Double-click on Nuclear data node, then Nuclei. The list of nuclei is displayed now.
To quickly locate a given nuclide, click a nuclide node, e.g. “1H”, then quickly start typing the symbol of the searched isotope. In our case, type “152”. The data browser now locates the first nuclide with the typed mass number.
Double-click on 152Eu node, the open its 13.5-year 152Eu isomer and its 152Eu EC decay.
If you check the list of radiations, you can observe the two 443-keV gamma lines of this EC decay.
Click the first 443-keV radiation in the list, and select Radiation properties task at the right.
The radiation's property editor window appears now.
If a check mark can be seen beside a specific usage type, then this radiation will be used for that selected purpose.
Remove the check mark beside “Detector efficiency calibration”.
When you click this check box, the change will be immediately stored in the database, and next time the efficiency analysis module will not use this radiation.