Ota, Masakazu; Tanaka, Taku*
Journal of Environmental Radioactivity, 201, p.5 - 18, 2019/05
CH released from deep underground radioactive waste disposal facilities can be a belowground source of CO owing to microbial oxidation of CH to CO in soils. Environmental C models assume that the transfer of CO from soil to plant occurs via foliar uptake of CO. Nevertheless, the importance of CO root uptake is not well understood. In the present study, belowground transport and oxidation of CH were modeled and incorporated into an existing land surface CO model (SOLVEG-II) to assess the importance of root uptake on CO transfer to plants. Performance of the model in calculating the belowground dynamics of CH was validated by simulating a field experiment of CH injection into subsoil. The model was then applied to C transfer in a hypothetical ecosystem impacted by continuous CH input from the water table (bottom of one-meter thick soil). In a shallowly rooted ecosystem with rooting depth of 11 cm, foliar uptake of CO was significant, accounting for 80% of the C accumulation in the leaves. In a deeply rooted ecosystem (rooting depth of 97 cm), where the root penetrated to depths close to the water-table, more than half (63%) the C accumulated in the leaves was transferred by the root uptake. We found that CO root uptake in this ecosystem depended on the distribution of methane oxidation in the soil; all C accumulated in the leaves was transferred by the root uptake when methane oxidation occurred at considerable depths (e-folding depths of 20 cm, or 80 cm). These results indicate that CO root uptake contributes significantly to CO transfer to plants if CH oxidation occurs at great depths and roots penetrate deeply into the soil.
Nakata, Hisakazu; Sakai, Akihiro; Amazawa, Hiroya; Sakamoto, Yoshiaki
Nippon Genshiryoku Gakkai-Shi, 59(8), p.447 - 449, 2017/08
Removed soil except those that may be reusable/recyclable would be finally disposed of. A general view is obtained in regards to a disposal concept of low level radioactive wastes generated from research, industrial and medical facilities, for the purpose of contributing to designing final disposal facilities of removed soil. It is analyzed to investigate the issues relating to cost evaluation in order to reasonably carry out that design, referring to a cost evaluation methodology applied to a trench-type disposal facility, which has been planned by JAEA, with impermeable layers.
Mihara, Morihiro; Hirano, Fumio; Takayama, Yusuke; Kyokawa, Hiroyuki*; Ono, Shintaro*
Genshiryoku Bakkuendo Kenkyu (CD-ROM), 24(1), p.15 - 25, 2017/06
A computer program MACBECE has been developed to provide rigorous calculations of the long-term mechanical behavior of a TRU waste geological repository. Consideration is given to the expected chemical alteration of repository components, including cementitious materials and bentonite, and the mechanical interactions between repository and host rock. The long-term mechanical behavior of a TRU waste repository was evaluated in a deep soft rock site, where creep deformation is likely to occur from the initial construction phase to 10 years after repository closure. It was found that the stress didn't fall into a singularity of yield surface of the EC model applied to the mechanical behavior model of bentonite. The calculated displacement of the inner diameter of the repository, considering mechanical interaction between repository and host rock, was about half that of a result in 2nd progress report on R&D for TRU waste disposal in Japan.
Okada, Shota; Izumo, Sari; Nakata, Hisakazu; Tsuji, Tomoyuki; Sakai, Akihiro; Amazawa, Hiroya
JAEA-Technology 2016-023, 129 Pages, 2016/11
Waste packages must meet the technical requirements. This is because JAEA has been preparing an operating procedure manual for quality control of radioactive waste disposal to be applied to the processing of the waste packages. Raw wastes generated by JAEA are segregated and stored by a method specified in the manual. The composition of raw wastes was characterized on the basis of records of the segregation process. Simulated waste packages were produced by placing the waste materials in a 200 liter drum, which was then filled with mortar, followed by curing in a controlled manner. The static load test was conducted to measure deformation and strain performance of the simulated waste package. Compression apparatuses which can imitate loading conditions in pit-type and trench-type facility that are planned by JAEA were used. Based on the test result, waste packages produced in accordance with the manual met the technical requirement under the condition.
*; Tanai, Kenji; *
JNC-TN8420 2001-007, 86 Pages, 2002/02
The objectives of this study is to identify the research issues, which are to be conducted in the future underground research laboratory, about operation and logistics systems for the planning of future research and development program. The research programs and experiments,etc. were investigated for the geological disposal projects in overseas sedimentary rocks and coastal geological environments aiming to reflect in the future underground research facility plan in Japan. In the investigation, information on the engineered-barrier performance, design and construction of underground facilities, tunnel support, transportation and emplacement, and backfilling technology, etc. were collected. Based on these informations, the purpose, the content, and the result of each investigations and tests were arranged. The strategy and the aim in the entire underground research facility, and the flow of investigations and tests, etc. were also arranged from the purpose, the relations and the sequence of each investigation and experiment, and the usage of results, etc.
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
JNC-TN8200 2001-005, 54 Pages, 2001/08
Uchida, Masahiro; Yoshino, Naoto
JNC-TN8410 2001-016, 36 Pages, 2001/05
This technical report summarizes sampling of the natural rock including conductive fracture. Hydraulic test was conducted at the target fracture prior to excavation. Objective of the sample was to reproduce same transmissivity at LABROCK by adjusting normal stress. This report was originally compiled by PNC in october, 1993.
Uchida, Masahiro; Yoshino, Naoto
JNC-TN8410 2001-015, 35 Pages, 2001/05
This technical report summarizes excavation and preparation of the natural rock block sample used in LABROCK. This report was originally compiled by PNC in March, 1993.
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)
KURRI-KR-56, p.58 - 79, 2001/03
no abstracts in English
Makino, Hitoshi; ; Miyahara, Kaname
JNC-TN8400 2000-033, 74 Pages, 2000/11
Natural phenomena is one of the potential factors perturbing the long-term stability of the geological environment, and for natural phenomena, it is necessary to consider uncertainties relevant to time, frequency and effect. Therefore it will be important to have information about the potential impacts of natural phenomena on the safety functions of geological disposal system in the future by assuming that natural phenomena perturbs the safety functions of the geological disposal system. In this report, we have considered 4 natural phenomena, 'uplift, subsidence and denudation', 'climatic and sea-level changes', 'earthquakes and fault movement' and 'volcanism', which had been extracted by investigation in foreign countries and by considering the characteristics of Japan as natural phenomena which may perturb the long-term stability of the geological environment. And we have considered mainly typical effects of naturaI phenomena on geological environment and investigated the typical impacts of those natural phenomena on the safety functions of the geological disposal system. On perturbation scenarios, the maximum of total doses have been less than regulatory guidelines in foreign countries in all situations except the cases assuming that a new fault, which causes significant pathway of groundwater flow and nuclide migration, intersects the waste packages. In the case, the maximum of total doses may reach the same level as regulatory guidelines in foreign countries or natural radiation exposure in Japan depending on fault generation time or grandwater flow rate through the fault. And, on isolation failure scenarios, it has been implied that nuclide mass/flux originated from geological disposal is comparable level with nuclide mass/flux in natural environment. These results could give useful information about the potential impacts of natural phenomena on the safety functions of geological disposal system, and also could show the potential importance of ...
JNC-TN1440 2000-009, 150 Pages, 2000/11
no abstracts in English
; Sukegawa, Yasuhiro*; Suzuki, Satoshi*; ; ; *; Miyo, Hiroaki
JNC-TN8440 2000-022, 180 Pages, 2000/10
At outside waste strage pits, containers for strage of wastes corroded and were flooded, and it was confirmed on August 26, 1997. Confirmation of contamination of the pits outskirts, installation of sheets to prevent rainwater from flowing into the pits, drawing stay water were executed, promptly. Design and authorization works of the work house and waste treatment devices to take out wastes of the pits were executed too. After construction of the work house, taking out wastes of the pits started, and finished on April 10, 1998. Investigations of the inflow point of rainwater and leak of stay water were executed next. The results were reported to Science and Technology Agency (STA), adjoining authorities on December 21, 1998. After decontamination of the pits inner walls to background level of the radioactivity which included general concrete, control area was removed, and the pits were closed by concrete. Measures of closing of the pits were prepared from the middle of August, 1999, and dismantlement of unnecessary instruments started. Decontamination of the pits started from the beginning of September, 1999. The above works finished on June 30, 2000. After decontamination of the pits, STA, adjoining authorities confirmed the dircumstances. Work pouring concrete into the pits was executed three times (three levels), and finished on August 31, 2000. In addition to above, the amount of concrete poured into the pits was about 1,200 m. These data compiled the inspection of contamination in measures of closing of the pits.
; Ishibashi, Yuzo; ; Miyo, Hiroaki; Sukegawa, Yasuhiro*; *; Suzuki, Satoshi*
JNC-TN8440 2000-020, 500 Pages, 2000/10
At outside waste storage pits, containers for storage of wastes corroded and were flooded, and it was confirmed on August 26, 1997. Confirmation of contamination of the pits outskirts, installation of sheets to prevent rainwater from flowing into the pits, drawing stay water were executed, promptly. Design and authorization works of the work house and waste treatment devices to take out wastes of the pits were executed too. After construction of the work house, taking out wastes of the pits started, and finished on April 10, 1998. Investigations of the inflow point of rainwater and leak of stay water were executed next. The results were reported to Science and Thechnology Agency (STA), adjoining authorities on December 21, 1998. After decontamination of the pits inner walls to background level of the radioactivity which included general concrete, control area was removed, and the pits were closed by concrete. Measures of closing of the pits were prepared from the middle of August, 1999, and dismantlement of unnecessary instruments started. Decontamination of the pits started from the begining of September, 1999. The above works finished on June 30, 2000. After decontamination of the pits, STA, adjoining authorities confirmed the circumstances. Work pouring concrete into the pits was executed three times (three levels), and finished on August 31, 2000. In addition t0 above, the amount of concrete poured into the pits was about 1,200 m.
Owada, Hitoshi*; Mihara, Morihiro; *; *
JNC-TN8400 2000-027, 19 Pages, 2000/08
Bactch leaching experiments of granite with the artifitial cement leachate and the leachate of low-alkalinity-cement (LW) were carried out to evaluate the effect of the hiperalkaline plume on the environment of the high-level and TRU radioactive waste repository. Dissolution of Si and Al from feldspar included in the granite and precipitation of C-S-H were confirmed from the results of the leaching experiments with artifitial cement leachate. From this result it was found that the composition of sorrounding rock changed. It also suggested that the retardation factor of migration of radionuclides would change. On the contrary, only decrease of concentrations in Si, Al and Ca in the leachate was observed in the experiment with LW. This result might indicate that C-S-H and/or C-A-S-H precipitated as secondary minerals in the LW case. From these results, it was considered that the hiperalkaline plume from the cementitious leachate might caused the change of disposal conditions such as the change in distribution coefficients of rock by precipitation of the secondary mineral and the increase in hydraulic conductivity by the dissolution of rock. On the other hand, the influences of the LW would be comparatively small, because LW and granite might equilibrate in short time.
Mine, Tatsuya*; Mihara, Morihiro;
JNC-TN8430 2000-010, 27 Pages, 2000/07
In the geological disposal system of the radioactive wastes, gas generation by microorganism could be significant for the assessment of this system, because organic material included in groundwater, buffer material and wastes might serve as carbon sources for microorganisms. In this study, gas generation tests using microorganisms were carried out under anaerobic condition. The amount of methane and carbon dioxide that were generated by activity of Methane Producing Bacteria (MPB) were measured with humic acid, acetic acid and cellulose as carbon sources. The results showed that methane was not generated from humic acid by activity of MPB. However, in the case of using acetic acid and cellulose, methane was generated, but at high pH condition (pH=10), the amount of generated methane was lower than at low pH (pH=7). It was not clear whether the pH would affect the amount of generated carbon dioxide.
Mine, Tatsuya*; Mihara, Morihiro;
JNC-TN8430 2000-009, 35 Pages, 2000/07
In the geological disposal system of TRU wastes, nitrogen generation by denitrifying bacteria could provide significant impact on the assessment of this system, because nitrate contained in process concentrated liquid waste might be electron acceptor for denitrifying bacteria. In this study, the activities and tolerance of denitrifying bacteria under disposal condition were investigated. pseudomonas denitrificans as denitrifying bacteria was used. The results showed that Pseudomonas denitrificans had activity under reducing condition, but under high pH condition (PH9.5), the activity of Pseudomonas denitrificans was not detected. It is possible that the activity of Pseudomonas denitrificans would be low under disposal condition.
Kato, Hiroshige*; Sato, Mitsuyoshi*; Owada, Hitoshi*; Mihara, Morihiro;
JNC-TN8430 2000-008, 53 Pages, 2000/05
Cementitious materials will be used in TRU waste disposal repository. In such cases, it is considered that the migration of alkaline leachates from cementitious materials, so called high pH plume, will cause dissolution of rock and precipitation of secondary minerals. In addition, the high pH plume will move along the flow of groundwater, so it is predicted that rock formation and components of high pH groundwater vary with time and space. However, time and spatial dependence of the variations of secondary minerals and groundwater components has not been clarified. In order to acquire the data of variations of secondary minerals and groundwater components, we carried out the rock alteration experiments with column method. The crushed granodiorite was filled into 4 meters length column (3.7 cm) and artificial cement leachate (pH=13.3; Na=0,1 mol/l, K=0.1 mol/l, Ca=0.002 mol/l) was streamed at flow rates of 0.1 ml/min for 7 months at 80C. As the result, secondary minerals confirmed on the rock were calcite and C-S-H at upstream of column and C-S-H at mid-downstream. The pH value of the fluid dominated by Na and K did not be decreased by reaction with the rock. In this study, the data relating to the effect of high pH plume on rock over the long term was acquired.
Mine, Tatsuya*; Mihara, Morihiro; ; *; *
JNC-TN8430 2000-003, 33 Pages, 2000/04
On the geological disposal system of the radioactive wastes, the activities of the microorganisms that could degrade the asphalt might be significant for the assessment of the system performance. As the main effects of the biodegradation of the asphalt, the fluctuation of leaching behavior of the nuclides included in asphalt waste has been indicated. In this study, the asphalt biodegradation test was carried out. The microorganism of which asphalt degradation ability was comparatively higher under aerobic condition and anaerobic condition was used. The asphalt biodegradation rate was calculated and it was evaluated whether the asphalt biodegradation in this system could occur. The results show that the asphalt biodegradation rate under anaerobic and high alkali condition will be 300 times lower than under aerobic and neutral pH.