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Journal Articles

Conceptual design of direct $$^{rm 99m}$$Tc production facility at the high temperature engineering test reactor

Ho, H. Q.; Ishida, Hiroki*; Hamamoto, Shimpei; Ishii, Toshiaki; Fujimoto, Nozomu*; Takaki, Naoyuki*; Ishitsuka, Etsuo

Nuclear Engineering and Design, 352, p.110174_1 - 110174_7, 2019/10

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

JAEA Reports

Report of summer holiday practical training 2018; Feasibility study on nuclear battery using HTTR core; Feasibility study for nuclear design

Ishitsuka, Etsuo; Matsunaka, Kazuaki*; Ishida, Hiroki*; Ho, H. Q.; Ishii, Toshiaki; Hamamoto, Shimpei; Takamatsu, Kuniyoshi; Kenzhina, I.*; Chikhray, Y.*; Kondo, Atsushi*; et al.

JAEA-Technology 2019-008, 12 Pages, 2019/07


As a summer holiday practical training 2018, the feasibility study for nuclear design of a nuclear battery using HTTR core was carried out. As a result, it is become clear that the continuous operations for about 30 years at 2 MW, about 25 years at 3 MW, about 18 years at 4 MW, about 15 years at 5 MW are possible. As an image of thermal design, the image of the nuclear battery consisting a cooling system with natural convection and a power generation system with no moving equipment is proposed. Further feasibility study to confirm the feasibility of nuclear battery will be carried out in training of next fiscal year.

Journal Articles

Role of multichance fission in the description of fission-fragment mass distributions at high energies

Hirose, Kentaro; Nishio, Katsuhisa; Tanaka, Shoya*; L$'e$guillon, R.*; Makii, Hiroyuki; Nishinaka, Ichiro*; Orlandi, R.; Tsukada, Kazuaki; Smallcombe, J.*; Vermeulen, M. J.; et al.

Physical Review Letters, 119(22), p.222501_1 - 222501_6, 2017/12

 Times Cited Count:26 Percentile:7.98(Physics, Multidisciplinary)

Fission-fragment mass distributions were measured for $$^{237-240}$$U, $$^{239-242}$$Np and $$^{241-244}$$Pu populated in the excitation-energy range from 10 to 60 MeV by multi-nucleon transfer channels in the reaction $$^{18}$$O + $$^{238}$$U at the JAEA tandem facility. Among them, the data for $$^{240}$$U and $$^{240,241,242}$$Np were observed for the first time. It was found that the mass distributions for all the studied nuclides maintain a double-humped shape up to the highest measured energy in contrast to expectations of predominantly symmetric fission due to the washing out of nuclear shell effects. From a comparison with the dynamical calculation based on the fluctuation-dissipation model, this behavior of the mass distributions was unambiguously attributed to the effect of multi-chance fission.

Journal Articles

Method to reduce long-lived fission products by nuclear transmutations with fast spectrum reactors

Chiba, Satoshi*; Wakabayashi, Toshio*; Tachi, Yoshiaki; Takaki, Naoyuki*; Terashima, Atsunori*; Okumura, Shin*; Yoshida, Tadashi*

Scientific Reports (Internet), 7(1), p.13961_1 - 13961_10, 2017/10

 Times Cited Count:9 Percentile:12.6(Multidisciplinary Sciences)

Transmutation of long-lived fission products (LLFPs: $$^{79}$$Se, $$^{93}$$Zr, $$^{99}$$Tc, $$^{107}$$Pd, $$^{129}$$I, and $$^{135}$$Cs) into short-lived or non-radioactive nuclides by fast neutron spectrum reactors without isotope separation has been proposed as a solution to the problem of radioactive wastes disposal. Despite investigation of many methods, such transmutation remains technologically difficult. To establish an effective and efficient transmutation system, we propose a novel neutron moderator material, yttrium deuteride (YD$$_{2}$$), to soften the neutron spectrum leaking from the reactor core. Neutron energy spectra and effective half-lives of LLFPs, transmutation rates, and support ratios were evaluated with the continuous-energy Monte Carlo code MVP-II/MVP-BURN and the JENDL-4.0 cross section library. With the YD$$_{2}$$ moderator in the radial blanket and shield regions, effective half-lives drastically decreased from 10$$^{6}$$ to 10$$^{2}$$ years and the support ratios reached 1.0 for all six LLFPs. This successful development and implementation of a transmutation system for LLFPs without isotope separation contribute to developing a self-consuming cycle of LLFPs using fast spectrum reactors to reduce radioactive waste.

Journal Articles

Fission fragments mass distributions of nuclei populated by the multinucleon transfer channels of the $$^{18}$$O + $$^{232}$$Th reaction

L$'e$guillon, R.; Nishio, Katsuhisa; Hirose, Kentaro; Makii, Hiroyuki; Nishinaka, Ichiro*; Orlandi, R.; Tsukada, Kazuaki; Smallcombe, J.*; Chiba, Satoshi*; Aritomo, Yoshihiro*; et al.

Physics Letters B, 761, p.125 - 130, 2016/10

 Times Cited Count:27 Percentile:6.1(Astronomy & Astrophysics)

Journal Articles

Parametric survey for benefit of partitioning and transmutation technology in terms of high-level radioactive waste disposal

Oigawa, Hiroyuki; Yokoo, Takeshi*; Nishihara, Kenji; Morita, Yasuji; Ikeda, Takao*; Takaki, Naoyuki*

Journal of Nuclear Science and Technology, 44(3), p.398 - 404, 2007/03

 Times Cited Count:16 Percentile:23.78(Nuclear Science & Technology)

Benefit of implementing Partitioning and Transmutation (P&T) technology was parametrically surveyed in terms of high-level radioactive waste (HLW) disposal by discussing possible reduction of the geological repository area. The results showed that, by recycling minor actinides (MA), the placement area could be reduced by 17-29% in the case of UO$$_{2}$$-LWR and by 63-85% in the case of MOX-LWR in comparison with the conventional PUREX reprocessing. This significant impact in MOX fuel was caused by the recycle of $$^{241}$$Am which was a long-term heat source. Further 70-80% reduction of the placement area in comparison with the MA-recovery case could be expected by partitioning the fission products (FP) into several groups for both fuel types.

Journal Articles

Parametric survey on possible impact of partitioning and transmutation of high-level radioactive waste

Oigawa, Hiroyuki; Yokoo, Takeshi*; Nishihara, Kenji; Morita, Yasuji; Ikeda, Takao*; Takaki, Naoyuki*

Proceedings of International Conference on Nuclear Energy System for Future Generation and Global Sustainability (GLOBAL 2005) (CD-ROM), 6 Pages, 2005/10

The benefit of implementing Partitioning and Transmutation (P&T) of high-level wastes was parametrically surveyed. The possible reduction of the geological repository area was estimated. By recycling minor actinides (MA), the repository area required for unit spent fuel was reduced significantly in the case of MOX-LWR. This effect was caused by removal of $$^{241}$$Am which is a long-term heat source. By partitioning the fission products, in addition to MA recycling, further 70-80% reduction from the MA-recovery case can be expected for both UO$$_2$$ and MOX. This significant reduction was independent of the cooling time before the partitioning process.

Journal Articles

Conceptual design study of LLFP transmutation fast reactor cores in the "feasibility study" in Japan

Naganuma, Masayuki; Takaki, Naoyuki*; Aida, Tatsuya; Mizuno, Tomoyasu

Proceedings of International Conference on Nuclear Energy System for Future Generation and Global Sustainability (GLOBAL 2005) (CD-ROM), 6 Pages, 2005/10

In this paper, promising loading method of LLFP target assemblies and LLFP transmutation performances of typical cores designed in phase-II of FS are described. As for loading method, in-core loading type is found to be most promising in LLFP inventory. LLFP transmutation performances are evaluated by applying the in-core loading method. As a result, every core is confirmed to have capability to transmute LLFP amount more than generated one for 99Tc and 129I in keeping the breeding performance.

JAEA Reports

Design Study on Core and Fuel Properties of Sodium Cooled Fast Reactor (Mixed Oxide Fuel Core); Results in JFY2003

Naganuma, Masayuki; Ogawa, Takashi; Takaki, Naoyuki; Mizuno, Tomoyasu

JNC-TN9400 2004-039, 160 Pages, 2004/06


Sodium cooled fast reactor (mixed oxide fuel core) is one of promising candidates in Feasibility Study on Commercialized Fast Reactor Cycle System in Japan (FS). Its design study has been conducted thorough FS. In JFY2003's study, two types of core were evaluated. One is "Compact type" that follows a conventional type, and the other is "High internal conversion type (HIC type)". The HIC type is core concept aiming to reduce fuel cycle cost by increasing total average burn-up. As actual measurements, large diameter fuel pins are applied to increase the internal conversion, the amount of blankets is reduced as much as possible. The main results are summarized as follows:(1) Large scale reactor (Power 1,500 MWe)The cores to satisfy requirements and targets of FS could be constructed in Compact type and HIC type. Both types of core are found to enable to attain over 1.1 of breeding ratio at initial deployment of FBR with radial blankets and 1.04 of breeding ratio at major share stage of FBR without radial blankets under 150 GWd/t of core average burn-up.The total average burn-ups of HIS type core are 91 GWd/t at initial deployment and 110 GWd/t at major share stage. The fuel cycle cost reduces by 20~40 % in comparison to Compact type core. On the other hand, HIC type core becomes large in core diameter and increases the plant construction cost. However, that effect is very benign, unit cost of electricity generation that takes account of fuel cycle cost and plant construction cost is found to decrease. HIC type is recognized to be superior to Compact type in economics.(2) Medium scale reactor (Power 750 MWe)The cores to satisfy requirements and targets of FS could be constructed in Compact type and HIC type. The tendencies of both cores' characteristics are same as those in the larger scale reactor, and the decrease of unit cost of electricity generation is found to be larger than that in the large scale reactor.

JAEA Reports

Feasibility Study on Commercialization of Fast Breeder Reactor Cycle Systems Interim Report of Phase II; Technical Study Report for Reactor Plant Systems

Konomura, Mamoru; Ogawa, Takashi; Okano, Yasushi; Yamaguchi, Hiroyuki; Murakami, Tsutomu; Takaki, Naoyuki; Nishiguchi, Youhei; Sugino, Kazuteru; Naganuma, Masayuki; Hishida, Masahiko; et al.

JNC-TN9400 2004-035, 2071 Pages, 2004/06


The attractive concepts for Sodium-, lead-bismuth-, helium- and water-cooled FBRs have been created through using typical plant features and employing advanced technologies. Efforts on evaluating technological prospects of feasibility have been paid for these concepts. Also, it was comfirmed if these concepts satisfy design requierments of capability and performance presumed in the feasibilty study on commertialization of Fast Breeder Reactor Systems. As results, it was concluded that the selection of sodium-cooled reactor was most rational for practical use of FBR technologies in 2015.

JAEA Reports

Design Studies on Small Fast Reactor Cores(III)

Sanda, Toshio; Okano, Yasushi; Takaki, Naoyuki; Naganuma, Masayuki; Uto, Nariaki; Mizuno, Tomoyasu

JNC-TN9400 2004-031, 154 Pages, 2004/06


Some concepts of small fast reactors have been studied as part of the "Feasibility Studies on Commercialized Fast Reactor Cycle System (FS)", and the core design study has been performed at two main features of "long-life core " and "enhanced passive safety" in the FS phase II. Based on the previous study, 165MWe forced circulation sodium cooled reactor with control rods was studied as the promising concept from a viewpoint of economical efficiency in JFY 2003. In the present study, the fuel reloading interval of 20 years and outlet temperature of 550 deg-C are targeted under following condition as thicker metal fuel pin diameter (less than or equal) 15mm, lower pressure drop (less than or equal) 0.75kg/cm2, and smller core diameter (less than or equal) 3m by sodium void reactivity restriction relief into design conditions avoiding core melt without SASS at ATWS. The prospect of achievement of the fuel reloading interval of 20 years and outlet temperature of 550 deg-C was acquired for "Higher Temperature Core" and "Higher Temperature and Smller Core" without blanket fuels by using a sodium-cooled metal-fueled core with single Pu enrichment fuel which has high potential of small change of space distribution of power density and high breeding ratio. These cores have core height / diameter of 127/293cm and 164/260cm, fuel burnup of 77 and 80 GWd/t, burnup reactivity of 1.2 and 1.5% (delta)k/kk', breeding ratio of 1.06 and 1.07 and coolanat void reactivity of 6 and 8${$}$, respectively. Control rod reactivity balance, fuel soundness and shielding performance were checked that these were satisfied. Moreover, since the reactivity change due to burnup was small, the possibility of long-term operation which does not require a control rod movement was also examined. In addition, the "Higher Temperature Core" was recommended for a promising core of phase-II middle time since core melt would be avoided without SASS at ATWS. Furthermore, the applicability of the Feher heat cycl

JAEA Reports

Feasibility Study of Large-Scale Helium GCFR employing Coated Particle Fuel (Designs and Comparison of Horizontal-/Ascending-Flow Cooling Fuel Assembly Cores); Annual Report of JFY2003

Okano, Yasushi; Takaki, Naoyuki; Sanda, Toshio; Mizuno, Tomoyasu

JNC-TN9400 2004-027, 203 Pages, 2004/06


He-cooled fast reactor employing coated-particle nitride fuel has been taken an interest as a part of feasibility study project of fast reactor reactor designs. Two fuel assembly (F/A) configurations have been considered as candidates. One configuration is 'Horizontal flow cooling compartment F/A', the other is 'Ascending flow cooling block F/A'. This MS deals with the best-to-date core designs with 120GWd/t average core discharge burnup to compare core/safety performances of two configuration designs. as an annual report of JFY2003.

JAEA Reports

Fuel and Core Design Study of the Sodium-cooled Fast Reactors; Studies on Metallic Fuel Cores in the JFY2003

Sugino, Kazuteru; Ogawa, Takashi; Naganuma, Masayuki; Takaki, Naoyuki

JNC-TN9400 2004-030, 117 Pages, 2004/05


For the requirement of superior economics and safety in the future commercial FBR period, metal fuel cores have been investigated, that have advantage of higher breeding capability and lower fuel inventory compared with oxide fuel cores. In this study, attractive concepts of large-size (electric output of 1,500MWe) and middle-size (750MWe) sodium cooled metal fuel core of compact type and high outlet temperature type have been constructed.

JAEA Reports

LLFP Transmutation Performance in Sodium, Pb-Bi and He Cooled Fast Reactors, II

Takaki, Naoyuki; Naganuma, Masayuki; Mizuno, Tomoyasu

JNC-TN9400 2004-028, 105 Pages, 2004/05


The LLFP transmutation performances of Sodium, Pb-Bi and He cooled fast reactors examined in the feasibility study have been investigated from view points of nuclear, thermal and material characteristics. Key design restrictions in order to assure the integrity of LLFP assembly are caused by the internal pressure of Iodine pins and the permeation of hydrogen of moderator Zr-H. These fast reactors might be feasible to cope with LLFP transmutation without any severe design modification.

JAEA Reports

Design Studies on Small Fast Reactor Cores (II)

Takaki, Naoyuki; ; Mizuno, Tomoyasu

JNC-TN9400 2003-066, 110 Pages, 2003/07


Core design studies have been performed to make a comparative evaluation on the effects of different reactivity control mechanisms and different coolant circulation methods of small fast reactors as follows, (a) 150MWe reflector-controlled forced-circulation core, (b) 150MWe forced-circulation core with control rods, (c) 150Me natural-circulation core with control rods and (d) 50MWe forced-circulation core with control rods. In the present study, the fuel reloading interval of 10 years is targeted under following conditions as fuel pin diameter $$<$$ 8.5mm, pressure drop for forced-circulation core $$<$$ 0.75kg/cm2 and sodium void reactivity for forced-circulation core $$<$$ 2$.The reactivity control mechanism of the reflector-controlled core is composed of movable radial reflector and a few additional control rods. This core attains 10 years long life and burnup of about 48GWd/t. The ATWS analyses indicate the possible passive safety feature which does not rely on the effects of radial expansion of core support plate and self-actuated shutdown system.The core with control rods shows slightly superior criticality than the reflector-controlled core due to the closer arrangement of radial reflectors. The shorter core column length and reduced fuel inventory result in improvements on the sodium void reactivity and burnup of fuels. This core also shows possible passive safety features in case of ATWS events. Ten years of control rod life time is calculated to be achievable from a viewpoint of absorber cladding mechanical interactions. Large core diameter of about 3.3m and small pin gap less than 1mm are common problems of the reflector-controlled core and core with control rods. Those are ascribed to the sodium void reactivity limitation and further works considering the economy and fabrication feasibility are necessary. The natural-circulation core with low pressure drop has large core diameter of about 3.8m and low fuel burnup of around 36GWd/t. A prominent characteristic

JAEA Reports

LLFP Transmutation Performance in Sodium,Pb-Bi and He Cooled Fast Reactors

Takaki, Naoyuki; Naganuma, Masayuki; Mizuno, Tomoyasu

JNC-TN9400 2003-054, 84 Pages, 2003/07


The performance of Sodium, Pb-Bi and He cooled fast reactors in terms of LLFP transmutation has been investigated from view points of nuclear, thermal and material characteristics. The targeted LLFP are two elements as I and Tc. Transmutation performance target set here is simultaneous achievement of the ratio of transmutation rate / production rate of 1.0 and transmutation ratio of 30% at the removal. In the thermal hydraulic analysis for the cores loaded with LLFP assemblies, it is turned out that the hydrogen penetration is still the most significant design restriction of the required coolant flow rate. MOX fueled sodium cooled and Pb-Bi cooled reactors loaded with LLFP assemblies in the core periphery region have a potential to transmute self-produced LLFP at 30% of transmutation rate without significant design modification. As for He cooled reactor, the transmutation rate is below the target value in this study.

JAEA Reports

Fuel and Core Design Study of the Sodium-cooled Fast Reactors; Studies on Metallic Fuel Cores in the JFY2002

Sugino, Kazuteru; Mizuno, Tomoyasu; Takaki, Naoyuki

JNC-TN9400 2003-056, 62 Pages, 2003/06


Based on the results obtained in the former feasibility study, the metallic fueled core of ordinary-type, that is, 2-region homogeneous core, has been established aiming at the improvement in the core performance, and subsequent comparison has been performed with the mixed oxide fueled core. Further, the attractive concept of the metallic fueled core of high outlet temperature has been constructed which has good nuclear features as a metallic fueled core and has identical outlet temperature to mixed oxide fuelled core. Following items have been found as a result of the investigation on the ordinary-type core.- The metallic fueled core whose maximum fast neutron fluence (En$$>$$0.1MeV) is set identical (5$$times$$10$$^{23}$$n/cm$$^{2)}$$to the mixed oxide fueled cores with core discharge burnup 150GWd/t has sufficient core performances as a metallic fueled core, e.g. higher breeding ratio and longer operation period compared with mixed oxide fueled cores, but the core discharge burnup is limited up to 100GWd/t. However effective discharge burnup including the contribution of the blanket region is comparative to mixed oxide cores under the same breeding ratio condition.- In order to enlarge the core discharge burnup to 150GWd/t keeping the core performance identical to above mentioned core's, the irradiation deformation of structural material should be reduced to that of mixed oxide fueled cores. Further the maximum fast neutron fluence reaches to 7 - 8$$times$$10$$^{23}$$n/cm$$^{2}$$(En$$>$$0.1MeV). The investigations on the core of high outlet temperature have clarified following items.

Journal Articles

Design Study on Sodium Cooled Fast Reactor Core Loaded with LLFP Transmutation Sub-Assemblies

Takaki, Naoyuki; Mizuno, Tomoyasu

GENES/ANP2003 NO1169, 0 Pages, 2003/00

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 capab

Journal Articles

Transmutation of cesium-135 with fast reactors

Oki, Shigeo; Takaki, Naoyuki

OECD/NEA Dai-7-Kai Bunri Henkan(P&T) Joho Kokan Kaigi, 943 Pages, 2003/00


Journal Articles

LMFBR Design and its Evolution, 2; Core Design of LMFBR

Mizuno, Tomoyasu; Uto, Nariaki; Takaki, Naoyuki

Proceedings of International Conference on Global Environment and Advanced Nuclear Power Plants (GENES4/ANP 2003) (Internet), 0 Pages, 2003/00

Sodium-cooled core design studies are performed. MOX fuel core with axial blanket partial elimination subassembly due to safety consideration is studied. This type of core with high internal conversion ratio possesses capability of achieving 26 months of

49 (Records 1-20 displayed on this page)