The Experts below are selected from a list of 12636 Experts worldwide ranked by ideXlab platform

Guo H. - One of the best experts on this subject based on the ideXlab platform.

  • Design Directions of Optimized Reactivity Control Systems in Sodium Fast Reactors
    'Elsevier BV', 2019
    Co-Authors: Guo H., Sciora P., Buiron L., Kooyman T.
    Abstract:

    International audienceIn sodium fast reactors, the Control Rods, a movable cluster of open pins with boron carbide as absorber, are almost the only approach to Control reactivity. Boron-10 has a good absorption ability in fast spectrum and its enrichment can be adjusted to satisfy various requirements. However, boron carbide behavior under irradiation and the liability coming from the high initial core excess reactivity justify the optimization of reactivity Control in Generation-IV fast reactors. This paper discusses the relationship between boron-10 enrichment in the Control Rods and reactivity management using a series of representative cores. Then, various alternatives designs to improve or supplement classical Control Rods are discussed and their feasibility is investigated. The results show that large cores with small power density have usually small reactivity loss and thus the effective Control system design is limited by the shutdown function, e.g. the need to keep enough negative reactivity stored in the Rods to stop the chain reaction at any time. In these cores, alternative absorbers can be considered for boron carbide substitution, among which hafnium hydride based materials are good candidates. Moreover, the limited introduction of moderating materials is also a potential solution to optimize the Control Rods in such fast reactors.The main constraints on the reactivity Control system will be found for the cores with high reactivity loss, which are usually small modular or prototype cores. In these cores, Control Rods with high boron-10 enrichment are required for reactivity loss compensation. At the same time, the significant excess reactivity in the core will worsen the core behavior in case of inadvertent rod withdrawal for instance. The coupling of absorbing material and large quantities of moderating material enables the loading of burnable poisons in the core. Burnable poisons are able to share the reactivity loss compensation function with the Control Rods and thus enhance core inherent safety

  • Optimization of reactivity Control in a small modular sodium-cooled fast reactor
    'Elsevier BV', 2019
    Co-Authors: Guo H., Sciora P., Buiron L., Kooyman T.
    Abstract:

    International audienceThe small modular sodium-cooled fast reactor (SMSFR) is an important component of Generation-IV reactors. The objective of this work is to improve the reactivity Control in SMSFR by using innovative systems, including burnable poisons and optimized Control Rods. SMSFR with MOX fuel usually exhibits high burnup reactivity loss that leads to high excess reactivity and potential fuel melting in Control rod withdrawal (CRW) accidents, which becomes an important constraint on the safety and economic efficiency of SMSFR. This work applies two types of burnable poisons in a SMSFR to reduce the excess reactivity. The first one homogenously loads minor actinides in the fuel. The second one combines absorber and moderators in specific assemblies. The influence of burnable poisons on the core characteristics is discussed and integrated into the analysis of CRW accidents. The results show that burnable poisons improve the safety performance of the core in a significant way. Burnable poisons also lessen the demand for the number, absorption ability, and insertion depth of Control Rods. Two optimized Control rod designs with rare earth oxides (Eu2O3 and Gd2O3) and moderators are compared to the conventional design with natural boron carbide (B4C). The optimized designs show improved neutronic and safety performance.Available via license: CC BY-NC-ND 4.

  • Evaluation of the Control Rods Withdrawal in a Small Modular Sodium Fast Reactor and Analysis of the Impact on the Core Design
    INTERNATIONAL CONGRESS ON ADVANCES IN NUCLEAR POWER PLANTS, 2019
    Co-Authors: Guo H., Sciora P., Kooyman T., Buiron L.
    Abstract:

    International audienceNuclear reactors exhibit excess reactivity at start-up to ensure continuous operation over the length of the fuel cycle. For sodium fast reactors, this excess reactivity should cover burn-up reactivity loss, operation margin and uncertainty margin. However, contrary to light water reactors, Control Rods are the only available mean of reactivity Control, boron dilution in sodium being not possible. Therefore, at the beginning of cycle, one part of Control Rods should be inserted into the core to balance this excess reactivity. The Control Rods are then withdrawn slowly during the cycle to compensate for burn-up reactivity loss. The malfunction of a Control rod mechanism would lead to a so-called Control rod withdrawal (CRW) accident that is considered as a typical event for unprotected transient over-power. This event could lead to the local melting of fuel assemblies and even to the global melting of the core. As a consequence, this accident must be evaluated at the core design stage to ensure good margins.This paper proposes to use the newly deterministic code APOLLO3 to optimize the model of the con-trol Rods, the transient calculation code MAT4DYN to calculate in the core response to a CRW, and the GERMINAL code to study the fuel pin thermal-mechanical behavior during incidental conditions.This methodology is applied in a small sodium fast reactor that has an important reactivity loss and thus a high excess reactivity at start-up. The space for the implementation is limited by its mechanical motors especially for small reactors. To achieve the objectives defined for Generation-IV reactors, the CRW accident becomes the limiting factor for small modular fast reactors by comparing with other requirements such as maximum fuel burn-up. Three different options are proposed and studied to obtain core designs with a favorable behavior in case of CRW accident. The first solution is to reduce calculation uncertainty, but this is long process. The second solution is to enhance Doppler constant. The last solution is the application of new system, such as burnable poisons, to compensate for reactivity loss. This paper investigates the required ability of such potential systems and its impact on the core design

  • Advanced method for depletion calculation of Control Rods in sodium fast reactors
    'Elsevier BV', 2018
    Co-Authors: Guo H., Archier P., Jf. Vidal, Buiron L.
    Abstract:

    International audienceNeutronic simulations with high accuracy are required for the development of future sodium fast reactors. The lattice-core paradigm used for deterministic codes is able to save computation resources and improve calculation speed, but it defies the accurate depletion calculation. This paper focuses on the development and validation of an improved method, in the deterministic code APOLLO3, for the depletion calculation of Control Rods. The absorber depletion is validated for different Control Rods designs from cluster type configuration to core configuration. The lattice calculation in APOLLO3 shows a good adaptability to complex geometries with alternative absorbers and moderators. The self-shielding effect and its variation under neutron irradiation is the key issue for the accurate simulation of Control Rods. Therefore, updating cross-sections according to the burn-up improves significantly the accuracy on the depletion calculation

  • ADVANCED METHOD FOR NEUTRONIC SIMULATION OF Control Rods IN SODIUM FAST REACTORS NUMERICAL AND EXPERIMENTAL VALIDATION
    HAL CCSD, 2018
    Co-Authors: Guo H., Sciora P., Buiron L., Archier P., Ey. Garcia-cervantes, Faure B., Rimpault G.
    Abstract:

    International audienceHigh accuracy neutronic simulations are required for the development of Generation-IV sodium cooled fast reactors (SFR). This paper therefore focuses on the development and validation of an improved calculation method in APOLLO3 deterministic code to predict the reactivity Control system in SFR. This method relies on the lattice-core paradigm and the generation of few group effective cross-sections. Those are computed over small lattice geometries with detailed descriptions of structures but no heterogeneity correction method. Two models are considered at the core level the first one relies on homogeneous descriptions for all assemblies (fuel, Control Rods, reflector, diluent, etc.), whereas the second one takes into account the heterogeneity of absorber pins (semi-heterogeneous description).In order to assess the robustness of calculation methods, a validation work is achieved for three distinct SFR cores. A numerical validation is first performed for the SFR-3600-MOX core taken from the international WPRS benchmark. Then an experimental validation work is conducted for the Control Rods measurements from SUPERPHENIX start-up experiments. The last case of application is the ASTRID CFV core. At the cross-sections generation stage, the results show a good coherence with reference Monte Carlo calculations for both spatial and energy distributions. At the core level, it is shown that the homogeneous description of the Control Rods induces an overestimation of the reactivity worth while the semi-heterogeneous model significantly improves the results

Buiron L. - One of the best experts on this subject based on the ideXlab platform.

  • Design Directions of Optimized Reactivity Control Systems in Sodium Fast Reactors
    'Elsevier BV', 2019
    Co-Authors: Guo H., Sciora P., Buiron L., Kooyman T.
    Abstract:

    International audienceIn sodium fast reactors, the Control Rods, a movable cluster of open pins with boron carbide as absorber, are almost the only approach to Control reactivity. Boron-10 has a good absorption ability in fast spectrum and its enrichment can be adjusted to satisfy various requirements. However, boron carbide behavior under irradiation and the liability coming from the high initial core excess reactivity justify the optimization of reactivity Control in Generation-IV fast reactors. This paper discusses the relationship between boron-10 enrichment in the Control Rods and reactivity management using a series of representative cores. Then, various alternatives designs to improve or supplement classical Control Rods are discussed and their feasibility is investigated. The results show that large cores with small power density have usually small reactivity loss and thus the effective Control system design is limited by the shutdown function, e.g. the need to keep enough negative reactivity stored in the Rods to stop the chain reaction at any time. In these cores, alternative absorbers can be considered for boron carbide substitution, among which hafnium hydride based materials are good candidates. Moreover, the limited introduction of moderating materials is also a potential solution to optimize the Control Rods in such fast reactors.The main constraints on the reactivity Control system will be found for the cores with high reactivity loss, which are usually small modular or prototype cores. In these cores, Control Rods with high boron-10 enrichment are required for reactivity loss compensation. At the same time, the significant excess reactivity in the core will worsen the core behavior in case of inadvertent rod withdrawal for instance. The coupling of absorbing material and large quantities of moderating material enables the loading of burnable poisons in the core. Burnable poisons are able to share the reactivity loss compensation function with the Control Rods and thus enhance core inherent safety

  • Optimization of reactivity Control in a small modular sodium-cooled fast reactor
    'Elsevier BV', 2019
    Co-Authors: Guo H., Sciora P., Buiron L., Kooyman T.
    Abstract:

    International audienceThe small modular sodium-cooled fast reactor (SMSFR) is an important component of Generation-IV reactors. The objective of this work is to improve the reactivity Control in SMSFR by using innovative systems, including burnable poisons and optimized Control Rods. SMSFR with MOX fuel usually exhibits high burnup reactivity loss that leads to high excess reactivity and potential fuel melting in Control rod withdrawal (CRW) accidents, which becomes an important constraint on the safety and economic efficiency of SMSFR. This work applies two types of burnable poisons in a SMSFR to reduce the excess reactivity. The first one homogenously loads minor actinides in the fuel. The second one combines absorber and moderators in specific assemblies. The influence of burnable poisons on the core characteristics is discussed and integrated into the analysis of CRW accidents. The results show that burnable poisons improve the safety performance of the core in a significant way. Burnable poisons also lessen the demand for the number, absorption ability, and insertion depth of Control Rods. Two optimized Control rod designs with rare earth oxides (Eu2O3 and Gd2O3) and moderators are compared to the conventional design with natural boron carbide (B4C). The optimized designs show improved neutronic and safety performance.Available via license: CC BY-NC-ND 4.

  • Evaluation of the Control Rods Withdrawal in a Small Modular Sodium Fast Reactor and Analysis of the Impact on the Core Design
    INTERNATIONAL CONGRESS ON ADVANCES IN NUCLEAR POWER PLANTS, 2019
    Co-Authors: Guo H., Sciora P., Kooyman T., Buiron L.
    Abstract:

    International audienceNuclear reactors exhibit excess reactivity at start-up to ensure continuous operation over the length of the fuel cycle. For sodium fast reactors, this excess reactivity should cover burn-up reactivity loss, operation margin and uncertainty margin. However, contrary to light water reactors, Control Rods are the only available mean of reactivity Control, boron dilution in sodium being not possible. Therefore, at the beginning of cycle, one part of Control Rods should be inserted into the core to balance this excess reactivity. The Control Rods are then withdrawn slowly during the cycle to compensate for burn-up reactivity loss. The malfunction of a Control rod mechanism would lead to a so-called Control rod withdrawal (CRW) accident that is considered as a typical event for unprotected transient over-power. This event could lead to the local melting of fuel assemblies and even to the global melting of the core. As a consequence, this accident must be evaluated at the core design stage to ensure good margins.This paper proposes to use the newly deterministic code APOLLO3 to optimize the model of the con-trol Rods, the transient calculation code MAT4DYN to calculate in the core response to a CRW, and the GERMINAL code to study the fuel pin thermal-mechanical behavior during incidental conditions.This methodology is applied in a small sodium fast reactor that has an important reactivity loss and thus a high excess reactivity at start-up. The space for the implementation is limited by its mechanical motors especially for small reactors. To achieve the objectives defined for Generation-IV reactors, the CRW accident becomes the limiting factor for small modular fast reactors by comparing with other requirements such as maximum fuel burn-up. Three different options are proposed and studied to obtain core designs with a favorable behavior in case of CRW accident. The first solution is to reduce calculation uncertainty, but this is long process. The second solution is to enhance Doppler constant. The last solution is the application of new system, such as burnable poisons, to compensate for reactivity loss. This paper investigates the required ability of such potential systems and its impact on the core design

  • Advanced method for depletion calculation of Control Rods in sodium fast reactors
    'Elsevier BV', 2018
    Co-Authors: Guo H., Archier P., Jf. Vidal, Buiron L.
    Abstract:

    International audienceNeutronic simulations with high accuracy are required for the development of future sodium fast reactors. The lattice-core paradigm used for deterministic codes is able to save computation resources and improve calculation speed, but it defies the accurate depletion calculation. This paper focuses on the development and validation of an improved method, in the deterministic code APOLLO3, for the depletion calculation of Control Rods. The absorber depletion is validated for different Control Rods designs from cluster type configuration to core configuration. The lattice calculation in APOLLO3 shows a good adaptability to complex geometries with alternative absorbers and moderators. The self-shielding effect and its variation under neutron irradiation is the key issue for the accurate simulation of Control Rods. Therefore, updating cross-sections according to the burn-up improves significantly the accuracy on the depletion calculation

  • ADVANCED METHOD FOR NEUTRONIC SIMULATION OF Control Rods IN SODIUM FAST REACTORS NUMERICAL AND EXPERIMENTAL VALIDATION
    HAL CCSD, 2018
    Co-Authors: Guo H., Sciora P., Buiron L., Archier P., Ey. Garcia-cervantes, Faure B., Rimpault G.
    Abstract:

    International audienceHigh accuracy neutronic simulations are required for the development of Generation-IV sodium cooled fast reactors (SFR). This paper therefore focuses on the development and validation of an improved calculation method in APOLLO3 deterministic code to predict the reactivity Control system in SFR. This method relies on the lattice-core paradigm and the generation of few group effective cross-sections. Those are computed over small lattice geometries with detailed descriptions of structures but no heterogeneity correction method. Two models are considered at the core level the first one relies on homogeneous descriptions for all assemblies (fuel, Control Rods, reflector, diluent, etc.), whereas the second one takes into account the heterogeneity of absorber pins (semi-heterogeneous description).In order to assess the robustness of calculation methods, a validation work is achieved for three distinct SFR cores. A numerical validation is first performed for the SFR-3600-MOX core taken from the international WPRS benchmark. Then an experimental validation work is conducted for the Control Rods measurements from SUPERPHENIX start-up experiments. The last case of application is the ASTRID CFV core. At the cross-sections generation stage, the results show a good coherence with reference Monte Carlo calculations for both spatial and energy distributions. At the core level, it is shown that the homogeneous description of the Control Rods induces an overestimation of the reactivity worth while the semi-heterogeneous model significantly improves the results

H. Guo - One of the best experts on this subject based on the ideXlab platform.

  • designs of Control Rods with strong absorption ability for small fast reactors
    Nuclear Engineering and Design, 2020
    Co-Authors: H. Guo, L. Buiron, P Sciora, T Kooyman
    Abstract:

    Abstract Small fast reactors usually exhibit high neutron leakage and low breeding capability, while modular design demands long cycle length and compact core. These characteristics raise the requirement of Control Rods with strong absorption ability and long operating lifetime. In this paper, Control Rods with 90% 10B enriched B4C, 90% 10B enriched HfB2-90, and HfH1.62 are designed and assessed in a small sodium fast reactor. Results show that the operating lifetime of high 10B enriched B4C is limited by its burnup and temperature. Even with small pin design, 90% 10B enriched B4C is not able to stay safe as long as the fuel in a no refueling scenario. HfB2 can tolerate a longer residence time compared to the fuel. The absorption ability of HfB2 can be higher than B4C if the geometry effect is accounted for. HfH1.62 absorber is feasible in normal situations, but its absorption ability is inferior to B4C or HfB2 and will be significantly reduced at high temperature due to the hydrogen desorption issue. The spatial self-shielding effect increases with the absorption ability of Control Rods. In order to mitigate the heterogeneous distribution, two solutions are investigated in this paper. The radially mixed designs, with HfB2 at the outermost pins and B4C in the inner pins, do not extend the operating lifetime but increase the manufacturing complicity and the cost of raw materials. The substitution of absorber with a hydride moderator is able to keep high absorption ability and long operating lifetime of Control Rods while saving the investment of expensive absorber. Moreover, the local effects and hydrogen desorption of hydride moderators are acceptable.

  • optimization of reactivity Control in a small modular sodium cooled fast reactor
    Nuclear Engineering and Technology, 2020
    Co-Authors: H. Guo, L. Buiron, P Sciora, T Kooyman
    Abstract:

    Abstract The small modular sodium-cooled fast reactor (SMSFR) is an important component of Generation-IV reactors. The objective of this work is to improve the reactivity Control in SMSFR by using innovative systems, including burnable poisons and optimized Control Rods. SMSFR with MOX fuel usually exhibits high burnup reactivity loss that leads to high excess reactivity and potential fuel melting in Control rod withdrawal (CRW) accidents, which becomes an important constraint on the safety and economic efficiency of SMSFR. This work applies two types of burnable poisons in a SMSFR to reduce the excess reactivity. The first one homogenously loads minor actinides in the fuel. The second one combines absorber and moderators in specific assemblies. The influence of burnable poisons on the core characteristics is discussed and integrated into the analysis of CRW accidents. The results show that burnable poisons improve the safety performance of the core in a significant way. Burnable poisons also lessen the demand for the number, absorption ability, and insertion depth of Control Rods. Two optimized Control rod designs with rare earth oxides (Eu2O3 and Gd2O3) and moderators are compared to the conventional design with natural boron carbide (B4C). The optimized designs show improved neutronic and safety performance.

  • advanced method for neutronic simulation of Control Rods in sodium fast reactors numerical and experimental validation
    Annals of Nuclear Energy, 2019
    Co-Authors: H. Guo, L. Buiron, P. Archier, P Sciora, E Garcia, Bastien Faure, G Rimpault
    Abstract:

    Abstract High accuracy neutronic simulations are required for the development of Generation-IV sodium cooled fast reactors (SFR). This paper therefore focuses on the development and validation of an improved calculation method in APOLLO3® deterministic code to predict the reactivity Control system in SFR. This method relies on the “lattice-core” paradigm and the generation of few group effective cross-sections. Those are computed over small lattice geometries with detailed descriptions of structures but no heterogeneity correction method. Two models are considered at the core level: the first one relies on homogeneous descriptions for all assemblies (fuel, Control Rods, reflector, diluent, etc.), whereas the second one takes into account the heterogeneity of absorber pins (semi-heterogeneous description). In order to assess the robustness of calculation methods, a validation work is achieved for three distinct SFR cores. A numerical validation is first performed for the SFR-3600-MOX core taken from the international WPRS benchmark. Then an experimental validation work is conducted for the Control Rods measurements from SUPERPHENIX start-up experiments. The last case of application is the ASTRID CFV core. At the cross-sections generation stage, the results show a good coherence with reference Monte Carlo calculations for both spatial and energy distributions. At the core level, it is shown that the homogeneous description of the Control Rods induces an overestimation of the reactivity worth while the semi-heterogeneous model significantly improves the results.

  • Advanced method for depletion calculation of Control Rods in sodium fast reactors
    Annals of Nuclear Energy, 2018
    Co-Authors: H. Guo, Jf. Vidal, P. Archier, L. Buiron
    Abstract:

    Neutronic simulations with high accuracy are required for the development of future sodium fast reactors. The lattice-core paradigm used for deterministic codes is able to save computation resources and improve calculation speed, but it defies the accurate depletion calculation. This paper focuses on the development and validation of an improved method, in the deterministic code APOLLO3, for the depletion calculation of Control Rods. The absorber depletion is validated for different Control Rods designs from cluster type configuration to core configuration. The lattice calculation in APOLLO3 shows a good adaptability to complex geometries with alternative absorbers and moderators. The self-shielding effect and its variation under neutron irradiation is the key issue for the accurate simulation of Control Rods. Therefore, updating cross-sections according to the burn-up improves significantly the accuracy on the depletion calculation.

Liang Cheng - One of the best experts on this subject based on the ideXlab platform.

  • numerical investigation of fluid flow past circular cylinder with multiple Control Rods at low reynolds number
    Journal of Fluids and Structures, 2014
    Co-Authors: Mingming Liu, Guoqiang Tang, Bin Teng, Zhendong Cui, Ming Zhao, Liang Cheng
    Abstract:

    Abstract Laminar flow past a circular cylinder with multiple small-diameter Control Rods is numerically investigated in this study. The effects of rod-to-cylinder spacing ratio, rod and cylinder diameter ratio, cylinder Reynolds number, number of Control Rods and angle of attack on the hydrodynamics of the main circular cylinder are investigated. Four different flow regimes are identified based on the mechanism of lift and drag reduction. The range of rod-to-cylinder spacing ratio where significant force suppression can be achieved is found to become narrower as the Reynolds number increases in the laminar regime, but is insensitive to the diameter ratio. The numerical results for the case with six identical small Control Rods at Re=200 show that the lift fluctuation on the main cylinder can be suppressed significantly for a large range of spacing ratio and various diameter ratios, while the drag reduction on the main cylinder is also achieved simultaneously. The six-Control-rod arrangement has shown better performance in flow Control than the arrangements with less Control Rods, especially in terms of force reduction at various angles of attack.

Kooyman T. - One of the best experts on this subject based on the ideXlab platform.

  • Design Directions of Optimized Reactivity Control Systems in Sodium Fast Reactors
    'Elsevier BV', 2019
    Co-Authors: Guo H., Sciora P., Buiron L., Kooyman T.
    Abstract:

    International audienceIn sodium fast reactors, the Control Rods, a movable cluster of open pins with boron carbide as absorber, are almost the only approach to Control reactivity. Boron-10 has a good absorption ability in fast spectrum and its enrichment can be adjusted to satisfy various requirements. However, boron carbide behavior under irradiation and the liability coming from the high initial core excess reactivity justify the optimization of reactivity Control in Generation-IV fast reactors. This paper discusses the relationship between boron-10 enrichment in the Control Rods and reactivity management using a series of representative cores. Then, various alternatives designs to improve or supplement classical Control Rods are discussed and their feasibility is investigated. The results show that large cores with small power density have usually small reactivity loss and thus the effective Control system design is limited by the shutdown function, e.g. the need to keep enough negative reactivity stored in the Rods to stop the chain reaction at any time. In these cores, alternative absorbers can be considered for boron carbide substitution, among which hafnium hydride based materials are good candidates. Moreover, the limited introduction of moderating materials is also a potential solution to optimize the Control Rods in such fast reactors.The main constraints on the reactivity Control system will be found for the cores with high reactivity loss, which are usually small modular or prototype cores. In these cores, Control Rods with high boron-10 enrichment are required for reactivity loss compensation. At the same time, the significant excess reactivity in the core will worsen the core behavior in case of inadvertent rod withdrawal for instance. The coupling of absorbing material and large quantities of moderating material enables the loading of burnable poisons in the core. Burnable poisons are able to share the reactivity loss compensation function with the Control Rods and thus enhance core inherent safety

  • Optimization of reactivity Control in a small modular sodium-cooled fast reactor
    'Elsevier BV', 2019
    Co-Authors: Guo H., Sciora P., Buiron L., Kooyman T.
    Abstract:

    International audienceThe small modular sodium-cooled fast reactor (SMSFR) is an important component of Generation-IV reactors. The objective of this work is to improve the reactivity Control in SMSFR by using innovative systems, including burnable poisons and optimized Control Rods. SMSFR with MOX fuel usually exhibits high burnup reactivity loss that leads to high excess reactivity and potential fuel melting in Control rod withdrawal (CRW) accidents, which becomes an important constraint on the safety and economic efficiency of SMSFR. This work applies two types of burnable poisons in a SMSFR to reduce the excess reactivity. The first one homogenously loads minor actinides in the fuel. The second one combines absorber and moderators in specific assemblies. The influence of burnable poisons on the core characteristics is discussed and integrated into the analysis of CRW accidents. The results show that burnable poisons improve the safety performance of the core in a significant way. Burnable poisons also lessen the demand for the number, absorption ability, and insertion depth of Control Rods. Two optimized Control rod designs with rare earth oxides (Eu2O3 and Gd2O3) and moderators are compared to the conventional design with natural boron carbide (B4C). The optimized designs show improved neutronic and safety performance.Available via license: CC BY-NC-ND 4.

  • Evaluation of the Control Rods Withdrawal in a Small Modular Sodium Fast Reactor and Analysis of the Impact on the Core Design
    INTERNATIONAL CONGRESS ON ADVANCES IN NUCLEAR POWER PLANTS, 2019
    Co-Authors: Guo H., Sciora P., Kooyman T., Buiron L.
    Abstract:

    International audienceNuclear reactors exhibit excess reactivity at start-up to ensure continuous operation over the length of the fuel cycle. For sodium fast reactors, this excess reactivity should cover burn-up reactivity loss, operation margin and uncertainty margin. However, contrary to light water reactors, Control Rods are the only available mean of reactivity Control, boron dilution in sodium being not possible. Therefore, at the beginning of cycle, one part of Control Rods should be inserted into the core to balance this excess reactivity. The Control Rods are then withdrawn slowly during the cycle to compensate for burn-up reactivity loss. The malfunction of a Control rod mechanism would lead to a so-called Control rod withdrawal (CRW) accident that is considered as a typical event for unprotected transient over-power. This event could lead to the local melting of fuel assemblies and even to the global melting of the core. As a consequence, this accident must be evaluated at the core design stage to ensure good margins.This paper proposes to use the newly deterministic code APOLLO3 to optimize the model of the con-trol Rods, the transient calculation code MAT4DYN to calculate in the core response to a CRW, and the GERMINAL code to study the fuel pin thermal-mechanical behavior during incidental conditions.This methodology is applied in a small sodium fast reactor that has an important reactivity loss and thus a high excess reactivity at start-up. The space for the implementation is limited by its mechanical motors especially for small reactors. To achieve the objectives defined for Generation-IV reactors, the CRW accident becomes the limiting factor for small modular fast reactors by comparing with other requirements such as maximum fuel burn-up. Three different options are proposed and studied to obtain core designs with a favorable behavior in case of CRW accident. The first solution is to reduce calculation uncertainty, but this is long process. The second solution is to enhance Doppler constant. The last solution is the application of new system, such as burnable poisons, to compensate for reactivity loss. This paper investigates the required ability of such potential systems and its impact on the core design