The Experts below are selected from a list of 64779 Experts worldwide ranked by ideXlab platform
Yonghee Kim - One of the best experts on this subject based on the ideXlab platform.
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HIGH-PERFORMANCE MULTI-BATCH FUEL MANAGEMENTS FOR THE ADVANCED SOLUBLE-BORON-FREE ATOM CORE
'EDP Sciences', 2021Co-Authors: Xuan Ha Nguyen, Seongdong Jang, Yonghee KimAbstract:The autonomous transportable on-demand reactor module (ATOM), a 450 MWth PWR-type small modular reactor (SMR), is under development at Korea Advanced Institute of Science and Technology (KAIST). The ATOM core is designed for soluble-boron-free and passive autonomous load-following operations by utilizing successfully an advanced Reactivity Control technology, centrally-shielded burnable absorber (CSBA). To enhance the ATOM core safety, CrAl-coated Zircaloy-4 is adopted as an accident-tolerant-fuel cladding. For a long operational cycle, the reference ATOM core has primarily accomplished with a single-batch fuel management (FM). In this paper, for more flexible operation and enhanced fuel utilization, various multi-batch FMs are investigated while the core performance is maintained in terms of both neutronic and safety aspects. These aspects are refueling pattern, cycle length, burnup Reactivity swing, discharge burnup, axial and radial power peaking factor (PPF), total PPF, and temperature coefficients. Several refueling types are examined: In-out (low leakage), out-in (flattened power), and randomly scattered schemes. In addition, new heavy reflector designs, ZrO2 and PbO, are introduced instead of stainless steel reflector for an improved core performance. Moreover, a new CSBA loading pattern is also proposed for an effective Reactivity Control of multi-batch FM strategy. Numerical results show that with a two-batch FM the cycle length can achieve above 2 years with an average discharge burnup of 40 GWd/tU, while the burnup Reactivity swing remains less than 1,200 pcm. On top of that, the coolant and fuel temperature coefficients are highly negative at the beginning of cycle and power profile is comparable to that with the single-batch FM. All calculations in these multi-physics assessments of the ATOM core are performed using a Monte Carlo-diffusion hybrid code system based on Monte Carlo Serpent 2 and nodal diffusion COREDAX codes
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an advanced core design for a soluble boron free small modular reactor atom with centrally shielded burnable absorber
Nuclear Engineering and Technology, 2019Co-Authors: Xuan Ha Nguyen, Chihyung Kim, Yonghee KimAbstract:Abstract A complete solution for a soluble-boron-free (SBF) small modular reactor (SMR) is pursued with a new burnable absorber concept, namely centrally-shielded burnable absorber (CSBA). Neutronic flexibility of the CSBA design has been discussed with fuel assembly (FA) analyses. Major design parameters and goals of the SBF SMR are discussed in view of the reactor core design and three CSBA designs are introduced to achieve both a very low burnup Reactivity swing (BRS) and minimal residual Reactivity of the CSBA. It is demonstrated that the core achieves a long cycle length (∼37 months) and high burnup (∼30 GWd/tU), while the BRS is only about 1100 pcm and the radial power distribution is rather flat. This research also introduces a supplementary Reactivity Control mechanism using stainless steel as mechanical shim (MS) rod to obtain the criticality during normal operation. A further analysis is performed to investigate the local power peaking of the CSBA-loaded FA at MS-rodded condition. Moreover, a simple B4C-based Control rod arrangement is proposed to assure a sufficient shutdown margin even at the cold-zero-power condition. All calculations in this neutronic-thermal hydraulic coupled investigation of the 3D SBF SMR core are completed by a two-step Monte Carlo-diffusion hybrid methodology.
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An advanced core design for a soluble-boron-free small modular reactor ATOM with centrally-shielded burnable absorber
Elsevier, 2019Co-Authors: Xuan Ha Nguyen, Chihyung Kim, Yonghee KimAbstract:A complete solution for a soluble-boron-free (SBF) small modular reactor (SMR) is pursued with a new burnable absorber concept, namely centrally-shielded burnable absorber (CSBA). Neutronic flexibility of the CSBA design has been discussed with fuel assembly (FA) analyses. Major design parameters and goals of the SBF SMR are discussed in view of the reactor core design and three CSBA designs are introduced to achieve both a very low burnup Reactivity swing (BRS) and minimal residual Reactivity of the CSBA. It is demonstrated that the core achieves a long cycle length (∼37 months) and high burnup (∼30 GWd/tU), while the BRS is only about 1100 pcm and the radial power distribution is rather flat. This research also introduces a supplementary Reactivity Control mechanism using stainless steel as mechanical shim (MS) rod to obtain the criticality during normal operation. A further analysis is performed to investigate the local power peaking of the CSBA-loaded FA at MS-rodded condition. Moreover, a simple B4C-based Control rod arrangement is proposed to assure a sufficient shutdown margin even at the cold-zero-power condition. All calculations in this neutronic-thermal hydraulic coupled investigation of the 3D SBF SMR core are completed by a two-step Monte Carlo-diffusion hybrid methodology. Keywords: Small modular reactor, Soluble-boron-free (SBF), Centrally-shielded burnable absorber (CSBA), ATOM, Serpent-COREDA
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advancements in the development of low enriched uranium nuclear thermal rockets
Energy Procedia, 2017Co-Authors: Paolo Venneri, Yonghee KimAbstract:Abstract This paper presents an overview of the latest developments in the designing of low-enriched uranium nuclear thermal rockets (LEU-NTR). The concept is first introduced and explained in the context of human exploration of Mars and the development time frames associated with current and future research. The need for LEU fuel is established and the process by which LEU fuel is introduced is described. The importance of the moderator to fuel ratio is explained and the size limitations associated with the cooling requirements of the core are detailed. Once the general performance and neutronic requirements have been established, a series of design issues are identified including current trends for their successful resolution. These include the minimization of active Reactivity Control in reactor operation and the resolution of the full-submersion criticality accident. The implementation of spectral shift absorbers, rapid depletion neutron poisons, specialized axial and radial reflectors, and enhanced core hydrogen worth are briefly explored and compared. Following this overview of limitations and design requirements for LEU-NTRs, the possibility for different thrust levels is explored. Here, a comparison of two thrust classes is provided along with a development of requirements that govern the minimum core size for each thrust class.
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passive Reactivity Control of nuclear thermal propulsion reactors
Nuclear Technology, 2017Co-Authors: Paolo Venneri, Michael Eades, Yonghee KimAbstract:This paper explores the possibility of passively Controlling the Reactivity of a nuclear thermal propulsion (NTP) reactor. The objective of this study is to limit the use of the radial Control drums to start-up and shutdown procedures and ensure that the exact same operation is performed for each full-power burn. To achieve the goal, this work considers several design measures, which include a low-density burnable absorber in the tie-tube components of the core, the use of variable hydrogen density in the moderator element coolant passages, and the judicious selection of a modified mission profile to maximize the decay of 135Xe after operation. In addition, the improved stability from the enhanced fuel temperature feedback due to the implementation of low-enriched-uranium fuel is also exploited for the realization of passive Reactivity Control. In this work, a passive Reactivity Control system is implemented in the Superb Use of Low Enriched Uranium (SULEU) NTP core and analyzed in terms of its ability to...
Ehud Greenspan - One of the best experts on this subject based on the ideXlab platform.
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neutronic impact of autonomous Reactivity Control system inclusion in a breed and burn core
Progress in Nuclear Energy, 2020Co-Authors: Chris Keckler, Massimiliano Fratoni, Ehud GreenspanAbstract:Abstract This study examines the impacts induced in a large breed-and-burn core through the inclusion of Autonomous Reactivity Control (ARC) systems from the neutronics perspective. A combination of numerical and analytical techniques are used to conservatively quantify the Reactivity penalty, amount of additional tritium production, and depletion of the system absorber fluid. The Reactivity penalty is found to be negligibly small, with the largest impact resulting from the removal of fuel material to make room for the ARC system tubes. Similarly, the depletion of the absorber fluid is found to be negligible compared to the amount of fluid present. It is found that the production of tritium within the active core is also small in comparison to that which is nominally produced, while tritium production within the lower ARC system reservoir may be of concern if not adequately considered during the assembly design phase. This issue is explored and a mitigation technique is proposed. Ultimately this study concludes that there are no issues from the steady-state neutronics perspective preventing incorporation of ARC systems into typical breed-and-burn cores.
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tailoring the response of autonomous Reactivity Control arc systems
Annals of Nuclear Energy, 2017Co-Authors: Staffan Qvist, C Hellesen, Allen E Dubberley, Malwina Gradecka, T H Fanning, Ehud GreenspanAbstract:The Autonomous Reactivity Control (ARC) system was developed to ensure inherent safety of Generation IV reactors while having a minimal impact on reactor performance and economic viability. In this ...
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autonomous Reactivity Control arc principles geometry and design process
Nuclear Engineering and Design, 2016Co-Authors: Staffan Qvist, C Hellesen, Roman Thiele, Allen E Dubberley, Malwina Gradecka, Ehud GreenspanAbstract:The Autonomous Reactivity Control (ARC) system was developed to ensure inherent safety performance of Generation-IV reactors while having a minimal impact on reactor performance and economic viabil ...
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an autonomous Reactivity Control system for improved fast reactor safety
Progress in Nuclear Energy, 2014Co-Authors: Staffan Qvist, Ehud GreenspanAbstract:Abstract The Autonomous Reactivity Control (ARC) system is a new safety device that can passively provide negative Reactivity feedback in fast reactors that is sufficient to compensate for the positive coolant density Reactivity feedback even in large low-leakage cores. The ARC system is actuated by the inherent physical property of thermal expansion, and has a very small effect on core neutronics at standard operating conditions. Additionally, the ARC system does not have an identified failure mode that can introduce positive Reactivity in to the core. An ARC system can be installed in conventional fuel assemblies by replacing a limited number of fuel rods with rods that fill a safety function, providing negative Reactivity to the core in the event of coolant temperature rise above nominal. These rods are of the same outer dimensions as the fuel rods, but contain smaller-diameter inner rods that are connected to liquid-filled reservoirs at the top and bottom of the assemblies. The reservoirs are filled with two separate liquids that stay liquid and immiscible throughout the applicable temperature range of fast reactor operation. The lower reservoir contains a “neutron poison” liquid with a high neutron absorption cross-section. The upper reservoir is filled with a separate liquid with a small neutron absorption cross-section. As the temperature in the assembly increases, the liquids in the reservoirs thermally expand, effectively pushing the absorbing liquid up toward the active core region while compressing the inert gas that fills the volume above the liquid between the inner and outer tubes of the ARC rods. The ARC system can be installed, or retrofitted in to existing systems, in every fuel assembly in the core. Since ARC installations in individual fuel assemblies operate independently, the system has a high level of redundancy. ARC-systems respond to local transients as well as core-wide accident scenarios. After actuation, the system automatically returns to its initial state as temperatures decrease, without the need for intervention by reactor operators. The ARC system concept and design considerations are described and illustrated.
Aiden Peakman - One of the best experts on this subject based on the ideXlab platform.
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the core design of a small modular pressurised water reactor for commercial marine propulsion
Progress in Nuclear Energy, 2019Co-Authors: Aiden Peakman, Hywel Owen, T J AbramAbstract:Abstract If international agreements regarding the need to significantly reduce greenhouse gas emissions are to be met then there is a high probability that the shipping industry will have to dramatically reduce its greenhouse gas emissions. For emission reductions from ships greater than around 40% then alternatives to fossil fuels - such as nuclear energy - will very likely be required. A Small Modular Pressurised Water Reactor design has been developed specifically to meet the requirements of a large container ship with a power requirement of 110 MWe. Container ships have a number of requirements - including a small crew size and reduced outages associated with refuelling - that result in a greater focus on design simplifications, including the elimination of the chemical Reactivity Control system during power operation and a long core life. We have developed a novel, soluble-boron free, low power density core that does not require refuelling for 15 years. The neutronic and fuel performance behaviour of this system has been studied with conventional UO 2 fuel. The size of the pressure vessel has been limited to 3.5 m in diameter. Furthermore, to ensure the survivability of the cladding material, the coolant outlet temperature has been reduced to 285 °C from 320 °C as in conventional GWe-class PWRs, with a resulting reduction in thermal efficiency to 25%. The UO 2 core design was able to satisfactorily meet the majority of requirements placed upon the system assuming that fuel rod burnups can be limited to 100 GWd/tHM. The core developed here represents the first workable design of a commercial marine reactor using conventional fuel, which makes realistic the idea of using nuclear reactors for shipping.
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the core design of a small modular pressurised water reactor for commercial marine propulsion
arXiv: Applied Physics, 2019Co-Authors: Aiden Peakman, Hywel Owen, T J AbramAbstract:If international agreements regarding the need to significantly reduce greenhouse gas emissions are to be met then there is a high probability that the shipping industry will have to dramatically reduce its greenhouse gas emissions. For emission reductions from ships greater than around 40\% then alternatives to fossil fuels - such as nuclear energy - will very likely be required. A Small Modular Pressurised Water Reactor design has been developed specifically to meet the requirements of a large container ship with a power requirement of 110~MWe. Container ships have a number of requirements - including a small crew size and reduced outages associated with refuelling - that result in a greater focus on design simplifications, including the elimination of the chemical Reactivity Control system during power operation and a long core life. We have developed a novel, soluble-boron free, low power density core that does not require refuelling for 15 years. The neutronic and fuel performance behaviour of this system has been studied with conventional UO2 fuel. The size of the pressure vessel has been limited to 3.5 metres in diameter. Furthermore, to ensure the survivability of the cladding material, the coolant outlet temperature has been reduced to 285degC from 320degC as in conventional GWe-class PWRs, with a resulting reduction in thermal efficiency to 25%. The UO2 core design was able to satisfactorily meet the majority of requirements placed upon the system assuming that fuel rod burnups can be limited to 100 GWd/tHM. The core developed here represents the first workable design of a commercial marine reactor using conventional fuel, which makes realistic the idea of using nuclear reactors for shipping.
Staffan Qvist - One of the best experts on this subject based on the ideXlab platform.
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tailoring the response of autonomous Reactivity Control arc systems
Annals of Nuclear Energy, 2017Co-Authors: Staffan Qvist, C Hellesen, Allen E Dubberley, Malwina Gradecka, T H Fanning, Ehud GreenspanAbstract:The Autonomous Reactivity Control (ARC) system was developed to ensure inherent safety of Generation IV reactors while having a minimal impact on reactor performance and economic viability. In this ...
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autonomous Reactivity Control arc principles geometry and design process
Nuclear Engineering and Design, 2016Co-Authors: Staffan Qvist, C Hellesen, Roman Thiele, Allen E Dubberley, Malwina Gradecka, Ehud GreenspanAbstract:The Autonomous Reactivity Control (ARC) system was developed to ensure inherent safety performance of Generation-IV reactors while having a minimal impact on reactor performance and economic viabil ...
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an autonomous Reactivity Control system for improved fast reactor safety
Progress in Nuclear Energy, 2014Co-Authors: Staffan Qvist, Ehud GreenspanAbstract:Abstract The Autonomous Reactivity Control (ARC) system is a new safety device that can passively provide negative Reactivity feedback in fast reactors that is sufficient to compensate for the positive coolant density Reactivity feedback even in large low-leakage cores. The ARC system is actuated by the inherent physical property of thermal expansion, and has a very small effect on core neutronics at standard operating conditions. Additionally, the ARC system does not have an identified failure mode that can introduce positive Reactivity in to the core. An ARC system can be installed in conventional fuel assemblies by replacing a limited number of fuel rods with rods that fill a safety function, providing negative Reactivity to the core in the event of coolant temperature rise above nominal. These rods are of the same outer dimensions as the fuel rods, but contain smaller-diameter inner rods that are connected to liquid-filled reservoirs at the top and bottom of the assemblies. The reservoirs are filled with two separate liquids that stay liquid and immiscible throughout the applicable temperature range of fast reactor operation. The lower reservoir contains a “neutron poison” liquid with a high neutron absorption cross-section. The upper reservoir is filled with a separate liquid with a small neutron absorption cross-section. As the temperature in the assembly increases, the liquids in the reservoirs thermally expand, effectively pushing the absorbing liquid up toward the active core region while compressing the inert gas that fills the volume above the liquid between the inner and outer tubes of the ARC rods. The ARC system can be installed, or retrofitted in to existing systems, in every fuel assembly in the core. Since ARC installations in individual fuel assemblies operate independently, the system has a high level of redundancy. ARC-systems respond to local transients as well as core-wide accident scenarios. After actuation, the system automatically returns to its initial state as temperatures decrease, without the need for intervention by reactor operators. The ARC system concept and design considerations are described and illustrated.
T J Abram - One of the best experts on this subject based on the ideXlab platform.
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the core design of a small modular pressurised water reactor for commercial marine propulsion
Progress in Nuclear Energy, 2019Co-Authors: Aiden Peakman, Hywel Owen, T J AbramAbstract:Abstract If international agreements regarding the need to significantly reduce greenhouse gas emissions are to be met then there is a high probability that the shipping industry will have to dramatically reduce its greenhouse gas emissions. For emission reductions from ships greater than around 40% then alternatives to fossil fuels - such as nuclear energy - will very likely be required. A Small Modular Pressurised Water Reactor design has been developed specifically to meet the requirements of a large container ship with a power requirement of 110 MWe. Container ships have a number of requirements - including a small crew size and reduced outages associated with refuelling - that result in a greater focus on design simplifications, including the elimination of the chemical Reactivity Control system during power operation and a long core life. We have developed a novel, soluble-boron free, low power density core that does not require refuelling for 15 years. The neutronic and fuel performance behaviour of this system has been studied with conventional UO 2 fuel. The size of the pressure vessel has been limited to 3.5 m in diameter. Furthermore, to ensure the survivability of the cladding material, the coolant outlet temperature has been reduced to 285 °C from 320 °C as in conventional GWe-class PWRs, with a resulting reduction in thermal efficiency to 25%. The UO 2 core design was able to satisfactorily meet the majority of requirements placed upon the system assuming that fuel rod burnups can be limited to 100 GWd/tHM. The core developed here represents the first workable design of a commercial marine reactor using conventional fuel, which makes realistic the idea of using nuclear reactors for shipping.
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the core design of a small modular pressurised water reactor for commercial marine propulsion
arXiv: Applied Physics, 2019Co-Authors: Aiden Peakman, Hywel Owen, T J AbramAbstract:If international agreements regarding the need to significantly reduce greenhouse gas emissions are to be met then there is a high probability that the shipping industry will have to dramatically reduce its greenhouse gas emissions. For emission reductions from ships greater than around 40\% then alternatives to fossil fuels - such as nuclear energy - will very likely be required. A Small Modular Pressurised Water Reactor design has been developed specifically to meet the requirements of a large container ship with a power requirement of 110~MWe. Container ships have a number of requirements - including a small crew size and reduced outages associated with refuelling - that result in a greater focus on design simplifications, including the elimination of the chemical Reactivity Control system during power operation and a long core life. We have developed a novel, soluble-boron free, low power density core that does not require refuelling for 15 years. The neutronic and fuel performance behaviour of this system has been studied with conventional UO2 fuel. The size of the pressure vessel has been limited to 3.5 metres in diameter. Furthermore, to ensure the survivability of the cladding material, the coolant outlet temperature has been reduced to 285degC from 320degC as in conventional GWe-class PWRs, with a resulting reduction in thermal efficiency to 25%. The UO2 core design was able to satisfactorily meet the majority of requirements placed upon the system assuming that fuel rod burnups can be limited to 100 GWd/tHM. The core developed here represents the first workable design of a commercial marine reactor using conventional fuel, which makes realistic the idea of using nuclear reactors for shipping.
