Why is My MCNP Burnup Calculation Failing?

[Rafimah]

TL;DR Summary

I'm trying to learn to calculate burnup in MCNP but I'm having some difficulties

Hi everyone, I'm a newbie to MCNP, I'm trying to calculate burnup for this pellet I include here in a PWR in an infinitely repeated geometry, but it seems to be failing for some reason. I get the error message:

ctm = 0.00 nrn = 0
dump 1 on file runtpp.h5 nps = 0 coll = 0
source distribution written to file srcte cycle= 0
xact is done
cp0 = 0.18
Geometry error: no cell found.
run terminated because 10 particles got lost.
=====> 4.05 M histories/hr (based on wall-clock time in mcrun)
warning. 10 particles got lost
warning. no final keff estimate made because no active cycles run.
ctm = 0.00 nrn = 189
dump 2 on file runtpp.h5 nps = 10 coll = 0
mcrun is done

Can anyone help me out with this? I imagine it has to do with the "geometry error: no cell found" line but I don't understand the issue. The cell seems alright to me and the ksrc point is inside the cylinder.

Any help would be very appreciated!

 

[Alex A]

"20 0 1 2 -3"
This is the void, so it needs to be all space you don't care about. Everything above AS WELL AS everything below AS WELL AS everything outside the cylinder. So you need the union operator :

1:2:-3

As a rule of thumb, expect to use the union operator a lot in the void cell specification. I've not checked anything else and this is not yet a repeated geometry, the simplest way to do that would be to put the pellet in a reflecting box.

I was going to welcome you to PF, but unusually for an MCNP question you have other posts. Welcome to Nuclear Engineering anyway @Rafimah !