The work reported herein was conducted in response to an ITER Task to demonstrate experimentally that pulsed and continuous operations of a D-T neutron source lead, in general, to differing impacts on inventory of induced radioactivity, on one hand, and to verify calculational methods, on the other. In a series of experiments conducted for the purpose, half lives of observed radioisotopes varied from 1 minute (25Na) to 271 days (57Co). Relatively short pulse lengths, 1 minute to 3 minute duration, were chosen. A pneumatic transport system was employed to transport foils of niobium, iron, aluminum. vanadium, nickel, and magnesium for irradiation close to the D-T neutron source. Three duty factors and two kinds of power levels were used for various neutron pulse trains.

The experimental data was processed to obtain ratio of inventories in pulsed to continuous operation scenarios for each of the observed radioisotope. We observe a large reduction in radioactive inventories for values of t1/2/p (half life/pulse duration) lying in the range of 1 to 10. Interestingly, random power pulse trains show even larger reduction in radioactive inventory: the ratio of inventories drops to ~0.14 for t1/2/p = 3.15 (27Mg) for a duty factor of 20% and a train of 10 pulses, whereas it would have hit a minimum of 0.33 for t1/2/p = 3.53 for constant power level.