JPS602606B

PURPOSE:To obtain a device for precisely measuring a recycle flow rate in furnace core by forming an orifice at a cooling material inlet of a fuel support member of a pressure container of a nuclear reactor. CONSTITUTION:Cooling material from a lower part in a pressure container of a nuclear reactor is planned to flow into the respective fuel assembly 14 through a cooling material passing hole 20 to which an orifice plate 21 is fitted, a cooling material flow-in port 19 and a cooling material communicating passage 16. Further, a pressure tap 25 of an upstream side pressure guide pipe 23 is disposed upstream of the orifice plate 21. The downstream side pressure guide pipe 26 is connected to a downstream side communicating hole 30 through an elbow 29, connecting member 27, a through hole 28, an elbow 32, a bellow pipe 33, and a fitting member 34. Thus, by obtaining the differential pressure between the upstream side and the downstream side of the orifice plate 21, the recycle flow rate in the furnace core of the cooling material can be measured accurately.