I started working on a an automated burnup sequence for group constant generation, capable of handling branch calculations. The work is still under way, but as a first step I implemented a kind of a restart feature in version 2.1.17, that could be useful for other purposes as well.
The idea is relatively simple. First run a burnup calculation with entry:
in the input file. The code should write a binary file <file>, which contains the nuclide compositions of all materials for all burnup steps. This file can then be read in another calculation by setting:
Instead of starting from the initial composition defined in the input, the calculation should now start from burnup step with burnup <bu>, using compositions from the previous run. The input file can be different from the run where the restart file was written, the only limitation is that the names of the burnable materials must be the same, and the same nuclides must be found in the compositions.
I want to emphasize that this feature is mainly intended to be used by another calculation routine in an automated manner, so there are certain limitations on what can and cannot be done. Basically the geometry, compositions of non-burnable materials, temperatures, etc. can be changed, but not the names or compositions of burnable materials. Changing cross section, decay or fission yield libraries or cut-offs may also change which nuclides are included in the material compositions and cause the calculation to fail.