Dynamics of shut-off rod drop in a PHWR

Passive temperature compensation in hydraulic dashpot used for the shut-off rod drive mechanism of a nuclear reactor

“…As soon as the rod reaches the top position, motor is cut-off and the rod remains at that position, due to irreversibility of worm gear design. During reactor scram, the EM clutch is de-energized and rod falls freely due to gravity (Taliyan et al, 1994). A set of pick-up rings are used, which lapse one over the other bringing hydraulic dashpot into action precisely at the desired position (typically 90% of rod drop).…”

Methodology for a numerical simulation of an insertion or a drop of the rod cluster control assembly in a PWR

“…The kinematics of the rod were obtained by using the dynamic force balance. He developed an empirical formula for the friction factor in the dash-pot, depending on the flow clearance geometry (Taliyan et al, 1994).…”