Harvesting krypton isotopes from the off-gas of an irradiated water target to generate Br-76 and Br-77

A flowing-water target was irradiated with a 150 MeV/nucleon beam of Kr-78 at the National Superconducting Cyclotron Laboratory to produce Kr-77 and Kr-76. Real-time gamma-imaging measurements revealed the mass transport of the krypton radioisotopes through the target-water processing, or "isotope harvesting", system. The production rates were determined to be 2.7(1) x 10(-4) nuclei of Kr-76 and 1.18(6) x 10(-2) nuclei of Kr-77 formed per incident Kr-78 ion. Utilizing an off-gas processing line as part of the isotope harvesting system, a total of 7.2(1) MBq of Kr-76 and 19.1(6) MBq of Kr-77 were collected in cold traps. Through the decay, the daughter radionuclides Br-76 and Br-77 were generated and removed from the traps with an average efficiency of 77 +/- 12%. Due to the differences in half-lives of Kr-76 and Kr-77, it was possible to isolate a pure sample of Br-76 with 99.9% radionuclidic purity. The successful collection of krypton radioisotopes to generate Br-76 and Br-77 demonstrates the feasibility of gas-phase isotope harvesting from irradiated accelerator cooling-water. Larger-scale collections are planned for collecting by-product radionuclides from the Facility for Rare Isotope Beams.