U.S. Nuclear Regulatory Commission
Question 145: Automated personnel contamination monitors ("portal monitors") are used at nuclear power plants to detect radioactive surface contamination on the skin and clothing of workers. The alarm setpoints for these monitors are maintained very low to detect low levels of surface contamination and hot particles. Implementation of the "respirator ALARA rule," [10 CFR 20.1702 and 20.1703 (b) (1)] may result in intakes of radioactive material by workers that will trigger the alarms on these monitors. Would the NRC object if, to facilitate compliance with the "new respirator ALARA rule", portal monitor set points were raised to a more reasonable level?
Answer: Set points for automated personnel contamination monitors are established by, and can be changed by, licensees without NRC approval. NRC has no requirement that licensees use automated personnel monitors nor does it have numerical guidance on set points for these monitors (unless a licensee has committed to using automated personnel contamination monitors, with a particular set point in a license application). However, if a licensee uses these monitors and the monitor alarms because of an intake (rather than because of external contamination), that intake should be evaluated. The question implies that the detection of small intakes of radioactive material using these monitors is undesirable and should be avoided by raising the monitor set points above their current levels. This is not necessarily the case. At least one nuclear power reactor licensee has recognized that the sensitivity of these monitors for detecting intakes can be used to advantage in internal "passive internal monitoring program" for workers for whom individual monitoring for intake is not required by 10 CFR 20.1502 (b). That licensee plans to use these monitors with a setpoint that results in the reliable detection of internal contamination equivalent to 1% of the ALI for mixtures of radionuclides encountered in the licensee's plant.
(Reference: 10 CFR 20.1702)