Decay-only photon source logic misunderstanding

User Support
1

Hi there,
I’ve bee trying out the development feature (coming among other things from PR #2234) of decay photon sources. In that process, as a super simple test case, I set up a sphere of Cs137 to decay into Ba137.
My first attempt was to simply run the depletion algorithm for a set of time steps and extract the number of atoms of Cs and Ba at each step. This resulted in plot1.png, which clearly is not right.

If I however reinitialize my source at every timestep by extracting the new material vector (for the material filling the sphere) and subsequently calling decay_photon_energy on that, for use as a source, I get plot2.png which must be right. This process is rather slow and awkward though.
Is there a simpler way that I’ve just missed? Or should I have a go at setting it up myself?
cheers
Erik
plot1
plot2

2

Since posting this I have figured it out. One simply needs to update the source energy distribution between steps. Otherwise all transport steps will be as if the source were undepleted, and cause unphysically high “burnup”.

3

Thanks for following up! Sorry your post got stuck in a spam filter – I wasn’t getting notifications about those and just realized there were a whole bunch. Anyway, glad to hear you got it figured out.