Design and operational features of the low temperature fissiochemical loop

A low temperature in-pile loop for the irradiation of chemical reactants, especially by fission fragments, has been designed, constructed and operated successfully.The main features of the loop are briefly described : the capsule for sample irradiation, the design and performance of the helium cooling system and safety considerations.Gaseous chemical reactants charged in an instrumented double capsule at pressures up to 20 kg/cm2, can be irradiated in a nuclear reactor at any temperature between +20" and -190C, for periods up t o 5 hr.The thermal performance of the helium cooling system was in good agreement with the design calculations.Irradiations of ethylene and other gases could be conducted at an absorbed fission fragment dose rate of about 20Mrad/hr, which is several times larger than the background reactor radiation.Thus, chemical reaction studies by fission fragments can be safely conducted at ambient to low temperatures in this loop.