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Journal Articles

Density stratification breakup by a vertical jet; Experimental and numerical investigation on the effect of dynamic change of turbulent Schmidt number

Abe, Satoshi; Studer, E.*; Ishigaki, Masahiro; Shibamoto, Yasuteru; Yonomoto, Taisuke

Nuclear Engineering and Design, 368, p.110785_1 - 110785_14, 2020/11

JAEA Reports

Survey on the radioactive substance in the coastal areas near Fukushima Prefecture in FY2019 (Contract research)

Misono, Toshiharu; Tsuruta, Tadahiko; Nakanishi, Takahiro; Sanada, Yukihisa; Shiribiki, Takehiko; Miyamoto, Kenji*; Urabe, Yoshimi*

JAEA-Research 2020-008, 166 Pages, 2020/10

JAEA-Research-2020-008.pdf:13.11MB
JAEA-Research-2020-008(errata).pdf:0.92MB

After the accident at TEPCO Fukushima Daiichi Nuclear Power Station (1F), marine monitoring survey on radioactive substances have been conducted with financially supported by the Nuclear Regulatory Agency from FY2019. Results obtain in the project in FY2019 are presented in this report. Based on scientific grounds, the concept necessary for "progress of sea area monitoring" was arranged for the future medium- to long-term investigation of radiocesium concentrations. As basic information of survey frequency revise, a seabed topography and sediment distribution survey was conducted, and an attempt was made to understand the relationship between the seabed topography and the grain size distribution of bottom sediment. A columnar core sample was collected in the coastal area and analyzed for radioactive cesium concentration. In order to understand the dynamics of radioactive cesium contained in suspended matter flowing in from a river, suspended solids was collected using a sediment trap and the concentration of radioactive cesium was measured. We re-analyzed the towed monitoring data that had been implemented since 2013, and tried to improve the accuracy of the radioactive cesium distribution estimation map in the coastal area.

Journal Articles

Experimental investigation of density stratification behavior during outer surface cooling of a containment vessel with the CIGMA facility

Ishigaki, Masahiro; Abe, Satoshi; Shibamoto, Yasuteru; Yonomoto, Taisuke

Nuclear Engineering and Design, 367, p.110790_1 - 110790_15, 2020/10

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

no abstracts in English

JAEA Reports

Development of MIG2DF Version 2

Takai, Shizuka; Kimura, Hideo*; Uchikoshi, Emiko*; Munakata, Masahiro; Takeda, Seiji

JAEA-Data/Code 2020-007, 174 Pages, 2020/09

JAEA-Data-Code-2020-007.pdf:4.23MB

The MIG2DF computer code is a computer program that simulates groundwater flow and radionuclide transport in porous media for the safety assessment of radioactive waste disposal. The original version of MIG2DF was released in 1992. The original code employs a two-dimensional (vertical or horizontal cross-section, or an axisymmetric configuration) finite-element method to approximate the governing equations for density-dependent saturated-unsaturated groundwater flow and radionuclide transport. Meanwhile, for geological disposal of radioactive wastes, landscape evolution such as uplift and erosion needs to be assessed as a long-term geological and climate events, considering site conditions. In coastal areas, the impact to groundwater flow by change of salinity distribution to sea level change also needs to be considered. To deal with these events in the assessment, we have revised the original version of MIG2DF and developed the external program which enables MIG2DF to consider unsteady landscape evolution. In these developments, this report describes an upgrade of MIG2DF (Version 2) and presents the configuration, equations, methods, and verification. This reports also give the explanation external programs of MIG2DF: PASS-TRAC (the particle tracking code), PASS-PRE (the code for dataset preparation), and PASS-POST (the post-processing visualization system).

Journal Articles

Background correction method for portable thyroid dose monitor using gamma-ray spectrometer developed at JAEA in high dose rate environment

Tanimura, Yoshihiko; Yoshitomi, Hiroshi; Nishino, Sho; Takahashi, Masa

Radiation Measurements, 137, p.106389_1 - 106389_5, 2020/09

 Times Cited Count:0

A portable thyroid dose monitoring system has been developed at the Japan Atomic Energy Agency (JAEA) to assess the thyroid equivalent dose for workers and members of the public in a high dose rate environment. The background (B.G.) photon correction is required for an accurate measurement in a high dose rate environment at an early stage after a nuclear accident. We developed the B.G. photon correction method using cylindrical PMMA phantoms.

Journal Articles

Unsteady natural convection in a cylindrical containment vessel (CIGMA) with external wall cooling; Numerical CFD simulation

Hamdani, A.; Abe, Satoshi; Ishigaki, Masahiro; Shibamoto, Yasuteru; Yonomoto, Taisuke

Energies (Internet), 13(14), p.3652_1 - 3652_22, 2020/07

 Times Cited Count:0

Journal Articles

Four-point-bend tests on high-burnup advanced fuel cladding tubes after exposure to simulated LOCA conditions

Narukawa, Takafumi; Amaya, Masaki

Journal of Nuclear Science and Technology, 57(7), p.782 - 791, 2020/07

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

Journal Articles

Method for groundwater monitoring on the disposal of radioactive waste

Murakami, Hiroaki; Iwatsuki, Teruki; Takeuchi, Ryuji; Nishiyama, Nariaki*

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 27(1), p.22 - 33, 2020/06

Geological disposal of radioactive waste requires the large amounts of fundamental technical knowledge throughout the project. Monitoring is carried out to collect site-relevant information for the creation of an environmental database, to assist in the decision-making process, etc. We summarized the current technical level and problems of the groundwater monitoring in the world. Through the research and technology development so far, the technologies have been developed for drilling borehole in the geological environment survey prior to monitoring and the selection of the monitoring site. However, the following technical developments are remaining issues: long-term operation method of monitoring equipment, retrieving method of monitoring equipment after long-term operation, transport method of backfill material for borehole sealing, technical basis for the sealing performance when the borehole-protective casing and strainer tube are left.

Journal Articles

Prototype test of a portable thyroid dose monitoring system using gamma-ray spectrometers

Nishino, Sho; Tanimura, Yoshihiko; Yoshitomi, Hiroshi; Takahashi, Masa

Radiation Measurements, 134, p.106292_1 - 106292_5, 2020/06

 Times Cited Count:2 Percentile:100(Nuclear Science & Technology)

In the situation of a severe nuclear accident, radioiodine monitoring in thyroid should be performed for a large number of people immediately after accident. The portable thyroid dose monitoring system which can be used in a high dose rate condition is in development. In this presentation, the result of performance test using prototype model will be described.

Journal Articles

Experimental and analytical investigation of formation and cooling phenomena in high temperature debris bed

Hotta, Akitoshi*; Akiba, Miyuki*; Morita, Akinobu*; Konovalenko, A.*; Vilanueva, W.*; Bechta, S.*; Komlev, A.*; Thakre, S.*; Hoseyni, S. M.*; Sk$"o$ld, P.*; et al.

Journal of Nuclear Science and Technology, 57(4), p.353 - 369, 2020/04

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

Journal Articles

Crack growth evaluation for cracked stainless and carbon steel pipes under large seismic cyclic loading

Yamaguchi, Yoshihito; Katsuyama, Jinya; Li, Y.; Onizawa, Kunio

Journal of Pressure Vessel Technology, 142(2), p.021906_1 - 021906_11, 2020/04

 Times Cited Count:0 Percentile:100(Engineering, Mechanical)

Journal Articles

Improvements on evaluation functions of a probabilistic fracture mechanics analysis code for reactor pressure vessels

Lu, K.; Katsuyama, Jinya; Li, Y.

Journal of Pressure Vessel Technology, 142(2), p.021208_1 - 021208_11, 2020/04

 Times Cited Count:0 Percentile:100(Engineering, Mechanical)

Journal Articles

Guideline on probabilistic fracture mechanics analysis for Japanese reactor pressure vessels

Katsuyama, Jinya; Osakabe, Kazuya*; Uno, Shumpei*; Li, Y.; Yoshimura, Shinobu*

Journal of Pressure Vessel Technology, 142(2), p.021205_1 - 021205_10, 2020/04

 Times Cited Count:0 Percentile:100(Engineering, Mechanical)

no abstracts in English

Journal Articles

A Study of a calibration technique for a newly developed thyroid monitor and its uncertainties due to body size for radioiodine measurements

Yoshitomi, Hiroshi; Nishino, Sho; Tanimura, Yoshihiko; Takahashi, Masa

Radiation Measurements, 133, p.106279_1 - 106279_6, 2020/04

 Times Cited Count:2 Percentile:100(Nuclear Science & Technology)

Uncertainty of the body size on the counting efficiency of a newly developed thyroid monitor was estimated by Monte Carlo simulations using several voxel phantoms. Overlying tissue thickness was a major impact factor on the counting efficiency. As a result, uncertainty related to the body size of the monitored subject was found to be 25%.

JAEA Reports

Investigations on distribution of radioactive substances owing to the FDNPP accident in the fiscal year 2018 (Contract research)

Group for Fukushima Mapping Project

JAEA-Technology 2019-019, 135 Pages, 2020/03

JAEA-Technology-2019-019.pdf:22.01MB

After the accident at TEPCO Fukushima Daiichi Nuclear Power Station (FDNPS), distribution situation survey on radioactive materials have been conducted with financially supported by the Ministry of Education, Culture, Sports, Science and Technology (later the Nuclear Regulatory Agency) from June 2011 to FY2018. Results obtained in the project in FY2018 are presented in this report. Car-borne surveys, a flat ground measurement using survey meters, a walk survey and an unmanned helicopter survey were carried out to obtain air dose rate data. Air dose rate distribution maps were created and temporal changes of air dose rate were analyzed. Regarding radiocesium deposition in the soil, depth profile survey in the soil and in-situ measurement were performed. Based on these measurement results, effective half-life of the air dose rate and the deposition were evaluated. Considering radiation monitoring data obtained in previous surveys and the installation positions of existing monitoring posts, we tried to make the "score" of the importance of measurement points. Using the Bayesian hierarchical modeling approach, we obtained a map that integrated the air dose rate distribution data obtained from aircraft monitoring, car-borne surveys, and walk surveys for the entire region within 80 km from the FDNPS. The measurement results for FY2018 were published on the "Expansion Site of Distribution Map of Radiation Dose", and measurement data were stored as CSV format. Radiation monitoring and environmental sample analysis owing to the comprehensive radiation monitoring plan were carried out.

JAEA Reports

Development of database of dose reduction factor for reducing equivalent doses to the thyroid by implementing iodine thyroid blocking (Contract research)

Kimura, Masanori; Munakata, Masahiro; Hato, Shinji*; Kanno, Mitsuhiro*

JAEA-Data/Code 2020-002, 38 Pages, 2020/03

JAEA-Data-Code-2020-002.pdf:3.23MB

To consider the method of implementing urgent protective actions in a nuclear accident appropriately, the authors have been assessing the effects of reducing doses by taking urgent protective actions using a Level 3 Probabilistic Risk Assessment (PRA) code, the OSCAAR, developed by the JAEA. Iodine thyroid blocking is an effective urgent protective action to reduce equivalent doses to the thyroid due to inhalation of radioactive iodine. However, the timing of the administration of stable iodine (SI) is important to maximize the effectiveness for thyroidal blocking. Therefore, the careful consideration should be given to the most effective way of iodine thyroid blocking when preparing off-site emergency plans. In the present study, the authors developed a new metabolic model for thyroid by combining the respiratory tract model (Publ.66) and gastrointestinal tract model (Publ.30) of the ICRP with a metabolic model for thyroid (Johnson's model) in order to calculate the behavior of radioiodine and stable iodine in the body more realistically. The model is useful to evaluate the effect of the administration of SI for reducing equivalent doses to the thyroid depending on the its timing. We also calculated the reduction factor for equivalent doses to the thyroid in order to the thyroid by using the model, and then developed the its database for the OSCAAR. Consequently, the OSCAAR can evaluate the effectiveness for thyroidal blocking realistically and promptly.

Journal Articles

Irradiation growth behavior of improved alloys for fuel cladding

Kakiuchi, Kazuo; Amaya, Masaki

Nippon Genshiryoku Gakkai Wabun Rombunshi, 19(1), p.24 - 33, 2020/03

The irradiation growth behavior of the improved Zr alloys for light-water reactor fuel cladding was investigated. The coupon specimens, which were prepared from fuel cladding tubes with improved Zr alloys, had been irradiated in the Halden reactor in Norway at temperatures of 300 and 320$$^{circ}$$C under a typical water chemistry condition of PWR and 240$$^{circ}$$C under the coolant condition of the Halden reactor up to a fast neutron fluence of $$sim$$ 8$$times$$10$$^{21}$$ (n/cm$$^{2}$$, E $$>$$1 MeV). During and after the irradiation test, the amount of irradiation growth of each specimen was evaluated. The effect of the difference in alloy composition on irradiation growth behavior seemed insignificant if the other conditions e.g. the final heat treatment condition at fabrication, irradiation temperature and the amount of hydrogen pre-charged in the specimen were the same.

Journal Articles

Experimental research on pool scrubbing of particles of radioactive materials

Akiba, Miyuki*; Hotta, Akitoshi*; Abe, Yutaka*; Sun, Haomin

Nippon Genshiryoku Gakkai Wabun Rombunshi, 19(1), p.1 - 15, 2020/02

Tests at three different scales were conducted in order to understand the mechanisms of pool scrubbing. In the small-scale separate effect test, high resolution two-phase flow measurement techniques such as a high-speed camera, wire mesh sensor and PIV were applied to capture the behaviors of a single bubble and two-phase flow structures. In the large-scale integral effect test, the dependence of the aerosol removal efficiency on submergence and pool temperature was measured under constant pressure and depressurized conditions. To clarify relationships between individual phenomena and combined phenomena observed in two tests, the mid-scale integral effect test was undertaken.

Journal Articles

A New probabilistic evaluation model for weld residual stress

Mano, Akihiro; Katsuyama, Jinya; Miyamoto, Yuhei*; Yamaguchi, Yoshihito; Li, Y.

International Journal of Pressure Vessels and Piping, 179, p.103945_1 - 103945_6, 2020/01

 Times Cited Count:0 Percentile:100(Engineering, Multidisciplinary)

Weld residual stress (WRS) is one of the most important factors in the structural integrity assessment of piping welds, and it is considered a driving force for crack growth. It is characterized by large uncertainty. For more rational assessment, it is important to consider the uncertainty of WRS for evaluating crack growth behavior in probabilistic fracture mechanics (PFM) analysis. In existing PFM analysis codes, WRS uncertainty is set by statistically processing the results of multiple finite element analyses. This process depends on the individual performing PFM analysis, which may lead to uncertainties whose sources would be different from the original WRS. In this study, we developed a new WRS evaluation model based on Fourier transformation, and the model was incorporated into PASCAL-SP, which has been developed by Japan Atomic Energy Agency. Through improvements to the code, WRS uncertainty can be considered automatically and appropriately by inputting multiple WRS analysis results directly as input data for PFM analysis.

Journal Articles

Fracture limit of high-burnup advanced fuel cladding tubes under loss-of-coolant accident conditions

Narukawa, Takafumi; Amaya, Masaki

Journal of Nuclear Science and Technology, 57(1), p.68 - 78, 2020/01

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

482 (Records 1-20 displayed on this page)