1,053,018. Fuel elements; control rods. COMMISSARIAT A L'ENERGIE ATOMIQUE. May 7, 1965 [May 12, 1964], No. 19452/65. Heading G6C. A fuel cell of a reactor of the submerged type comprises a parallelepipedic casing made of a material which exhibits little neutron-absorption, a series of parallel fuel plates of fissile material disposed inside this casing, and two plane parallel neutron-absorbent plates linked at one end by a stirrup, the two plates being parallel with the fuel plates and slidable in the casing. The linked plates are guided by longitudinal grooves in the opposite sides of the casing normal to the plates. The plates may be used for emergency shut-down and for this reason a piston secured to the stirrup enters a cylinder mounted within the casing towards the end of the free fall of the rod, the piston and cylinder forming an hydraulic damping system. The stirrup is perforated with a large number of holes in order to reduce the braking effect of the stirrup when the rod is falling freely. The cylinder completely blocks the top of the casing and coolant water from the reactor tank flowing upwards over the fissile plates passes out through holes in the walls of the casing.