10.100. Operation and maintenance charges include the payroll for the plant, clerical, engineering, and administrative staffs, and the costs of main­tenance materials and supplies, including chemicals for the treatment of reactor and condenser water and radioactive wastes produced in the reactor installation. In the same category are the costs of such miscellaneous items as liability insurance, public relations, training of new workers, travel, etc. In general, however, operation and maintenance costs contribute a rela­tively small proportion to the overall energy costs.