radguide

19 Radiation for Radionuclide Users = 1376 dpm Instrument Operation and Calibration Whether an active detection system is stationary or portable, it must be properly maintained and calibrated in order to provide valid measurements. The specific requirements in this area, in terms of calibration frequencies and procedures, are generally detailed in an institution’s license application. Ideally, calibrations should involve the use of a National Institute of Standards and Technology ( NIST ) traceable source with radiation of similar type and energy to that being monitored. The date of the most recent calibration, the date the next calibration is due, and the signature of the person who performed the calibration must be indicated by a sticker attached to each instrument (the sticker may also indicate the counting efficiencies determined for various radionuclides). In addition to these formal calibrations (which are generally done on at least an annual basis), a check of the instrument’s response to radiation should be performed with a small radioactive source each time the instrument is operated. The range of acceptable response to this check source should also be listed on the instrument. Passive Detection Methods Radiation detection methods that do not require a power source are referred to as “passive” methods or systems. The detection medium is usually a solid and is used almost exclusively to characterize cumulative dose rather than dose rate or particle fluence rate (as is the case for many active detection systems). An important use for such detectors is as personnel dosimeters (i.e., devices used to assess an individual’s cumulative external radiation exposure). The two principal types of personnel dosimeters are film badges and thermoluminescent dosimeters (TLD). These are discussed in detail in Part V, Section 5.0 under “Personnel Monitoring”.