Iodine sorption/desorption from low-alloy steel and graphite. Draft

Tests have been performed at Oak Ridge National Laboratory on the sorptive behavior of iodine on two prominent HTGR primary circuit materials - type H-451 graphite, which is the selected core graphite, and a low-alloy steel (T-22), a type which is employed in the lower temperature regions of the primary system. The main emphasis of the work is the determination of equilibrium sorptive capacities for very low iodine partial pressures. Toward this goal, the test procedures allow on-line determination of sorptive capacity down to iodine partial pressures of approx. 10/sup -11/ bar in helium at a total pressure of 1 atm. The apparatus employed is of the helium flow-through type. Detectors monitor the degree of sorption on specimens and traps, which, together with the helium flowrate and source vapor pressure, yield a continuous determination of iodine mass transport.