| 摘要 |
<P>PROBLEM TO BE SOLVED: To make a recirculation flow rate lower than an existing layout while maintaining a thermal margin, and to enlarge a water temperature control width of a core entrance during a water supply temperature control operation. <P>SOLUTION: In the present invention, a water rod which is disposed between a plurality of fuel rods and inside which cooling water flows comprises: a coolant rising flow path having a coolant inflow port opened below a lower tie plate; a coolant lowering flow path having a coolant discharge port opened above the lower tie plate; and a flow path connection part for connecting the coolant rising flow path and the coolant lowering flow path above a filling part of fuel pellets and below an upper tie plate. At least one air vent hole is provided on an upper end of the coolant rising flow path and/or an upper end of the coolant lowering flow path. <P>COPYRIGHT: (C)2013,JPO&INPIT |
