| 摘要 |
PURPOSE:To shorten a periodic inspection period and to improve working efficiency by segmenting regions where control rods move upward and downward by thin sheets on the diagonal lines of the rectangular cross section of fuel assemblies. CONSTITUTION:Control rod guides 6 for segmenting the regions where the cruciform type control rods move upward and downward are provided on the thin sheets on the diagonal lines of the cross section of the rectangular fuel assemblies 1 formed by bundling fuel rods 4 by using upper tie plates 5, etc. Four pieces each of the assemblies 1 are loaded into the rectangular sectional spaces formed of upper grid plates 3 to constitute a reactor core. The regions which are formed of the guides 6 and where the control rods move upward and downward do not interfere with the grid plates 3. Fuel element parts 8a-8d having the 4 triangular cross sections segmented by the guides 6 with each of the fuel assemblies form a virtual fuel assembly by the element parts 8a-8d of the adjacent assemblies 1 and the guides 6 of the respective assemblies 1 if such reactor core is constituted. There are no heat generating sources and a liquid phase is relatively easily formable in the regions on the lower sides of the grid plates 3 of such virtual fuel assemblies. The period inspection period is thus shortened without particularly disposing a water rod. |
