thorium fuel in a Pebble-Bed Fluoride salt-cooled High temperature Reactor (PB-FHR) is investigated to find the feasible region of high discharge burnup and negative Flibe (2LiF-BeF 2 ) salt Temperature Reactivity Coefficient (TRC). Dispersion fuel or pellet fuel with SiC cladding and SiC matrix is used to replace the tristructural-isotropic (TRISO) coated particle system for increasing fuel loading and decreasing excessive moderation. To analyze the neutronic characteristics, an equilibrium calculation method of thorium fuel self-sustainability is developed. We have compared two refueling schemes (mixing flow pattern and directional flow pattern) and two kinds of reflector materials (SiC and graphite). This method found that the feasible region of breeding and negative Flibe TRC is between 20 vol% and 62 vol% fuel loading in the fuel. A discharge burnup could be achieved up to about 200 MWd/kgHM. The case with directional flow pattern and SiC reflector showed superior burnup characteristics but the worst radial power peak factor, while the case with mixing flow pattern and SiC reflector, which was the best tradeoff between discharge burnup and radial power peak factor, could provide burnup of 140 MWd/kgHM and about 1.4 radial power peak factor with 50 vol% dispersion fuel. In addition, Flibe salt displays good neutron properties as a coolant of quasi-fast reactors due to the strong 9 Be(n,2n) reaction and low neutron absorption of 6 Li (even at 1000 ppm) in fast spectrum. Preliminary thermal hydraulic calculation shows good safety margin. The greatest challenge of this reactor may be the decades irradiation time of the pebble fuel.

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Thorium breeder and burner fuel cycles in reduced-moderation LWRs compared to fast reactors

Cited by 15 publications

References 16 publications

The effectiveness of full actinide recycle as a nuclear waste management strategy when implemented over a limited timeframe – Part II: Thorium fuel cycle

The effectiveness of full actinide recycle as a nuclear waste management strategy when implemented over a limited timeframe – Part II: Thorium fuel cycle

Conceptual design of an innovative reduced moderation thorium‐fueled small modular reactor with heavy‐water coolant

Sustainability of thorium-uranium in pebble-bed fluoride salt-cooled high temperature reactor

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