Control Dosimeters – What Are They and How Are They Used?
A commonly asked question is, “What is a control dosimeter?” The control dosimeter measures external radiation exposure from natural background radiation sources during the monitoring period and incidental exposure that may occur during shipment of the dosimeters.
Control dosimeters are identical to personal dosimeters used to monitor occupational exposure in the workplace. At least one control dosimeter is needed for each type of dosimeter that personnel are using in the workplace. For example, if your employees are wearing Luxel+® badges and Saturn® rings, you would have a control dosimeter for each type.
During our analysis of your used dosimeters, the dose received by the control dosimeters is subtracted from the worn/used dosimeters. Therefore, they should not be issued to radiation workers or used for any other purpose.
Are Control Dosimeter(s) Necessary?
Significant sources of external background radiation include cosmic radiation that is scattered in the atmosphere as it interacts with matter, terrestrial sources of radiation in the soil, and in building materials where dosimeters are used. We are all exposed to sources of natural background radiation. External (non-occupational) sources of radiation make up a very small part of the total background radiation exposure that we receive.
Control dosimeters are needed to provide a measurement of that external radiation so we can calculate an accurate measure of occupational dose. Occupational dose is received as a result of your employment using radiation sources.
When personal and control dosimeters are returned to LANDAUER for analysis, the background radiation dose measured by control dosimeters is subtracted from the total dose measured. The difference between the control dosimeter dose and the personal dosimeter dose is the dose that you received as a result of working with radiation sources (i.e. the occupational dose).
How are Control Dosimeters Used?
Control dosimeters should be placed in locations away from radiation sources at your facility. Ideally, control dosimeters should be stored in the same area where personal dosimeters are stored when they are not in use. Locating dosimeter storage locations near the entrances to radiation work areas serves to remind employees to use and store them properly. The Radiation Safety Officer or dosimetry program manager should approve all dosimeter storage locations.
The control dosimeter should never be issued to a radiation worker or stored within a shielded container. Doing so will distort background radiation measurements.
Frank has accumulated extensive expertise in radiation safety policies and procedures by working as a Radiologic Technologist, Army Radiation Safety Officer, instructor, and inspector. Frank's 35+ years of experience include managing radiation safety programs, conducting radiation surveys/inspections, and implementing safety measures to minimize radiation exposure. Frank worked as a radiographer before obtaining a degree in Radiologic Sciences and a commission in the US Army as a Nuclear Medical Science Officer, retiring as a Lieutenant Colonel.