Do irradiation facilities generate radioactive wastes?
At gamma irradiation facilities, cobalt-60, or less commonly cesium-137, produce the ionizing radiation beam. Both radionuclides eventually decay to non-radioactive isotopes. The waste produced from irradiators is the spent source. Sources are removed from the irradiator when the radioactivity falls to approximately 6% and 12% of the initial level. Cobalt-60 sources decay to 50% in about 5 years, and to 6 to 12% of their original radioactivity in about 16 to 21 years. They metallic cobalt pellets are shipped back to the manufacturer in hardened steel shipping canisters, which have undergone extensive testing to ensure their integrity in an accident. In the unlikely event of a broken canister, it would not leak or spread in the environment. Cesium-137 sources decay to 50% in about 31 years. As a result they are replaced infrequently. When they are replaced, the old cesium sources are also shipped in hardened steel canisters. Since cesium-137 has most commonly been used in the form of a
