4.5. Control of uncertainty propagation

The use of yield and neutron flux uncertainty propagation is controlled by the IERTDCHO parameter; it toggles whether the uncertainties are considered (=1) or not (=0). If using the new default reduced file formats for [T-Dchain] by setting IREDUFMT= 1, all of the necessary uncertainty information is included in the basic [T-Track] (*.dtrk) and [T-Yield] (*.dyld) output files.

If using the older IREDUFMT= 0 formatted files, there is an additional automatically-generated [T-Yield] file (*_err.dyld) which contains the yield uncertainty information. In this case, HENMTCF must also be specified and is the filename of the yield uncertainty file passed to DCHAIN. By default in [T-Dchain], IERTDCHO is equal to 1 and HENMTCF is set to equal to ``<NAME>``_err.dyld where ``<NAME>`` was the value provided to the file argument of [T-Dchain]. If the user selects IERTDCHO=0 (or IREDUFMT=1) in [T-Dchain], HENMTCF is still written with its default value but commented out in the DCHAIN input deck (allowing for fast re-enabling later, if desired).

Enabling this functionality (which was implemented in 2019) does modify the formatting of the primary activation output file (*.act) and the ANGEL input file (*.ang) with new columns for these statistical uncertainty values. If using scripts to automatically parse either of these files, please do keep this formatting difference in mind.