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JAEA Reports

SCHERN: Analysis program for chemical behavior of nitrogen oxide in accident of evaporation to dryness by boiling of reprocessed high level liquid waste in Fuel Reprocessing Facilities

Hiyama, Mina*; Tamaki, Hitoshi; Yoshida, Kazuo

JAEA-Data/Code 2019-006, 17 Pages, 2019/07

JAEA-Data-Code-2019-006.pdf:1.84MB

An accident of evaporation to dryness by boiling of high level liquid waste (HLLW) is postulated as one of the severe accidents caused by the loss of cooling function at a fuel reprocessing plant. In this case, volatile radioactive materials, such as ruthenium (Ru) are released from the tanks with water and nitric-acid mixed vapor into atmosphere. In addition to this, nitrogen oxides (NOx) are also released formed by the thermal decomposition of metal nitrates of fission products (FP) in HLLW. It has been observed experimentally that NOx affects strongly to the transport behavior of Ru at the anticipated atmosphere condition in cells and/or compartments of the facility building. Chemical reactions of NOx with water and nitric acid are also recognized as the complex phenomena to undergo simultaneously in the vapor and liquid phases. An analysis program has been developed to simulate chemical reaction coupled with the thermo-hydraulic condition in the flow paths in the facility building.

Journal Articles

Treatment technology of highly radioactive solid waste generated by experimental tests and sample analysis in reprocessing facilities

Goto, Yuichi; Inada, Satoshi; Kuno, Takehiko; Mori, Eito*

Nippon Hozen Gakkai Dai-16-Kai Gakujutsu Koenkai Yoshishu, p.221 - 224, 2019/07

Test equipment, containers, and analytical wastes, generated by experiments using spent fuel pieces in hot cell of Operation Testing Laboratory and by analysis of highly active liquid wastes in hot analytical cell line of Tokai Reprocessing Plant, are treated as highly radioactive solid wastes. These wastes are stored in specific shielded containers called waste cask and then transport to the storage facility. The treatment of these highly radioactive solid wastes have been carried out for 40 years with upgrading waste taking out system and transportation device. As a results, automation of several procedures have been achieved utilizing conventional equipment, and work efficiency and safety have been improved.

Journal Articles

Analysis of chemical behavior of nitrogen oxide formed by thermal decomposition of FP nitrates in accident of evaporation to dryness by boiling of reprocessed high-level liquid waste

Yoshida, Kazuo; Tamaki, Hitoshi; Yoshida, Naoki; Yoshida, Ryoichiro; Amano, Yuki; Abe, Hitoshi

Nippon Genshiryoku Gakkai Wabun Rombunshi, 18(2), p.69 - 80, 2019/06

An accident of evaporation to dryness by boiling of high level liquid waste (HLLW) is postulated as one of the severe accidents at a fuel reprocessing plant. In this case, volatile radioactive materials, such as ruthenium (Ru) are released from the tanks with water and nitric-acid mixed vapor into atmosphere. In addition to this, nitrogen oxides are also released formed by the thermal decomposition of metal nitrates of fission products (FP) in HLLW. It has been observed experimentally that nitrogen oxide affects strongly to the transport behavior of Ru. Chemical reactions of nitrogen oxide with water and nitric acid are also recognized as the complex phenomena to undergo simultaneously in the vapor and liquid phases. An analysis method has been developed with coupling two types of computer codes to simulate not only thermo-hydraulic behavior but also chemical reactions in the flow paths of carrier gases. A simulation study has been also carried out with a typical facility building.

Journal Articles

Introduction and implementation of physical protection measures including trustworthiness program at Tokai Reprocessing Facilities

Nakamura, Hironobu; Kimura, Takashi; Yamazaki, Katsuyuki; Kitao, Takahiko; Tasaki, Takashi; Iida, Toru

Proceedings of International Conference on Physical Protection of Nuclear Material and Nuclear Facilities (Internet), 9 Pages, 2018/09

After the accident of Fukushima Daiichi Nuclear Power Station, to develop effective security measures based on the lesson learned from such crisis and to meet the IAEA Nuclear Security Recommendations (INFCIRC/225/Rev.5), NRA in Japan made a partial amendment of the regulations concerning the reprocessing activity in 2012. The Tokai reprocessing facility implemented all of those security measures by the end of March 2014. Those new measures help us to keep high degree of security level and contributed to our planned operations to reduce the potential risk of the plant. On the other hand, the trustworthiness program was newly introduced in 2016, based on the trustworthiness policy determined by NRA. The implementing entity of the program is JAEA for the Tokai Reprocessing Facility and is required for both the persons afford unescorted access to Category I and II, CAS/SAS, and the persons afford access to the sensitive information. Those who are involved this program will be judged before engaging the work whether they might act as insider to cause or assist radiological sabotage or unauthorized removal of nuclear material, or leak sensitive information. The program is expected as a measure against insider at reprocessing facilities, and is expected to be enforced around the autumn of 2017. As well as the establishment of security measures, the promoting nuclear security culture for all employees was a big challenge. The Tokai reprocessing facility have introduced several security culture activities, such as case study education of security events done by a small group and putting up the security culture poster and so on. This paper presents introduction and implementation with effectiveness of security measures in the Tokai reprocessing facilities and the future security measures applied to the reprocessing facilities are discussed.

Journal Articles

Demonstration of $$gamma$$-ray pipe-monitoring capabilities for real-time process monitoring safeguards applications in reprocessing facilities

Rodriguez, D.; Tanigawa, Masafumi; Nishimura, Kazuaki; Mukai, Yasunobu; Nakamura, Hironobu; Kurita, Tsutomu; Takamine, Jun; Suzuki, Satoshi*; Sekine, Megumi; Rossi, F.; et al.

Journal of Nuclear Science and Technology, 55(7), p.792 - 804, 2018/07

 Percentile:100(Nuclear Science & Technology)

Nuclear material in reprocessing facilities is safeguarded by random sample verification with additional continuous monitoring applied to solution masses and volume in important tanks to maintain continuity-of-knowledge of process operation. Measuring the unique $$gamma$$ rays of each solution as the material flows through pipes connecting all tanks and process apparatuses could potentially improve process monitoring by verifying the compositions in real time. We tested this $$gamma$$ ray pipe-monitoring method using plutonium-nitrate solution transferred between tanks at the PCDF-TRP. The $$gamma$$ rays were measured using a lanthanum-bromide detector with a list-mode data acquisition system to obtain both time and energy of $$gamma$$-ray. The analysis and results of this measurement demonstrate an ability to determine isotopic composition, process timing, flow rate, and volume of solution flowing through pipes, introducing a viable capability for process monitoring safeguards verification.

JAEA Reports

Development of correlation of gaseous ruthenium transfer rate to condensed water in accident of evaporation to dryness by boiling of reprocessed high level liquid waste in Fuel Reprocessing Facilities

Yoshida, Kazuo; Tamaki, Hitoshi; Yoshida, Naoki; Amano, Yuki; Abe, Hitoshi

JAEA-Research 2017-015, 18 Pages, 2018/01

JAEA-Research-2017-015.pdf:3.08MB

An accident of evaporation to dryness by boiling of high level liquid waste is postulated as one of the severe accidents at a fuel reprocessing facility. It was observed at the experiments that a large amount of ruthenium (Ru) is volatilized and transfer to the vapor phase in the tank. The nitric acid and water mixed vapor released from the tank is condensed. Volatilized Ru is expected to transfer into the condensed water at the compartments in the building. Quantitative estimation of the amount of Ru transferred condensed water is key issues to evaluate the reduction the amount of Ru through leak path in the facility building. This report presents that a correlation has been developed for Ru transfer rate to condensed water with vapor condensing rate based on the experimental results and additional thermal-hydraulic simulation of the experiments. Applicability of the correlation has been also demonstrated with the accident simulation of typical facilities in full-scale.

Journal Articles

Effect of chloride ion on corrosion behavior of SUS316L-grade stainless steel in nitric acid solutions containing seawater components under $$gamma$$-ray irradiation

Sano, Yuichi; Ambai, Hiromu; Takeuchi, Masayuki; Iijima, Shizuka; Uchida, Naoki

Journal of Nuclear Materials, 493, p.200 - 206, 2017/09

 Times Cited Count:3 Percentile:27.27(Materials Science, Multidisciplinary)

Concerning the Fukushima Daiichi Nuclear Power Plant accident, we investigated the effect of chloride ion on the corrosion behavior of SUS316L stainless steel, which is a typical material for the equipment used in reprocessing, in HNO$$_{3}$$ solution containing seawater components, including under the $$gamma$$-ray irradiation condition. Electrochemical and immersion tests were carried out using a mixture of HNO$$_{3}$$ and artificial seawater (ASW). In the HNO$$_{3}$$ solution containing high amounts of ASW, the cathodic current densities increased and uniform corrosion progressed. This might be caused by strong oxidants, such as Cl$$_{2}$$ and NOCl, generated in the reaction between HNO$$_{3}$$ and Cl$$^{-}$$ ions. The corrosion rate decreased with the immersion time at low concentrations of HNO$$_{3}$$, while it increased at high concentrations. Under the $$gamma$$-ray irradiation condition, the corrosion rate decreased due to the suppression of the cathodic reactions by the reaction between the above oxidants and HNO$$_{2}$$ generated by radiolysis.

Journal Articles

HEPA filter clogging and volatile material release under solvent fire accident in fuel reprocessing facility

Ono, Takuya; Watanabe, Koji; Tashiro, Shinsuke; Amano, Yuki; Abe, Hitoshi

Proceedings of 25th International Conference on Nuclear Engineering (ICONE-25) (CD-ROM), 7 Pages, 2017/07

After the Fukushima-Daiichi accident, countermeasures against the severe accident are newly required as regulatory items for nuclear facilities. Organic solvent fire in cell was defined as one of the accidents in the fuel reprocessing plant. When the solvent burns, aerosols including soot are released. The substances clog HEPA filters in the ventilation system and their breakthrough may happen because of differential pressure rising. Moreover, the fire can also release volatile radioactive gaseous species, which can pass through HEPA filters. These phenomena are important for evaluation of confinement capability of the facility and public exposure. We have investigated, in relating to the clogging behavior, release behavior of aerosols as well as of volatile materials from burnt solvent. In the presentation, we will report experimental data and evaluation results obtained from recent research.

Journal Articles

Hydrogen absorption behavior on zirconium under $$gamma$$-radiolysis of nitric acid solution

Ishijima, Yasuhiro; Ueno, Fumiyoshi; Abe, Hitoshi

Nippon Genshiryoku Gakkai Wabun Rombunshi, 16(2), p.100 - 106, 2017/05

Zirconium (Zr) has been used as a structural material at the spent nuclear fuel reprocessing plant in Japan because of its excellent corrosion resistance against nitric acid solution. And the radiolytic hydrogen is known to be generated in the spent nuclear fuel solution. Zr is known to be highly susceptible to hydrogen embrittlement. Therefore, evaluating the radiolytic hydrogen absorption behavior of Zr in nitric acid solution (HNO$$_{3}$$) is essential. In this study, immersion tests were conducted on Zr in nitric acid solutions under $$gamma$$-ray irradiation to evaluate its radiolytic hydrogen absorption behavior. Results showed that hydrogen concentration on Zr increased both in 1-3 mol/L HNO$$_{3}$$ and pure water at 5 and 7 kGy/h after immersion. The amount of hydrogen absorption on Zr under $$gamma$$-ray irradiation had a direct correlation with the radiolytic hydrogen generation value in HNO$$_{3}$$. The results of glow discharge optical emission spectrometry, thermal desorption spectroscopy, and X-ray diffraction result shows that the absorbed radiolytic hydrogen generated a hydride on the surface of Zr.

Journal Articles

Development of metal corrosion testing method simulating equipment of reprocessing of spent nuclear fuels

Matsueda, Makoto; Irisawa, Eriko; Kato, Chiaki; Matsui, Hiroki

Proceedings of 54th Annual Meeting of Hot Laboratories and Remote Handling (HOTLAB 2017) (Internet), 4 Pages, 2017/00

In the PUREX method, spent fuels are dissolved with nitric acid media. The reprocessing solution containing Fission Products derived from spent fuels is very corrosive to metal materials, the corrosion problem often appears on the surface stainless steel devices. The oxidizing metal ions such as Ruthenium (Ru) and Neptunium (Np) in the process solution is the key reason for severe corrosion of stainless steel. In order to obtain the corrosion rate of stainless steel, we installed the corrosion test apparatus inside an airtight concrete cell in a hot laboratory (the WAste Safety TEsting Facility (WASTEF) of the Japan Atomic Energy Agency), and performed the corrosion tests of stainless steel in the heated nitric acid solution containing Np. The corrosion tests were performed in the temperature range from room temperature to boiling point for 500 hours per batch. The results show that the presence of Np accelerate the stainless steel corrosion in the nitric acid solution.

Journal Articles

Characterization of the insoluble sludge from the dissolution of irradiated fast breeder reactor fuel

Aihara, Haruka; Arai, Yoichi; Shibata, Atsuhiro; Nomura, Kazunori; Takeuchi, Masayuki

Procedia Chemistry, 21, p.279 - 284, 2016/12

BB2015-3214.pdf:0.31MB

 Times Cited Count:1 Percentile:20.72

JAEA Reports

Development of analytical model for condensation of vapor mixture of nitric acid and water affected volatilized ruthenium behavior in accident of evaporation to dryness by boiling of reprocessed high level liquid waste at fuel reprocessing facilities

Yoshida, Kazuo

JAEA-Research 2016-012, 24 Pages, 2016/08

JAEA-Research-2016-012.pdf:3.04MB

An accident of evaporation to dryness by boiling of high level liquid waste is postulated as one of the severe accidents. In this case, Ru volatilization increases in liquid waste temperature over 120 centigrade at later boiling and dry out phases. It has been observed at the experiments with actual and synthetic liquid waste that some amount of Ru volatilizes and transfers into condensed nitric acid solution at those phases. The nitric acid and water vapor from waste tank condenses at compartments of actual facilities building. The volatilized Ru could transfer into condensed liquid. It is key issues for quantifying the amount of transferred Ru through the facility building to simulate these thermodynamic and chemical behaviors. An analytical model has been proposed in this report based on the condensation mechanisms of nitric acid and water in vapor-liquid equilibria. It has been also carried out to review the thermodynamic properties of nitric acid solution.

JAEA Reports

Accident analysis of evaporation to dryness by boiling of reprocessed high level liquid waste at fuel reprocessing facilities with considering severe accident measures

Yoshida, Kazuo

JAEA-Research 2016-004, 15 Pages, 2016/06

JAEA-Research-2016-004.pdf:2.22MB

An accident of evaporation to dryness by boiling of high level liquid waste is postulated as one of the severe accidents caused by the loss of cooling function at a fuel reprocessing plant. In this case, some amount of fission products (FPs) will be transferred to the vapor phase in the tank, and could be released to the environment. Two mitigative accident measures have been proposed by the licensee. One of them is injecting cold water to waste tanks to prevent dryness and another is leading generated vapor through temporary duct to huge spaces in the facility to condense to liquid. Thermal-hydraulics and aerosol transport behaviors in compartments of a typical facility building have been analyzed based on the scenario with these accident measures. The effects of measures are discussed form a view point of the reduction of radioactive material release to environment.

Journal Articles

Release of radioactive materials from high active liquid waste in small-scale hot test for boiling accident in reprocessing plant

Yamane, Yuichi; Amano, Yuki; Tashiro, Shinsuke; Abe, Hitoshi; Uchiyama, Gunzo; Yoshida, Kazuo; Ishikawa, Jun

Journal of Nuclear Science and Technology, 53(6), p.783 - 789, 2016/06

 Times Cited Count:1 Percentile:76.09(Nuclear Science & Technology)

The release behavior of radioactive materials from high active liquid waste (HALW) has been experimentally investigated under boiling accident conditions. In the experiments using HALW obtained through laboratory scale reprocessing, release ratio was measured for the FP nuclides such as Ru, $$^{99}$$Tc, Cs, Sr, Nd, Y, Mo, Rh and actinides such as $$^{242}$$Cm, $$^{241}$$Am. As a result, the release ratio was 0.20 for Ru and 1$$times$$$$10^{-4}$$ for the FP and Ac nuclides. Ru was released into the gas phase in the form of both mist and gas. For its released amount, weak dependency was found to the initial concentration in the test solution. The release ratio decreased with the initial concentration. For other FP nuclides and actinides as non-volatile, released into the gas phase in the form of mist, the released amount increased with the initial concentration. The release ratio of Ru and NOx concentration increased with temperature of the test solutions. They were released almost at the same temperature between 200 and 300$$^{circ}$$C. Size distribution of the mist and other particle was measured.

Journal Articles

Purification of uranium products in crystallization system for nuclear fuel reprocessing

Takeuchi, Masayuki; Yano, Kimihiko; Shibata, Atsuhiro; Sambommatsu, Yuji*; Nakamura, Kazuhito*; Chikazawa, Takahiro*; Hirasawa, Izumi*

Journal of Nuclear Science and Technology, 53(4), p.521 - 528, 2016/04

 Times Cited Count:1 Percentile:76.09(Nuclear Science & Technology)

Journal Articles

Analysis of release and transport of aerial radioactive materials in accident of evaporation to dryness caused by boiling of reprocessed high-level liquid waste

Yoshida, Kazuo; Ishikawa, Jun; Abe, Hitoshi

Nippon Genshiryoku Gakkai Wabun Rombunshi, 14(4), p.213 - 226, 2015/12

An accident of evaporation to dryness by boiling of high level liquid waste (HLLW) is postulated as one of the severe accidents to occur caused by the loss of cooling function at a fuel reprocessing plant. In this case, some amount of fission products (FPs) will be transferred to the vapor phase in the tank, and could be released to the environment. Therefore, the quantitative estimation of transport and release behavior of FPs is one of the key issues in the assessment of the accident consequence. To resolve this issue, a systematic analysis method with computer codes has been developed based on the phenomenological behavior in boiling accident of HLLW. A simulation study demonstrated that the behaviors of liquid waste temperature and entrainment of mists were in good agreement with the experimental results during early boiling phase

JAEA Reports

Study of treatment method for damaged fuel removed from the spent fuel pool; Outline of annual report for JFY 2013 and 2014 (Contract research)

Iijima, Shizuka; Uchida, Naoki; Taguchi, Katsuya; Washiya, Tadahiro

JAEA-Review 2015-018, 39 Pages, 2015/11

JAEA-Review-2015-018.pdf:3.95MB

There is a possibility that the fuel assemblies stored in the spent fuel pool (SFP) at Fukushima Daiichi NPS (or Nuclear Power Station) are not only exposed to seawater and concrete fragments, but also damaged by fallen rubbles. We checked the reprocessing experiences of leak fuels at Tokai Reprocessing Plant and overseas reprocessing facilities, and the storage conditions and the checked and inspected results of the fuel stored in the SFP at Fukushima Daiichi NPS, after that, we listed up the technological problems with reprocessing damaged nuclear fuels and selected elements of the research for the purpose of drawing indicators to make a judgmental decision of the possibility of damaged nuclear fuels reprocessing. And we drew the indicators to make a judgmental decision on the possibility of reprocessing based on the results of the examination and the study about elements of the research.

Journal Articles

Study on the behavior of radiolytically produced hydrogen in a high-level liquid waste tank of a reprocessing plant; Comparison between actual and simulated solutions

Kinuhata, Hiroshi*; Yamamoto, Masahiko; Taguchi, Shigeo; Surugaya, Naoki; Sato, Soichi; Kodama, Takashi*; Tamauchi, Yoshikazu*; Shibata, Yuki*; Anzai, Kiyoshi*; Matsuoka, Shingo*

Nuclear Technology, 192(2), p.155 - 159, 2015/11

 Percentile:100(Nuclear Science & Technology)

Experiments using a small-scale apparatus with 30 ml actual high-level liquid waste from the Tokai Reprocessing Plant were carried out to show that the hydrogen concentration in the gas phase reaches a steady-state value of much less than 4% (lower explosive limit) in the absence of sweeping-air. The H$$_{2}$$ concentration reached a steady-state value as was expected and it was compared with a value predicted from an equation with parameters which had been obtained using the simulated solution. Satisfactory agreement showed that the Pd-ion catalytic H$$_{2}$$ consumption reaction previously found in the simulated solution proceeded equally well in the actual solution.

Journal Articles

Application of turbidity measurement for evaluation of two-phase separation in ${it N}$,${it N}$-dialkylamides-nitric acid systems

Tsutsui, Nao; Ban, Yasutoshi; Hakamatsuka, Yasuyuki; Urabe, Shunichi; Matsumura, Tatsuro

Proceedings of 21st International Conference & Exhibition; Nuclear Fuel Cycle for a Low-Carbon Future (GLOBAL 2015) (USB Flash Drive), p.1153 - 1157, 2015/09

${it N}$,${it N}$-Dialkylamides are promising alternative extractants to tri-${it n}$-butyl phosphate in the reprocessing of spent nuclear fuels, but the two-phase separation between their organic and aqueous phases has not been evaluated quantitatively. ${it N}$,${it N}$-Di(2-ethylhexyl)-2,2-dimethylpropanamide (DEHDMPA) in ${it n}$-dodecane were agitated with uranyl nitrate-containing nitric acid, and their turbidities and their uranium distribution ratios were measured with respect to the time for the quantitative evaluation. Increasing DEHDMPA, uranium, and nitric acid concentrations enhanced turbidities. Although turbidities decreased with respect to the time, uranium distribution ratios slightly changed, indicating the observed turbidities did not affect these uranium distribution ratios significantly. Therefore, DEHDMPA may act as suitable extractant for uranium in nitric acid from two-phase separation viewpoint, and turbidity may be an indicator for extractant performance evaluation.

Journal Articles

Development of nitride fuel cycle technology for transmutation of minor actinides

Hayashi, Hirokazu; Nishi, Tsuyoshi*; Sato, Takumi; Kurata, Masaki

Proceedings of 21st International Conference & Exhibition; Nuclear Fuel Cycle for a Low-Carbon Future (GLOBAL 2015) (USB Flash Drive), p.1811 - 1817, 2015/09

Transmutation of long-lived radioactive nuclides including minor actinides (MA: Np, Am, Cm) has been studied in Japan Atomic Energy Agency (JAEA). Accelerator-driven system (ADS) is regarded as one of the powerful tools for transmutation of MA under the double strata fuel cycle concept. Uranium-free nitride fuel was chosen as the first candidate fuel for MA transmutation using ADS. To improve the transmutation ratio of MA, reprocessing of spent fuel and reusing MA recovered from the spent fuels is necessary. Our target is to transmute 99% of MA arisen from commercial power reactor fuel cycle, with which the period until the radiotoxicity drops below that of natural uranium can be shorten from about 5000 years to about 300 years. A pyrochemical process has been proposed as the first candidate for reprocessing of the spent nitride fuel. This paper overviews the current status of the nitride fuel cycle technology. Our recent study on fuel fabrication, fuel property measurements, reprocessing of spent fuel, development of the property database of MA nitride fuel, and fuel behavior simulation code are introduced. Our research and development (R&D) plan based on the roadmap of the development is also introduced.

149 (Records 1-20 displayed on this page)