GB978499A - Improvements relating to liquid-moderated nuclear reactors - Google Patents

Abstract

978,499. Nuclear reactors. EUROPEAN ATOMIC ENERGY COMMUNITY (EURATOM). Oct. 3, 1963 [Oct. 5,1962], No. 39030/63. Heading G6C. A nuclear reactor is provided with a tube extending through the core and containing two fuel elements, one inadiated and the other non-inadiated, and with means for moving the fuel elements so that alternately one is within the core and the other outside and vice-versa; the change in neutron flux can be measured so that the effective crosssection of the inadiated fuel element can be determined. In the drawing a tube 12 extends from a plug 2, in the top of the reactor shield, through the pressure vessel 13, containing the heavy water modulated reactor core, and through a lower extension 16 of the pressure vessel. A support rod 5 extends through.tube 12 and carries an inadiated fuel rod 8 and a non-irradiated fuel rod 9 separated by graphite 10 of the same thickness as the bottom reflector 11 of the reactor. A reciprocating device 1 is adapted to move the rod 5 alternately from the position shown, with rod 8 in the core and rod 9 in the extension 16, to a position with rod 9 in the core and rod 8 outside the core but within the reactor shielding. The lower end of tube 12 is surrounded by reflector material 21 and concrete shielding material 23, an annular gap being left between these materials and the walls of the extension 16 to allow heavy water to pass to a duct 24 containing a safety valve (not shown) for draining the pressure vessel. The tube 12 can also be used for other oscillation experiments in which the flux is modulated by a variable neutron source. A second tube can be introduced upwards into tube 12, the tube containing a target which is bombarded by pulsed charged particles from an accelerator or containing a neutron source connected to a locating device.