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Journal Articles

Research on activation assessment of a reactor structural materials for decommissioning

Seki, Misaki; Ishikawa, Koji*; Nagata, Hiroshi; Otsuka, Kaoru; Omori, Takazumi; Hanakawa, Hiroki; Ide, Hiroshi; Tsuchiya, Kunihiko; Sano, Tadafumi*; Fujihara, Yasuyuki*; et al.

KURNS Progress Report 2018, P. 257, 2019/08

no abstracts in English

JAEA Reports

Study on the evaluation method to determine the radioactivity concentration in radioactive waste generated from the dismantling of research reactors

Murakami, Masashi; Hoshino, Yuzuru; Nakatani, Takayoshi; Sugaya, Toshikatsu; Fukumura, Nobuo*; Sanda, Toshio*; Sakai, Akihiro

JAEA-Technology 2019-003, 50 Pages, 2019/06

JAEA-Technology-2019-003.pdf:4.42MB

Toward the establishment of a common approach to determine the radioactivity concentrations in dismantling wastes arising from research reactors, radionuclide concentrations in the reactor structure materials of aluminum, carbon steel, shield concrete, and graphite of TRIGA Mark II reactor at Rikkyo University, Japan, were evaluated with both radiochemical analysis and theoretical calculation. The measured nuclides by the radiochemical analysis were $$^{3}$$H, $$^{60}$$Co, and $$^{63}$$Ni in aluminum, $$^{3}$$H, $$^{60}$$Co, $$^{63}$$Ni, and $$^{152}$$Eu in carbon steel, $$^{3}$$H, $$^{60}$$Co, and $$^{152}$$Eu in shield concrete, and $$^{3}$$H, $$^{14}$$C, $$^{60}$$Co, $$^{63}$$Ni, and $$^{152}$$Eu in graphite. Neutron-flux distributions and neutron-induced activities were computed with DORT and ORIGEN-ARP codes, respectively. Using the results of material composition analysis, radioactivity concentrations were conservatively predicted with good accuracy except for graphite material.

Journal Articles

Risk communication at Horonobe Underground Research Center, using the Public Information House and Underground Research Laboratory

Osawa, Hideaki; Nogami, Toshinobu; Hoshino, Masato; Tokunaga, Hiroaki*; Horikoshi, Hidehiko*

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 26(1), p.45 - 55, 2019/06

Japan Atomic Energy Agency has performed risk communication at Horonobe Underground Research Center, using the Public Information House and Underground Research Laboratory (URL), to promote understanding R&D of geological disposal technology and waste disposal against public. In this paper, we conducted the analysis of questionnaire investigation performing after visiting those facilities from FY2013 to FY2017. The results show that long-term safety would gain prominent attention as agita factor by growing understanding. The results also shows that visiting to those facility would become valuable experience to understand geological disposal because, for example, respondents with visiting to URL positively evaluated necessity, appropriates and safety of geological disposal, compared with those without visiting URL.

Journal Articles

Effects of trust and procedural fairness on public acceptance of siting a repository for high-level radioactive waste

Osawa, Hideaki; Otomo, Shoji*; Hirose, Yukio*; Onuma, Susumu*

Ningen Kankyogaku Kenkyu, 17(1), p.59 - 64, 2019/06

This study examined the determinants of public acceptance of siting a repository for High-level radioactive waste (HLW), focusing on procedural fairness and trust. To examine the presumption, the study implemented a hypothetical scenario experiment that manipulated two factors: an opportunity of voice as an antecedent of procedural fairness and similarity value to the authority as a component of trust. Results indicated that affective reaction, procedural fairness, and trust determined public acceptance. A process analysis indicated that the effect of procedural fairness was strengthened when the trust on similarity was negative.

Journal Articles

Importance of root uptake of $$^{14}$$CO$$_{2}$$ on $$^{14}$$C transfer to plants impacted by below-ground $$^{14}$$CH$$_{4}$$ release

Ota, Masakazu; Tanaka, Taku*

Journal of Environmental Radioactivity, 201, p.5 - 18, 2019/05

 Percentile:100(Environmental Sciences)

$$^{14}$$CH$$_{4}$$ released from deep underground radioactive waste disposal facilities can be a belowground source of $$^{14}$$CO$$_{2}$$ owing to microbial oxidation of $$^{14}$$CH$$_{4}$$ to $$^{14}$$CO$$_{2}$$ in soils. Environmental $$^{14}$$C models assume that the transfer of $$^{14}$$CO$$_{2}$$ from soil to plant occurs via foliar uptake of $$^{14}$$CO$$_{2}$$. Nevertheless, the importance of $$^{14}$$CO$$_{2}$$ root uptake is not well understood. In the present study, belowground transport and oxidation of $$^{14}$$CH$$_{4}$$ were modeled and incorporated into an existing land surface $$^{14}$$CO$$_{2}$$ model (SOLVEG-II) to assess the importance of root uptake on $$^{14}$$CO$$_{2}$$ transfer to plants. Performance of the model in calculating the belowground dynamics of $$^{14}$$CH$$_{4}$$ was validated by simulating a field experiment of $$^{13}$$CH$$_{4}$$ injection into subsoil. The model was then applied to $$^{14}$$C transfer in a hypothetical ecosystem impacted by continuous $$^{14}$$CH$$_{4}$$ 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 $$^{14}$$CO$$_{2}$$ was significant, accounting for 80% of the $$^{14}$$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 $$^{14}$$C accumulated in the leaves was transferred by the root uptake. We found that $$^{14}$$CO$$_{2}$$ root uptake in this ecosystem depended on the distribution of methane oxidation in the soil; all $$^{14}$$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 $$^{14}$$CO$$_{2}$$ root uptake contributes significantly to $$^{14}$$CO$$_{2}$$ transfer to plants if $$^{14}$$CH$$_{4}$$ oxidation occurs at great depths and roots penetrate deeply into the soil.

Journal Articles

Study on decontamination of steel surface contaminated with uranium hexafluoride by acidic electrolytic water

Nakayama, Takuya; Nomura, Mitsuo; Mita, Yutaka; Yonekawa, Hitoshi*; Bunbai, Misako*; Yaita, Yumi*; Murata, Eiichi*; Hosaka, Katsumi*; Sugitsue, Noritake

Proceedings of 2019 International Congress on Advances in Nuclear Power Plants (ICAPP 2019) (Internet), 8 Pages, 2019/05

Clearance of contaminated metal is important for recycling and volume reduction of radioactive waste. Among applicable decontamination technologies, immersion method with ultrasonic cleaning is considered to be effective for metal materials having various shapes. in this study is to demonstrate decontamination of carbon steel contaminated by uranium hexafluoride to the target level for clearance (less than 0.04 Bq/cm$$^{2}$$), and minimize secondary waste. In this test, acidic electrolytic water, dilute hydrochloric acid, dilute sulfuric acid and ozone water with various pH and redox potential were used as decontamination solutions to be tested. We found that acidic electrolytic water is effective solution for decontamination of carbon steel contaminated by uranium hexafluoride. It could be decontaminate less than target level for clearance, and reduced secondary waste relatively.

JAEA Reports

Study on the basic system of the common non-destructive radioactivity measuring equipment for disposal of radioactive wastes generated from research, industrial and medical facilities

Izumo, Sari; Hayashi, Hirokazu; Nakata, Hisakazu; Amazawa, Hiroya; Motoyama, Mitsushi*; Sakai, Akihiro

JAEA-Technology 2018-018, 39 Pages, 2019/03

JAEA-Technology-2018-018.pdf:2.8MB

JAEA has planed the near surface disposal of LLW generated from research, industrial, and medical facilities. Maximum radioactivity concentration of each waste and total radioactivity of disposed wastes are needed to be less than the permitted values in the license of disposal facility. Thus, it is important not to evaluate the radioactivity of each waste in unduly conservative ways so as to dispose of the total amount of the waste that is originally planned. Accordingly, the detection limit is required to be as low as the clearance level for the very low level radioactive waste planned to be disposed of trench-type. In this report, the feasibility of the non-destructive assay method is studied by model calculations for gamma emitters. It is confirmed that the detection limit less than the clearance level can be achieved as regards the box type metal container that is difficult to measure. This report summarizes the requirements for the non-destructive measuring equipment.

JAEA Reports

Biosphere assessment methodology commonly applicable to varouis disposal concepts

Kato, Tomoko; Fukaya, Yukiko*; Sugiyama, Takeshi*; Nakai, Kunihiro*; Oda, Chie; Oi, Takao

JAEA-Data/Code 2019-002, 162 Pages, 2019/03

JAEA-Data-Code-2019-002.pdf:2.78MB

The radioactive waste generated from Fukushima Daiichi Nuclear Power Plant (FDNPP) accident have features such as wide range of contamination level (from low to high) and huge amount etc. It would be necessary for the waste from the FDNPP accident to construct suitable disposal concept and dispose safely and reasonably. To develop suitable disposal concepts for the waste from the FDNPP accident, applicability of the present disposal concepts (deep geological disposal, sub-surface disposal, near-surface disposal (trench type and concrete pit type), etc) is being discussed. For such disucssion it would be expected to be able to use common scenarios, models and parameter sets for various disposal concepts. Therefore, as a preliminary study to standardize such scenarios, models and parameter sets, a standardized biosphere model and parameter set which are applicable to the biospohere assessment for various disposal concepts were developed as an example refering to the existing biosphere models, parameters defined for present disposal concepts and latest findings. And, a set of flux-to-dose conversion factors calculated with the standardized biosphere model and parameter set was also demonstrated.

Journal Articles

Decision-making process on selection of management policy for high-level radioactive waste; As an example of Switzerland and United Kingdom

Osawa, Hideaki; Hirose, Yukio*; Onuma, Susumu*; Otomo, Shoji*

Shakai Anzengaku Kenkyu, 9, p.145 - 160, 2019/03

We compared decision-making process on selection of management policy for high-level radioactive waste between Switzerland and UK by document review. The decision-making was performed extraction of options, establishment of comparative criteria, assessment and selection of options in turn. As comparative criteria, safety and intergenerational fairness etc. were considered to be important. The position of 'Deal with it now by waste disposal' emphasizing the responsibility of the present generation had a trade-off relation with that of 'Leave it until later by long-term storage' emphasizing the rights of future generations. The sense of values, recusing HLW repository as so-called troublesome facility against future and present generation, appeared to be mitigated through the consideration of trade-off relation described above. As a result, both countries have chosen waste disposal considering reversibility of decisions and retrievability of radioactive waste.

Journal Articles

Decision-making process on site selection for the deep geological repository of high-level radioactive waste; As an example of Switzerland and United Kingdom

Osawa, Hideaki; Hirose, Yukio*; Onuma, Susumu*; Otomo, Shoji*

Shakai Anzengaku Kenkyu, 9, p.161 - 176, 2019/03

We compared site selection process by a voluntarism and partnership approach in UK, and that by screening based primarily on technical criteria with the main emphasis on safety in Switzerland, by document review. The voluntarism and partnership approach in UK is based on the ethical consideration that fairness in siting facilities could only be achieved by the enhancement of well-being and public acceptability based on a willingness to participate and a right to withdraw from a siting process. On the other hand, it could be interpreted that the screening approach with the main emphasis on safety in Switzerland would be based on the concept of the ignorance of veil, hypothesized that people would accept the decision if they consent the decision way beforehand under condition everyone could be involved in as a potential interest party.

JAEA Reports

Comparison of potential radiotoxicity of actinide elements; Data for consideration of optimum recovery of actinide elements

Morita, Yasuji; Nishihara, Kenji; Tsubata, Yasuhiro

JAEA-Data/Code 2018-017, 32 Pages, 2019/02

JAEA-Data-Code-2018-017.pdf:2.35MB

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$$_{2}$$ 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.

JAEA Reports

Report on cause investigation and countermeasure of leakage trace from the drum

Shimomura, Yusuke; Sato, Takuya; Fukui, Yasutaka; Kudo, Kenji; Yoshioka, Tatsuji

JAEA-Review 2018-023, 220 Pages, 2019/01

JAEA-Review-2018-023.pdf:15.6MB

On September 11, 2015, leaky traces of bituminized wastes were confirmed from four drums filled with bituminization in waste packages storage yard (II) of waste management facility in Oarai Research and Development Center. Moreover, even after the subsequent investigation, a leakage trace was found from one bituminous drum on November 10, 2015. Furthermore, on December 2, 2015, there was no a leakage trace in one bituminous drum, however the upper lid was found to be intensely corroded. To investigate the causes and the countermeasures for leakages of bituminized wastes from the drums, we have set up a Work Group to investigate the causes and the countermeasures to leakage traces from the drums. This report is based on "Report on Cause Investigation and Countermeasure of Leakage Trace from the Drum" summarized by this working group, the report was reconstructed including the contents clarified in the subsequent document investigation.

JAEA Reports

Safety measures in the melting facilities of The Advanced Volume Reduction Facilities; Document collection of discussion meetings related to melting facilities

Iketani, Shotaro; Yokobori, Tomohiko; Ishikawa, Joji; Yasuhara, Toshiyuki*; Kozawa, Toshiyuki*; Takaizumi, Hirohide*; Monma, Takeshi*; Kurosawa, Shingo*; Iseda, Hirokatsu; Kishimoto, Katsumi; et al.

JAEA-Review 2018-016, 46 Pages, 2018/12

JAEA-Review-2018-016.pdf:12.79MB

Japan Atomic Energy Agency (JAEA) adopts melting process for the waste processing and packaging method of radioactive miscellaneous solid waste in NSRI because melting process is effective in radioactivity evaluation, volume reduction, and stabilization treatment. Metal melting processing facilities, Incinerator, and Nonmetal melting processing facilities (hereinafter referred to as melting process facilities) have taken lots of safety measures, including measures for preventing the recurrence of the fire accidents. To exchange opinions and discuss the validity of these measures and so on with internal personnel and external experts, "Discussions on Melting Process Facilities" was held. As a document collection, this paper summarizes presentation materials of discussion meetings. Presentation materials describe "Outline of AVRF", "Safety measures in the melting facilities in WVRF", "Operation management of the melting facilities in WVRF", "Comparison of the past accident cases between facilities in and outside Japan and WVRF", and "Introduction of past accident cases and safety measures in other facilities from each committee".

Journal Articles

A Spectroscopic technique for analysis developed in the field of unclear energy

Kusaka, Ryoji

Bunko Kenkyu, 67(6), p.239 - 240, 2018/12

A spectroscopic technique for analysis developed by collaboration between Japan Atomic Energy Agency (JAEA) and Quantum and Radiological Science and Technology (QST) is discussed for readers outside the field of nuclear energy. This paper introduces a quantitative analysis for $$^{107}$$Pd radioisotope contained in a spent nuclear fuel by using laser-induced photoreduction and inductively coupled plasma mass spectrometry (ICP-MS). The importance and problems of quantitative analysis for radioisotopes in spent nuclear fuels are described, and the principle, advantages, and future applications of the spectroscopic technique are discussed.

Journal Articles

Can the decision way by the "veil of ignorance" promote public acceptance?; A Hypothetical scenario survey about selecting a candidate site for geological disposal of high level radioactive waste in Japan

Onuma, Susumu*; Hirose, Yukio*; Osawa, Hideaki; Otomo, Shoji*; Yokoyama, Miki*

Nippon Risuku Kenkyu Gakkai Dai-31-Kai Nenji Taikai Koen Rombunshu (USB Flash Drive), 6 Pages, 2018/11

One reason of not being decided a candidate site for geological disposal of high level radioactive waste is that strong opposition occurs once a name of the place where residents live even if they can understand the necessity of the facility. Therefore, we hypothesized that people would accept the decision if they consent the decision way beforehand under the condition everyone can be involved in as a potential interest party (the ignorance of veil). A hypothetical scenario survey was conducted in Japan. The results revealed that the decision way and the decision under the ignorance of veil were likely to be accepted more than the current decision way even if they became candidate site. Moreover, the decision way under the ignorance of veil was evaluated higher procedural fairness, while the current way was low procedural fairness.

Journal Articles

Development of cement based encapsulation for low radioactive liquid waste in Tokai Reprocessing Plant

Matsushima, Ryotatsu; Sato, Fuminori; Saito, Yasuo; Atarashi, Daiki*

Proceedings of 3rd International Symposium on Cement-based Materials for Nuclear Wastes (NUWCEM 2018) (USB Flash Drive), 4 Pages, 2018/10

At TRP, LWTF was constructed as a facility for processing low radioactive liquid waste and solid waste generated at TRP, and a cold test is been carrying out. In this facility, initially, nitrate waste liquid after separation of nuclides generated with treatment of low radioactive liquid waste was to be solidified by using borate. However, at present, it is necessary to decompose the nitrate in the liquid waste to reduce the environmental burden. For the reason, as a plan to replace the nitrate with the carbonate and to make it as a cement based encapsulation, we are studying for the introduction of the facility. Currently, as a cement solidification technology development for this liquid waste, we are studying the application of cement material based on blast furnace slag (BFS) as a main component. In this report, we show the results of the test conducted on the actual scale (200 L drum can scale).

Journal Articles

Diffusion behavior of D$$_{2}$$O in Fe$$_{3}$$O$$_{4}$$ film on Fe formed in an NaOH solution containing oxidants

Haruna, Takumi*; Miyataki, Yuki*; Hirohata, Yohei*; Shibata, Toshio*; Taniguchi, Naoki; Tachikawa, Hirokazu*

Zairyo To Kankyo, 67(9), p.375 - 380, 2018/09

This research aimed to confirm the formation of Fe$$_{3}$$O$$_{4}$$ film on Fe immersed in aqueous 45 mass% NaOH solution containing some oxidants at the boiling temperature, to recognize the optimum immersion time for the formation of thick and protective film, and to reveal the absorption behavior of D$$_{2}$$O in the Fe$$_{3}$$O$$_{4}$$ film at room temperature. The results were obtained as follows. It was confirmed that Fe$$_{3}$$O$$_{4}$$ film was formed on Fe immersed in the NaOH solution for a time more than 0.6 ks, and the film thickness increased parabolically with an increase in the immersion time. D$$_{2}$$O absorption test was carried out to the films formed in the NaOH solution for immersion times of 1.2 and 3.6 ks. An amount of D$$_{2}$$O absorbed into the film increased with an increase in an absorption time up to 1000 ks, and an absorption time more than 1000 ks made an amount of D$$_{2}$$O constant. The constant amount of D$$_{2}$$O was larger for the film formed on Fe immersed in the NaOH solution for 3.6 ks than that for 1.2 ks. The transient of the amount of D$$_{2}$$O absorbed into the film was analyzed on the basis of Fick's law for diffusion, and diffusion coefficients of D$$_{2}$$O were obtained to be 5.1$$times$$10$$^{-15}$$ cm$$^{2}$$ s$$^{-1}$$ and 9.9$$times$$10$$^{-15}$$ cm$$^{2}$$ s$$^{-1}$$ for the films formed for 1.2 and 3.6 ks, respectively. Therefore it was estimated that the diffusion coefficient of the Fe$$_{3}$$O$$_{4}$$ film was in the region from 5.1$$times$$10$$^{-15}$$ cm$$^{2}$$ s$$^{-1}$$ to 9.9$$times$$10$$^{-15}$$ cm$$^{2}$$ s$$^{-1}$$.

JAEA Reports

Horonobe Underground Research Laboratory Project; Investigation program for the 2018 fiscal year

Hanamuro, Takahiro

JAEA-Review 2018-011, 20 Pages, 2018/08

JAEA-Review-2018-011.pdf:2.77MB

As part of the research and development program on geological disposal of high-level radioactive waste (HLW), the Horonobe Underground Research Center, a division of the Japan Atomic Energy Agency (JAEA), is implementing the Horonobe Underground Research Laboratory Project (Horonobe URL Project) with the aim at investigating sedimentary rock formations. According to the research plan described in the 3rd Mid- and Long-term Plan of JAEA, according to the Horonobe URL Project, "Near-field performance study", "Demonstration of repository design option", and "Verification of crustal-movement buffering capacity of sedimentary rocks" are the top priority issues, and schedule for finishing the project and backfill plan will be decides by the end of 2019 Fiscal Year. The Horonobe URL Project is planned to extend over a period of about 20 years. This report summarizes the investigation program for the 2018 fiscal year (2018/2019).

JAEA Reports

Study on the evaluation methodology of the radioactivity concentration in low-level radioactive wastes generated from JRR-2 & JRR-3

Hayashi, Hirokazu; Izumo, Sari; Nakata, Hisakazu; Amazawa, Hiroya; Sakai, Akihiro

JAEA-Technology 2018-001, 66 Pages, 2018/06

JAEA-Technology-2018-001.pdf:4.12MB

It is necessary to establish evaluation methodology of radioactivity concentrations of each radionuclide in waste packages for operation of the Near-surface Trench disposal and Sub-surface Pit disposal facility in near future, which has been preparing for low-level radioactive wastes generated from research facilities in JAEA. The radionuclides containing in waste packages generated from both JRR-2 and JRR-3, which are H-3, C-14, Cl-36, Co-60, Ni-63, Sr-90, Nb-94, Tc-99, Ag-108m, I-129, Cs-137, Eu-152, Eu-154, U-234, U-238, Pu-239+240, Pu-238+Am-241, Cm-243+244, were evaluated their density based on radiochemical analysis data, and the Evaluation Methodology of the Radioactivity Concentration such as Scaling Factor method and mean activity concentration method was studied in this report.

Journal Articles

Optimization of disposal method and scenario to reduce high level waste volume and repository footprint for HTGR

Fukaya, Yuji; Goto, Minoru; Ohashi, Hirofumi; Nishihara, Tetsuo; Tsubata, Yasuhiro; Matsumura, Tatsuro

Annals of Nuclear Energy, 116, p.224 - 234, 2018/06

 Times Cited Count:1 Percentile:38.14(Nuclear Science & Technology)

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.

1833 (Records 1-20 displayed on this page)