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JAEA Reports

Annual report of Nuclear Emergency Assistance and Training Center (April 1, 2009 - March 31, 2010)

Kanamori, Masashi; Shirakawa, Yusuke; Yamashita, Toshiyuki; Okuno, Hiroshi; Terunuma, Hiroshi; Ikeda, Takeshi; Sato, Sohei; Terakado, Naoya; Nagakura, Tomohiro; Fukumoto, Masahiro; et al.

JAEA-Review 2010-037, 60 Pages, 2010/09

JAEA-Review-2010-037.pdf:3.11MB

When a nuclear emergency occurs in Japan, the Japan Atomic Energy Agency (JAEA) provides technical support to the National government, local governments, police, fire station and license holder etc. They are designated public organizations conforming to the basic law on emergency preparedness and the basic plan for disaster countermeasures. The Nuclear Emergency Assistance & Training Center (NEAT) of JAEA provides a comprehensive range of technical support activities to an off-site center in case of a nuclear emergency. Specifically, NEAT gives technical advice and information, provides for the dispatch of specialist as required, supplies emergency equipments and materials to the national government and municipal office. NEAT provide various lectures and training course concerning nuclear disaster prevention for those personnel taking an active part in emergency response organizations at normal time. And NEAT researches on nuclear disaster prevention and also cooperate with international organizations. This annual report summarized the activities of JAEA/NEAT in the fiscal year 2009.

JAEA Reports

Long term treatment of waste TBP/n-dodecane with steam reforming system

Sone, Tomoyuki; Nakagawa, Akinori; Koyama, Hayato; Gunji, Kiyoshi; Nonaka, Kazuharu; Sasaki, Toshiki; Tashiro, Kiyoshi; Yamashita, Toshiyuki

JAEA-Technology 2009-023, 33 Pages, 2009/06

JAEA-Technology-2009-023.pdf:8.11MB

Steam reforming (SR) method consists of the gasification process in which organics are vaporized and decomposed with superheated steam and the oxidation process in which vaporized organics are decomposed by oxidizing reaction with heated air. 2,500L of waste TBP/n-dodecane contaminated with uranium was treated using the demonstration scale steam reforming system to examine the performance of the system. Results obtained in this study show that the temperature in the SR system was controlled under the self-regulation temperature, the concentration of CO and NOx in the off-gas were controlled less than 100ppm and 250ppm respectively, the distribution ratio of uranium to off-gas treatment system was under 0.12% and the gasification ratio of waste TBP was more than 99%. This long-term waste treatment test has demonstrated that the SR system can safely and effectively reduce the volume of the waste.

JAEA Reports

Thermal treatment for TRU waste sorting

Sasaki, Toshiki; Aoyama, Yoshio; Yamashita, Toshiyuki

JAEA-Technology 2009-001, 33 Pages, 2009/03

JAEA-Technology-2009-001.pdf:2.92MB

A thermal treatment that can automatically unpack TRU waste and remove hazardous materials has been developed to reduce the risk of radiation exposure and save operation cost. The thermal treatment is a process of removing plastic wrapping and hazardous material from TRU waste by heating waste at 500 to 700 $^{circ}$ C. Plastic wrappings of simulated wastes were removed using a laboratory scale thermal treatment system. Celluloses and isoprene rubbers that must be removed from waste for disposal were pyrolyzed by the treatment. Although the thermal treatment can separate lead and aluminum from the waste, a further technical development is needed to separate lead and aluminum. Future technology development subjects for the TRU waste thermal treatment system are summarized.

Journal Articles

Fuel performance evaluation of rock-like oxide fuels

Shirasu, Noriko; Kuramoto, Kenichi; Nakano, Yoshihiro; Yamashita, Toshiyuki; Kimura, Yasuhiko; Nihei, Yasuo; Ogawa, Toru

Journal of Nuclear Materials, 376(1), p.88 - 97, 2008/05

https://doi.org/10.1016/j.jnucmat.2008.01.019

Times Cited Count：13 Percentile：64.63(Materials Science, Multidisciplinary)

The concept of the rock-like oxide (ROX) fuel has been developed for the annihilation of excess plutonium in light water reactors. Irradiation tests and post-irradiation examinations were carried out on candidate ROX fuels. The ternary fuel of YSZ-spinel-corundum system, the single-phase fuels of YSZ, the particle dispersed fuels of YSZ in spinel or corundum matrix, and the blended fuels of YSZ and spinel or corundum matrix were fabricated and submitted to irradiation tests. The fuels containing spinel showed chemical instabilities with the vaporization of MgO component, which caused fuel restructuring. The swelling behavior was improved with the particle-dispersed fuels. However, the particle-dispersed fuels showed higher fractional gas release (FGR) than blended type fuels. The FGR of YSZ single-phase fuels were comparable to what would be expected for UO $_{2}$ fuels. The YSZ single-phase fuel showed the best irradiation performance among the ROX fuels investigated.

Journal Articles

Study of rock-like oxide fuels under irradiation

Shirasu, Noriko; Kuramoto, Kenichi; Nakano, Yoshihiro; Yamashita, Toshiyuki; Ogawa, Toru

Journal of Power and Energy Systems (Internet), 2(1), p.145 - 152, 2008/00

https://doi.org/10.1299/jpes.2.145

To evaluate the irradiation behavior of the rock-like oxide fuel, irradiation experiments were carried out. Three fuels were prepared; a single phase fuel of yttria-stabilized zirconia containing UO $_{2}$ (U-YSZ) and two types of particle-dispersed fuels of U-YSZ particles in spinel or corundum matrix. These fuels were irradiated in JRR-3 for about 280 days. The burnups were about 11% FIMA. The fission gas release rate (FGR) was determined by puncture test and gas analysis. Corundum-based fuel showed extremely high FGR (88%). The temperature of U-YSZ single-phase fuel pellets was highest among the fuels, because of its low thermal conductivity. Nevertheless the U-YSZ single-phase fuel showed very low FGR (5%). Microstructure analyses of irradiated fuel pellets were carried out by ceramography and EPMA. The restructuring of fuel pellet was not observed in the spinel-based fuel irradiated below 1400 K.

Journal Articles

Study of rock-like oxide fuels under irradiation

Shirasu, Noriko; Kuramoto, Kenichi; Nakano, Yoshihiro; Yamashita, Toshiyuki; Ogawa, Toru

Proceedings of 15th International Conference on Nuclear Engineering (ICONE-15) (CD-ROM), 7 Pages, 2007/04

To evaluate the irradiation behavior of the rock-like oxide fuel, irradiation experiments were carried out. Three fuels were prepared; a single phase fuel of yttria-stabilized zirconia containing UO $_{2}$ (U-YSZ) and two particle-dispersed fuels of U-YSZ particles in spinel or corundum matrix. These fuels were irradiated in JRR-3 for about 280 days. The burnups were about 11% FIMA. The fission gas release rate (FGR) was determined by puncture test and gas analysis. Corundum-based fuel showed extremely high FGR (88%). On the other hand, the U-YSZ single-phase fuel showed very low FGR (5%). Microstructure analyses for irradiated fuel pellets were carried out by ceramography and EPMA. The restructuring of fuel pellet was not observed in the spinel-based fuel irradiated below 1400 K. Significant appearance changes were not also observed for corundum-based fuel.

Journal Articles

Post-irradiation examination on particle dispersed rock-like oxide fuel

Shirasu, Noriko; Kuramoto, Kenichi*; Yamashita, Toshiyuki; Ichise, Kenichi; Ono, Katsuto; Nihei, Yasuo

Journal of Nuclear Materials, 352(1-3), p.365 - 371, 2006/06

https://doi.org/10.1016/j.jnucmat.2006.03.002

Times Cited Count：4 Percentile：30.68(Materials Science, Multidisciplinary)

To evaluate irradiation behavior of the ROX fuel, irradiation experiment was carried out using 20% enriched U instead of Pu. Three fuels were prepared; a single phase fuel of YSZ containing UO $_{2}$ (U-YSZ), two particle-dispersed fuels of U-YSZ particle in spinel or corundum matrix. The U-YSZ particles were prepared by crashing presintered U-YSZ pellets and by sieving them. These fuels were irradiated in Japan Research Reactor No.3 for 13 cycles, about 300 days. Though many cracks were observed in the pellets by X-ray photographs, significant appearance changes were not observed for all fuel pins. Distribution of typical FPs was analyzed by the scanning over the fuel pin. Non-volatile nuclide remained in the fuel pellet. On the other hand, a part of Cs moved to the gaps between the pellets and to the insulators. $^{134}$ Cs and $^{137}$ Cs showed different distributions at the plenum. Fuel pellets were taken out from fuel pins without bonding. Spinel decomposition and subsequent restructuring were not observed probably due to low irradiation temperature.

JAEA Reports

Proceedings of the 9th Symposium on JAERI's Reimei Research Program; June 28-29, 2005

Yamashita, Toshiyuki

JAERI-Conf 2005-011, 205 Pages, 2005/09

JAERI-Conf-2005-011.pdf:39.4MB

The Reimei (Dawn) Research Program is a research project based on public application to be conducted within the framework of the Reimei Research Promotion project of the Japan Atomic Energy Research Institute. The objective of the program is to encourage original and/or unique ideas in the field of fundamental nuclear science and nuclear energy. The Symposium on JAERI's Reimei Research Program carried out in the 2004 fiscal year was held at Tokai Research Establishment on 28th and 29th of June 2005. 38 papers were reported through the short presentation followed by the poster presentation. These presented papers were compiled in the proceedings. We hope that new researches will be grown and developed by the help of Reimei Research Promotion project.

Journal Articles

Phase equilibria and thermal expansion of CaTiO $_{3}$ doped with neptunium

Sato, Tsuyoshi*; Yamashita, Toshiyuki; Matsui, Tsuneo*

Journal of Nuclear Materials, 344(1-3), p.67 - 72, 2005/09

https://doi.org/10.1016/j.jnucmat.2005.04.018

Times Cited Count：3 Percentile：24.22(Materials Science, Multidisciplinary)

Phase relationships between NpO $_{2}$ and CaTiO $_{3}$ or Ca(Ti, Al)O $_{3}$ were investigated by X-ray diffraction (XRD) analysis, using specimens prepared at 1773 K in Ar-8%H $_{2}$ . Single phase solid solutions were formed 0-7.5 mol%Np and 1-10 mol%Np for CaTiO $_{3}$ and Ca(Ti, Al)O $_{3}$ , respectively. By substituting Al for Ti in CaTiO $_{3}$ , Np solubility in Ca(Ti, Al)O $_{3}$ increased. Solubility of Np was compared with those of U and Pu, and was discussed with oxidation states and ionic radii of dopants. Thermal expansions of (Ca,Np)TiO $_{3}$ were measured from room temperature to 1273 K in Ar-8%H $_{2}$ using high-temperature XRD technique. These specimens showed nearly the same value of volumetric thermal expansion coefficients, suggesting that the incorporation of tetravalent Np into CaTiO $_{3}$ had practically no effect on stabilization of the crystal lattice. This finding was in a marked contrast to that of Pu doped CaTiO $_{3}$ , where pronounced stabilization in the crystal was observed by incorporating Pu into CaTiO $_{3}$ .

Journal Articles

Oxygen potential measurements of fluorite-type Zr $_{0.5}$ Pu $_{0.5}$ O $_{2-y}$ by EMF method

Otobe, Haruyoshi; Nakamura, Akio; Yamashita, Toshiyuki; Minato, Kazuo

Journal of Nuclear Materials, 344(1-3), p.219 - 222, 2005/09

https://doi.org/10.1016/j.jnucmat.2005.04.045

Times Cited Count：3 Percentile：24.22(Materials Science, Multidisciplinary)

Actinides-bearing zirconias are prominent candidate materials for various nuclear applications: targets for actinide transmutation, inert material fuels, radioactive waste forms, etc. In this study, the oxygen potential (g(O $_{2}$ )) behavior of fluorite-type (F-type) Zr $_{0.5}$ Pu $_{0.5}$ O $_{2-y}$ has been measured by EMF method using the zirconia oxygen sensor. It was found that the g(O $_{2}$ ) values of F-type Zr $_{0.5}$ Pu $_{0.5}$ O $_{2-y}$ were about 150 kJ/mol higher than those of F-type PuO $_{2-y}$ at the same oxygen-nonstoichiometric (O/M) values. The g(O $_{2}$ ) values of F-type Zr $_{0.5}$ Pu $_{0.5}$ O $_{2-y}$ were 50 kJ/mol lower than those of pyrochlore Zr $_{2}$ Pu $_{2}$ O $_{7+x}$ at the same O/M values. These results suggest that the g(O $_{2}$ ) behavior depends on the cation and anion ordering/disordering, in addition to the cation composition ratio (Zr/Pu).

Journal Articles

Mass-spectrometric study of PuCd $_{2}$

Nakajima, Kunihisa; Arai, Yasuo; Yamashita, Toshiyuki

Journal of Physics and Chemistry of Solids, 66(2-4), p.639 - 642, 2005/02

https://doi.org/10.1016/j.jpcs.2004.06.072

Times Cited Count：2 Percentile：12.62(Chemistry, Multidisciplinary)

PuCd $_{2}$ intermetallic compound was prepared by heating pure Pu and Cd metals at about 950K. PuCd $_{2}$ was found to be a prototype of CdI $_{2}$ by means of powder X-ray diffractometry. Mass-spectrometric experiment was performed in the temperature range of 650-770K. It was found that the vapor pressures of Cd over PuCd $_{2}$ +Pu were three to five orders of magnitude lower than those over Cd in this temperature range. From these vapor pressures, Gibbs free energy of formation of PuCd $_{2}$ was evaluated.

Journal Articles

Electrochemical behaviors of PuN and (U, Pu)N in LiCl-KCl eutectic melts

Shirai, Osamu; Kato, Tetsuya*; Iwai, Takashi; Arai, Yasuo; Yamashita, Toshiyuki

Journal of Physics and Chemistry of Solids, 66(2-4), p.456 - 460, 2005/02

https://doi.org/10.1016/j.jpcs.2004.06.040

Times Cited Count：8 Percentile：37.11(Chemistry, Multidisciplinary)

Electrochemical behaviors of PuN and (U, Pu)N in the LiCl-KCl eutectic melt containing UCl $_{3}$ and PuCl $_{3}$ at 773 K were investigated by cyclic voltammetry. The electrochemical dissolution of PuN and (U, Pu)N began nearly at -1.0 V vs. the Ag/AgCl reference electrode. The rest potentials of PuN and (U, Pu)N were observed at about 0.15 V more negative potential than that of UN since the equilibrium potential of UN is about 0.15 V more positive than that of PuN. In the cyclic voltammogram measured by using (U, Pu)N as the working electrode, a steep rise of the positive current was observed at more positive potential than -0.4 V in analogy with the cyclic voltammogram measured by using UN as the working electrode. In addition, there were two anodic current waves in the voltammogram with (U, Pu)N, though the wave form was not clear. This indicates that UN and PuN would be dissolved independently irrespective of formation of the solid solution, (U, Pu)N.

Journal Articles

Oxygen potential and defect structure of oxygen-excess pyrochlore Ce $_{2}$ Zr $_{2}$ O $_{7+x}$

Otobe, Haruyoshi; Nakamura, Akio; Yamashita, Toshiyuki; Minato, Kazuo

Journal of Physics and Chemistry of Solids, 66(2-4), p.329 - 334, 2005/02

https://doi.org/10.1016/j.jpcs.2004.07.015

Times Cited Count：23 Percentile：65.92(Chemistry, Multidisciplinary)

Pyrochlore-type (P-type) zirconias have been attracting significant research interest as disposable forms of high-level radioactive waste. In this work, we have clarified the oxygen potentials (g(O $_{2}$ )) vs. oxygen nonstoichiometry (x) and temperature relations of P-type Ce $_{2}$ Zr $_{2}$ O $_{7+x}$ by the emf method and determined the lattice parameters (a0) with respect to x by XRD method.

Journal Articles

Development of Rock-like Oxide Fuel, an innovative nuclear fuel for burning plutonium

Yamashita, Toshiyuki

Seramikkusu, 39(10), p.817 - 821, 2004/10

https://ci.nii.ac.jp/naid/10013742635

no abstracts in English

Journal Articles

A New type of neptunyl(VI) hydroxide which is topologically similar to -UO $_{2}$ (OH) $_{2}$

Nakada, Masami; Kitazawa, Takafumi*; Saito, Takashi*; Wang, J.*; Takeda, Masuo*; Yamashita, Toshiyuki; Saeki, Masakatsu

Bulletin of the Chemical Society of Japan, 76(7), p.1375 - 1378, 2003/07

https://doi.org/10.1246/bcsj.76.1375

Times Cited Count：6 Percentile：30.03(Chemistry, Multidisciplinary)

no abstracts in English

Journal Articles

Irradiation behavior of rock-like oxide fuels

Yamashita, Toshiyuki; Kuramoto, Kenichi; Shirasu, Noriko; Nakano, Yoshihiro; Akie, Hiroshi; Nagashima, Hisao; Kimura, Yasuhiko; Omichi, Toshihiko*

Journal of Nuclear Materials, 320(1-2), p.126 - 132, 2003/07

https://doi.org/10.1016/S0022-3115(03)00178-8

Times Cited Count：10 Percentile：56.43(Materials Science, Multidisciplinary)

Two irradiation tests on the rock-like oxide (ROX) fuels, small disk-shape fuel targets and pellet-type fuels, were performed in order to clarify in-pile irradiation stabilities. Swelling, fractional fission gas release (FGR) and phase change were examined by puncture test, profilometry and ceramography. YSZ single-phase fuel showed an excellent irradiation behavior, ie. low fission gas release (less than 3%), negligible swelling and no appreciable restructuring. The particle dispersed fuels showed lower swelling and higher fission gas release than those of mechanically blended fuels. Spinel decomposition and subsequence restructuring in the spinel matrix fuels was observed for the first time in the present investigation. It would be possible to reduce the FGR of the spinel matrix fuels, if the maximum fuels temperature is limited below 1700 K where neither spinel decomposition nor restructuring was observed. Damaged area of spinel matrix due to fission fragment irradiation seemed to be confined to thin layers around the surface of YSZ particles.

Journal Articles

Morphology change of rock-like oxide fuels in reactivity-initiated-accident simulation tests

Nakamura, Takehiko; Sasajima, Hideo; Yamashita, Toshiyuki; Uetsuka, Hiroshi

Journal of Nuclear Materials, 319, p.95 - 101, 2003/06

https://doi.org/10.1016/S0022-3115(03)00139-9

Times Cited Count：2 Percentile：19(Materials Science, Multidisciplinary)

Pulse irradiation tests under simulated RIA conditions were performed with three types of ROX fuels. Single phase YSZ, homogeneous mixture of YSZ/spinel and YSZ particle dispersed in spinel type ROX fuels were pulse irradiated in the Nuclear Safety Research Reactor (NSRR). Mode and threshold of the fuel failure including its consequences were investigated under the RIA conditions. The fuel failure occurred in a burst type mode in all the three types of ROX fuel tests with considerable fuel melting. Even though the mode was quite different from those of UO $_{2}$ fuel, failure threshold enthalpies of the ROX fuels were close to that of UO $_{2}$ fuel at about 10 GJ m $^{-3}$ . The consequence of the failure of the ROX fuels was different from the one of UO $_{2}$ fuel, because molten fuel dispersal occurred at lower enthalpies in the ROX fuel tests. Change of the fuel structure and material interaction in the transient heating conditions were examined through optical and secondary electron microscopy, and electron probe micro analysis.

Journal Articles

Irradiation effects on yttria-stabilized Zirconia irradiated with neon ions

Hojo, Tomohiro; Aihara, Jun; Hojo, Kiichi; Furuno, Shigemi*; Yamamoto, Hiroyuki; Nitani, Noriko; Yamashita, Toshiyuki; Minato, Kazuo; Sakuma, Takaaki*

Journal of Nuclear Materials, 319, p.81 - 86, 2003/06

https://doi.org/10.1016/S0022-3115(03)00137-5

Times Cited Count：18 Percentile：74.43(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles