Questions regarding Batch, Energy Grid and use of cross section file?

User Support
1

Hello There,

I am using first time the stochastic code i.e. OpenMC. I have some question. I have read USer’s guide and theory.

  1. Reading the Documents I cannot understand the concept of Batch in Eigenvalue Element, is it same as generations?
  2. Also I could not understand energy grid concept and unionized energy grid.
  3. I do not understand how to use cross section file and what kind of input should given for particular material in material.xml file? like for H-1 ? so that it will read cross section file correctly.

Can you please help me out these fundamental questions?

Thank you for Help.

Darpan.

2

Hi Darpan,

  1. A batch is used for statistical purposes; a fission generation is used to iterate on the fission source in an eigenvalue problem. In high dominance ratio problems, it is useful to group multiple fission generations into a single batch so that the reported variances are not underestimated.
  2. The unionized energy grid is just a technique to speed up cross section lookups. It is a memory/computation tradeoff – it makes the calculation faster at the expense of using more memory. Whether you are using or not using the unionized energy grid, your results should be exactly the same.
  3. OpenMC relies on ACE-format cross sections. You will need ACE cross section data in order to run a simulation. The cross_sections.xml tells OpenMC where to find particular cross sections, and optionally assigns “aliases” to tables in an ACE file. All the pre-generated cross_sections.xml files have aliases set up so that when you are creating a materials.xml file, you can put, e.g. . For further information, take a look here.

Best regards,
Paul

3

Thank you Paul for your detailed description.