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Journal Articles

Development of in-reactor observation system using Cherenkov light(VI)

Takeuchi, Tomoaki; Yamamoto, Keiichi; Otsuka, Noriaki; Shibata, Hiroshi; Shibata, Akira; Takemoto, Noriyuki; Tsuchiya, Kunihiko; Sano, Tadafumi*; Unesaki, Hironobu*; Fujihara, Yasuyuki*; et al.

KURRI Progress Report 2014, P. 108, 2015/07

Investigation of a relation between output power and brightness of Cherenkov light of a specific fuel element at KUR by a CCD camera was performed due to a development of a real-time in-core measurement technique using Cherenkov light. The results indicate that the inhomogeneous distribution of output power and the shadow of the control-rod guide tubes and the other irradiation equipment have significant effects on the brightness of the Cherenkov light. These effects could be suppressed by using a number of cameras located at various positions.

JAEA Reports

Application of Cherenkov light observation to reactor measurements, 1; Estimation of reactor power from Cherenkov light intensity

Yamamoto, Keiichi; Takeuchi, Tomoaki; Sano, Tadafumi*; Homma, Ryohei*; Kimura, Nobuaki; Otsuka, Noriaki; Kosuge, Fumiaki*; Nakajima, Ken*; Tsuchiya, Kunihiko

JAEA-Technology 2014-028, 56 Pages, 2015/01

JAEA-Technology-2014-028.pdf:9.23MB

Development of the reactor measurement system was started to obtain real-time in-core nuclear and thermal information, where the quantity measurement of brightness of Cherenkov light was applied. The system would be applied as monitoring system in severe accidents and for advanced operation management technology in existing LWRs. In this report, the calculation and the observation results were summarized about the quantity of the Cherenkov light caused by the $$gamma$$ and $$beta$$ ray emitted from the fuels in the core of Kyoto University Research Reactor.

Journal Articles

Development of in-reactor observation system using Cherenkov light, 5

Otsuka, Noriaki; Takeuchi, Tomoaki; Yamamoto, Keiichi; Shibata, Akira; Kimura, Nobuaki; Takemoto, Noriyuki; Tanimoto, Masataka; Tsuchiya, Kunihiko; Sano, Tadafumi*; Unesaki, Hironobu*; et al.

KURRI Progress Report 2013, P. 215, 2014/10

Investigation of a relation between reactor power and brightness of Cherenkov light at Kyoto University Research reactor (KUR) by a CCD camera was performed due to a development of a real-time in-core measurement technique using Cherenkov light. Analyzing the brightness value of individual RGB color component at each pixel, some of the G and B brightness values reached the maximum value of 8-bit binary number, i.e. 255, above about 2-3 MW. Therefore, we corrected the G and B brightness values by the R signals whose brightness value did not saturate even at 5 MW, the maximum reactor power of KUR. Then, the total brightness value was in proportion to the reactor power after the correction. These results indicate the reactor power can be estimated by the observation of Cherenkov light.

Journal Articles

Survey on effect of crystal texture of beryllium on total cross-section to improve neutronic evaluation in JMTR

Takemoto, Noriyuki; Imaizumi, Tomomi; Kimura, Nobuaki; Tsuchiya, Kunihiko; Hori, Junichi*; Sano, Tadafumi*; Nakajima, Ken*

Proceedings of International Conference on the Physics of Reactors; The Role of Reactor Physics toward a Sustainable Future (PHYSOR 2014) (CD-ROM), 11 Pages, 2014/09

Neutronic evaluations in JMTR have been performed for irradiation tests by Monte Carlo method with thermal neutron scattering law, S($$alpha$$, $$beta$$), data for beryllium metal, etc. The calculation accuracy of fast and thermal neutron fluxes are $$pm$$10% and $$pm$$30%, respectively. Analytical and experimental investigations to achieve higher calculation accuracy, especially for the thermal neutron flux up to the fast neutron flux level, have been therefore performed to offer higher value data technically to the JMTR users. In order to investigate an effect of fabrication method of beryllium material on the calculation accuracy, total cross-sections of beryllium specimens were measured using KURRI-LINAC, and it was found that the total cross-section was different from the theoretical one, and depended on the crystal texture, etc. The S($$alpha$$, $$beta$$) was adjusted based on the measured data, and the applicability to the neutronic evaluation in the JMTR was verified.

Journal Articles

"Relative rates method" for evaluating the effect of potential geological environmental change due to uplift/erosion to radionuclide migration of high-level radioactive waste

Ebashi, Takeshi; Kawamura, Makoto*; Inagaki, Manabu*; Koo, Shigeru*; Shibata, Masahiro; Itazu, Toru; Nakajima, Kunihiko*; Miyahara, Kaname; Apted, M. J.*

Materials Research Society Symposium Proceedings, Vol.1665, p.39 - 45, 2014/07

In Japan, the likelihood of uplift/erosion on repository performance and waste isolation can be typically greatly reduced or excluded by careful siting, however, the inability to completely exclude the uplift/erosion scenario may require an analysis of the consequences of such a scenario. For this purpose, an assessment approach has been developed to more realistically treat the effect of uplift/erosion for a hypothetical repository located in sedimentary host rock. A key advantage to this approach is the extrapolation of the geohistory of modern analogue sites to develop credible initial inputs for future volunteer sites that may be poorly characterized at the initial stages of site investigation. In addition, the approach provides a systematic basis for bounding the range of possible evolution in thermal-hydrological-mechanical-chemical conditions of a repository experiencing different uplift/ erosion rates.

Journal Articles

Development of in-reactor observation system using Cherenkov light, 4

Kimura, Nobuaki; Takeuchi, Tomoaki; Shibata, Akira; Takemoto, Noriyuki; Kimura, Akihiro; Naka, Michihiro; Nishikata, Kaori; Tanimoto, Masataka; Tsuchiya, Kunihiko; Sano, Tadafumi*; et al.

KURRI Progress Report 2012, P. 209, 2013/10

In research reactors, CCD cameras are used to observe reactor core for reactor operation management, e.g. to prevent debris from falling. In order to measure the reactor power and fuel burnup exactly by means of observation of Cherenkov light, the development of the on-line measurement device started in 2009. In this study, the wavelength and the absolute irradiance of the Cherenkov light were measured by a spectrometer, and the Cherenkov light was observed by the CCD camera. As a result, the measurement value is good agreement with the nominal value. On the other hand, the value by the visible imaging system was obtained the same tendency of nominal transmittance value of ND-filters.

Journal Articles

Bounding analysis of uplift and erosion scenario for an HLW repository

Wakasugi, Keiichiro; Nakajima, Kunihiko*; Shimemoto, Hidenori; Shibata, Masahiro; Yamaguchi, Masaaki

Proceedings of 21st International Conference on Nuclear Engineering (ICONE-21) (DVD-ROM), 9 Pages, 2013/07

In Japan, uplift and erosion scenarios must be analysed since this natural phenomena would be inevitable at most sites in Japan. It's increasingly important to enhance the confidence of the assessment for the uplift and erosion scenarios, as no assessment cut-off times have yet been defined. In this context, this study carried out bounding analysis to find out parameter conditions to satisfy hypothetical dose criteria. The results show that there are no cases that satisfy 10 microSv/y. However, all cases are below 300 microSv/y. The discussion also implies that to accelerate the release from the EBS for minimising the dose in later phase is inadequate and ineffective at all, due to multiple barriers and multiple safety functions. In principal, the influence of uplift and erosion should be reduced by appropriate site selection and design as much as possible to ensure the sufficient nuclides decay while the repository is staying at the deep underground.

Journal Articles

Development of in-reactor observation system using Cherenkov light, 3

Kimura, Nobuaki; Takemoto, Noriyuki; Nagata, Hiroshi; Kimura, Akihiro; Naka, Michihiro; Nishikata, Kaori; Tanimoto, Masataka; Tsuchiya, Kunihiko; Sano, Tadafumi*; Unesaki, Hironobu*; et al.

KURRI Progress Report 2011, P. 219, 2012/10

In research reactors, a CCD camera is used to observe reactor core for reactor operation management, e.g. to prevent debris falling. In order to measure the reactor power and fuel burnup exactly by means of observation of Cherenkov light and $$gamma$$ ray information, the development of the on-line measurement device has been started since 2009. In this study, as a part of development of in-reactor surveillance, wavelength and absolute irradiance of Cherenkov light were measured by spectroscopy, and Cherenkov light was observed by the CCD camera. The neutral density filters (ND-filters) were used to investigate the transmittance of Cherenkov light in these measurements.

JAEA Reports

Design, fabrication and transportation of Si rotating device

Kimura, Nobuaki; Imaizumi, Tomomi; Takemoto, Noriyuki; Tanimoto, Masataka; Saito, Takashi; Hori, Naohiko; Tsuchiya, Kunihiko; Romanova, N. K.*; Gizatulin, S.*; Martyushov, A.*; et al.

JAEA-Technology 2012-012, 34 Pages, 2012/06

JAEA-Technology-2012-012.pdf:12.91MB

Si semiconductor production by Neutron Transmutation Doping (NTD) method using the Japan Materials Testing Reactor (JMTR) has been investigated in Neutron Irradiation and Testing Reactor Center, Japan Atomic Energy Agency (JAEA) in order to expand industry use. As a part of investigations, irradiation test of silicon ingot for development of NTD-Si with high quality was planned using WWR-K in Institute of Nuclear Physics (INP), National Nuclear Center of Republic of Kazakhstan (NNC-RK) based on one of specific topics of cooperation (STC), Irradiation Technology for NTD-Si (STC No.II-4), on the implementing arrangement between NNC-RK and the JAEA for "Nuclear Technology on Testing/Research Reactors" in cooperation in research and development in nuclear energy and technology. As for the irradiation test, Si rotating device was fabricated in JAEA, and the fabricated device was transported with irradiation specimens from JAEA to INP-NNC-RK. This report described the design, the fabrication, the performance test of the Si rotating device and transportation procedures.

Journal Articles

Development on in-reactor observation system using cherenkov light, 2

Takemoto, Noriyuki; Tsuchiya, Kunihiko; Nagao, Yoshiharu; Kitagishi, Shigeru; Naka, Michihiro; Kimura, Akihiro; Sano, Tadafumi*; Unesaki, Hironobu*; Yoshimoto, Takaaki*; Nakajima, Ken*; et al.

KURRI Progress Report 2010, P. 204, 2011/10

no abstracts in English

Journal Articles

Development on in-reactor observation system using cherenkov light

Tsuchiya, Kunihiko; Kitagishi, Shigeru; Nagao, Yoshiharu; Takemoto, Noriyuki; Naka, Michihiro; Kimura, Akihiro; Sano, Tadafumi*; Unesaki, Hironobu*; Yoshimoto, Takaaki*; Nakajima, Ken*; et al.

KURRI Progress Report 2009, P. 196, 2010/10

no abstracts in English

JAEA Reports

Study and design of safety assessment model based on H12 reference case using GoldSim

Nakajima, Kunihiko*; Koo, Shigeru*; Ebina, Takanori*; Ebashi, Takeshi; Inagaki, Manabu

JAEA-Data/Code 2009-009, 62 Pages, 2009/07

JAEA-Data-Code-2009-009.pdf:19.19MB

Reference case of safety assessment analysis at the H12 report was calculated using the numerical code MESHNOTE and MATRICS mainly. On the other hand, recently general simulation software witch has a character of object-oriented is globally used and the numerical code GoldSim is typical software. After the H12 report, probability theory analysis and sensitivity analysis using GoldSim have carried out by statistical method for the purpose of following up safety assessment analysis at the H12 report. On this report, details of the method for the model design using GoldSim are summarized, and to confirm calculation reproducibility, verification between the H12 report and GoldSim results were carried out. And the guide book of calculation method using GoldSim is maintained for other investigators at JAEA who want to calculate reference case on the H12 report. In the future, application resources on this report will be able to upgrade probability theory analysis and other conceptual models.

JAEA Reports

Illustration of an approach to evaluate the effect of the uplift and denudation for a groundwater scenario of a geological disposal concept in a hypothetical sedimentary rock

Ebashi, Takeshi; Kawamura, Makoto; Inagaki, Manabu; Koo, Shigeru*; Shibata, Masahiro; Itazu, Toru; Nakajima, Kunihiko*; Miyahara, Kaname

JAEA-Research 2008-117, 36 Pages, 2009/03

JAEA-Research-2008-117.pdf:3.18MB

It is considered that it is possible to avoid the effect of the uplift and denudation process on geological disposal system by siting and a repository design. However, since the uplift/denudation continues far into the future, it is important to enhance the confidence of the methodology to evaluate such an effect, based on the understanding of geohistorical information and potential impact on the disposal system. This paper presents an evolution pattern of the geological environment and the influence analysis in terms of system performance affected by the uplift and denudation process based on the relevant conceptual models for groundwater scenarios of the disposal system for a hypothetical sedimentary rock. As a result, it is indicated that the conceptual model is capable to identify a specific combination of patterns of system evolution of the geological environment in terms of features on the uplift and denudation process, and also provides technical basis for setting up parameters of nuclide migration model and the subsequent influence analysis. Consequently, it is also indicated that the evaluation methodology applied in this study is valuable to evaluate the uplift/denudation phenomena with specific geological environment, and the results obtained by the analysis could be valuable information for site investigation and/or the prediction of a future change trend for the uplift/denudation.

Journal Articles

Application of a comprehensive sensitivity analysis method on the safety assessment of TRU waste disposal in Japan

Oi, Takao; Takase, Hiroyasu*; Inagaki, Manabu; Oyamada, Kiyoshi*; Sone, Tomoyuki; Mihara, Morihiro; Ebashi, Takeshi; Nakajima, Kunihiko*

Materials Research Society Symposium Proceedings, Vol.985, p.129 - 134, 2007/00

A comprehensive sensitivity analysis method has been developed with the aim of providing quantitative information in an efficient manner. This methodology is composed of the following two components: (1) a statistical method with random sampling of independent parameters, which identifies important parameters and extracts threshold values of parameters and/or combinations yielding a "successful condition" where maximum dose does not exceed a target value, (2) A nuclide migration model that as far as possible incorporates a comprehensive set of phenomena occurring within the repository. This approach was applied as part of a safety assessment of the geological disposal of TRU waste in Japan (TRU-2). It was shown that the concept of TRU waste disposal is robust from the point of view of safety.

JAEA Reports

Application of decision tree technique to sensitivity analysis for results of radionuclide migration calculations, 2

Nakajima, Kunihiko*; Makino, Hitoshi

JAEA-Data/Code 2006-013, 31 Pages, 2006/06

JAEA-Data-Code-2006-013.pdf:3.63MB

In the safety assessment of geological disposal system, data uncertainty is inherent by the heterogeneity of the field in the natural geological environment and the change of the geological environment condition with the progress in the time and insufficient of understanding and information, and it is difficult to perfectly remove them. It is important to safety assessment that understanding influence of the uncertainty of parameter on the result of the Monte Carlo simulation considering data uncertainty. In our study, examining the range of application and the accuracy of the decision tree analysis technique by various approaches in the sensitivity analysis, and examining the object various results including the maximum value of all doses (others, the time of the maximum value of all doses, the identification of dominant nuclides). As a result, it was shown to be applicable for various purposes using the decision tree analysis technique to the sensitivity analysis.

JAEA Reports

Application of Decision Tree Technique to Sensitivity Analysis for Results of Radionuclide Migration Calculations

Nakajima, Kunihiko*; Makino, Hitoshi

JNC-TN8400 2005-001, 32 Pages, 2005/03

JNC-TN8400-2005-001.pdf:0.93MB

Uncertainties are always present in the parameters used for the nuclide migration analysis in the geological disposal system. These uncertainties affect the result of such analyses, e.g., and the identification of dominant nuclides. It is very important to identify the parameters causing the significant impact on the results, and to investigate the influence of identified parameters in order to recognize R&D items with respect to the development of geological disposal system and understanding of the system performance. In our study, the decision tree analysis technique was examined in the sensitivity analysis as a method for investigation of the influences of the parameters and for complement existing sensitivity analysis. As a result, results obtained from Monte Carlo simulation with parameter uncertainties could be distinguished with not only important parameters but also with their quantitative conditions (e.g., ranges of parameter values). Furthermore, information obtained from the decision tree analysis could be used 1) to categorize the results obtained from the nuclide migration analysis for a given parameter set, 2) to show prospective effect of reduction to parameter uncertainties on the results.

JAEA Reports

Scoping calculation of nuclides migration in engineering barrier system for effect of volume expansion due to overpack corrosion and intrusion of the buffer material

; ; Ishiguro, Katsuhiko; Nakajima, Kunihiko*;

JNC-TN8400 99-087, 41 Pages, 1999/11

JNC-TN8400-99-087.pdf:2.78MB

Corrosion of the carbon steel overpack leads to a volume expansion since the specific gravity of corrosion products is smaller than carbon steel. The buffer material is compressed due to the corrosive swelling, reducing its thickness and porosity. On the other hand, Buffer material may be extruded into fractures of the surrounding rock and this may lead to a deterioration of the planned functions of the buffer, including retardation of nuclides migration and colloid filtration. In this study, the sensitivity analyses for the effect of volume expansion and intrusion of the buffer material on nuclide migration in the engineering barrier system are carried out. The sensitivity analyses were performed on the decrease in the thickness of the buffer material in the radial direction caused by the corrosive swelling, and the change in the porosity and dry density of the buffer caused by both compaction due to corrosive swelling and intrusion of buffer material. As results, it was found the maximum release rates of relatively shorter half-life nuclides from the outside of the buffer material decreased for taking into account of a volume expansion due to overpack corrosion. On the other hand, the maximum release rates increased when the intrusion of buffer material was also taking into account. It was, however, the maximum release rates of longer half-life nuclides, such as Cs-137 and Np-237, were insensitive to the change of buffer material thickness, and porosity and dry density of buffer.

Journal Articles

Concept of JT-60 Super Upgrade

Ninomiya, Hiromasa; Kamada, Yutaka; Miya, Naoyuki; *; *; Oikawa, Akira; Sakasai, Akira; Takahashi, Yoshikazu; Takizuka, Tomonori; ; et al.

15th IEEE/NPSS Symp. on Fusion Engineering,Vol. 1, 0, p.374 - 377, 1993/00

no abstracts in English

JAEA Reports

None

Nakajima, Kunihiko*; ; ; Sasaki, Noriaki; Ishikawa, Hirohisa

PNC-TN8410 92-068, 96 Pages, 1992/06

PNC-TN8410-92-068.pdf:2.4MB

None

JAEA Reports

None

; Nakajima, Kunihiko*; ; ; Ishiguro, Katsuhiko

PNC-TN1410 92-086, 135 Pages, 1992/01

PNC-TN1410-92-086.pdf:3.69MB

no abstracts in English

30 (Records 1-20 displayed on this page)