The feasibility of Th-²³³U fueled, homogenous breeder reactor based on matured conventional LWR t... more The feasibility of Th-²³³U fueled, homogenous breeder reactor based on matured conventional LWR technology was studied. The famous demonstration at Shipping-port showed that the Th-²³³U fueled, heterogeneous PWR with four different lattice fuels was possible to breed fissile but its low averaged burn-up including blanket fuel and the complicated core configuration were not suitable for economically competitive reactor. The authors
A 1500MWe sodium-cooled MOX fuel core loaded with LLFP sub-assemblies has been studied. The LLFP ... more A 1500MWe sodium-cooled MOX fuel core loaded with LLFP sub-assemblies has been studied. The LLFP sub-assembly contains either iodine compound pins or technetium metal pins with zirconium-hydride pins as neutron moderator to improve the transmutation capability. Neutronic and thermal-hydraulic performances are discussed with wide range of loading patterns of LLFP sub-assemblies. The most significant design limitation for LLFP sub-assembly is found to be the temperature of the moderator pins that determines the dissociated hydrogen penetration rate. To ensure the sufficient cooling for moderator pins, about 10 % of the primary system coolant flow rate is necessary to be distributed to the LLFP sub-assemblies. To transmute self-produced I and Tc simultaneously in a sodium-cooled fast reactor, it is required to apply measures for reducing hydrogen penetration from claddings of Zr-H pins and design modifications such as subdividing of coolant flow partition of the core.
Generally, an FBR (fast breeder reactor) core with U-Pu fuel has flat geometry to enhance a neutr... more Generally, an FBR (fast breeder reactor) core with U-Pu fuel has flat geometry to enhance a neutron leakage and reduce a sodium void reactivity. Thus, the neutron economy isn’t good in the FBR core. Although the η value of U-Th fuel is smaller than U-Pu fuel in a fast spectrum, that of U-Th fuel has smaller energy dependence than Pu-U fuel. Then, if we use U-Th fuel for FBR, the sodium void reactivity will be decreased. In addition, we possibly can extend a core height to enhance the neutron economy [1]. In this paper, we assume to use a Th-UO2 fuel for an FBR core to achieve a low void reactivity. We adjust the reactor specifications to obtain the optimized aspect ratio (core height/diameter) under the design constraint conditions which are quoted from Pu-U fueled JSFR. However, the breeding ratio is aimed at 1.0 as a first step. To obtain the exact breeding ratio, the effects of cooling time and loss in reprocessing etc. should be considered. Those are not treated in the present s...
An investigation on the nuclear transmutation of elemental long-lived fission product (LLFP) in a... more An investigation on the nuclear transmutation of elemental long-lived fission product (LLFP) in a fast reactor is being conducted focusing on the I-129 LLFP (half-life 15.7 million years) to reduce the environmental burden. The LLFP assembly is loaded into the radial blanket region of a Japanese MONJU class sodium-cooled fast reactor (710 MWth, 148 days/cycle). The iodine element containing I-129 LLFP (without isotope separation) is mixed with YD2 and/or YH2 moderator material to enhance the nuclear transmutation rate. We studied the optimal moderator volume fraction to maximize the transmutation rate (TR, %/year) and the support factor (SF is defined as the ratio of transmuted to produced LLFP). We also investigated the effect of LLFP assembly loading position in the radial blanket and the severe power peak appeared at the fuel assembly adjacent to the LLFP assembly.
The feasibility of Th-²³³U fueled, homogenous breeder reactor based on matured conventional LWR t... more The feasibility of Th-²³³U fueled, homogenous breeder reactor based on matured conventional LWR technology was studied. The famous demonstration at Shipping-port showed that the Th-²³³U fueled, heterogeneous PWR with four different lattice fuels was possible to breed fissile but its low averaged burn-up including blanket fuel and the complicated core configuration were not suitable for economically competitive reactor. The authors
A 1500MWe sodium-cooled MOX fuel core loaded with LLFP sub-assemblies has been studied. The LLFP ... more A 1500MWe sodium-cooled MOX fuel core loaded with LLFP sub-assemblies has been studied. The LLFP sub-assembly contains either iodine compound pins or technetium metal pins with zirconium-hydride pins as neutron moderator to improve the transmutation capability. Neutronic and thermal-hydraulic performances are discussed with wide range of loading patterns of LLFP sub-assemblies. The most significant design limitation for LLFP sub-assembly is found to be the temperature of the moderator pins that determines the dissociated hydrogen penetration rate. To ensure the sufficient cooling for moderator pins, about 10 % of the primary system coolant flow rate is necessary to be distributed to the LLFP sub-assemblies. To transmute self-produced I and Tc simultaneously in a sodium-cooled fast reactor, it is required to apply measures for reducing hydrogen penetration from claddings of Zr-H pins and design modifications such as subdividing of coolant flow partition of the core.
Generally, an FBR (fast breeder reactor) core with U-Pu fuel has flat geometry to enhance a neutr... more Generally, an FBR (fast breeder reactor) core with U-Pu fuel has flat geometry to enhance a neutron leakage and reduce a sodium void reactivity. Thus, the neutron economy isn’t good in the FBR core. Although the η value of U-Th fuel is smaller than U-Pu fuel in a fast spectrum, that of U-Th fuel has smaller energy dependence than Pu-U fuel. Then, if we use U-Th fuel for FBR, the sodium void reactivity will be decreased. In addition, we possibly can extend a core height to enhance the neutron economy [1]. In this paper, we assume to use a Th-UO2 fuel for an FBR core to achieve a low void reactivity. We adjust the reactor specifications to obtain the optimized aspect ratio (core height/diameter) under the design constraint conditions which are quoted from Pu-U fueled JSFR. However, the breeding ratio is aimed at 1.0 as a first step. To obtain the exact breeding ratio, the effects of cooling time and loss in reprocessing etc. should be considered. Those are not treated in the present s...
An investigation on the nuclear transmutation of elemental long-lived fission product (LLFP) in a... more An investigation on the nuclear transmutation of elemental long-lived fission product (LLFP) in a fast reactor is being conducted focusing on the I-129 LLFP (half-life 15.7 million years) to reduce the environmental burden. The LLFP assembly is loaded into the radial blanket region of a Japanese MONJU class sodium-cooled fast reactor (710 MWth, 148 days/cycle). The iodine element containing I-129 LLFP (without isotope separation) is mixed with YD2 and/or YH2 moderator material to enhance the nuclear transmutation rate. We studied the optimal moderator volume fraction to maximize the transmutation rate (TR, %/year) and the support factor (SF is defined as the ratio of transmuted to produced LLFP). We also investigated the effect of LLFP assembly loading position in the radial blanket and the severe power peak appeared at the fuel assembly adjacent to the LLFP assembly.
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Papers by Naoyuki Takaki