Heavy water-moderated molten salt reactors(HWMSRs)are novel molten salt reactors that adopt heavy water rather than graphite as the moderator while employing liquid fuel.Owing to the high moderating ratio of the heavy...Heavy water-moderated molten salt reactors(HWMSRs)are novel molten salt reactors that adopt heavy water rather than graphite as the moderator while employing liquid fuel.Owing to the high moderating ratio of the heavy water moderator and the utilization of liquid fuel,HWMSRs can achieve a high neutron economy.In this study,a large-scale small modular HWMSR with a thermal power of 500 MWth was proposed and studied.The criticality of the core was evaluated using an in-house critical search calculation code(CSCC),which was developed based on Standardized Computer Analyses for Licensing Evaluation,version 6.1.The preliminary fuel cycle performances(initial conversion ratio(CR),initialfissile fuel loading mass,and temperature coefficient)were investigated by varying the lattice pitch(P)and the molten salt volume fraction(VF).The results demonstrate that the temperature coefficient can be negative over the range of investigated Ps and VFs for both 233U-Th and LEU-Th fuels.A core with a P of 20 cm and a VF of 20%is recommended for 233U-Th and LEU-Th fuels to achieve a high performance of initial CR and fuel loading.Regarding TRU-Th fuel,a core with a smaller P(~5 cm)and larger VF(~24%)is recommended to obtain a negative temperature coefficient.展开更多
With respect to a liquid-fueled molten salt reactor(MSR),the temperature coefficient of reactivity mainly includes the moderator temperature coefficient(MTC)and the fuel salt temperature coefficient(FSTC).The FSTC is ...With respect to a liquid-fueled molten salt reactor(MSR),the temperature coefficient of reactivity mainly includes the moderator temperature coefficient(MTC)and the fuel salt temperature coefficient(FSTC).The FSTC is typically divided into the Doppler coefficient and the density coefficient.In order to compensate for the potentially positive MTC,the FSTC should be sufficiently negative,and this is mostly optimized in terms of the geometry aspect in pioneering studies.However,the properties of fuel salt also directly influence the FSTC.Thus,the effects of different fuel salt compositions including the^(235)U enrichment,heavy metal proportion in salt phase(HM proportion),and the^7Li enrichment on FSTC are investigated from the viewpoint of the essential six-factor formula.The analysis is based on an undermoderated MSR.With respect to the Doppler coefficient,the temperature coefficient of the fast fission factors(a_T(ξ))is positive and those of the resonance escape probability(a_T(p)),thermal reproduction factor(a_T(g)),thermal utilization factor(a_T(f)),and total non-leakage probability(a_T(λ))are negative.With respect to the density coefficient,a_T(p)and a_T(g)are positive,while the others are negative.The results indicate that the effects of the^(235)U enrichment and HM on FSTC are mainly reflected in a_T(e)and a_T(p),which are the dominant factors when the neutron spectrum is relatively hard.Furthermore,the^7Li enrichment influences FSTC by a_T(f)and a_T(λ),which are the key factors in a relative soft spectrum.In order to obtain a more negative FSTC for an under-moderated MSR,the possible positive density coefficient,especially its a_T(p),should be suppressed.Thus,a lower^(235)U enrichment(albeit higher than a certain value,5 wt%in this article)along with a lower HM proportion and/or a higher^7Li enrichment are recommended.The analyses provide an approach to achieve a more suitable fuel salt composition with a sufficiently negative FSTC.展开更多
To optimize the temperature coefficient of reactivity(TCR)for a graphite-moderated and liquid-fueled molten salt reactor,the effects of fuel salt composition on the fuel salt temperature coefficient of reactivity(FSTC...To optimize the temperature coefficient of reactivity(TCR)for a graphite-moderated and liquid-fueled molten salt reactor,the effects of fuel salt composition on the fuel salt temperature coefficient of reactivity(FSTC)were investigated in our earlier work.In this study,we aim to provide a more comprehensive analysis of the TCR by considering the effects of the graphite-moderator temperature coefficient of reactivity(MTC).The effects of^235U enrichment and heavy metal(HM)proportion in the salt mixture on the MTC are investigated from the perspective of the six-factor formula based on a full-core model.For the MTC(labeled“αTM”),the temperature coefficient of the fast fission factors(αTM(ε))is positive,while those of the resonance escape probability(αTM(p)),the thermal reproduction factor(αTM(η)),the thermal utilization factor(αTM(f)),and the total non-leakage probability(αTM(A))are negative.The results reveal that the magnitudes ofαTM(ε)andαTM(p)for the MTC are similar.Thus,variations in the MTC with^235U enrichment for different HM proportions are mainly dependent onαTM(η),αTM(A),andαTM(f),but especially on the former two.To obtain a more negative MTC,a lower HM proportion and/or a lower 235U enrichment is recommended.Together with our previous studies on the FSTC,a relatively soft neutron spectrum could strengthen the TCR with a sufficiently negative MTC.展开更多
The solid fuel thorium molten salt reactor(TMSR-SF1) is a 10-MWth fluoride-cooled pebble bed reactor. As a new reactor concept, one of the major limiting factors to reactor lifetime is radiation-induced material damag...The solid fuel thorium molten salt reactor(TMSR-SF1) is a 10-MWth fluoride-cooled pebble bed reactor. As a new reactor concept, one of the major limiting factors to reactor lifetime is radiation-induced material damage. The fast neutron flux(E > 0.1 MeV) can be used to assess possible radiation damage. Hence, a method for calculating high-resolution fast neutron flux distribution of the full-scale TMSR-SF1 reactor is required. In this study,a two-step subsection approach based on MCNP5 involving a global variance reduction method, referred to as forward-weighted consistent adjoint-driven importance sampling, was implemented to provide fast neutron flux distribution throughout the TMSR-SF1 facility. In addition,instead of using the general source specification cards, the user-provided SOURCE subroutine in MCNP5 source code was employed to implement a source biasing technique specialized for TMSR-SF1. In contrast to the one-step analog approach, the two-step subsection approach eliminates zero-scored mesh tally cells and obtains tally results with extremely uniform and low relative uncertainties.Furthermore, the maximum fast neutron fluxes of the main components in TMSR-SF1 are provided, which can be used for radiation damage assessment of the structural materials.展开更多
基金supported by the Chinese TMSR Strategic Pioneer Science and Technology Project(No.XDA02010000)the National Natural Science Foundation of China(No.11905285)+1 种基金the National Natural Science Foundation of China(No.11790321)the Frontier Science Key Program of the Chinese Academy of Sciences(No.QYZDY-SSW-JSC016)。
文摘Heavy water-moderated molten salt reactors(HWMSRs)are novel molten salt reactors that adopt heavy water rather than graphite as the moderator while employing liquid fuel.Owing to the high moderating ratio of the heavy water moderator and the utilization of liquid fuel,HWMSRs can achieve a high neutron economy.In this study,a large-scale small modular HWMSR with a thermal power of 500 MWth was proposed and studied.The criticality of the core was evaluated using an in-house critical search calculation code(CSCC),which was developed based on Standardized Computer Analyses for Licensing Evaluation,version 6.1.The preliminary fuel cycle performances(initial conversion ratio(CR),initialfissile fuel loading mass,and temperature coefficient)were investigated by varying the lattice pitch(P)and the molten salt volume fraction(VF).The results demonstrate that the temperature coefficient can be negative over the range of investigated Ps and VFs for both 233U-Th and LEU-Th fuels.A core with a P of 20 cm and a VF of 20%is recommended for 233U-Th and LEU-Th fuels to achieve a high performance of initial CR and fuel loading.Regarding TRU-Th fuel,a core with a smaller P(~5 cm)and larger VF(~24%)is recommended to obtain a negative temperature coefficient.
基金supported by the Chinese TMSR Strategic Pioneer Science and Technology Project(No.XDA02010000)the Frontier Science Key Program of the Chinese Academy of Sciences(No.QYZDY-SSW-JSC016)
文摘With respect to a liquid-fueled molten salt reactor(MSR),the temperature coefficient of reactivity mainly includes the moderator temperature coefficient(MTC)and the fuel salt temperature coefficient(FSTC).The FSTC is typically divided into the Doppler coefficient and the density coefficient.In order to compensate for the potentially positive MTC,the FSTC should be sufficiently negative,and this is mostly optimized in terms of the geometry aspect in pioneering studies.However,the properties of fuel salt also directly influence the FSTC.Thus,the effects of different fuel salt compositions including the^(235)U enrichment,heavy metal proportion in salt phase(HM proportion),and the^7Li enrichment on FSTC are investigated from the viewpoint of the essential six-factor formula.The analysis is based on an undermoderated MSR.With respect to the Doppler coefficient,the temperature coefficient of the fast fission factors(a_T(ξ))is positive and those of the resonance escape probability(a_T(p)),thermal reproduction factor(a_T(g)),thermal utilization factor(a_T(f)),and total non-leakage probability(a_T(λ))are negative.With respect to the density coefficient,a_T(p)and a_T(g)are positive,while the others are negative.The results indicate that the effects of the^(235)U enrichment and HM on FSTC are mainly reflected in a_T(e)and a_T(p),which are the dominant factors when the neutron spectrum is relatively hard.Furthermore,the^7Li enrichment influences FSTC by a_T(f)and a_T(λ),which are the key factors in a relative soft spectrum.In order to obtain a more negative FSTC for an under-moderated MSR,the possible positive density coefficient,especially its a_T(p),should be suppressed.Thus,a lower^(235)U enrichment(albeit higher than a certain value,5 wt%in this article)along with a lower HM proportion and/or a higher^7Li enrichment are recommended.The analyses provide an approach to achieve a more suitable fuel salt composition with a sufficiently negative FSTC.
基金supported by the Chinese TMSR Strategic Pioneer Science and Technology Project(No.XDA02010000)the Frontier Science Key Program of the Chinese Academy of Sciences(No.QYZDY-SSW-JSC016)
文摘To optimize the temperature coefficient of reactivity(TCR)for a graphite-moderated and liquid-fueled molten salt reactor,the effects of fuel salt composition on the fuel salt temperature coefficient of reactivity(FSTC)were investigated in our earlier work.In this study,we aim to provide a more comprehensive analysis of the TCR by considering the effects of the graphite-moderator temperature coefficient of reactivity(MTC).The effects of^235U enrichment and heavy metal(HM)proportion in the salt mixture on the MTC are investigated from the perspective of the six-factor formula based on a full-core model.For the MTC(labeled“αTM”),the temperature coefficient of the fast fission factors(αTM(ε))is positive,while those of the resonance escape probability(αTM(p)),the thermal reproduction factor(αTM(η)),the thermal utilization factor(αTM(f)),and the total non-leakage probability(αTM(A))are negative.The results reveal that the magnitudes ofαTM(ε)andαTM(p)for the MTC are similar.Thus,variations in the MTC with^235U enrichment for different HM proportions are mainly dependent onαTM(η),αTM(A),andαTM(f),but especially on the former two.To obtain a more negative MTC,a lower HM proportion and/or a lower 235U enrichment is recommended.Together with our previous studies on the FSTC,a relatively soft neutron spectrum could strengthen the TCR with a sufficiently negative MTC.
基金supported by the Chinese TMSR Strategic Pioneer Science and Technology Project(No.XDA02010000)the Frontier Science Key Program of Chinese Academy of Sciences(No.QYZDY-SSW-JSC016)
文摘The solid fuel thorium molten salt reactor(TMSR-SF1) is a 10-MWth fluoride-cooled pebble bed reactor. As a new reactor concept, one of the major limiting factors to reactor lifetime is radiation-induced material damage. The fast neutron flux(E > 0.1 MeV) can be used to assess possible radiation damage. Hence, a method for calculating high-resolution fast neutron flux distribution of the full-scale TMSR-SF1 reactor is required. In this study,a two-step subsection approach based on MCNP5 involving a global variance reduction method, referred to as forward-weighted consistent adjoint-driven importance sampling, was implemented to provide fast neutron flux distribution throughout the TMSR-SF1 facility. In addition,instead of using the general source specification cards, the user-provided SOURCE subroutine in MCNP5 source code was employed to implement a source biasing technique specialized for TMSR-SF1. In contrast to the one-step analog approach, the two-step subsection approach eliminates zero-scored mesh tally cells and obtains tally results with extremely uniform and low relative uncertainties.Furthermore, the maximum fast neutron fluxes of the main components in TMSR-SF1 are provided, which can be used for radiation damage assessment of the structural materials.
