Can of coca cola or other
voltmeter or multimeter
9 volt battery
1 can opener
connector 9 volt battery
Connect the electronics components of the way I explain in this scheme.
use aluminum foil to cover the open side of the can.
To test it use americium from smoke detctores, blankets lamp, luminescent hands containing radium.
if there is intense radiation it only shows the battery voltage, but if there is a source of much radiation it shows much higher voltages than the battery.
If you want to also use one of those other projects that are more accurate, but more complex.