23The spherical micro-cells are a semi-transparent photovoltaic (PV) technology which can 24 contribute to improve the sustainability of greenhouse systems. Previous prototypes were 25 tested in laboratory conditions, but the size was not suitable for the greenhouse roof 26 application. In this work, a new prototype has been developed and tested on a real 27 greenhouse roof. The semi-transparent PV module (STM) was composed by 4800 28 spherical silicon micro-cells (1.2 mm diameter) sandwiched between glass plates and 29 integrated on a greenhouse roof with 26.5° slope. The STM was 910 mm long and 610 mm 30 wide to match the size of the greenhouse framework. The percentage of the STM area 31 covered with micro-cells was 2.3%, reaching 9.7% considering the metallic conductors. 32 The cell density was 2 cells cm -2 and the measured perpendicular light transmissivity of the 33 semi-transparent area was 73%. The characteristics of the prototype were compared with 34 those of a conventional planar multi-crystalline silicon module (CPM). The module 35 conversion efficiency was steadily around 0.2% over wide incident sunlight angle. The 36 micro-cells never completely eclipse the incident sunlight when observed from more than 1 37 m distance from the roof, keeping the eclipsing level at 9.7%. The yield factor of the STM 38 © 2015. This manuscript version is made available under the Elsevier user license http://www.elsevier.com/open-access/userlicense/1.0/ 2 was slightly higher than the CPM because of the isotropic properties of the spherical cells, 39 which are able to use both the sky-incident and the ground-reflected irradiation for energy 40 production, irrespective of the module slope. The prototype STM is promising for 41 greenhouse roof applications and its performance can be improved by increasing the 42 conversion efficiency. 43 44

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Sodium-water reaction (SWR) in a steam generator of sodium-cooled fast reactor (SFR) is a significant phenomenon for safety assessment of the system. One of the top concerns in the SWR is an overheating rupture phenomenon in which a neighbor heat transfer tube fails instantaneously because of a deterioration of structural integrity under a high temperature condition. Hence, the heat transfer coefficient on the tube surface is of importance. Since hydrogen gas is generated in the SWR and liquid water will evaporate quickly due to depressurization, the reaction region is covered with a multi-phase flow structure, and thus the value of the heat transfer coefficient will vary widely. In the present paper, a correlation diagram has been developed between the heat transfer coefficient and the void fraction based on one dimensional homogeneous flow simulation. Furthermore, the transient of void fraction in SWAT-1R experiment is investigated using the diagram.

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