
The criteria used for deciding when to stop halving intervals
during resonance reconstruction are complex. Modern resonance
evaluations can be very detailed, yielding hundreds of thousands
of energy points when fully expanded. These very large
tabulations are expensive to produce, to store, and to Doppler
broaden or average. However, almost all of the uses of
RECONR output result in integrating over the cross sections;
this is true for both Doppler broadening and multigroup
averaging, and it is also true for all ultimate applications,
even continuousenergy Monte Carlo transport calculations.
Therefore, if the reconstructed resonance cross sections contain
features that cause negligible effect on these integrals, these
features can be removed without affecting the ultimate results
significantly. This is why RECONR includes an option for
carrying out "integral thinning" while it is generating its
resonance cross sections.
The main user input to RECONR is the reconstruction tolerance,
ERR . It is given as a fractional quantity,
e.g., 0.001, to represent 0.1%. The default behavior
is to set the auxiliary thinning parameters to standard values
ERRMAX=20*ERR and ERRINT=ERR/10000 .
RECONR will then always halve intervals until the fractional
difference between the computed cross sections and the
interpolates are less than ERRMAX for all reactions.
Once this has been achieved for an interval, it will check to
see how much the panel will change the resonance intergal. If
the change is smaller than ERRINT, the subdivision process will
be terminated. When the subdivision terminates, it is possible
to make a rough estimate of the effect of the termination on the
resonance integral. As an example of this process, here is
an example of the output provided by RECONR when processing
U238 from ENDF/BVI:
