Gamma intensities in a symmetric case

[Clara Rojas]

Hello! 

I’m running a case in KENO and ORIGEN to calculate the gamma intensity in four pieces positioned in the corner of a 4 pins assembly. They have been irradiated by flux during a cycle of 700 days, and they are positioned symmetrically inside the model. ORIGEN prints out the gamma spectrum for the decay period. The problem is that I’m running a symmetric case as the 4 pieces are in the top of the assembly at the same distance from the square assembly. However, if I run them as different materials(but same composition and symmetric relative position), ORIGEN prints same differences in the spectrum that I’m not sure why they are produced. For example, the four outputs for each piece are:

4.33664E+11 p/s

6.11451E+11 p/s

5.95895E+11 p/s

5.47582E+11 p/s

 

So, as you can see, there are some variations between intensities. Are these variations expected or they must be due to an input error?

 

Thanks in advance! 

[Shane Hart]

Clara,

How are you running the case and getting the fluxes?  Is this a TRITON run using KENO for the transport solve?  If so, it's possible that the convergence of the Monte Carlo solve on the flux in those regions is not the greatest.  You should be able to see the uncertainty of the flux in those depletion regions somewhere.  If the regions are small, and you're not running many histories, it's possible this could explain most of the discrepencies.

Regards,

Shane

[Clara Rojas]

Hi, Shane. Yes, I was using KENO for the transport solve and as you said, I checked the number of generations and uncertainties of the flux and they were not very fine. So, probably that is the issue. I'm going to run an input with more histories.

Thank you so much!

Regards,

Clara.