Abstract: A hydraulically based control rod drive system that is contained within the pressure vessel is disclosed for positioning the control rods relative to fuel rods positioned in a nuclear core of a boiling water reactor. Hydraulic jacks mounted on an open grid located entirely within the pressure vessel at a position above the nuclear core are used to position the control rods. Suitable jack and grid structures, as well as a hydraulic control arrangements are described.

Abstract: The control rod drive is removed from the top of the reactor. The control rod drive is attached at its upper end to the bottom end of the control rod drive guide tube. The control rod guide tube in turn couples at a rotationally locked bayonet fitting to the top of the control rod drive housing. Locking of the bayonet fitting occurs thru the orificed fuel support casting. The orificed fuel support casting, is locked from rotation at a pin located on the reactor core plate. The control rod guide tube in turn locks rotationally to the orificed fuel support casting. During refueling, the fuel bundles and the orificed fuel support casting are removed, freeing the control rod guide tube and its depending drive for rotation. Thereafter, a fitting captures the control rod guide tubes at coolant inflow apertures and rotates the guide tubes and the depending drives.

Abstract: In a hydraulic system of a control rod drive for insertion of control rods, a test apparatus and test process is disclosed for determining the integrity of the hydraulic system check valve for preventing inadvertent control rod ejection responsive to the reactor pressure. The check valve is located between a hydraulic valve for causing rod insertion and the hydraulic cylinder. In this interval downstream of the check valve, alteration is made to the hydraulic path by the installation of a conduit with a quick disconnect connected through an isolation valve. Test apparatus for temporary connection at the disconnect is disclosed consisting of a small positive displacement piston and cylinder. The small positive displacement piston and cylinder connects to the quick disconnect through a complementary quick disconnect fitting and a rapidly opening toggle valve. Provision is made for timing the excursion of piston in the piston and cylinder preferably by end of stroke microswitches.

Abstract: A velocity limiting device providing greater resistance to motion through a fluid in one direction than in the opposite direction. The device includes a toroidally shaped control member having a smooth generally conical surface on one side for low resistance movement through the fluid in the one direction. On its opposite side the control member is formed with at least one groove providing a concave surface spaced from which is an arrangement of vanes forming a jet for directing a stream of fluid into the groove upon movement in the opposite direction whereby the resultant increase in fluid turbulence increases resistance to rapid movement in this opposite direction.