MCNP: Critical Mass of UO2 (10% Enrichment)

[Tema3212]

TL;DR Summary

Critical mass UO2 with an enrichment of 10%.

I wrote a program to determine the critical mass of uranium oxide with an enrichment of 10%. I got a keff approximately equal to 1 with the selected volume and density (attached a file). Is it possible to somehow run the program without writing the initial density and volume into the conditions? So that the program itself finds these values in the process of operation. After all, the practical density of UO2 varies from 10.4 to 10.9 gr/cm^3 and the volume and mass change accordingly

 

[anorlunda]

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I wrote a program to determine the critical mass of uranium oxide with an enrichment of 10%. It turned out keff approximately equal to 1 for the selected volume and density (attached file). Is it possible to somehow run the program without writing the initial density and volume into the conditions? So that the program itself finds these values in the process. After all, the practical density of UO2 ranges from 10.4 to 10.9 g / cm ^ 3, and the volume and mass change accordingly.

 

[Alex A]

I couldn't get the file to run without adding imp:n=0 to the void cell. I've simplified the geometry, removing an undeclared region and a surface.

When doing a kcode, the program isn't solving for k so much as it is searching for k. I don't know any way of getting mcnp to do what you want directly.

For such a simple problem there is a trick. Density * Radius appears to be an invariant. So if you run for Density=10.4 and Radius = 66.5 you have the same answer for all problems where Density * Radius = 691.6

So if the fuel has a density of 10.8 then 691.6/10.8 to gives you the radius without having to run again. Volume of a sphere * density to get the mass - this will change.

Critical mass uranium dioxide
c Cell Card                                                    
1 1  -10.4  -1 imp:n=1 
999 0        1 imp:n=0

c Surface Card
1 so  66.5

c Data Card
m1   92235 0.08815 92238 0.79333
     8016 0.11852                                                        
c Criticaly Control Card                                      
kcode 1000 1.0  50  600                                                
ksrc    0  0  0                                                        

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