It actually could work pretty well. A Geiger counter is essentially a current gain device. Ionizing radiation passes through the chamber and excites free electrons which travel towards high voltage plates. The gain comes when the drifting positive ions collide with other gas particles and knock additional electrons free, starting the process again.
Rad source goes missing? Current stops flowing in the GC. HV power failure? Current stops flowing. GC falls out of the vehicle? Current stops flowing.
In any of these cases, you make the system shout an annoying beep that everyone within 250m of the vehicle can hear and somebody checks on it.
Rad source goes missing? Current stops flowing in the GC. HV power failure? Current stops flowing. GC falls out of the vehicle? Current stops flowing.
In any of these cases, you make the system shout an annoying beep that everyone within 250m of the vehicle can hear and somebody checks on it.