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Araki, Shohei; Aizawa, Eiju; Murakami, Takahiko; Arakaki, Yu; Tada, Yuta; Kamikawa, Yutaka; Hasegawa, Kenta; Yoshikawa, Tomoki; Sumiya, Masato; Seki, Masakazu; et al.
Annals of Nuclear Energy, 217, p.111323_1 - 111323_8, 2025/07
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)JAEA has modified the STACY from a homogeneous system using solution fuel to a heterogeneous system using fuel rods in order to obtain criticality characteristics of fuel debris. The modification of the STACY was completed in December 2023. A series of performance inspections were conducted for the start of experimental operations. A new thermal power calibration is required for the performance inspections in order to operate at less than 200 W, which is the permitted thermal power. However, the thermal power measurement method and calibration data used in the former STACY is no longer available due to the modification of the modified STACY. We measured the thermal power of the STACY using the activation method that was improved to adapt to the measurement condition and calibrated the power meter system. Since the positions where activation foils could be installed were very limited, the thermal power was evaluated using numerical calculations supplemented by experimental data. Neutron flux data at the positions of the activation foil was measured by the activation method. Neutron distribution in the core was calculated by the Monte Carlo code MVP. A response function of the activation foil was calculated using the PHITS. The uncertainty of the thermal power measurement was conservatively estimated to be about 15%. Four operations were conducted for the thermal power measurement. The power meter was calibrated by using three operational data and tested with the one operational data. It was found that the indicated value of the meter adjusted by the STACY before the modification work would tend to overestimate the actual output by about 40%. In addition, the current calibration was able to calibrate the meter to within 3% accuracy.
Sono, Hiroki; Tsukamoto, Michio; Aizawa, Eiju; Takeuchi, Masaki; Fukaya, Yuji; Iseda, Hirokatsu*; Ogawa, Kazuhiko; Sakuraba, Koichi; Tonoike, Kotaro
UTNL-R-0446, p.3_1 - 3_10, 2005/03
This report describes an investigation and countermeasures of the unexpected reactor shutdown of the TRACY facility at the Japan Atomic Energy Research Institute on June 17, 2004, caused by a malfunction of a safety rod of the facility. As a result of the investigation, the principal cause of the malfunction was ascribed to a drop in attraction of a binding magnet for the safety rod by a small piece of a foreign material. The following countermeasures were taken against its recurrence: prevention of incidence of foreign materials, reduction of the chance of intrusion of foreign materials into devices, and certain detection of foreign materials. This lesson learned through the experience is expected to be shared with the staffs concerned in reactor operation and maintenance.
-ray exposure rate from short-lived fission products under criticality accident conditionsYanagisawa, Hiroshi; Ono, Akio; Aizawa, Eiju
Journal of Nuclear Science and Technology, 39(5), p.499 - 505, 2002/05
Times Cited Count：4 Percentile：28.64(Nuclear Science & Technology)no abstracts in English
Aizawa, Eiju; Ogawa, Kazuhiko; Sakuraba, Koichi; Tsukamoto, Michio; Sugawara, Susumu; Takeuchi, Masaki*; Miyauchi, Masakatsu; Yanagisawa, Hiroshi; Ono, Akio
JAERI-Tech 2002-031, 120 Pages, 2002/03
JAERI-Tech-2002-031.pdf:4.32MB
TRACY (Transient Experiment Critical Facility) in NUCEF (Nuclear Safety Research Facility) is the pulse-type critical facility using uranyl nitrate solution which can carry out various supercritical experiments changing reactivity addition up to 3$.TRACY achieved its first criticality on 20th December 1995,and transient operations have been conducted Since1996.This report summarizes the operation data of 176 experiments from the first criticality to FY2000.
Nakajima, Ken; Yamane, Yuichi; Ogawa, Kazuhiko; Aizawa, Eiju; Yanagisawa, Hiroshi; Miyoshi, Yoshinori
JAERI-Data/Code 2002-007, 123 Pages, 2002/03
JAERI-Data-Code-2002-007.pdf:4.34MB
no abstracts in English
Nakajima, Ken; Yamane, Yuichi; Ogawa, Kazuhiko; Aizawa, Eiju; Yanagisawa, Hiroshi; Miyoshi, Yoshinori
JAERI-Data/Code 2002-006, 176 Pages, 2002/03
JAERI-Data-Code-2002-006.pdf:6.33MB
no abstracts in English
Nakajima, Ken; Yamane, Yuichi; Ogawa, Kazuhiko; Aizawa, Eiju; Yanagisawa, Hiroshi; Miyoshi, Yoshinori
JAERI-Data/Code 2002-005, 158 Pages, 2002/03
JAERI-Data-Code-2002-005.pdf:6.55MB
no abstracts in English
Yanagisawa, Hiroshi; Ono, Akio; Ogawa, Kazuhiko; Aizawa, Eiju; Yokoyama, Mitsutaka*
Journal of Nuclear Science and Technology, 38(8), p.591 - 599, 2001/08
Times Cited Count：6 Percentile：43.38(Nuclear Science & Technology)no abstracts in English
Ogawa, Kazuhiko; Morita, Toshio*; Yanagisawa, Hiroshi; Aizawa, Eiju; Sakuraba, Koichi; Sugawara, Susumu; Ono, Akio
Journal of Nuclear Science and Technology, 37(12), p.1088 - 1097, 2000/12
no abstracts in English
Araki, Shohei; Arakaki, Yu; Maekawa, Tomoyuki; Murakami, Takahiko; Hasegawa, Kenta; Yoshikawa, Tomoki; Tada, Yuta; Kamikawa, Yutaka; Sumiya, Masato; Seki, Masakazu; et al.
no journal, ,
In the TEPCO's Fukushima Daiichi Nuclear Power Plant accident, fuel debris was formed by fuel melting and mixing with in-core structures. Although the detailed properties of the fuel debris are still unknown, it is thought to contain materials such as iron and concrete. Then, in order to understand the criticality characteristics of fuel debris, JAEA is conducting a comprehensive numerical analysis assuming the composition of fuel debris containing concrete and iron. However, integral experimental data including these materials are scarce, and the validation of the analytical results has not been fully investigated. Thus, JAEA modified the criticality facility STACY in order to obtain experimental data that will contribute to the validation. This report describes the outline and status of the modified-STACY, and the plan is also presented.
Hasegawa, Kenta; Arakaki, Yu; Murakami, Takahiko; Sumiya, Masato; Aizawa, Eiju; Seki, Masakazu; Ishii, Junichi; Araki, Shohei; Izawa, Kazuhiko; Gunji, Satoshi
no journal, ,
no abstracts in English
Araki, Shohei; Murakami, Takahiko; Kamikawa, Yutaka; Arakaki, Yu; Tada, Yuta; Aizawa, Eiju; Ishii, Junichi; Seki, Masakazu; Izawa, Kazuhiko; Gunji, Satoshi
no journal, ,
We conducted thermal power measurements and thermal power calibration for a performance test in the modified STACY. The activation method was adopted in the thermal power measurements. The core for the measurements consisted of 253 fuel rods and a sample driver. The gold foils used for the activation foil method were installed in the sample driver. The operation was carried out twice, at 20-W and 50-W. The neutron flux in the core and the response of the gold foil were calculated using MVP and PHITS, respectively, with JENDL-5 as the nuclear data. In each measurement, the integrated power was 4.2-Wh and 8.9-Wh, respectively. The indicated power with default setting was found to be about 50% higher than the evaluated value.
Gunji, Satoshi; Araki, Shohei; Aizawa, Eiju; Ishii, Junichi; Izawa, Kazuhiko; Iwahashi, Daiki*; Shiba, Shigeki*
no journal, ,
no abstracts in English
Aizawa, Eiju; Yamane, Yuichi
no journal, ,
TRACY (Transient experiment critical facility) is a reactor to perform supercritical experiments using low-enriched uranyl nitrate aqueous solution. In a supercritical experiment, up to 3$ of reactivity is inserted by withdrawing a control rod, called "transient rod," from the center of the core tank or feeding fuel solution into the core tank.Since 1996, TRACY supercritical experiments have been performed and transient data such as power, temperature and pressure have been measured and evaluated. Furthermore, we have developed a system to observe solution behavior under criticality accident condition for the elucidation of transient events. Those experiences we have gained through the TRACY experiments will be presented at the lecture in the 46th reactor physics summer seminar of the Atomic Energy Society of Japan.
Kamikawa, Yutaka; Arakaki, Yu; Yoshikawa, Tomoki; Hasegawa, Kenta; Aizawa, Eiju; Seki, Masakazu; Ishii, Junichi; Araki, Shohei; Izawa, Kazuhiko; Gunji, Satoshi
no journal, ,
JAEA resumed Static Experiment Critical Facility (STACY) operation in August 2024 after the renewal of the core to a light-water moderated heterogeneous critical assembly for the criticality experiments to clarify the criticality characteristics of the fuel debris. JAEA is currently proceeding the test operation along with pre-service inspections of the core loaded with debris structural material rods to study the nuclear characteristics of the fuel debris. In addition, for experiments simulating the properties of fuel debris, assuming the mixture of core internals and fuels, JAEA manufactures Stainless steel rods (debris structural material rods (iron)), Aluminum alloy rods which are filled with concrete pellets (debris structural material rods (concrete)), which are processed into the same shape as the fuel rods, Refillable fuel rods which have cylindrical shapes, made of zirconium alloy with a detachable end stopper, and Loading tubes which are made of aluminum alloy or zirconium alloy. In this presentation, we report on the fabrication of the experimental loadings such as debris structural material rods and the status of the pre-service inspections.
Gunji, Satoshi; Araki, Shohei; Dechenaux, B.*; Brovchenko, M.*; Aizawa, Eiju; Seki, Masakazu; Arakaki, Yu; Yoshikawa, Tomoki; Izawa, Kazuhiko
no journal, ,
Non-uniformity of the composition is an issue when evaluating fuel debris's criticality characteristics. Critical experiments using the modified STACY are planned to validate the criticality effects of the non-uniformity. In this presentation, the results of the critical experiment their experimental core arrangements have large non-uniformity effects, and their experimental analyses are shown.
