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Kazuya Idemitsu Last modified date:2020.09.28



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Homepage
https://kyushu-u.pure.elsevier.com/en/persons/kazuya-idemitsu
 Reseacher Profiling Tool Kyushu University Pure
Phone
092-802-3492
Fax
092-802-3501
Academic Degree
Ph.D
Country of degree conferring institution (Overseas)
No
Field of Specialization
Nuclear Engineering
Total Priod of education and research career in the foreign country
01years06months
Outline Activities
I am studying on nuclear materials especially nuclear fuels and radioactive wastes. For new nuclear fuels, our group are developing sol-gel method to fabricate cermet fuels, ceramic in metal matrix, which will be used in LWR, FBR and ADS. For waste management, our group is researching dissolution of glass waste, sorption of radionuclides on natural minerals and migration of radionuclides in the minerals.
Research
Research Interests
  • Migration Behavior of Selenium in the Presence of Iron in Bentonite
    keyword : Se, XAFS, electro-migration, bentonite, migration behavior, reducing condition, corrosion
    2012.04~2014.03.
  • Study on cement based waste for radioactive iodine
    keyword : Iodine, cement, XAFS, electro-migration, bentonite, migration behavior, reducing condition, corrosion
    2008.04~2012.03.
  • Migration behavior of radioactive elements in compacted bentonite by electro-migration method
    keyword : electro-migration, bentonite, migration behavior, reducing condition, corrosion
    2002.04~2010.03.
Current and Past Project
  • Plutonium incineration in a uranium-free fuel by a once-throuh cycle in LRWs followed by geological disposal of the rock-like materials as a high level waste is researched. Guidelines for the choice of inert matrix and burnable poison are disscussed for burning both LRR grade and weapon grade plutonium.
Academic Activities
Papers
1. Kazuya Idemitsu, Ryota Yamada, #Masayuki Hirakawa, #Yuki Kakoi, Yaohiro Inagaki, Tatsumi Arima, Migration Behavior of Copper in Compacted bentonite Using Electromigration Technique, MRS Advances Vol.5 Issue3-4, pp. 141-147, Jamuary 2020, Cambridge University Press, DOI: 10.1557/adv.2020.55, 5, 3-4, 141-147, 2020.01.
2. Kazuya Idemitsu, Ryota Yamada, Masayuki Hirakawa, Yuki Kakoi, Hajime Arimitsu, Yaohiro Inagaki, Tatsumi Arima, Effect of Carbonate on the Migration Behavior of Strontium in Compacted Bentonite, MRS Advances, 10.1557/adv.2019.81, 4, 17-18, 1021-1027, 2019.01, The apparent diffusion coefficients of strontium in compacted bentonites were investigated at various concentrations of NaHCO3. Purified sodium bentonite Kunipia-F® was compacted with a jig into cylindrical pellets 10 mm in diameter and 10 mm high with dry densities of 1.0 to 1.6 Mg/m 3 . Each bentonite pellet was inserted into an acrylic resin column and saturated with carbonated water containing 0.1 to 1.0 M NaHCO3 for more than 1 month. The face of the bentonite specimen was spiked with 5 μL of 1.0 M SrCl2 tracer solution. After a few weeks, the strontium diffusion profiles were measured by inductively coupled plasma-mass spectrometry. The apparent diffusion coefficients of strontium decreased slightly with increasing dry density. NaHCO3 concentrations of 0.5 M decreased the apparent diffusion coefficients of strontium by half at a dry density of 1.0 Mg/m 3 and quarter at 1.6 Mg/m 3 . At a higher NaHCO3 concentration of 1.0 M, no strontium diffusion profile was observed, whereas white precipitate was observed on the face of the bentonite specimen where it was spiked with strontium. This white precipitate could be strontianite, which is strontium carbonate. Diffusion experiments using cesium were carried out for comparison, and the presence of carbonate had no effect on the apparent diffusion coefficient..
3. Kazuya Idemitsu, Kazuyuki Fujii, Noriyuki Maeda, Yuki Kakoi, Noriya Okubo, Yaohiro Inagaki, Tatsumi Arima, Effect of Carbonate on the Migration Behavior of Lanthanides in Compacted Bentonite, MRS Advances, 10.1557/adv.2018.184, 3, 21, 1155-1160, 2018.01, The apparent diffusion coefficients of La, Nd, Eu, Dy, Er, and Lu in compacted bentonites were investigated at various bicarbonate concentrations. The apparent diffusion coefficients of these lanthanides tended to decrease with increasing dry density. At bicarbonate concentrations below 0.25 M, lanthanum had the largest diffusion coefficient (ca. 10-13 m2/s) at 1.0 Mg/m3, and the diffusion coefficient decreased with increasing atomic number. On the other hand, at bicarbonate concentrations above 0.25 M, lutetium had the largest diffusion coefficient, and the diffusion coefficient decreased with decreasing atomic number. In particular, lanthanum and neodymium had diffusion coefficients below 10-14 m2/s, even at 1.0 Mg/m3. The diffusion coefficient of europium was around 10-13 m2/s at 1.0 Mg/m3 and was influenced less by the bicarbonate concentration. The diffusion coefficient of lutetium increased from 2 × 10-14 to 10-12 m2/s as the bicarbonate concentration was increased to 1.0 M. The concentration of carbonate ion in the pore water of bentonite is estimated to be much lower than that in solutions in contact with bentonite from the viewpoints of solubility and chemical species of lanthanides..
4. Kazuya Idemitsu, Noriya Okubo, Yaohiro Inagaki, Tatsumi Arima, Daisuke Akiyama, Kenji Konashi, Makoto Watanabe, Plutonium Migration in Compacted Bentonite with Iron Corrosion for 15 Years, MRS Advances, 10.1557/adv.2017.12, 2, 12, 693-698, 2017.01, In disposal of high-level radioactive waste, carbon steel overpack will be corroded after closure of the repository, creating a reducing, low-pH environment around the repository. A plutonium diffusion experiment was performed over 15 years with Kunigel V1, which is a typical Japanese bentonite that contains about 50% montmorillonite, in contact with an iron coupon. A tracer solution (10 L) containing 1 kBq of 238Pu was applied at the interface between the iron coupon and compacted bentonite that was saturated with deionized water. After the diffusion period, the plutonium distribution in the bentonite specimen was measured with an alpha scintillation counter, and the iron and sodium distributions were obtained by inductively coupled plasma-mass spectrometry. Plutonium penetrated into the bentonite to a depth of 2 mm, and more than 90% of plutonium remained in corrosion product at the interface. The bentonite around the interface was dark green like green rust or magnetite according to visual observation. Iron was detected throughout the bentonite and there was a particularly high iron concentration from the interface to a depth of 2 mm, whereas the sodium concentration decreased slightly from the interface to 2 mm. We proposed that ferrous ions diffused into bentonite as the iron coupon corroded and precipitated such as magnetite. The magnetite precipitation would decrease the bentonite pH, resulting in the dissolution and migration of plutonium. Small cracks were also observed 2 to 6 mm from the interface and could have been formed by the migration of hydrogen generated by corrosion..
5. Ryo Hamada, Noriyuki Maeda, Kazuya Idemitsu, Yaohiro Inagaki, Tatsumi Arima, Daisuke Akiyama, Kenji Konashi, Makoto Watanabe, Shin Ichi Koyama, Effect of pH on Plutonium Migration Behavior in Compacted Bentonite, MRS Advances, 10.1557/adv.2017.183, 1, 61, 4011-4017, 2016.01, In disposing of high-level radioactive waste, the drop in pH in the repository as the iron overpack corrodes must be considered. Plutonium migration behavior may be affected by the pH of pore water in compacted bentonite barriers in high-level waste repositories. To examine the effect of pH on migration behavior, H-bentonite was prepared by treating Japanese Na-bentonite, Kunipia-F, with hydrochloric acid. Diffusion experiments were performed with mixtures of Na- and H-bentonites. The pH value in the pore water of the water-saturated bentonite mixtures decreased from 8 to 3 as the mixing ratio of H-bentonite increased. Diffusion experiments were carried out by using 238Pu then apparent diffusion coefficients were determined from the plutonium distribution in the specimens. The apparent diffusion coefficients were on the order of 10-13 to 10-12 m2/s at pH values lower than 4, whereas they were less than 10-14 m2/s at pH values higher than 6.5. These results indicate that plutonium diffused faster as Pu3+ or PuO2 2+ due to disproportionation at lower pH while plutonium could be retarded as Pu(OH)4 0 by sorption on bentonite at higher pH..
6. Kazuya Idemitsu, Tomofumi Sakuragi, Current Status of Immobilization Techniques for Geological Disposal of Radioactive Iodine in Japan, Proceedings of Materials Research Society Symposium on Scientific Basis for Nuclear Waste Management XXXVIII, 10.1557/opl.2015.297, Vol.1744, pp., 2015.04.
7. Daisuke Akiyama, Kazuya Idemitsu, Yaohiro Inagaki, tatsumi arima, Kenji Konashi, Shinichi Koyama, Migration behavior of plutonium affected by ferrous ion in compacted bentonite by using electrochemical technique, Proceedings of Materials Research Society Symposium on Scientific Basis for Nuclear Waste Management XXXVII, Vol.1665, pp.79-84, 2015.02.
8. Kazuya Idemitsu, Hikaru Kozaki, Daisuke Akiyama, Masanao Kishimoto, Masaru Yuhara, Noriyuki Maeda, Yaohiro Inagaki, Tatsumi Arima, Migration behavior of selenium in the presence of iron in Bentonite, Journal of Fluid Mechanics, 10.1557/opl.2014.641, 1665, 2014.11, Selenium (Se) is an important element for assessing the safety of high-level waste disposal. Se is redox-sensitive, and its oxidation state varies from -2 to 6 depending on the redox conditions and pH of the solution. Large quantities of ferrous ions formed in bentonite due to corrosion of carbon steel overpack after the closure of a repository are expected to maintain a reducing environment near the repository. Therefore, the migration behavior of Se in the presence of Fe in bentonite was investigated by electrochemical experiments. Na2SeO3 solution was used as tracer solution. Dry density range of bentonite was from 0.8 to 1.4 ×103 kg/m3. Results indicated that Se was strongly retained by the processes such as precipitation reaction with ferrous ions in bentonite. Se K-edge X-ray absorption near-edge structure (XANES) measurements were performed at the BL-11 beamline at SAGA Light Source, and the results revealed that the oxidation state of Se in the bentonite remained Se(IV)..
9. Kazuya Idemitsu, Yoshihiko Matsuki, Masanao Kishimoto, Yaohiro Inagaki, Tatsumi Arima, Yoshiko Haruguchi, Yu Yamashita, Michitaka Sasoh, Migration of Iodine Solidified in Ettringite into Compacted Bentonite, Advances in Materials Science for Environmental and Energy Technologies II, 10.1002/9781118751176, 241, 23-34, 2013.08, Nuclear reprocessing plants produce materials containing radioactive iodine-129. Cement can be used to immobilize and solidify radioactive iodine by fixing it in the form of the iodate ion in the mineral ettringite. Because the half-life of 129I is 15.7 million years, radioactive wastes that contain 129I require disposal by burial deep underground. In the disposal of such wastes, compacted bentonite is used as a buffer material as well as the disposal of high-level radioactive wastes. Because there is a concern that radioactive iodine could leak from disposed wastes by diffusion through compacted bentonite over a long period, the release behavior of iodine from ettringite was examined by means of electromigration studies in compacted bentonite. Most of the calcium and iodine is retained within the structure of iodate-containing ettringite (IO3-AFt), even if the chemical form of iodine changes from iodate to iodide ion as a result of reaction with ferrous ions. However, acid produced by precipitation of ferric hydroxide might destroy the structure of IO3-AFt in cementitious materials and cause release of iodine. It might therefore be necessary to adopt measures to prevent intrusion of acid or ferrous ions into cementitious wastes containing radioactive iodine..
10. Kazuya Idemitsu, Daisuke Akiyama, Yoshihiko Matsuki, Yusuke Irie, Yaohiro Inagaki, Tatsumi Arima, Migration Behaviour of Lanthanides in Compacted Bentonite with Iron Corrosion Product Using Electrochemical Method
, Proceedings of Materials Research Society Symposium on Scientific Basis for Nuclear Waste Management XXXV, Vol.1475, pp.611-616, 2012.07.
11. Y.Matsuki, K.Idemitsu, D.Akiyama, Y.Inagaki, T.Arima, Migration Behavior of Iodine in Compacted Bentonite, Proceedings of the10th International Conference GLOBAL2011, No.500826, 2011.12.
12. Kazuya Idemitsu, Daisuke Akiyama, Akira Eto, Yoshihiko Matsuki, Yaohiro Inagaki, Tatsumi Arima, Migration Behavior of Alkali Earth Ions in Compacted Bentonite with Iron Corrosion Product Using Electrochemical Method, Proceedings of Materials Research Society Symposium on Scientific Basis for Nuclear Waste Management XXXIV, Vol.1265, pp.227-232, 2010.11.
13. Kazuya Idemitsu, Hirotomo Ikeuchi, Daisuke Akiyama, Yaohiro Inagaki, Tatsumi Arima, Migration Behavior of Potassium and Rubidium in Compacted Bentonite Under Reducing Condition with Iron Corrosion Product, Proceedings of Materials Research Society Symposium on Scientific Basis for Nuclear Waste Management XXXIII, Vol.1193 pp.453-460, 2010.02.
14. K. Idemitsu, H. Ikeuchi, S. A. Nessa, Y. Inagaki, T. Arima, S. Yamazaki, T. Mitsugashira, M. Hara, Y. Suzuki, Migration Behavior of Plutonium in Compacted Bentonite Under Reducing Conditions Controlled with Potentiostat, Proceedings of Materials Research Society Symposium on Scientific Basis for Nuclear Waste Management XXXII, Vol.1124 pp.283-288, 2009.06.
15. Kauzya. IDEMITSU, Syeda Afsarun NESSA, Shigeru. YAMAZAKI, Hirotomo IKEUCHI, Yaohiro. INAGAKI , T. ARIMA, Migration Behavior of Ferrous Ion in Compacted Bentonite Under Reducing Conditions Controlled with Potentioatat., Proceedings of Materials Research Society Symposium on Scientific Basis for Nuclear Waste Management XXXI, Vol.1107, pp.501-508, 2008.09.
16. K. IDEMITSU, Y. YAMASAKI, Syeda Afsarun NESSA, Y. INAGAKI , T. ARIMA, T.MITSUGASHIRA, M.HARA and Y.SUZUKI, Migration Behavior of Plutonium in Compacted Bentonite Under Reducing Condition using Electromigration, Proceedings of Materials Research Society Symposium on Scientific Basis for Nuclear Waste Management XXX, Vol.985, pp.443-448, 2007.06.
17. Syeda Afsarun NESSA, K. IDEMITSU, Y. YAMASAKI, Y. INAGAKI and T. ARIMA, Measurement of pH of the Compacted Bentonite under the Reducing Condition, Memoirs of the Faculty of Engineering Kyushu University, Vol. 67 No.1 pp. 25-31, 2007.03.
18. S. MIYAMOTO, S. UEHARA, M. SASOH, M. SATO, M. TOYOHARA, K.IDEMITSU, S. MATSUMURA, Characterization of Cement Alteration Process by Transmission Electron Microscopy with High Spatial Resolution, Journal of Nuclear Science and Technology, Vol.43, No.11, pp.1370-1378, 2006.11.
19. Y. Inagaki, T. Saruwatari, K. Idemitsu, T. Arima, A. Shinkai, H. Yoshikawa, M. Yui, Temperature Dependence of Long-term Alteration Rate for Aqueous Alteration of P0798 Simulated Waste Glass under Smectite Forming Conditions., Proceedings of Materials Research Society Symposium on Scientific Basis for Nuclear Waste Management XXIX, Vol.932, pp.321-328, 2006.06.
20. K. Yamaguchi, Y. Inagaki, T. Saruwatari, K. Idemitsu, T. Arima, H. Yoshikawa, M. Yui, Kinetics of Aqueous Alteration of P0798 Simulated Waste Glass in the Presence of Bentonite., Proceedings of Materials Research Society Symposium on Scientific Basis for Nuclear Waste Management XXIX, Vol.932, pp.385-392, 2006.06.
21. K. Idemitsu, M. Yamamoto, Y. Yamasaki, Y. Inagaki , T. Arima, Migration Behavior of Cesium in Compacted Bentonite under Reducing Conditions Using Electromigration., Proceedings of Materials Research Society Symposium on Scientific Basis for Nuclear Waste Management XXIX, Vol.932, pp.943-950, 2006.06.
22. Tatsumi ARIMA, Sho YAMASAKI, Yaohiro INAGAKI, Kazuya IDEMITSU , Evaluation of Thermal Conductivity of Hypostoichiometric (U,Pu)O2-x Solid Solution by Molecular Dynamics Simulation at Temperatures up to 2000 K., Journal of Alloys and Compounds, Vol.415, pp.43-50, 2006.05.
23. Y. INAGAKI, A. SHINKAI, K. IDEMITSU, T. ARIMA, H. YOSHIKAWA, M. YUI, Aqueous alteration of Japanese simulated waste glass P0798: Effects of alteration-pjase formation on alteration rate and cesium retention, Journal of Nuclear Materials, 354 (2006) 171-184, 2006.04.
24. M. OBATA, Y. INAGAKI, T. SASAKI, K.IDEMITSU, Aqueous Corrosion Behavior of Glass Phase of Simulated Low Level Waste Form Produced by In-can type Induction-Heated Melting, Journal of Nuclear Science and Technology, Vol.43, No.2, pp.270-275, 2006.02.
25. X.XIA, K. IDEMITSU, T. ARIMA, Y. INAGAKI, T. ISHIDERA, S. KUROSAWA, K. IIJIMA, H. SATO, Corrosion of carbon steel in compacted bentonite and its effect on neptunium diffusion under reducing condition, Applied Clay Science, 10.1016/j.clay.2004.01.002, 28, 1-4, 89-100, Vol.28, pp.89-100, 2005.01.
26. K. IDEMITSU, X. XIA, Y. KIKUCHI, Y. INAGAKI, T. ARIMA, Migration Behavior of Ferrous Ions in Compacted Bentonite under Reducing Condition by Using Electromigration, Proceedings of Materials Research Society Symposium on Scientific Basis for Nuclear Waste Management XXVIII, 824, 491-496, Vol.824, pp.491-496, 2004.12.
27. K. IDEMITSU, X. XIA, Y. KIKUCHI, Y. INAGAKI, T. ARIMA, T.MITSUGASHIRA, M.HARA,Y.SUZUKI, Migration Behavior of Plutonium in Compacted Bentonite under Reducing Condition by Using Electromigration, Proceedings of Materials Research Society Symposium on Scientific Basis for Nuclear Waste Management XXVII, 807, 591-596, Vol.807, pp.591-596, 2004.04.
28. K.IDEMITSU, S.YANO, X.XIA, Y.KIKUCHI, Y.INAGAKI, T.ARIMA, Migration behavior of iron ion in compacted bentonite under reducing condition by using electromigration, Proceedings of Materials Research Society Symposium on Scientific Basis for Nuclear Waste Management XXVI, 757, 657-664, Vol.757, pp.657-664, 2004.03.
29. T. Arima, T. Tateyama, K. Idemitsu, Y. Inagaki, Reaction of yttria-stabilized zirconia with zirconium, silicon and Zircaloy-4 at high temperature: a compatibility study for cermet fuels, Journal of Nuclear Materials, 10.1016/S0022-3115(03)00129-6, 319, 24-30, Vol.319 24-30, 2003.07.
30. K. Idemitsu, T. Arima, Y. Inagaki, S. Torikai, M.A. Pouchon, Manufacturing of zirconia microsphere doped with erbia, yttria and ceria by internal gelation process as a part of a cermet fuel, Journal of Nuclear Materials, 10.1016/S0022-3115(03)00130-2, 319, 31-36, Vol.319 31-36, 2003.07.
31. T. Arima, M. Takaki, I. Sato, K. Idemitsu, Y. Inagaki, H. Furuya, Reaction of modified SUS316 with tellurium under low oxygen potentials, Corrosion Science, 10.1016/s0010-938X(03)00022-2, 45, 8, 1757-1766, Vol.45 1757-1766, 2003.03.
32. X.XIA, K.IDEMITSU, T.MITSUGASHIRA, T.ARIMA, Y.INAGAKI, Plutonium Determination in Compacted Bentonite by Using PERALS, Journal of Nuclear Science and Technology, Suppllement 3, pp.572-575, 2002.11.
33. Y.INAGAKI, K.IDEMITSU, T.ARIMA, Alteration-phase Formation and Associated Cesium Release during Alteration of R7T7 Waste Glass, Proceedings of Materials Research Society Symposium on Scientific Basis for Nuclear Waste Management XXV, Vol.713, pp.589-596, 2002.06.
34. X.XIA, Y.INAGAKI, K.IDEMITSU, T.ARIMA, Iodine Release from Silver Iodide under Reducing Condition with Iron-bearing Materials, Proceedings of Materials Research Society Symposium on Scientific Basis for Nuclear Waste Management XXV, 713, 783-790, Vol.713, pp.783-790, 2002.06.
35. N.SAKAMOTO, T.ISHIDA, T.ARIMA, K.IDEMITSU, Y.INAGAKI, Concentrations of Radiocarbon and Isotope Compositions of Stable Carbon in Food, Journal of Nuclear Science and Technology, 10.3327/jnst.39.323, 39, 4, 323-328, Vol.39, No.4, pp.323-328, 2002.04.
36. I. Sato, M. Takaki, T. Arima, H. Furuya, K. Idemitsu, Y. Inagaki, Oxidation behavior of modified SUS316 (PNC316) stainless steel under low oxygen partial pressure, Journal of Nuclear Materials, 10.1016/S0022-3115(02)00872-3, 304, 1, 21-28, Vol.304 pp.21-28, 2002.04.
37. T.ARIMA, T.MASUZUMI, H. FURUYA, K.IDEMITSU, Y.INAGAKI, Reaction of Zircaloy-4 with tellurium under different oxygen potentials, Journal of Nuclear Materials, 10.1016/S0022-3115(02)00711-0, 301, 2-3, 90-97, Vol.301, pp.90-97, 2002.01.
38. T.ARIMA, T.MASUZUMI, H. FURUYA, K.IDEMITSU, Y.INAGAKI, The oxidation kinetics and the structure of the oxide film on Zircaloy before and after the kinetic transition, Journal of Nuclear Materials, 10.1016/S0022-3115(01)00453-6, 294, 1-2, 148-153, Vol.294, pp.148-153, 2001.06.
39. K.IDEMITSU, X.XIA, T.ICHISHIMA, H.FURUYA, Y.INAGAKI, T.ARIMA, T.MITSUGASHIRA, Y.SUZUKI, Diffusion of Pu in Compacted Bentonites in the Reducing Condition with Corrosion Products of Iron, Proceedings of Materials Research Society Symposium on Scientific Basis for Nuclear Waste Management XXIII, Vol.608, pp.261-266, 2000.11.
40. M. BURGHARTZ, G. LEDERGERBER, F. INGOLD, T. XIE, F. BOTTA, K.IDEMITSU, Concepts and First Fabrication Studies of Inert Matrix Fuel for the Incineration of Plutonium, Proceedings of Workshop on Advanced Reactors with Innovative Fuels, pp.267-276, 1999.11.
41. A.OKAMOTO, K.IDEMITSU, H.FURUYA, Y.INAGAKI, T.ARIMA, Distribution Coefficients and Apparent Diffusion Coefficients of Cs in Compacted Bentonites, Proceedings of Materials Research Society Symposium on Scientific Basis for Nuclear Waste Management XXII, 556, 1091-1098, Vol.556, pp.1091-1098, 1999.11.
42. I.SATO, H. FURUYA, T.ARIMA, K.IDEMITSU, K.YAMAMOTO, Behavior of Metallic Fission Products Zirconium and Barium in Fasr Reactor Fuel Irradiated to High Burnup, Journal of Nuclear Science and Technology, Vol.36, No.9, pp.775-780, 1999.09.
43. I.SATO, H. FURUYA, T.ARIMA, K.IDEMITSU, K.YAMAMOTO, Behavior of Metallic Fission Products in Uranium-plutonium Mixed Oxide Fuel, Journal of Nuclear Materials, 10.1016/S0022-3115(99)00071-9, 273, 3, 239-247, Vol.273, pp.239-247, 1999.02.
44. T.ARIMA, K.MORIYAMA, N.GAJA, H.FURUYA, K.IDEMITSU, Y.INAGAKI, Oxidation kinetics of Zircaloy-2 between 450°C and 600°C in Oxidizing Atmosphere, Journal of Nuclear Materials, 10.1016/S0022-3115(98)00069-5, 257, 1, 67-77, Vol.257, pp.67-77, 1998.04.
45. Kazuya Idemitsu, Y. Tachi, H. Furuya, Yaohiro Inagaki, Tatsumi Arima, Diffusion of Cs and Sr in compacted bentonites under reducing conditions and in the presence of corrosion products of iron, Materials Research Society Symposium - Proceedings, 506, 1997.12, In high-level waste repositories, a carbon steel overpack will be corroded by consuming oxygen trapped in the repository after closure. Iron corrosion products are expected to interfere with migration of radionuclides by filling the pore in bentonite and sorbing radionuclides. In this study the apparent diffusion coefficients of cesium and strontium were measured in compacted Na-bentonites (Kunigel V1 and Kunipia F, JAPAN) contacted with carbon steel and its corrosion products under reducing conditions or without carbon steel under oxidizing conditions for comparison. The apparent diffusion coefficients of cesium with and without corrosion product were 2.2 to 13×10-12 m2/s. The apparent diffusion coefficients of strontium with and without corrosion product were 3.1 to 2.5×10-12 m2/s. There were significant effects of dry density (0.8 to 2.0 g/cm3) and montmorillonite contents (50% for Kunigel V1 or 100% for Kunipia F). The presence of corrosion product decreased the apparent diffusion coefficients of Cs in both bentonites and that of Sr in Kunigel V1, especially at low dry density. This may be due to corrosion product filling the pore in the bentonite, decreasing the free pore size and density for diffusion..
46. Kazuya Idemitsu, Hirotaka Furuya, Teruo Hara, Yaohiro Inagaki, Migration of cesium, strontium and cobalt in water-saturated inada granite, journal of nuclear science and technology, 10.1080/18811248.1992.9731551, 29, 5, 454-460, 1992.05, Diffusivities of Cs, Sr and Co were measured in a water-saturated granite in an attempt to investigate the migration of radionuclides into the matrix of the rock. The measured penetration profiles of every tracer were composed of two parts. There were a steep slope near the surface and a gradual slope in the deeper part. These profiles were successfully explained by considering two diffusion paths in the granite. One diffusion path was fissure with a width of a few microns and another was network of submicron pores. The volume of submicron pores was approximately 80% of the total pore volume in the granite. The orders of magnitude of apparent diffusivities for all nuclides were 10"11 to 10|12m2/s through the fissure and 10_14mz/s through the network of pores. The ratio of geometrical factors in the two paths was also calculated from each apparent diffusivity and was almost unity. This calculated ratio suggests that the pore network in the granite matrix has a similar shape to the fissure, thus the microstructure of the granite seems to be fractal..
47. Kazuya Idemitsu, Katsuhiko Ishiguro, Yasuhisa Yusa, Noriaki Sasaki, Naomi Tsunoda, Plutonium diffusivity in compacted bentonite, Engineering Geology, 10.1016/0013-7952(90)90028-Y, 28, 3-4, 455-462, 1990.01, Measurements on plutonium diffusivity in water-saturated compacted bentonite were carried out. Representative specimens of sodium bentonite were taken from the Tsukinuno and Kuroishi mines situated in northeast Japan. Tsukinuno bentonite was divided into three types: raw type, purified Na-type, and H-type which was prepared by treating Na-type bentonite with hydrochloric acid. Kuroishi bentonite contained chlorite as impurity. H-type bentonite was used as reference for the convenience of profile measurement in bentonite, since plutonium diffusivity in H-type bentonite was considered to be larger than that in Na-type bentonite because of low pH and low swelling pressure of H-type bentonite. Sampled bentonite was compacted into pellets of 20 mm in diameter and 20 mm in height. Bulk densities of these specimens were 1200-1800 kg/m3 for purified Na-type and H-type bentonite and 1600 kg/m3 for raw type bentonite. Plutonium profiles obtained in H-type bentonite can be explained by diffusion equation with constant concentration source. Diffusivity ranges from 10-13 to 10 12 m2/s for H-type and Kuroishi impure sodium bentonite. Diffusivity in both raw type and purified Tsukinuno bentonite was was estimated to less than 10-14 M2/s. Diffusivity in H-type bentonite showed a tendency to decrease with increasing density. Influence of in bentonite was also studied. Quartz content up to 50% or hematite content up to 1% did not influence diffusivity significantly in H-type bentonite. The chemical species of plutonium in pore water of Na-type and H-type were estimated Pu(OH)3-; and PuO2-, respectively..
48. Masayasu Sugisaki, Satoru Mukai, Kazuya Idemitsu, Hirotaka Furuya, Isotope effect in heat of transport of H, D and T in Nb, Journal of Nuclear Materials, 10.1016/0022-3115(83)90346-X, 115, 1, 91-94, 1983.03, The thermal diffusion of hydrogen isotopes, H and D, in Nb was studied at an average temperature of 168°C. By analyzing the redistribution of hydrogen in Nb on the basis of the irreversible thermodynamics, the heat of transport Q* was determined for H and D as 9.5 kJ/mol and 16.0 kJ/mol, respectively. The large isotope dependence of Q* was concluded by comparing these values with the value of 18.8 kJ/mol for T, which was previously reported by the present authors. The diffusion coefficients of H and D were also determined from the transient process of redistribution and found to be in good agreement with those based on the Gorsky effect..
49. Masayasu Sugisaki, Kazuya Idemitsu, Satoru Mukai, Hirotaka Furuya, Thermal diffusion of tritium in Nb metal, Journal of Nuclear Materials, 10.1016/0022-3115(82)90811-X, 104, C, 1493-1497, 1981.01, Thermal diffusion phenomena of tritium in Nb metal are studied for temperatures between 100°-300°C. Some special types of apparatus and samples are developed to determine the distribution of tritium in the transient state of the thermal diffusion. By least squares fitting of the experimental data to the theoretical curve based on irreversible thermodynamics, the heat of transport, Q*, and the diffusion coefficient, D, of tritium at an average temperature of 200°C are determined to be 18.0 kJ/mol and 1.6 x 10-5 cm2/sec, respectively. The importance of the thermal diffusion phenomena is discussed in connection with tritium permeation through the first wall of a nuclear fusion reactor..
Presentations
1. Kazuya Idemitsu, #Keisuke Yoshida, Yaohiro Inagaki, Tatsumi Arima, Migration Behavior of Copper in Compacted Bentonite Using Electromigration Techniques, Scientific Basis for Nuclear Waste Management 2019, 2019.10.
2. Kazuya Idemitsu, #Ryota Yamada, #Masayuki Hirakawa, #Yuki Kakoi, #Hajime Arimitsu, Yaohiro Inagaki, Tatsumi Arima, Effect of Carbonate on the Migration Behavior of Strontium in Compacted Bentonite, Scientific Basis for Nuclear Waste Management 2018, 2018.11.
3. Kazuya Idemitsu, #Yuki Kakoi, #Hajime Arimitsu, Yaohiro Inagaki, Tatsumi Arima, Ultra-trace level measurement of neptunium in bentonite by using ICP-QQQ, International Conference on Ceramic Materials and Components for Energy and Environmental Applications (CMCEE-12), 2018.07.
4. Kazuya Idemitsu, Kazuyuki Fujii, Noriyuki Maeda, Yuki Kakoi, Noriya Okubo, Yaohiro Inagaki, Tatsumi Arima, Effect of Carbonate on the Migration Behavior of Lanthanides in Compacted Bentonite, Scientific Basis for Nuclear Waste Management 2017, 2017.11.
5. Kazuya Idemitsu, Noriya Okubo, Yaohiro Inagaki, Tatsumi Arima, Daisuke Akiyama, Kenji Konashi, Makoto Watanabe, Plutonium Migration in Compacted Bentonite with Iron Corrosion for 15 Years, Scientific Basis for Nuclear Waste Management XL, 2016.11.
6. Kazuya Idemitsu, Ryo Hamada, Yoshitaka Ogawa, Noriya Okubo, Yaohiro Inagaki, Tatsumi Arima, Salinity Dependence of Apparent Diffusion Coefficients of Selenite, Selenate, Molybdate and Iodate in Compacted Bentonite, Goldschmidt2016, 2016.06.
7. Yaohiro Inagaki, Ryo Matsumoto, Kazuya Idemitsu, Tatsumi Arima, Dissolution Kinetics of a Simplified Nuclear waste Glass, ISG, in MgCl2 Solution, Goldschmidt2016, 2016.06.
8. Ryo Hamada, Noriyuki Maeda, Kazuya Idemitsu, Yaohiro Inagaki, Tatsumi Arima, Daisuke Akiyama, Kenji Konashi, Makoto Watanabe, Shinichi Koyama, Effect of pH on Plutonium Migration Behavior in Compacted Bentonite, Scientific Basis for Nuclear Waste Management XXXIX, 2015.10.
9. Kazuya Idemitsu, Tomofumi Sakuragi, Immobilization Techniques for Geological Disposal of Radioactive Iodine in Japan, American Ceramics Society MS&T'15, 2015.10.
10. Kazuya Idemitsu, Tomofumi Sakuragi, Current Status of Immobilization Techniques for Geological Disposal of Radioactive Iodine in Japan, Scientific Basis for Nuclear Waste Management XXXVIII, 2014.12.
11. Noriyuki Maeda, Kazuya Idemitsu, Yusuke Irie, Daisuke Akiyama, Hikaru Kozaki, Tatsumi Arima, Yaohiro Inagaki, Migration Behavior of Cesium Molybdate in Compacted Bentonite, Scientific Basis for Nuclear Fuel Cycle II, 2014.08.
12. Kazuya Idemitsu, Hikaru Kozaki, Masaru Yuhara, Tatsumi Arima, Yaohiro Inagaki, Migration Behavior of Selenite in Compacted Bentonite, Scientific Basis for Nuclear Fuel Cycle II, 2014.08.
13. Tatsumi Arima, Kazuya Idemitsu, Yaohiro Inagaki, Katsuyuki Kawamjra, Yukio Tachi, Kenji Yotsuji, Diffusion and Adsorption of Uranyl ion in Clays: Molecular Dynamics Study, Scientific Basis for Nuclear Fuel Cycle II, 2014.08.
14. Daisuke Akiyama, Kazuya Idemitsu, Yaohiro Inagaki, Tatsumi Arima, Kenji Konashi, Shinichi Koyama, Migration behavior of plutonium affected by ferrous ion in compacted bentonite by using electrochemical technique, Scientific Basis for Nuclear Waste Management XXXV, 2013.10.
15. Kazuya Idemitsu, Hikaru Kozaki, Daisuke Akiyama, Masanao Kishimoto, Masaru Yuhara, Noriyuki Maeda, Yaohiro Inagaki, tatsumi arima, Migration Behavior of Selenium in the Presence of Iron in Bentonite, Scientific Basis for Nuclear Waste Management XXXV, 2013.10, Selenium (Se) is an important element for assessing the safety of high-level waste disposal. Se is redox-sensitive, and its oxidation state varies from -2 to 6 depending on the redox conditions and pH of the solution. Large quantities of ferrous ions formed in bentonite due to corrosion of carbon steel overpack after the closure of a repository are expected to maintain a reducing environment near the repository. Therefore, the migration behavior of Se in the presence of Fe in bentonite was investigated by electrochemical experiments. Na2SeO3 solution was used as tracer solution. Dry density range of bentonite was from 0.8 to 1.4 ×103 kg/m3.
Results indicated that Se was strongly retained by the processes such as precipitation reaction with ferrous ions in bentonite. Se K-edge X-ray absorption near-edge structure (XANES) measurements were performed at the BL-11 beamline at SAGA Light Source, and the results revealed that the oxidation state of Se in the bentonite remained Se(IV)..
16. Kazuya Idemitsu, Yaohiro Inagaki, Tatsumi Arima, Daisuke Akiyama, Yusuke Irie, Hikaru Kozaki, Migration Behavior of Cesium Molybdate in Compacted Bentonite, Materials Research Society 2012, 2012.11.
Awards
  • Best Paper Award on Nuclear and Environmental Technology Division by American Ceramic Society
    Migration of Iodine Solidified in Ettringite into Compacted Bentonite
  • Best Poster Award
    Migration Behavior of Selenium in the Presence of Iron in Bentonite
Educational
Educational Activities
Graduate school
Nuclear Fuels
Non-stoichiometric materials

Undergraduate
Physical chemistry
Analytical methods
Other Educational Activities
  • 2017.12.
  • 2016.11.
  • 2016.07.
  • 2015.12.
  • 2013.12.
  • 2010.12.
  • 2010.11.
  • 2010.10.
  • 2009.12.
  • 2008.10.
  • 2009.08.
  • 2006.12.
  • 2005.10.
  • 2005.07.
  • 2001.11.
  • 1999.08.
  • 1999.07.
  • 1998.06.