Simulation of Pu-238 Decay

[omarkhairallah]

Hi everyone, In my graduation project i am trying to simulate the decay of Pu-238 (in RTGs) and the dose from it on mcnp6.1.1b. I used the F6 tally and (PAR=sa) in the SDEF card to simulate the decay of alphas and also set the mode to ( MODE a e p ) to put the gammas and betas in consideration ( if any interactions could produce one of them and contribute to the total dose).

But i am facing some complexities, when using the F6 tally, the output is 0.21667 Mev per gram, which is when multiplied by the grams of the cell (145.6) and converting to watts, it's only 22 watts while the pellet of Pu-238 should produce 62.5 watts (In one RTG pellet) of decay heat, i want someone to help me with this because i dont know what's wrong.

You can find my input file attached.

 

[Alex A]

Hi @omarkhairallah,

Welcome to PhysicsForums.

I don't know what par=sa actually does. It's new in 6.1.1 and it looks up alpha decay information from decay tables and CINDER. I don't understand ACT either. When I use par=a erg=5.5 and remove ACT to make it run on my version the tally when multiplied by the mass is 5.4999 MeV. Which is trivially what it should be. Try removing ACT and if that doesn't fix it then the spontaneous alpha option isn't doing what you think it is.

 

[omarkhairallah]

Thank you @Alex A .