Control rod drives for LMFBR type reactors

Purpose: To keep incore gases from upward flowing to the driving system by the provision of a flow passage. Constitution: The flow passage is designed so that blow-down gases swirling around the driving extension shaft forces back the incore gases to an annular space. The blow-down gases flow downwardly along the spiral groove on the inner wall of a shielding sleeve and then flow out as a swirling stream into the annular space. Accordingly, the temperature distribution in the gases become uniform on cross section perpendicular to the driving extension shaft is made uniform in the annular space, which stabilize the flow of the blow-down gases. (J.P.N.)