United States Nuclear Regulatory Commission - Protecting People and the Environment

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


Page Last Reviewed/Updated Thursday, March 29, 2012