A PRIORI SCAN MINIMUM DETECTABLE CONCENTRATION CALCULATOR
SURFACE SOILS
NUREG-1507 Revision 1 (2020) Minimum Detectable Concentrations with Typical Radiation Survey Instruments for Various Contaminants and Field Conditions during a Decommissioning Action presents the standard method for calculating a priori scan minimum detectable concentration (MDCSCAN) values for soils or soil-like media. The MDCSCAN calculation depends on many factors and input parameters (each is described below), as shown in Equation 1 below.
This calculator uses the NUREG-1507 default geometry of a 0.25-m2 by 0.15-m small area of elevated activity , considering four sodium iodide (NaI) detectors and common radiological contaminants.
MDCSCAN Input
Enter the site-specific background count rates (RB) for a 1-inch by 1-inch (1×1)(NaI) detector, a 2×2 NaI detector, a 3×3 NaI detector, and a field instrument for detecting low-energy radiation (FIDLER), and values for the index of sensitivity (d') , the observation interval (i) , and the surveyor efficiency (p) . Two terms in Equation 1—the count-rate-to-exposure-rate ratio (CPMR) and the exposure-rate-to-concentration ratio (ERC) —have already been calculated for the specified detectors, source geometry, and radionuclides, so user input is not required. Then enter the relative fraction of each source radiological contaminant.
MDCSCAN Output
The MDCSCAN output presents results for all detectors, input parameters, and all of the source radionuclides listed. After entering values listed under headings “Parameters,” “Radionuclide Relative Values,” and “Background CPM,” push the calculate button on the bottom left of this page to retrieve results.
