1. Select Radionuclides and Decay Method

Select one or more primary radionuclides from the searchable list. Use the remove buttons on the selected chips if you need to adjust the mix. Then choose the decay method that was used to generate the Target Activity Concentrations (TACs). If multiple radionuclides are selected, Field Activity Concentrations (FACs) will be required in step 2.

2. Activity Concentrations

Enter the target activity concentration (TAC) using the unit selected in step 1 (pCi or Bq) for each radionuclide. Units can be per gram or per cm², depending on source depth. TACs are similar to PRGs. If multiple radionuclides are selected, enter the Field Activity Concentrations (FACs) as well. FACs are used to generate the isotopic ratio.

3. Detector Specifications

Select the source material, source depth, detector size, and detector height above the source. For volumetric options, the selected activity unit per gram is assumed; for the surface option (ground plane), the selected activity unit per cm² is assumed.

4. Results

The results are displayed in the final table. In the Number of Photons column, click the linked number to see the radionuclide's photon energies and yields. The GDR is shown in bold and is the instrument reading that must be achieved to meet the Target Activity.

• A Field or Target Activity (cpm) result of "-" indicates that no photons are generated by the radionuclide's decay chain. Radionuclides with 0 photons do not contribute to the total GDR.
• If a radionuclide emits photons outside the detector range, an asterisk appears next to the number of photons. Those photons are listed on the Photons page, which opens from the linked count.