Nuclear batteries on space probes

[nmsurobert]

I've been reading about this a bit and stumbled across something that said its desirable that the heat source not be something that emits a lot of gamma radiation.
Other than hazards to a technician, does this have any effect on the device its being used on? Why would it require extra shielding if its out in space?

Thanks.

 

[jedishrfu]

The radiation could affect the electronics being powered.

 

[nmsurobert]

The radiation could affect the electronics being powered.

thats what i was thinking but i wasn't sure. maybe the gamma ray just passes on through the electronics.
my initial thoughts were that they wanted a lot alpha particles hitting the inner walls of where the heat source is to create heat but i wasn't sure.
thought id ask the pros.

 

[mfb]

Gamma rays are harmful to electronics, and if they have high energies they can induce nuclear reactions harmful to basically all materials (although you need a very high dose before that becomes relevant).

 

[nmsurobert]

Gamma rays are harmful to electronics, and if they have high energies they can induce nuclear reactions harmful to basically all materials (although you need a very high dose before that becomes relevant).

would a gamma emitter generate less heat because of gamma rays ability to easily pass through objects?

 

[mfb]

A part of that energy is lost, sure.
The difference in overall activity is more important than that.

 

[nmsurobert]

A part of that energy is lost, sure.
The difference in overall activity is more important than that.

awesome. thanks guys.

 

[Nik_2213]

In addition to damaging the control system's electronics, the gamma rays may increase baseline noise in the probe's sensors. That would be bad...

 

[davenn]

I've been reading about this a bit and stumbled across something that said its desirable that the heat source not be something that emits a lot of gamma radiation.
Other than hazards to a technician, does this have any effect on the device its being used on? Why would it require extra shielding if its out in space?

Thanks.

Calling them batteries as in your thread title isn't really a good description. These units are called Radioisotope thermoelectric generators, RTG's and get used on spacecraft and also for remote location terrestrial power.

The radio isotopes used have been chosen specifically for their low gamma and neutron emission. Plutonium 238 is a common one used particularly because of high alpha emission and low gamma emission during decay. High alpha emission is desirable because of it's much higher heat production which equals better heat to electricity generation efficiency using the thermocouples.

In the early space probes like the Pioneer an Voyager ones, the RTG was often located at the end of a long boom well away from the
rest of the craft...

on the Voyagers' they were like this ...

the RTG's on the boom facing downwards
the magnetometers were on an even longer boom that can be seen heading towards the lower left of the image.
with the passing years development of RTG's has improved and are now often much closer to the main body of the space craft

on the New Horizons craft you can see the two RTG's sticking out on the left side...

a couple of other resources ...

https://solarsystem.nasa.gov/rps/rtg.cfm

https://en.wikipedia.org/wiki/GPHS-RTG
cheers
Dave