8022 - 7988 - Initiate and maintain occupancy by interrupting beam of occupancy sensor ...; Remark:

Because CF-252 sources also emit gamma radiation, a gamma alarm may also occur during this step. If this is unacceptable, either shield the gamma radiation emitted from the source with lead or hold the Cf-252 source near a neutron detector from behind the skid. The lead (Pb) shielding on the back of gamma detectors will help reduce the possibility of a gamma alarm during this step.