Activation Analysis of the Final Optics Assemblies at the National Ignition Facility

Commissioning shots have commenced at the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory. Within a year, the 192 laser beam facility will be operational and the experimental phase will begin. At each shot, the emitted neutrons will interact with surroundings, activating them, especially inside the target bay where the neutron flux is the highest. We are calculating the dose from those activated structures and objects in order to plan and minimize worker exposure during maintenance and normal NIF operation. This study presents the results of the activation analysis of the optics of the Final Optics Assemblies (FOA), which are a key contributor to worker exposure. There are 48 FOAs weighting three tons each, and routine change-out and maintenance of optics and optics modules is expected. We found that the effective dose from any optics is negligible 6 days after the last shot, and that the effective dose from frames is low but should be minimized not to reach the dose limit.