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Okamoto, Kaoru; Miyakawa, Shunichi; Mitsugi, Takeshi; Kitamura, Ryoichi
JNC TN9410 99-010, 350 Pages, 1999/06
In the needs of the fuel irradiation test in "Joyo" MK-III core, there have been required that the irradiation of high performance fuel at high liner heat rate to high burn-up range, or the irradiation of advanced fuel such as MA fuel and Vipac fuel. In order to carry out these irradiation tests, newly designed irradiation subassembly is required with special features of; (1)Capability of the re-assembling after post-irradiation examination, even if the number of fuel in the identical irradiation condition decreases because of intermediate inspection. (2)Enhanced flexibility of the irradiation temperature setting ( in the present, UNIS-B's has 6 cases on the maximum). (3)Sufficient flexibility for the coolant flow distribution in the subassembly by extending variety of the flow rate setting. UNIS-D is a fuel irradiation subassembly which has been developed from above viewpoints. It is a compartment loading type irradiation subassembly that is able to load maximum of 18 compartments. Two types of compartments 
-type and 
-typc arc prepared for UNIS-D. Thc sufficient consideration has also been made on the rc-assembling. A -type is the same compartment as the existing UNIS-B's and a -type is the newly designed one for UNIS-D. Three to five fuel pins are loaded into a -type compartment and only one pin is loadcd into a -type compartment. It is possible to carry out the irradiation test in a maximum of 18 test temperature conditions within a subassembly, since it has the sufficient flexibility for the coolant flow distribution. As for the development of UNIS-D, we have finished the detailed structure design and the design verification by the water flow examination, which confirmed that the UNIS-D exceeded its required performances in use and that its structure design was satisfactory.
Okamoto, Kaoru*; Makino, Yasushi*; Ono, Ayako; Yoshida, Hiroyuki
no journal, ,
JAEA has developed an advanced neutronics/thermal-hydraulics coupling simulation system, in which detailed two-phase flow simulation code (TPFIT or JUPITER) is applied to part of thermal-hydraulics. Those detailed codes can predict small-scale thermal-hydraulics behavior inside sub-channels of a fuel bundle, so that measurement data with high-resolutions in time and space are required to achieve the appropriate validation of the codes. In this study, Laser Doppler Velocimetry (LDV) is applied for measurements of velocity and void fraction in air-water dispersed bubbly flows. The LDV can obtain local measurement data without any disturbance to flow field. In particular, fluorescent particles are introduced for liquid velocity measurements in order to clearly distinguish recorded signals between gas and liquid phases. The measurement method and the results will be shown in this presentation.
Ono, Ayako; Okamoto, Kaoru*; Makino, Yasushi*; Hosokawa, Shigeo*; Yoshida, Hiroyuki
no journal, ,
JAEA has been developing an advanced neutronic/thermal-hydraulics coupling simulation system. In the system, the detailed thermal-hydraulics codes JUPITER and TPFIT, which are based on an interface-capturing method, will be adopted to simulate thermal-hydraulics in a fuel bundle. The experimental data and findings relating to the two-phase flow in a fuel bundle are needed to validate JUPITER and TPFIT. In this study, we propose a new measurement method to measure the bubbly flow in a narrow channel, such as a subchannel, by combining laser-doppler velocimetry and photodiodes. The proposed measurement method is cross-checked by a conductance probe and is confirmed for its validity.
