Why Does MCNP Delete Surfaces in Hexagonal Fuel Element Simulations?

[AlexFi]

TL;DR

tried to model gas cooled reactor, MCNP deleting surfaces

Hello
Tried to model gas cooled reactor with hexagonal fuel elements. MCNP keep deleting surfaces (If you could, run my input and check the .txto file) so the simulations won't run
Any advice?

 

[Alex A]

MCNP will delete coincident surfaces, this is normal. It's a bit like you have a table, and a chair, they might be complicated shapes but the bottom of all the legs of the table and the chair will be touching the floor, so you might have a lot of floor level surfaces that are actually all the same. When you build from macro bodies this will happen a lot, MCNP splits these into elementary surfaces and then gets rid of the duplicates.

 

[AlexFi]

Thanks for the explanation. It seems to me that MCNP deleted the entire cell and the simulation won't run because particles got lost. What would be a solution for this?

 

[Alex A]

Usually particles getting lost means part of the volume is undefined. In this case there is something beyond cell 9, that isn't defined, and you have no void cell.

 

[AlexFi]

Made some minor changes, added void cell
Still getting 'particle lost' and 'geometry error:no cell found' error message

 

[Grelbr42]

Hi Alex,

Have you got the plotting package for MCNP set up? If you view your file you will see you have dotted lines. It means that MCNP thinks that some cells are not properly defined. They may be such that the cells overlap. Or that there are regions with no cell defined.