Questions on coupling ONIX with a dissuion neutron solver

[tzhang0475]

Hi Julien,

 We are now planning a new development for an open source fuel behavior solver offbeat, which is coupling the ONIX code to the offbeat code as a burnup solver. The offbeat sovler based on the openfoam code and it includes a diffusion neutron solver that can calculate one-group neutron diffusion in the fuel for a structure/unstracture mesh. Now I have following questions regarding the capability of the ONIX code:

1. Can ONIX handle a case with hundruds of burnup cells or more (which is typical for a openfoam mesh) with different flux in each cell? 
2. As a diffusion solver, offbeat can not offer a tallied reaction rate like MC code for each isotope, but it is possible to calculate all these rates by simply times the one group flux with marco xs. However, in this way I understand that it is not possible to ask the ONIX code to calculate the one-group xs from the data library, do I get it right? On this sense, does it mean a fixed cross section library have to be prepared before the simulation? If so, does it mean the cross section will not change along with the burnup time step? Or may ONIX can handle such condition with the one group flux in each cell, the only thing I need to do is to tell the ONIX code what isotope inventory I need, this confuses me. 
3. I see xs_lib file in the data folder, it is for VVER, I am wondering how can this lib being used? Is there any example? If I want to create a new xs_lib for PWR, I can model an assembly and burn it, I do not know how to convert it to the xs_lib format, could you please offer me some hints?

Thank you very much and I am looking forward to hearing from you.

Cheers,
Tian