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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)