Journal of Nuclear Science and Technology, 59(11), p.1331 - 1344, 2022/11
The reactivity was estimated from a time profile of neutron count rate or a simulated data in a quasi-steady state after sudden change of reactivity or external neutron source strength. The estimation was based on the equation of power in subcritical quasi-steady state. The purpose of the study is to develop the method of timely reactivity estimation from complicated time profile of neutron count rate. The developed method was applied to the data simulating neutron count rate created by using one-point kinetics code, AGNES, and Poisson-distributed random noise and to the transient subcritical experiment data measured by using TRACY. The result shows that the difference of the estimated and reference value was within about 5% or less for ( -1) for simulated data and within about 7% or less for -1.4 and -3.1 for the experimental data. It was also shown that the possibility of the reactivity estimation several ten seconds after the status change.
Journal of Nuclear Science and Technology, 57(8), p.926 - 931, 2020/08
An equation of power in subcritical quasi-steady state has been derived based on one-point kinetics equations for the purpose of utilizing it for the development of timely reactivity estimation from complicated time profile of neutron count rate. It linearly relates power, , to a new variable , which is a function of time differential of the power. It has been confirmed by using one-point kinetics code, AGNES, that the calculated points () are perfectly in a line described by the new equation and that points () calculated from transient subcritical experiments by using TRACY made a line with a slope indicated by the new equation.
Sasaki, Shinji; Tanno, Takashi; Maeda, Koji
Proceedings of 54th Annual Meeting of Hot Laboratories and Remote Handling (HOTLAB 2017) (Internet), 6 Pages, 2017/00
During irradiation in a fast reactor, the microstructure change of the mixed oxide fuels and the changes of element distributions occur because of a radial temperature gradient. Therefore, it is important to study the irradiation behavior of MA-MOX for advancement of fast reactor fuels. In order to make detailed observations of microstructure and elemental analyses of MA-MOX, irradiated MA-MOX specimens were carried out PIE by using a FE-SEM equipped with WDX. Because fuel samples have high radio activities and emit alpha-particles, the instrument was modified. the instrument was installed in a lead shield box and the control unit was separately located outside the box. The microstructure changes were observed in irradiated MA-MOX specimen. The characteristic X-rays peaks were detected successfully. By measuring the intensities of characteristic X-rays, it was tried quantitative analysis of U, Pu, Am along radial direction of irradiated specimen.
Yasuda, Ryo; Matsubayashi, Masahito; Nakata, Masahito; Matsue, Hideaki; Nakanishi, Tomoko
Dai-5-Kai Hoshasen Ni Yoru Hihakai Hyoka Shimpojiumu Koen Rombunshu, p.31 - 34, 2005/02
Neutron radiography is an effectively nondestructive tool for inspection of irradiated nuclear fuels and materials. Neutron CT an neutron imaging plate methods, which are advanced techniques in the neutron radiography, enabled to obtain cross-section images and to evaluate an amount of the element compositions. This paper describes results of those methods using unirradiated fuels and materials and discussed the practicability of those methods to irradiated fuels and materials.
Ito, Mitsuo; Obara, Kazuhiro; Toida, Yukio*; Suzuki, Daisuke; Gunji, Katsubumi*; Watanabe, Kazuo
JAERI-Review 2004-007, 65 Pages, 2004/03
no abstracts in English
Department of Nuclear Energy System
JAERI-Review 2003-023, 232 Pages, 2003/09
The Department has carried out researches and developments (R&Ds) of innovative nuclear energy system and their related fundamental technologies to ensure the long-term energy supply in Japan. The report deals with the R&Ds of an innovative water reactor, called Reduced-Moderation Water Reactor (RMWR), which has the capability of multiple recycling and breeding of plutonium using light water reactor technologies. In addition, as basic studies and fundamental researches of nuclear energy system in general, described are intensive researches in the fields of reactor physics, thermal-hydraulics, nuclear data, nuclear fuels, and materials. These activities are essential not only for the R&Ds of innovative nuclear energy systems but also for the improvement of safety and reliability of current nuclear energy systems. The maintenance and operation of reactor engineering facilities belonging to the Department support experimental activities.
Hiura, Nobuo*; Yamaura, Takayuki; Motohashi, Yoshinobu*; Kobiyama, Mamoru*
Nihon Genshiryoku Gakkai Wabun Rombunshi, 1(2), p.202 - 208, 2002/06
The purpose of this study is to develop oxygen sensor which can measure the oxygen potential of the fuel in a nuclear reactor. The oxygen sensor with CaO stabilized zirconia solid electrolyte has been specially designed in order to prolong its life time. Electromotive force (EMF) of solid galvanic cell Ni/NiO|ZrO-CaO|Fe/FeO was measured in both the out-pile tests and the in-situ tests using Japan Material Testing Reactor (JMTR), and the characteristics of EMF was discussed. In the out-pile test, it was found that the EMF was almost equal to the theoretical values at temperatures ranging from 700 to 1,000, and the life span of the sensor was very long up to 980h at 800. In the in-situ test, it was found that the EMF showed almost the reliable values up to 300 h (neutron fluence (E 1 MeV) 1.510 m), at temperatures from 700 to 900. The imprecision of the EMF was found to be within 6% of the theoretical values up to 1,650 h irradiation time (neutron fluence (E 1 MeV) 8.010 m) at 800. The oxygen sensors were found to be applicable for the oxygen potential measurement of the fuels in a reactor.
Bunseki, 1993(11), p.883 - 889, 1993/00
no abstracts in English
JAERI-M 85-213, 378 Pages, 1986/02
no abstracts in English
Kurata, Masaki; Pham, V. H.; Nagae, Yuji
no journal, ,