"c_H_in_H2O" at different temperatures

User Support
1

Dear OpenMC community,

I’m trying to run a model that has supercritical water as coolant. For that reason, some water temperatures may go above 800K.

When adding the “s_alpha_beta” for water, I get an error because the file “c_H_in_H2O.h5” contains up to the temperature of 800K. For example:
“ERROR: Nuclear data library does not contain cross sections for c_H_in_H2O at temperatures that bound 827.0 K”.

Is it possible to simply “add” an extra temperature (for example 900K) to the existing file (from the OpenMC libraries page)?

If not:

  1. How can I generate this file, so that it is identical to the OpenMC library file but with an extra temperature?
  2. Is it enough to just generate a new “c_H_in_H2O.h5” file or is it necessary to generate more data files?

In case it is necessary to generate a new data library, I would appreciate very much a step-by-step procedure, so I can solve this (which is for my thesis) and also learn it for the future, as I have never had to generate particular nuclear data.

Best regards!
Juan

2

Unlike normal free-atom neutron cross sections, S(α,β) tables cannot just be arbitrarily Doppler broadened. Someone has to come up with the phonon frequency distribution for the material at a given temperature, and there is no analytic formula that relates that distribution at one temperature to the distribution at a lower temperature. As you’ve discovered, the current thermal scattering evaluation for H in H2O goes up to 800 K so unless someone comes along and develops a new thermal scattering evaluation for supercritical water, you are basically stuck with what we currently have.

There are only a handful of people in the world that work on generating thermal scattering evaluations. @Ignacio is involved in this area and might be able to give some more advice.