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Fukuda, Kodai
Proceedings of 4th Reactor Physics Asia Conference (RPHA2023) (Internet), 4 Pages, 2023/10
Brief evaluations were performed using the N-F model to quantitatively clarify the effect of thermal expansion on the consequences of criticality accidents in the water-moderated fuel-particle-dispersion system. The analysis clarified that ignoring thermal expansion can lead to underestimation or overestimation of the consequences by several tens of percent. It is concluded that evaluators can ignore the thermal expansion when they evaluate the consequences of the prompt supercritical transient in water-moderated solid fuel-dispersion systems, such as fuel debris systems. Only the Doppler effect can be considered when the fuel-temperature-feedback coefficient is prepared. However, depending on the required accuracy, the evaluators should take care of the error caused by ignoring thermal expansion.
Saito, Kimiaki; Kurihara, Osamu*; Matsuda, Norihiro; Takahara, Shogo; Sato, Tetsuro*
Radioisotopes, 65(2), p.93 - 112, 2016/02
Late information is introduced on dose evaluation due to external exposures which employ an important role in the exposures due to the Fukushima accident. First, merits and demerits of the currently used two methods, that is the estimation based air dose rates and the measurements using personal dosimeters, are discussed indicating some basic data after a fundamental concept of external dose evaluation is provided. Next, main activities are summarized on external dose measurements and evaluations after the accident. Finally, a new trial on dose evaluation in introduced.
rays and the exposure dosesSaito, Kimiaki; Endo, Akira
Radioisotopes, 63(12), p.585 - 602, 2014/12
The article provides the fundamental information necessary for the appropriate evaluation of exposure doses in the environment. The basic characteristics of environmental rays from typical environmental sources are introduced; then, the dose conversion coeffcients for the public at different ages are summarized which were obtained from the simulation considering the basic characteristics of environmental rays. Further, the variations of environmental exposure doses due to a variety of factors, and the relation of exposure doses to measured air dose rates are discussed.
Nojiri, Naoki; Shimakawa, Satoshi; Fujimoto, Nozomu; Goto, Minoru
Nuclear Engineering and Design, 233(1-3), p.283 - 290, 2004/10
Times Cited Count：12 Percentile：61.44(Nuclear Science & Technology)This paper describes the results of core physics test in start-up and power-up of the HTTR. The tests were conducted in order to ensure performance and safety of the high temperature gas cooled reactor, and was carried out to measure the critical approach, the excess reactivity, the shutdown margin, the control rod worth, the reactivity coefficient, the neutron flux distribution and the power distribution. The expected core performance and the required reactor safety characteristics were verified from the results of measurements and calculations.
Fujimoto, Nozomu; Nojiri, Naoki; Takada, Eiji*; Saito, Kenji; Kobayashi, Shoichi; Sawahata, Hiroaki; Kokusen, Shigeru
JAERI-Tech 2000-091, 49 Pages, 2001/03
no abstracts in English
; *; ; Nakamura, Jinichi; Uchida, Masaaki
JAERI-M 91-003, 38 Pages, 1991/02
no abstracts in English
Yamashita, Kiyonobu; Shindo, Ryuichi; Murata, Isao; Nakagawa, Shigeaki; Nakata, Tetsuo*; *
JAERI-M 90-008, 49 Pages, 1990/02
no abstracts in English
G.Xu*; Kumamaru, Hiroshige; Tasaka, Kanji
JAERI-M 89-178, 35 Pages, 1989/11
no abstracts in English
Iijima, Kazuki; Fujiwara, Kenso; Matoba, Daisuke*; Sasaki, Takayuki*
no journal, ,
Depth profiles of radionuclides discharged to the environment of Fukushima was obtained in the forest soil just nearby the Fukushima Daiichi Nuclear Power Station (FDNPS). According to characteristics of the depth profile, Pu-238 was originated from the FDNPS accident, while Pu-239+240 was mainly originated from global fallout. Comparing depth profiles attributed by the accident and global fallout can give understanding on the migration behavior of Pu in subsurface soil during decades. In this study, advection-dispersion model was applied to evaluate the depth profiles of Pu isotopes. The Kd values for global fallout Pu-239+240 agreed with those of Fukushima Pu-238 within around factor 3. Therefore, migration behavior of Pu could be understood by the advection-dispersion model.
