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Journal Articles

Improving the safety of the power supply system by separating the power supply circuit for control in the power distribution board in Tokai Reprocessing Plant

Goto, Sho; Aoki, Kenji; Morimoto, Kenji; Tsuboi, Masatoshi; Isozaki, Naohiko; Furukawa, Ryuichi; Kitagawa, Osamu; Fukaya, Yasuhiro*

Nihon Hozen Gakkai Dai-17-Kai Gakujutsu Koenkai Yoshishu, p.517 - 520, 2021/07

no abstracts in English

Journal Articles

Dose reduction measure in exchange work of valves used for agitation of highly active liquid waste in storage tank

Isozaki, Naohiko; Morimoto, Kenji; Furukawa, Ryuichi; Tsuboi, Masatoshi; Yada, Yuji; Miyoshi, Ryuta; Uchida, Toyomi; Ikezawa, Kazumi*; Kurosawa, Kenji*

Nihon Hozen Gakkai Dai-16-Kai Gakujutsu Koenkai Yoshishu, p.225 - 228, 2019/07

Highly active liquid waste, which is generated by the reprocessing of spent nuclear fuel, is stored in storage tank of Tokai Reprocessing Plant until it is vitrified. The waste solution in the tank is periodically agitated to avoid the precipitation of insoluble residues during the storage. Three way valves and ball valves have been located at the tank for agitation. Radiation dose rate at the valve location is high and operator's radiation exposure become a problem. Therefore, measures to reduce radiation exposure are performed and reported in this presentation.

Journal Articles

Complex chemistry with complex compounds

Eichler, R.*; Asai, Masato; Brand, H.*; Chiera, N. M.*; Di Nitto, A.*; Dressler, R.*; D$"u$llmann, Ch. E.*; Even, J.*; Fangli, F.*; Goetz, M.*; et al.

EPJ Web of Conferences, 131, p.07005_1 - 07005_7, 2016/12

 Times Cited Count:2 Percentile:65

In recent years gas-phase chemical studies assisted by physical pre-separation allowed for the productions and investigations of fragile single molecular species of superheavy elements. The latest highlight is the formation of very volatile hexacarbonyl compound of element 106, Sg(CO)$$_{6}$$. Following this success, second-generation experiments were performed to measure the first bond dissociation energy between the central metal atom and the surrounding ligand. The method using a tubular decomposition reactor was developed and successfully applied to short-lived Mo(CO)$$_{6}$$, W(CO)$$_{6}$$, and Sg(CO)$$_{6}$$.

Journal Articles

Decomposition studies of group 6 hexacarbonyl complexes, 1; Production and decomposition of Mo(CO)$$_6$$ and W(CO)$$_6$$

Usoltsev, I.*; Eichler, R.*; Wang, Y.*; Even, J.*; Yakushev, A.*; Haba, Hiromitsu*; Asai, Masato; Brand, H.*; Di Nitto, A.*; D$"u$llmann, Ch. E.*; et al.

Radiochimica Acta, 104(3), p.141 - 151, 2016/03

 Times Cited Count:28 Percentile:96.25(Chemistry, Inorganic & Nuclear)

Conditions of the production and decomposition of hexacarbonyl complexes of short-lived Mo and W isotopes were investigated to study thermal stability of the heaviest group 6 hexacarbonyl complex Sg(CO)$$_6$$. A tubular flow reactor was tested to decompose the hexacarbonyl complexes and to extract the first bond dissociation energies. A silver was found to be the most appropriate reaction surface to study the decomposition of the group 6 hexacarbonyl. It was found that the surface temperature at which the decomposition occurred was correlated to the first bond dissociation energy of Mo(CO)$$_6$$ and W(CO)$$_6$$, indicating that the first bond dissociation energy of Sg(CO)$$_6$$ could be determined with this technique.

Journal Articles

In situ synthesis of volatile carbonyl complexes with short-lived nuclides

Even, J.*; Ackermann, D.*; Asai, Masato; Block, M.*; Brand, H.*; Di Nitto, A.*; D$"u$llmann, Ch. E.*; Eichler, R.*; Fan, F.*; Haba, Hiromitsu*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 303(3), p.2457 - 2466, 2015/03

 Times Cited Count:13 Percentile:78.31(Chemistry, Analytical)

Rapid In situ synthesis of metal carbonyl complexes has been demonstrated using short-lived isotopes produced in nuclear fission and fusion reactions. The short-lived isotopes with high recoil energy directly react with carbon-monoxides and form carbonyl complexes. Only highly volatile complexes were fast transported in a gas stream to counting and chemistry devices. Short-lived Mo, Tc, Ru, Rh, W, Re, Os, and Ir were found to form volatile carbonyl complexes, while no volataile complex of Hf and Ta were detected. This technique has been applied to a chemical investigation of the superheavy element Sg (atomic number 106), and will be applicable to various fields of nuclear science with short-lived transition metal isotopes.

Journal Articles

Synthesis and detection of a Seaborgium carbonyl complex

Even, J.*; Yakushev, A.*; D$"u$llmann, Ch. E.*; Haba, Hiromitsu*; Asai, Masato; Sato, Tetsuya; Brand, H.*; Di Nitto, A.*; Eichler, R.*; Fan, F. L.*; et al.

Science, 345(6203), p.1491 - 1493, 2014/09

 Times Cited Count:57 Percentile:83.21(Multidisciplinary Sciences)

A new superheavy element complex, a seaborgium carbonyl, has been successfully synthesized, and its adsorption property has been studied using a cryo-thermochromatography and $$alpha$$-detection apparatus COMPACT. Nuclear reaction products of short-lived $$^{265}$$Sg preseparated with a gas-filled recoil ion separator GARIS at RIKEN were directly injected into a gas cell filled with He/CO mixture gas, and chemical reaction products of volatile carbonyl complexes were trasported to COMPACT. The Sg carbonyl complex detected with COMPACT was found to be very volatile with adsorption enthalpy of $$-$$50 kJ/mol, from which we have concluded that this complex should be a Sg hexacarbonyl Sg(CO)$$_{6}$$. This is the first synthesis of organometallic compounds of transactinide elements for which only simple inorganic comounds have been synthesized so far.

Journal Articles

Experiment and analyses for 14 MeV neutron streaming through a dogleg duct

Yamauchi, Michinori*; Ochiai, Kentaro; Morimoto, Yuichi*; Wada, Masayuki*; Sato, Satoshi; Nishitani, Takeo

Radiation Protection Dosimetry, 116(1-4), p.542 - 546, 2005/12

 Times Cited Count:3 Percentile:25.24(Environmental Sciences)

no abstracts in English

Journal Articles

Dogleg duct streaming experiment with 14 MeV neutron source

Morimoto, Yuichi*; Ochiai, Kentaro; Nishio, Takashi*; Wada, Masayuki*; Yamauchi, Michinori*; Nishitani, Takeo

Journal of Nuclear Science and Technology, 41(Suppl.4), p.42 - 45, 2004/03

no abstracts in English

Journal Articles

Shutdown dose evaluation experiment for ITER

Morimoto, Yuichi*; Ochiai, Kentaro; Sato, Satoshi; Hori, Junichi; Yamauchi, Michinori*; Nishitani, Takeo

Fusion Engineering and Design, 69(1-4), p.643 - 648, 2003/09

 Times Cited Count:3 Percentile:26.32(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Neutronics experiments for DEMO blanket at JAERI/FNS

Sato, Satoshi; Ochiai, Kentaro; Hori, Junichi; Verzilov, Y. M.; Klix, A.; Wada, Masayuki*; Terada, Yasuaki*; Yamauchi, Michinori*; Morimoto, Yuichi*; Nishitani, Takeo

Nuclear Fusion, 43(7), p.527 - 530, 2003/07

 Times Cited Count:15 Percentile:45.64(Physics, Fluids & Plasmas)

no abstracts in English

JAEA Reports

Chaotic behavior in a system simulating the pressure balanced injection system; Analysis of passive safety reactor behavior, JAERI's nuclear research promotion program, H12-012 (Contract research)

Madarame, Haruki*; Okamoto, Koji*; Tanaka, Gentaro*; Morimoto, Yuichiro*; Sato, Akira*; Kondo, Masaya

JAERI-Tech 2003-017, 156 Pages, 2003/03


no abstracts in English

Journal Articles

Development of in-vessel neutron monitor using micro-fission chambers for ITER

Yamauchi, Michinori*; Nishitani, Takeo; Ochiai, Kentaro; Morimoto, Yuichi*; Hori, Junichi; Ebisawa, Katsuyuki*; Kasai, Satoshi; Walker, C.*

Review of Scientific Instruments, 74(3), p.1730 - 1734, 2003/03

 Times Cited Count:22 Percentile:70.65(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Radioactivity production around the surface of a cooling water pipe in a D-T fusion reactor by sequential charged particle reactions

Hori, Junichi; Maekawa, Fujio; Wada, Masayuki*; Ochiai, Kentaro; Yamauchi, Michinori*; Morimoto, Yuichi*; Terada, Yasuaki; Klix, A.; Nishitani, Takeo

Fusion Engineering and Design, 63-64, p.271 - 276, 2002/12

 Times Cited Count:2 Percentile:17.6(Nuclear Science & Technology)

In order to the waste management method and the safety design of future D-T fusion reactor, it is important to consider the radioactivity productions via not only primary neutron reactions but also sequential charged particle reactions (SCPR). Especially, on the surface of a coolant channel many recoiled protons are generated by the neutron irradiation with coolant water, so it is apprehensive that the undesirable radioactive nuclide production yields via SCPR are enhanced. In this work, the laminated sample pieces of fusion material foils (V, Fe, W, Ti, Pb, Cu) were made and attached on a polyethylene board to simulate water flowing inside a coolant channel. They were irradiated with D-T neutrons. The effective radioactivity cross section and the depth distribution of the radioactivity production yields due to SCPR were obtained for each material. On the other hand, the estimated values were compared with the experimental ones.

Journal Articles

Decay heat measurement of fusion related materials in an ITER-like neutron field

Morimoto, Yuichi*; Ochiai, Kentaro; Maekawa, Fujio; Wada, Masayuki*; Nishitani, Takeo; Takeuchi, Hiroshi

Journal of Nuclear Materials, 307-311(Part2), p.1052 - 1056, 2002/12

 Times Cited Count:0 Percentile:0.01(Materials Science, Multidisciplinary)

Decay heat is one of the most important factors for the safety aspect of ITER. Especially, prediction of decay heat with uncertainty less than 15% for the three most important materials, i.e., copper, type-316 stainless steel (SS-316) and tungsten, is strongly requested by designers of ITER. To provide experimental decay heat data needed for validation of decay heat calculations for SS316 and copper, an experiment was conducted as the ITER/EDA task T-426. An ITER-like neutron field was constructed, and decay heat source distributions in thick copper and SS316 plates were measured with Whole Energy Absorption Spectrometer. The measured decay heat distributions in the thick sample plates were compared with the predicted values by MCNP calculations. It was found that the use of an effective activation cross section calculated by MCNP was needed to consider the self-shielding effects and, for both cases, MCNP calculations could predict decay heat adequately.

Journal Articles

Neutronics experiment of $$^{6}$$Li-enriched breeding blanket with Li$$_{2}$$TiO$$_{3}$$/Be/F82H assembly using D-T neutrons

Ochiai, Kentaro; Klix, A.; Hori, Junichi; Morimoto, Yuichi*; Wada, Masayuki*; Nishitani, Takeo

Journal of Nuclear Science and Technology, 39(Suppl.2), p.1147 - 1150, 2002/08

Thermal blanket type as one of conceptual designs for DEMO-fusion blanket is proposed. We have irradiated the trial blanket assembly which was stratified 95-% enriched Li2TiO3,F82H and beryllium block using Fusion Neutron Source (FNS) and verified the accuracy of these parameters by measurements of tritium and gamma-ray emitted from samples of95-% enriched Li2TiO3 and F82H. We have used the liquid scintillated counter as the method of tritium measurement. Activation foils, NE213, Si-SBD and Fission chamber have usedto measure neutron fluence. Moreover, we have concurrently measured the gamma rays of 56Mn, 54Mn, 187W and 51Cr was produced by 56Fe(n,p), 54Fe(n,p), 186W(n,g), 52Cr(n,2n) and 50Cr(n,g) in F82H. We have used the JENDL Fusion File library and MCNP to verify the accuracy tritium-production rate and 56Mn, 54Mn, 187W and 51Cr. From the results of above experiments, MCNP that uses the JENDL-FF nuclear data library can predict the nuclear parameters such as TPR, Nb, 56Mn, In and 54Mn in the test assemblies within an accuracy of 10%.

Journal Articles

Tritium measurements for $$^{6}$$Li-enriched Li$$_{2}$$TiO$$_{3}$$ breeding blanket experiments with D-T neutrons

Klix, A.; Ochiai, Kentaro; Terada, Yasuaki; Morimoto, Yuichi*; Yamauchi, Michinori*; Hori, Junichi; Nishitani, Takeo

Fusion Science and Technology, 41(3, Part2), p.1040 - 1043, 2002/05

$$^{6}$$Li-enriched Li$$_{2}$$TiO$$_{3}$$ is one of the candidate materials for the breeding blanket of the fusion DEMO reactor. Therefore, it is necessary to measure the tritium production performance and estimate the accuracy of the measurement method. The JAERI Fusion Neutronics Source (FNS) group has carried out experiments with breeding blanket mock-ups composed of layers of beryllium, ferritic steel F82H and enriched Li$$_{2}$$TiO$$_{3}$$. Pellets of enriched Li$$_{2}$$TiO$$_{3}$$ with a diameter of 12mm and a thickness of 2mm were used as detectors inside the tritium breeding layer. After irradiation, the pellets were dissolved and the tritium activity in the sample solution was measured by liquid scintillation counting. The experimentally obtained tritium production profile in the lithium titanate layer agreed well with MCNP calculations within the estimated error of the measured values (10%). The calculation-experiment ratio was close to one for all samples. Tritium loss from the pellet during storage time (a few days) was experimentally found to be negligible.

JAEA Reports

Performance test of micro-fission chambers for in-vessel neutron monitoring of ITER

Yamauchi, Michinori*; Nishitani, Takeo; Ochiai, Kentaro; Morimoto, Yuichi*; Hori, Junichi; Ebisawa, Katsuyuki*; Kasai, Satoshi

JAERI-Tech 2002-032, 41 Pages, 2002/03


A micro-fission chamber and a dummy chamber without uranium were fabricated and the performance was tested. They are designed to be installed inside the vacuum vessel of compact ITER (ITER-FEAT) for neutron monitoring. Vacuum leak rate of the chamber, resistances between central conductor and outer sheath, and mechanical strength up to 50G acceleration were confirmed to meet design criteria. Gamma-ray sensitivity was measured with $$^{60}$$Co gamma-ray irradiation facility at JAERI Takasaki. The output signals for gamma-rays in Campbelling mode were estimated to be less than 0.1% those by neutrons at the location behind the blanket module in ITER-FEAT. Detector response for 14 MeV neutrons was investigated with the FNS facility. Excellent linearity between count rates and neutron fluxes was confirmed. According to the test for the change of surrounding materials, the sensitivity was enhanced by slow-downed neutrons, which agreed with the calculation result by MCNP-4C code. As a result, it was concluded that the developed micro-fission chamber is applicable for ITER-FEAT.

Journal Articles

Benchmark experiment on silicon carbide with D-T neutrons and validation of nuclear data libraries

Maekawa, Fujio; Ochiai, Kentaro; Shibata, Keiichiro*; Kasugai, Yoshimi; Wada, Masayuki*; Morimoto, Yuichi*; Takeuchi, Hiroshi

Fusion Engineering and Design, 58-59, p.595 - 600, 2001/11

 Times Cited Count:11 Percentile:63.1(Nuclear Science & Technology)

no abstracts in English

JAEA Reports

Fusion neutronics plan in the development of fusion reactor; With the aim of realizing electric power

Nakamura, Hiroo; Morimoto, Yuichi*; Ochiai, Kentaro; Sugimoto, Masayoshi; Nishitani, Takeo; Takeuchi, Hiroshi

JAERI-Review 2000-016, 47 Pages, 2000/10


no abstracts in English

Oral presentation

$$alpha$$-$$gamma$$ coincidence spectroscopy of $$^{259}$$Rf using a mixed Cf target

Asai, Masato; Tsukada, Kazuaki; Kasamatsu, Yoshitaka*; Sato, Tetsuya; Toyoshima, Atsushi; Ishii, Yasuo; Takahashi, Ryuta; Nagame, Yuichiro; Ishii, Tetsuro; Nishinaka, Ichiro; et al.

no journal, , 

$$gamma$$ rays following the $$alpha$$ decay of $$^{259}$$Rf have been observed for the first time by means of $$alpha$$-$$gamma$$ coincidence spectroscopy. $$^{259}$$Rf was produced via the $$^{251}$$Cf($$^{12}$$C,4n)$$^{259}$$Rf reaction at the JAEA tandem accelerator. Two $$gamma$$ lines were observed at 97.3 and 146.7 keV in coincidence with the 8770 keV $$alpha$$ transition of $$^{259}$$Rf. The energy differences and intensities of these $$gamma$$ transitions, which are very similar to those in the $$alpha$$ decay of $$^{257}$$No with the same neutron number N = 155, allow us to assign the 3/2$$^{+}$$[622] configuration to the 146.7 keV level in $$^{255}$$No as well as to the ground state of $$^{259}$$Rf. This result indicates that the order of neutron orbitals should be inverted between $$^{255}$$Fm and $$^{257}$$No in $$N=155$$ isotones.

28 (Records 1-20 displayed on this page)