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Tokunaga, Sho; Horiguchi, Hironori; Nakamura, Takemi
JAEA-Technology 2023-001, 37 Pages, 2023/05
JAEA-Technology-2023-001.pdf:1.39MB
The cold neutron source (CNS) of the research reactor JRR-3 converts thermal neutrons generated in the reactor into low-energy cold neutrons by moderating them with liquid hydrogen stored in the moderator cell. Cold neutrons generated by the CNS are transported to experimental instruments using neutron conduits, and are used for many studies of physical properties, mainly in life science, polymer science, environmental science, etc. Improvement of cold neutron intensity is essential to maintain competitiveness with the world's research reactors in neutron science, and we are developing a new CNS that incorporates new knowledge. The current moderator cell for the CNS of JRR-3 is a stainless-steel container which is a canteen bottle type, and the cold neutron intensity can be improved by changing the material and shape. Therefore, the basic specifications of the new moderator cell were changed to aluminum alloy which has a smaller neutron absorption cross section, and the shape was optimized using a Monte Carlo code MCNP. Since these changes in specifications will result in changes in heat generation and heat transfer conditions, the CNS of JRR-3 was re-evaluated in terms of self-regulating characteristic, heat transport limits, heat resistance and pressure resistance, etc., to confirm its feasibility in thermal-hydraulic design. This report summarizes the results of the thermal-hydraulic design evaluation of the new moderator cell.
Tokunaga, Sho; Iguchi, Shintaro; Kawamura, Sho; Hirane, Nobuhiko
JAEA-Technology 2022-004, 74 Pages, 2023/02
JAEA-Technology-2022-004.pdf:2.46MB
In JRR-3, in response to the new regulatory standard for research reactors that is enforced December 2013, we submitted the application document of reactor installation license for the JRR-3 on September 2014, and acquired the permission on November 2018. Thereafter, we carried out impact assessment for internal overflow based on the design principles as described in the application document of reactor installation license for the JRR-3. There are two legal requirements for internal overflow. The first is to ensure that the necessary safety functions are not lost due to internal overflow that occur in the facility. The second is to prevent leakage of liquid containing radioactive materials outside the radiation controlled area in the event of an internal overflow. For these requirements, assuming each overflow source, it was confirmed that the necessary safety functions would not be lost and that liquid containing radioactive materials would not leak outside the controlled area. Regarding these assessments, design and construction plans were submitted in installments, and the approvals were obtained sequentially. This report shows the result that is impact assessment for internal overflow in JRR-3.
Nakamura, Takemi; Tokunaga, Sho; Kikuchi, Masanobu
no journal, ,
Research reactor JRR-3 on Japan Atomic Energy Agency plans to replace the cold neutron source moderator vessel. Conceptual design for high-performance moderator vessel was carried out for the purpose of increasing the cold neutron source. Since the optimum geometry of the moderator vessel was determined by the nuclear characteristic analysis, its characteristics are reported.
Nakamura, Takemi; Tokunaga, Sho; Kikuchi, Masanobu
no journal, ,
JRR-3 plans to replace the moderator cell of cold neutron source. The purpose of improve the strength of the cold neutron source, a conceptual design was carried out to improve the performance of the moderator cell. Since the optimum shape was determined by nuclear characteristic analysis, the characteristics of the new moderator cell are introduced.
Tokunaga, Sho; Nakamura, Takemi; Kikuchi, Masanobu
no journal, ,
Research reactor JRR-3 on Japan Atomic Energy Agency plans to replace the cold neutron source moderator vessel. Conceptual design for high-performance moderator vessel was carried out for the purpose of increasing the cold neutron source. The optimum geometry determined by the nuclear characteristic analysis was evaluated by flow analysis. Its characteristics are reported.
Tokunaga, Sho; Nakamura, Takemi; Kikuchi, Masanobu; Noguchi, Hironori*; Oda, Yasushi*
no journal, ,
In order to examine a hydrogen flow analysis method for the high-performance moderator vessel including the entire CNS system, a pipe network analysis of the entire system including the moderator vessel using RELAP5/MOD3.2 and a CFD analysis of the moderator vessel using ANSYS-FLUENT which added physical models that were not considered in a conceptual design were evaluated in combination. The validity of these calculations was compared using Sudo's equation, which is in good agreement with the results of the out-of-reactor operating test in the current canteen bottle moderator vessel.
Nakamura, Takemi; Tokunaga, Sho; Kikuchi, Masanobu
no journal, ,
To improve the performance of the JRR-3 cold neutron source, we are developing a high-performance moderator vessel made of A6061. When the helium refrigerator stops and the cooling capacity of the condenser is lost, the supply of liquid hydrogen to the moderator vessel stops, and the temperature of the moderator vessel heated by decay gamma rays increases. The maximum temperature of the vessel must not exceed 100 degrees, because A6061 in the temperature range of 100 degrees or higher has lower mechanical strength and is easy to cause creep. We calculated the heat generation of the high-performance moderator vessel and evaluated the soundness of the vessel by calculating the temporal change in temperature of the vessel after the helium refrigerator was stopped.
Kikuchi, Masanobu; Nakamura, Takemi; Tokunaga, Sho; Oda, Yasushi*
no journal, ,
The vessel shape was changed from the conceptual design to take manufacturability into consideration. The inner surface of the vessel is filleted, and the flat section is reinforced and tapered. To verify its validity, check for plastic deformation at maximum pressure.