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Nishi-Tokyo-shi, Japan

Doi R.,Japan Atomic Energy Agency | Tachikawa H.,Nuclear Safety Research Association | Yui M.,Japan Atomic Energy Agency
Journal of Nuclear Science and Technology | Year: 2010

To evaluate the long-term performance of a geological disposal system for high-level radioactive wastes (HLW), selenium-79 (Se) solubility and its solubility-limiting solid phase(s) were investigated in the presence of iron (Fe) under reducing conditions. Se is one of the key radionuclides in the safety assessment of a HLW repository because Se forms anions and has a low coefficient of sorption onto geological materials. The formation of Fe-Se solids is expected due to the release of Fe(II) by Fe overpack corrosion. Experiments in both bentonite-equilibrated and pure waters were performed in the presence of Fe under reducing conditions. With bentonite (Kunigel V1®), the experimental conditions were within the bounds of the FeSe2(cr) stability field when plotted on an Eh-pH diagram; however, no Se solid phases could be identified in the experiments by X-ray diffraction (XRD). With pure water, the experimental conditions were in the same FeSe2(cr) stability field. After 1 month, the experimental system was under a transitional condition which moved toward true equilibrium from oversaturation and Se concentration decreased as a likely result of the precipitation of FeSe2(cr), although it remains possible that FeSe(cr) controlled Se concentration if the water had an initial pH = 7. Se(cr) could not control Se concentration because Se concentration decreased to below Se solubility, even though XRD identified Se(cr) as the dominant solid phase. After 2 and 3.5 months, the transformation from Se(cr) to the Fe-Se solid phase (FeSe2(cr), FeSe(cr)) could be identified by XRD. © Atomic Energy Society of Japan. Source

Kawakami H.,Japan Nuclear Energy Safety Organization | Aoki H.,Japan Nuclear Energy Safety Organization | Tochiyama O.,Nuclear Safety Research Association | Suzuki A.,Japan Atomic Energy Agency
Transactions of the Atomic Energy Society of Japan | Year: 2011

This paper describes the objectives and specific applicational issues of the document authorized by the Nuclear Safety Commission entitled "Policy of the safety assessment of subsurface disposal after the period for active control", focusing on the policy of assessment for the appropriateness of burial depth. Concerning the burial depth of subsurface disposal, the proposal of 50-100 m from the surface has been made by the Atomic Energy Commission as a sufficient depth to avoid general usage of the underground environment, furthermore, taking into account these circumstances, the above document stipulates the new policy of assessment for the appropriateness of burial depth considering uplift/erosion noted in the safety assessment for long-lived radioactive materials. In the case of considering uplift/erosion, the isolation from the living environment planned in the original scheme will be gradually lost, the disposal facility will come close to the surface and become near-surface disposal in the long term. This paper describes the required roles of burial depth for subsurface disposal considering the long-term evolutional changes, introduces the physical protection capability to human intrusion as one of the protective functions of engineered barriers, and discusses the specific important issues related to the actual application. © 2011 Atomic Energy Society of Japan, All Rights Reserved. Source

Ishikawa I.,Toyo University | Kawai H.,TokyoUniversity of Science | Kobayashi Y.,Technostar Co. | Shioya R.,Toyo University | Yagawa G.,Nuclear Safety Research Association
Procedia Engineering | Year: 2014

We have been developing aneigenvalue analysis solver as a module of the ADVENTURE system; freely available computer aided engineering system for large-scale finite element analysis.In this paper, we introduce the preliminary development of sequentialeigenvalue analysis solver before parallelizing the solver. Thissequentialsolverhasasimple implementation of theinverse iteration method,and will be used for verificationofparallelsolver we plan to develop in next step.From the results of this solver, the influence of the assumption we will made for the next step parallel solver could be verified. © 2014 The Authors. Published by Elsevier Ltd. Source

Matsumoto M.,Japan National Institute of Radiological Sciences | Yamanaka T.,Japan Nuclear Energy Safety Organization | Hayakawa N.,MHI Nuclear Engineering Co. | Iwai S.,Japan Atomic Energy Agency | And 2 more authors.
Radiation Protection Dosimetry | Year: 2015

This paper describes the Basic Radionuclide vAlue for Internal Dosimetry (BRAID) code, which was developed to calculate the time-dependent activity distribution in each organ and tissue characterised by the biokinetic compartmental models provided by the International Commission on Radiological Protection (ICRP). Translocation from one compartment to the next is taken to be governed by first-order kinetics, which is formulated by the first-order differential equations. In the source program of this code, the conservation equations are solved for the mass balance that describes the transfer of a radionuclide between compartments. This code is applicable to the evaluation of the radioactivity of nuclides in an organ or tissue without modification of the source program. It is also possible to handle easily the cases of the revision of the biokinetic model or the application of a uniquely defined model by a user, because this code is designed so that all information on the biokinetic model structure is imported from an input file. The sample calculations are performed with the ICRP model, and the results are compared with the analytic solutions using simple models. It is suggested that this code provides sufficient result for the dose estimation and interpretation of monitoring data. © Oxford University Press, 2014. Source

Azad M.A.K.,Bangladesh Agricultural University | Mazumdar M.N.N.,Bangladesh Agricultural University | Chaki A.K.,Bangladesh Agricultural University | Ali M.,Bangladesh Agricultural University | And 8 more authors.
Sabrao Journal of Breeding and Genetics | Year: 2013

To investigate the possibility of inducing fixed mutants in M1 generation of rice, 150 seeds of the highly photoperiod-sensitive and tall indica type rice cv. Ashfal were irradiated with different doses of carbon ion beams from the Radiation Applied Biology Division, Quantum Beam Science Division, Japan Atomic Energy Agency. M1 was grown during boro (December-June) season and M2 during shorter days in aman season (July-December) in 2009, M3 was grown during the 2010 boro season. Nine M1 hills, 2 from each of 40, 120 and 160 Gy, and 1 from each of 60, 80 and 200 Gy headed, even under long days in boro season. None of the plants of parent Ashfal headed. Of the heading M1 plants that had plant height as the parent and that could not produce any seed, only the shorter plants produced seed. The M2 progenies took 85 days and 110 days for heading and maturity, respectively, during shorter days in aman season. In contrast, the parent Ashfal headed after 7 November and matured in 152 days. In M3 generation, the progenies bred true as in M2 for heading, maturity and plant height despite the fact that the number of Days taken were a little bit higher than M2. Simple sequence repeat analysis confirmed that the photoperiod-insensitive M1 plants that bred true in the M2 and M3 generations were not contamination of another photoperiod-insensitive variety as monomorphic bands were exhibited for the primer RM351 among the parent and the mutants. It was further confirmed by the fact that the parent Ashfal and the mutants had similar 1000-grain weight. Finally, it could be concluded that it is possible to induce fixed photoperiod-insensitive mutants with shorter plant height with 40- 200 Gy doses of carbon ion beams in M1 of indica type rice cv. Ashfal. © Society for the Advancement of Breeding Research in Asia and Oceania (SABRAO) 2013. Source

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