During the decommissioning of a legacy nuclear fission reactor, operators must retrieve and process highly radioactive control assemblies containing high-activity cobalt-60 (60Co^{60}\text{Co}60Co), which decays via beta-minus emission accompanied by the release of high-energy gamma photons.
Discuss the biological hazards associated with exposure to the radiation emitted by these control assemblies, and explain the physical principles behind the safety measures and engineering containment systems that decommissioning engineers must employ to protect personnel.