Control of uncertainty propagation
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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.