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Hazama, Taira; Mori, Tomoaki; ; Aihara, Nagafumi; ; Yoshida, Mamoru; *
JNC TN9400 2001-044, 136 Pages, 2001/05
JNC-TN9400-2001-044.pdf:3.97MB
A Subcriticality measurement technique was developed to improve safety and efficiency of criticality safety control in nuclear fuel processing facilities. In the development, two measurement techniques based on reactor noise analysis were selected as candidates of subcriticality measurement technique applicable to severe situations in FBR fuel reprocessing plants. The research activity was performed in Deuterium Critical Assembly (DCA) which was partly reconstructed from the original core of the advanced thermal reactor, so that light water and FBR type fuel could be used as in the FBR fuel reprocessing plants. Through the research, each technique was improved to satisfy criteria for subcriticality monitoring technique in FBR fuel reprocessing plant. Since the two techniques have basically different features while using common devices,thier combination would be a simple and reliable measurement system. This report summarizes processes and results of the research activity in DCA.
Aihara, Nagafumi
Nihon Genshiryoku Gakkai-Shi, 40(4), p.254 - 281, 1999/00
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)None
Tanimoto, Kenichi; Aihara, Nagafumi; ; ; ; ;
JNC TN9410 99-002, 320 Pages, 1998/11
The estimation of the amount of radioactive waste produced from nuclear facilities in O-arai Engineering Center was performed for the purpose of using it for countermeasure of decommissioning planning. The conditions and the result of the estimation are as follows; (1)The total amount of occurrence of radioactive waste is 18,820tons. As the items of the amount in radioactive level, the amount of 1GBq/t and over is 820 tons and that of under 1GBq/t is 18,000 tons. (2)The amount of metal waste is 5,820 tons and the amount of concrete is 13,000 tons. (3)Above calculation was based on related specifications, complete drawings, and visual observation. (4)To dismantle facilities, it must exfoliate the surface of wall. As for the polluted zone and the zone with possibility of pollution, it decided to exfoliate 5 cm in thickness from the surface of the wall. And, as for the zone that fundamentally pollution was not there, it decided to exfoliate surface 1cm in thickness from the surface of the wall. (5)Using the suitable decontamination technology and exfoliation technology can reduce the amount of radioactive waste. (6)In the facilities dealing with sealed source judging from the past record of operation, there is no contact with the radioactive material, etc. Therefore, it can be disposed of all the waste that comes out from the facilities as non-radioactive waste.
Yoshida, Mamoru; ; *; Aihara, Nagafumi
PNC TN9410 96-249, 60 Pages, 1996/09
A new fuel-rods storage rack has been manufactured to store DCA and JOYO type fuel-rods in a fuel-rods storage house attached to the Criticality Engineering Section Facility. For the manufacture of fuel-rods storage rack, a safety design evaluation was performed about criticality safety, earthquake-proof and dose equivalent rate. The calculation of design evaluation was performed by using SCALE-4, SAP-IV and ANISN code system, respectively. We could understand the following informations from the safety design evaluation: (1)As a result of criticality evaluation, a maximum Keff value was 0.568 by the use of JOYO type fuel-rods with all number of 300 fuel-rods. This means that the sub-criticality is kept in any situation. (2)As a result of earthquake-proof evaluation, it was confirmed that the new storage rack showed less value than the permitted stress from an analytical result when the yield point against the earthquake power of standard earthquake oscillation or the static earthquake power was set as a permitted limit. (3)As a result of evaluation for the dose equivalent rate, a maximum dose equivalent rate was a case by the use of DCA 3.4% enriched MOX fuel-rods with all number of 300 fuel-rods.
Aihara, Nagafumi; *
PNC TN9410 95-344, 61 Pages, 1995/12
Input constants of fuels or structural materials which compose the core were summarized to perform a nuclear calculation. These fuels or structural materials were produced to perform experiments of reactor physics by using deuterium critical Assembly(DCA). Although a part of DCA input constants were shown in the previous DCA handbook (I) published as the first edition(SN941 74-22), a report of this time was summarized on new fuels or structural materials produced after those such as multi-fuel rods cluster, high enriched fuels, fuels with Gd
O
and so on. Input constants are consisted of composition, density and dimension on each material and are made of score-sheets or mill- sheets based on the fabrication materials. These input constants are utilized for the analysis of criticality safety experiment to measure sub-criticality that is our program in near future.
Yoshida, Mamoru; ; Shobu, Nobuhiro; Aihara, Nagafumi;
PNC TN9700 95-001, 804 Pages, 1995/08
no abstracts in English
Aihara, Nagafumi; ;
PNC TN9410 91-135, 121 Pages, 1991/04
An analysis of nuclear characteristic of a driver region core has been performed in order to contribute for the experimental plan of criticality safety using Deuterium Critical Assembly (DCA). The driver region core is composed of two parts by the inner void region and outer driver region loaded with fuel clusters in the DCA core. The analysis was carried out by use of the coupled WIMS-ATR/TWOTRAN code system. From the present analysis, we could understand the effect of nuclear characteristic due to the parameter change of lattice pitch distance, coolant material, void region diameter, fuel loading pattern and so on for the driver region core. The items of nuclear characteristic obtained by the present analysis are effective multiplication factor, critical heavy water level, critical 
B concentration, control rod reactivity worth and so on. Furthermore, the analysis of nuclear characteristic of two region core, which is composed of test region including fuel material in the void region and driver region, will be performed as the near future work.
Aihara, Nagafumi; Fukumura, Nobuo; Kadotani, Hiroyuki*; Hachiya, Yuki
Nuclear Science and Engineering, 109, p.158 - 170, 1991/00
Times Cited Count：4 Percentile：47.84(Nuclear Science & Technology)None
Aihara, Nagafumi; Fukumura, Nobuo; M.J.Haire*
Proceedings of American Nuclear Society 1987 Annual Meeting, ,
None
