It is nonetheless recognized that low-level, chronic occupational exposures to some materials are difficult to avoid due to the types of material handled or processed, their chemical or physical forms, and the nature of operations, and that incidents may cause unplanned releases of radioactive material. Either or both of these conditions necessitate an internal dosimetry program at most DOE and DOE contractor facilities. 10 CFR 835 contains both primary and secondary limits for exposure of workers to external and internal sources of ionizing radiation in the workplace. The primary limits on internal exposures are expressed in terms of committed effective dose equivalent. The values were chosen to provide a safe working environment and to maintain exposures to within the primary exposure limits.
Air monitoring is the primary method for demonstrating compliance with workplace control limits.
Bioassay measurements that indicate a failure to control the workplace may indicate the need for improvements in workplace air monitoring. Internal dose evaluations, along with associated bioassay measurements, are the primary methods for demonstrating compliance with dose limits for protecting workers. This is discussed below under Section IV.D.7.