Morita, Yasuji; Nishihara, Kenji; Tsubata, Yasuhiro
JAEA-Data/Code 2018-017, 32 Pages, 2019/02
Potential radiotoxicity defined as a summation of intake dose was estimated for each actinide element to suppose target of recovery ratio of minor actinide (MA). Importance of each element from the viewpoint of the radiotoxicity was evaluated from the evolution of the radiotoxicity and ratio to the total radiotoxicity. In all the 4 types of spent fuels examined, Am is the most important element. For instance, the potential radiotoxicity of Am accounts for 93% of the total radiotoxicity of actinide elements in HLW produced by reprocessing of spent fuel from pressurized water reactor (PWR). Residual Pu after the recovery of 99.5% in reprocessing still gives contribution that cannot be ignored in radiotoxicity. When the burn-up of the UO fuel in PWR increased, the potential radiotoxicity of actinide elements increased almost in proportion to the burn-up, but in case of MOX fuel in PWR and minor-actinide-recycled MOX fuel in fast reactor, the radiotoxicity of actinide elements increased further. Much consideration is required for the recovery of actinide elements in HLW from different types of fuel.
Fukaya, Yuji; Goto, Minoru; Ohashi, Hirofumi; Nishihara, Tetsuo; Tsubata, Yasuhiro; Matsumura, Tatsuro
Annals of Nuclear Energy, 116, p.224 - 234, 2018/06
Optimization of disposal method and scenario to reduce volume of High Level Waste (HLW) and the footprint in a geological repository for High Temperature Gas-cooled Reactor (HTGR) has been performed. It was found that HTGR has great advantages to reducing HLW volume and its footprint, which are high burn-up, high thermal efficiency and pin-in-block type fuel, compared with those of LWR and has potential to reduce those more in the previous study. In this study, the scenario is optimized, and the geological repository layout is designed with the horizontal emplacement based on the KBS-3H concept instead of the vertical emplacement based on KBS-3V concept employed in the previous study. As a result, for direct disposal, the repository footprint can be reduced by 20 % by employing the horizontal without change of the scenario. By extending 40 years for cooling time before disposal, the footprint can be reduced by 50 %. For disposal with reprocessing, the number of canister generation can be reduced by 20 % by extending cooling time of 1.5 years between the discharge and reprocessing. The footprint per electricity generation can be reduced by 80 % by extending 40 years before disposal. Moreover, by employing four-group partitioning technology without transmutation, the footprint can be reduced by 90 % with cooling time of 150 years.
Fukaya, Yuji; Nishihara, Tetsuo
Nuclear Engineering and Design, 307, p.188 - 196, 2016/10
Reduction of High Level Waste (HLW) and footprint in a geological repository due to high burn-up and high thermal efficiency of High Temperature Gas-cooled Reactor (HTGR) has been investigated. A helium-cooled and graphite-moderated commercial HTGR was designed as a Gas Turbine High Temperature Reactor (GTHTR300), and the features are significantly high burn-up of approximately 120 GWd/t, high thermal efficiency around 50%, and pin-in-block type fuel. The pin-in-block type fuel was employed to reduce processed graphite volume in reprocessing, and effective waste loading method for direct disposal is proposed by applying the feature in this study. As a result, it is found that the number of canisters and its repository footprint per electricity generation can be reduced by 60% compared with LWR representative case for direct disposal because of the higher burn-up, higher thermal efficiency, less TRU generation, and effective waste loading proposed in this study for HTGR. For disposal with reprocessing, the number of canisters and its repository footprint per electricity generation can be reduced by 30% compared with LWR because of the 30% higher thermal efficiency of HTGR.
Genshikaku Kenkyu, 47(6), p.21 - 30, 2003/06
This paper describes the present state and future prospect of research and development on the separation of long-lived radionuclides from high-level waste (partitioning), which is indispensable for the transmutation of those nuclides. The main items described are composition of high-level waste, selection of elements to be separated, the purpose of partitioining, and development of partitioning process in JAERI.
Genshiryoku Bakkuendo Kenkyu, 9(1), p.35 - 42, 2002/09
Various microorganisms have been observed in deep geologic formation. The effects of such microorganisms on the performance of HLW disposal are still unknown. This paper reviews the studies of microbial effects on the long-term contaiment of HLW disposal, and discusses the future work to be carried out. Microbial reduction and oxidation and byproducts derived from microbial activities affect performance of HLW repository and have a potential to enhance actinides migration in geologic formation (degradation of the materials of repository, complex-formation, dissolution of actinides precipitates and occurrence of nm scale colloid formation). Potential microbial perturbation of performance of the barriers may enhance confinement of actinides by biomineralization, bioadsorption, bioaccumulation and precipitation. These studies indicate that further experiments are required to elucidate microbial effects on the performance of HLW disposal.
JNC TN1200 2001-007, 45 Pages, 2002/03
no abstracts in English
Kato, Hiroshige*; Mine, Tatsuya*; Mihara, Morihiro; Oi, Takao; Honda, Akira
JNC TN8400 2001-029, 63 Pages, 2002/01
Cementitious materials will be used for the TRU waste repository as a component of engineered barrier system. The distribution coefficients which represent the retardation of radionuclides migration for the cementitious materials would be one of the important parameter for the safety assessment. The much information of radionuclide sorption onto the cementitious materials has been accumulated through the study in the world. Therefore it is necessary to compile the information and Kd of the radionuclides reported in previous studies. In this report, the Kd of the important radionuclides, such as C, Ni, Se, Sr, Zr, Nb, Mo, Tc, Sn, I, Cs, Sm, Pb, Ra, Ac, Th, Pa, U, Np, Pu, Am, Cm, for the cementitious materials were compiled as the Sorption Database (SDB). For radionuclides to be sensitive to the redox potential, e.g. Se, Tc, Pa, U, Pu and Np, some Kds measured under the controlled atmosphere had been reported, and few Kds measured under the controlled redox potential had been reported. For Se, Mo, Sm, Cm and Ac, the distribution coefficients had not been reported, therefore distribution coefficients of Se and Mo for OPC (Ordinary Portland Cement) pastes were measured by batch sorption experiments and these data were added into the SDB.
Ito, Akira; Kawakami, Susumu; Yui, Mikazu
JNC TN8400 2001-028, 38 Pages, 2002/01
In a repository for high-level radioactive waste, coupled thermo -hydro -mechanical and chemical (THMC) processes will ocurr, involving the interactive processes between radioactive decay heat from the vitrified waste, infiltration of groundwater, swelling pressure generation and chemical evolution of the buffer material and porewater chemistry. In this program, numerical experiment system for the coupled THMC processes will be developed in order to predict the long-term performance of the near-field (engineered barrier and host rock) for various geological environments. The simulation code development has been started in FY 2001 and three development steps are planned, because (1)development will be continued for some years, (2)feasibility of numerical experiment have to be confirmed by using existing tools. This report presents the following items of the simulation code development for the coupled THMC processes. (1)First step of the simulation code development (2)Mass transport passways in compacted bentonite (3)Parallelization of the simulation code
Nakayama, Shinichi; Morita, Yasuji; Nishihara, Kenji
Proceedings of International Conference on Back-End of the Fuel Cycle: From Research to Solutions (GLOBAL 2001) (CD-ROM), 6 Pages, 2001/09
Production of lower-level radioactive wastes, as well as the reduction in radioactivity of HLW, is an important performance indicator in assessing the viability of a partitioning-transmutation system. We have begun to identify the chemical compositions and to quantify the amounts of radioactive wastes that may be generated by JAERI's processes. Long-lived radionuclides such as C and Ni and spallation products of Pb-Bi coolants such as Po (10 Bq/yr) are added to the existing inventory of these nuclides that are generated in the current fuel cycle. Spent salts of KCl-LiCl, which is not generated from the current fuel cycle, will be introduced as a waste.
JNC TN8200 2001-005, 54 Pages, 2001/08
Aoyagi, Takayoshi*; *; Mihara, Morihiro; Okutsu, Kazuo*; Maeda, Munehiro*
JNC TN8400 2001-024, 103 Pages, 2001/06
In the disposal concept of TRU waste, concentrated disposal of wastes forms in large cross-section underground cavities is envisaged, because most of TRU waste is no-heat producing in spite of large generated volume as compared with HLW. In the design of engineered barrier system based on large cross-section cavities, it is necessary to consider the long-term mechanical process such as creep displacement of the host rock from the viewpoint of the stability of engineered barrier system. In this study, the long-term creep displacement of the host rock was calculated using the non-linear viscoelasticity model and the effects on the stability of engineered barrier system was evaluated. As a result, in the disposal concept of crystalline rock, no creep displacement occurred at the time after 1 milion year. On the other hand, in the disposal concept of sedimentary rock, creep displacement of 8090mm occurred at the time after 1 milion year. Also, in this calculation, a maximum reduction of 45mm concerned with the thickness of buffer material was estimated. But these values resulted within allowance of design values. Therefore, these results show that the effects of the creep displacement on the stability of engieered barrier system would not be significant.
Yoshikawa, Hideki; Ishikawa, Hirohisa;
JNC TN8200 2001-004, 160 Pages, 2001/06
Genshikaku Kenkyu, 46(2), p.47 - 73, 2001/06
no abstracts in English
JNC TN8400 2001-012, 69 Pages, 2001/04
On understanding the radionuclide transport in natural barrier in radioactive waste isolation research, the macroscopic dispersion in heterogeneous permeability field in the underground rock is regarded as an important process. Therefore, we have conducted lots of tracer experiments by the MACRO II facility with an artificially constructed heterogeneous permeability field. In order to study the scale dependence of dispersion coefficients in case of laboratory experiments, we placed the flow cell horizontally, and conducted injection-withdraw tracer experiment with a single well. We have conducted I5 cases experiments. These cases were prepared by changing a position of single well and the injection-withdraw time. At each position we have conducted 9 cases and 6 cases experiments. In this report, we evaluated the macroscopic dispersion coefficients by the fitting of analytical solution to breakthrough curve measured by the 15 cases pumping tracer experiment. Consequently, we could evaluate the dispersion coefficients for 12 cases of 15 cases. Then, we discussed the relation between a injection-withdraw flow rate and a property of heterogeneous media and dispersion coefficient. The conclusions obtained from the results of the evaluation are summarized as follows, (1)It was found that the macroscopic dispersion coefficients tend to be increased with increase of the average radius of tracer front spread around a single well. (2)We have conducted any experiments with s single well settled at two positions. In case of that there is low permeability around a single well, we found dispersion coefficients are large. In case of that there is high permeability around a single well, we found dispersion coefficients are small. (3)In three cases that we could not evaluate because of incorrect accuracy of fitting, we have found it possible that there is some points that dispersion coefficients were strikingly small in tracer front.
Futakuchi, Katsuhito*; Hashimoto, Shuji*; Sakuramoto, Yuji*; ;
JNC TN8400 2001-007, 52 Pages, 2001/04
As a natural analogue, the authors investigted a Tertiary argillaceous bed and a Quarternary hypabyssal rock (porphyrite) which intruded into the argillaceous rock, distributed in the Nishikubiki district of Niigata prefecture in Japan. We examined the variation of clay mineral species in the argillaceous rock surrounding the intrusive rock and carried out thermal analyses for the argillaceous rock based on the coolig history of the intrusive rock. The predominant clay mineral varied from montmorillonite to illite through illite/montmorillonite interlayers with approaching to the intrusive rock. The thermal analyses indicated that the temperature descended from 270 to 15 C during the 7.5 10 years at alocalty of argillaceous rock containing 75% illite in the interlayers. On the assumption that the alteration from montmorillonite to illite was regarded as a first-order reaction, we evaluated the apparent activation energy based on the thermal condition mentioned above; about 103 kJ/mol was obtained for this illitization. This was within the range of values reported previously by laboratory experiments and/or examinations of natural illitizations.
Suzuki, Satoru; Kawamura, Katsuyuki*
JNC TN8400 2001-005, 41 Pages, 2001/04
A correlation between molecular structure and a vibrational spectrum of interlayer water in Na-smectite was investigated by means of Molecular Dymamics (MDs) simulations. Detailed comparison of simulation results with IR spectroscopic observations for the water-smectite system indicated good agreement. Internal vibrational spectra of water were obtained by the Fourier transformation of velocty auto-correlation function of hydrogen atom. A stretching vibrational spectrum of interlayer water consisted of a broad band with a peak top around 3400cm and a sharp peak around 3650 to 3700cm. The fomer broad band was assigned to O-H vibrations between water molecules as bulk water, while the latter band was attributed to O-H ones oriented to siloxane surface through hydrogen bonding. The hydrogen bond distance, determined as the shortest O-O distance by the radial distribution function (RDF), revealed that hydrogen bond distance between water and siloxane surface (O-O 3.0 -O = ca. 2.8 AA ). These results suggested that interaction between water molecule and siloxane surface weaker than that between water molecules, although they were forced to be oriented.
JNC TN8400 2001-022, 60 Pages, 2001/03
A numerical simulation code for the TRUEX (Transuranium Extraction) process was developed. Concentration profiles of americium and europium were calculated for some experiments of the counter current extraction system those were carried out in CPF (Chemical Processing Facility) by using the code. Calculation profiles were in agreement with the experimental results. Operational conditions were also examinted for the americium recovery experiment by the TRUEX process carried out in the Plutonium Fuel Center. It was shown that lowering the concentration of nitric acid in the scrub solution and decreasing the flow rate of solvent and strip solution was effective for improving the performance of the stripping step and reducing the volume of the waste solution. In order to find the optimum conditions for various experiments, this simulation code was modified to calculate the concentration profiles of other metal elements such as zirconium and iron and the effect of oxalic acid on the extraction behavior of the metal elements. The calculated concentration profiles of americium and europium were varied by this modification. In the experiment at CPF, the calculations were carried out to obtain recovery ratio of americium in the product stream with the amount of oxalic acid added to the process. This calculation result showed that it was possible to improve the performance of decontamination of fission products by increasing oxalic acid concentration added to the process. The calculation was also carried out for finding the optimum conditions of oxalic acid concentration added to the europium recovery process.
Fukumoto, Masahiro; Nishikawa, Yoshiaki*
JNC TN8400 2001-017, 355 Pages, 2001/03
The alkali hydrolysis experiments which seem to be important from the view point of the alteration mechanism using the following seven organic materials was performed as a part of the evaluation of the influence on the disposal of the organic materials contained in the TRU wastes. As a result of the alkali hydrolysis experiments (90C and 91d), each organic materials became those of lower molecular weight. The degradation products were able to be detected in the solution. The organic materials seem to be degraded to the organic matters which were confirmed in this study in a long term of disposal. The degradation products were shown below. Therefore, the evaluation of the influence on the migration of radionuclides by degradation products becomes important in the future. (1)Cement additives of Naphthalenesulfonic acid and Ligninsulfonic acid ( Naphthalenedisulfonic acid etc.) (2)Cement additives of polycarboxylic acid ( Oligomer of distal methoxypoly ethylene glycol.) (3)Ethylenediamine-N,N,N',N'-tetraacetic acid disodium salt ( Acetic acid desorped and cyclized organic matters from EDTA.) (4)Tributyl phosphate ( Dibutyl phthalate, n-butanol) (5)Poly vinyl acetate ( Acetic acid) (6)Nylon66 ( Adipic acid, Hexamethylenediamine) (7)Cured epoxy resin ( Glycerol poly glycidyl ether, Carboxylic acid)
Kato, Tomoko; ; *;
JNC TN8400 2001-014, 212 Pages, 2001/03
Reference Biospheres are regarded as tools which can be used for making reasonable estimates of radiological impacts for the purposes of safety assessment of geological disposal. Moreover, those are available for reducing the uncertainties based on future human environments and lifestyles. On the other hand, it is recognised that the parameter values have some uncertainties derived from experimental or sampling errors. It is possible to estimate the impacts of these uncertainties throughout the model by sensitivity analysis. Thus for this study, to evaluate the impact of the variation of migration conditions and exposure pathways, we changed some of migration and exposure parameters in turn, which were used in the compartment model where the geosphere-biosphere interface is a river in a plain.
Taniguchi, Naoki; Kawasaki, Manabu*; Fujiwara, Kazuo*
JNC TN8400 2001-011, 62 Pages, 2001/03
The corrosion of metallic materials used in natural environment are sometimes affected by microbial action. It is apprehended that microorganism living in deep underground or brought from ground surface during excavation makes an impact on overpack material for geological disposal of high-level radioactive waste. Sulfate reducing bacteria (SRB) is known to be one of the most representative microorganism which affects the corrosion of metals. In this study, the behavior of growth of SRB was investigated at first under the presence of bentonite as a main component of buffer material which encloses the overpack. The results of the tests showed that the population of SRB after the culture in synthetic sea water mixed with bentonite decreased with increasing the ratio of bentonite/solution. SRB was hardly grown in medium whose bentonite/solution ratio exceeded 1000g/l. As a conservative case, the effects of sulfide on the corrosion of overpack materials were also studied assuming high activity of SRB. Carbon steel, copper and titanium specimens were immersed in synthetic sea water purging 0.1MPa HS gas and the corrosion behavior was compared with the results in N gas purging environment. Obvious effect of sulfide on the corrosion of carbon steel was not observed, but the corrosion rates of copper specimens were accelerated several hundred times by purging HS gas. The absorption of hydrogen into titanium specimens was not affected by purging HS gas, but the difference of hydrogen absorption between pure titanium and titanium alloy containing 0.06%-Pd was observed.