Can FLUKA calculate multi-step Co-60 generation: Fe(p,x) --> multiple Co(n,gamma) --> Co-60?

Thanks for your reply @ctheis and also for sharing the paper! I also appreciate your advice on the Co-60 generation pathway. So certainly, my next step is to evaluate the activation with a more realistic beam shower and with the actual yoke geometry.

However, now knowing the dominant pathway to Co-60 is through trace Co in this case, I am still curious about my original question:

Of course, one will have difficulty finding pure Fe (100%) in reality, but I re-ran my input file with a pure Fe target and find no Co-60 scored by RESNUCL. I see plenty of Co-55 through Co-58 and also plenty of neutrons from a simple USRTRACK scoring, so my (crude) answer to my own question at the moment is “No” or “Maybe if I run many more primaries”. Can you or a colleague shine any light on this? Thanks!

By the way, I like the abbreviations used for ETM and DTM in the paper, which are much easier to say than the full phrase. :grin:


Hi Ted,

such multi-generation reactions are exotic in real nature and as such very difficult to reproduce with a Monte Carlo simulation where you maybe use 1e6 to 1e8 primaries which is only a tiny fraction of the particles we would expect to impinge in real life on a magnet yoke.

For radiological characterization at CERN we are also using the ActiWiz code for which is partially based on FLUKA data for high energy reactions and where we invested ~100 CPU years. There I actually see that we get some Co-60 and Co-60m (which will decay into the ground state) from pure iron. Yet the uncertainty is still very high which is not really surprising.

To give you an idea if I run a typical spectrum that we see in a magnet yoke after losing a 1.4 GeV proton beam, assuming 100% iron, 15 years of irradiation and 12 years of cooling:

Ti	44	8.905037e-11  +/-   0.41%	
Co	56	1.239095e-26  +/-   0.13%	
Co	57	6.018493e-16  +/-   0.98%	
Co	58	1.344835e-30  +/-   2.22%	
Co	60	1.494333e-15  +/-  43.40%	

So you can see that in principle the model of FLUKA is capable of treating these exotic reactions but it comes at a very high computational cost and usually they are overshadowed by other reaction channels.

Hope that helps

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