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spectrometry of terrestrial gamma rays using portable germanium detectors in area of 80 km radius around the Fukushima Daiichi Nuclear Power PlantMikami, Satoshi; Tanaka, Hiroyuki*; Okuda, Naotoshi*; Sakamoto, Ryuichi*; Ochi, Kotaro; Uno, Kiichiro*; Matsuda, Norihiro; Saito, Kimiaki
Nihon Genshiryoku Gakkai Wabun Rombunshi, 20(4), p.159 - 178, 2021/12
In order to know the background radiation level where the area affected by the Fukushima Daiichi Nuclear Power Plant accident in 2011, terrestrial gamma rays had been measured by using portable germanium detectors repeatedly from 2013 through 2019, at 370 locations within 80 km radius area centered on the Fukushima Daiichi Nuclear Power Plant. Radioactive concentrations of Uranium 238, Thorium 232, Potassium 40 and kerma rates in air due to terrestrial gamma rays were obtained at those locations based on the method of ICRU report 53. Averaged concentrations of 
U, 
Th and 
K were 18.8, 22.7, 428 Bq/kg, respectively, and kerma rate in air over the area was found to be 0.0402 
Gy/h. The obtained kerma rates in air were compared to those reported in literatures. It was confirmed that the data were correlated with each other, and were agreed within the range of their uncertainty. This is because the kerma rate in air due to terrestrial gamma rays is depend on geology. The similar trend to previous findings was observed that the kerma rate in air at locations geologically classified as Mesozoic era, Granite and Rhyolite were statistically significantly higher than the others.
Mikami, Satoshi; Tanaka, Hiroyuki*; Matsuda, Hideo*; Sato, Shoji*; Hoshide, Yoshifumi*; Okuda, Naotoshi*; Suzuki, Takeo*; Sakamoto, Ryuichi*; Ando, Masaki; Saito, Kimiaki
Journal of Environmental Radioactivity, 210, p.105941_1 - 105941_12, 2019/12
Times Cited Count：22 Percentile：66.33(Environmental Sciences)The deposition densities of radiocesium and the air dose rates were repeatedly measured in a large number of undisturbed fields within the 80km zone that surrounds the Fukushima Dai-ichi Nuclear Power Plant site between 2011 and 2016, and features of their temporal changes were clarified. The average air dose rate excluding background radiation in this zone decreased to about 20% of the initial value during the period from June 2011 to August 2016, which was essentially a result of the radioactive decay of 
Cs with a half-life of 2.06y. The air dose rate reduction was faster than that expected from the decay of radiocesium by a factor of about two, with most of this reduction being attributed to the penetration of radiocesium into the soil. The average deposition densities of Cs and 
Cs in fields that were not decontaminated were found to have decreased nearly according to their expected radioactive decay, which indicated that the movement of radiocesium in the horizontal direction was relatively small. The effect of decontamination was apparently observed in the measurements of air dose rates and deposition densities. Nominally, the average air dose rates in the measurement locations were reduced by about 20% by decontamination and other human activities, of which accurate quantitative analysis is and continue to be a challenge.
; Kamide, Hideki; ; Yamamoto, Kazuhiro
JNC TN9400 2002-027, 78 Pages, 2002/03
JNC-TN9400-2002-027.pdf:2.82MB
High burnup of the core is one of means to reduce the cost of a fast reactor and fuel cycle system. However, it is not enough to investigate thermohydraulics in the core, in which fuel and wrapper tube are deformed due to irradiation under high burnup condition. In this study, sodium experiment was performed to investigate fluid mixing in a wire-wrapped 37-pin subassembly model, which had local blockage and cross flow around the blockage. Such cross flow is one of elements of thermohydraulics in a deformed subassembly. The experimental results is useful to develop numerical simulation method for the deformed subassembly. Seven pins, each had different relative position to the blockage, were heated individually in the experiments. Temperature field in the subassembly was measured. Influences of the flow rate and heater power were also examined. A horizontal cross flow occurred in upstream region toward the blockage. It was observed that the temperature field was influenced by this cross flow. The measured temperature field showed that there was a bypass flow around the blockage, which flowed toward the center of subassembly. The cross flow due to the bypass flow reached the 3rd row of pins from the blockage. The swirl flow, resulted from the spacer wire, also influenced the temperature field. The obtained experimental data will be used to develop and verify a numerical simulation method for a deformed fuel subassembly.
; Kamide, Hideki; ;
JNC TN9400 2001-062, 145 Pages, 2001/02
JNC-TN9400-2001-062.pdf:4.67MB
The 37-pin bundle sodium experiment for porous local blockage was conducted to investigate the thermal-hydraulic field in the pin bundle with porous blockage and to obtain a verification data for numerical analysis. The test section simulated a fuel sub-assembly of 37-pin bundle with pin diameter and pin pitch, which was equivalent to the large-scale reactor. The test section was included the porous blockage in 14 subchannels of 2 rows near the wrapper tube wall. As the experimental condition, flow rate was changed from 107.5 to 10[%], and heater output was also changed up to 60[%]. The maximum temperature was shown on the pin surface near the upper end of blockage, which was surrounded by the blockages on all side. The vertical flows in porous blockage affected the temperature distribution, and the swirl flow caused by wire-spacer did not have particularly influence on temperature distribution. The profile of temperature distribution in the porous blockage was different between on the cases with high flow-rate/power (over 30[%]) condition and low flow-rate/power (less than 15[%]) condition. On the higher condition, the temperature in the porous blockage increased along horizontal direction from outer subchannel to inner subchannel. On the lower condition, the temperature distribution showed nearly flat profile on the horizontal cross-section. The wake region disappeared at the height of a 1/6 wire pitch from the upper end of porous blockage. The maximum temperature on large-scale reactor condition was evaluated based on the experimental result. The maximum temperature was about 670[
C] under the supposed blockage condition; porosity is 40[%], in 14 subchannels of 2 rows near the wrapper tube wall, and consisted of the stainless sphere 0.3[mm] diameter.
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Nihon Shokuhin Kogyo Gakkai-Shi, 23(7), p.283 - 287, 1976/07
no abstracts in English
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Shokuhin Shosha, 9(1-2), p.82 - 83, 1974/02
no abstracts in English
Tanaka, Masaaki; Ezure, Toshiki; Ishikawa, Nobuyuki; Miyakoshi, Hiroyuki; Shimizu, Ryo*; Nakamura, Hironori*; Oyama, Kazuhiro*
no journal, ,
Conceptual design of a sodium test facility AtheNa-RV/DHRS has been conducted for feasibility study of the diverse systems in decay heat removal under various operating conditions including severe accident. In accordance with the requirements for an integrated effect test facility, sodium test loop layout and the reactor vessel with in-vessel direct heat exchangers are proposed.
