Code Manual for CONTAIN 2.0 - Federation of American Scientists

as small pipes, cabling, etc. Impact with such structures maybe more likely to merely deflect the
debris than de-entrain it and these structures may not survive impact by large amounts of debris.
For compartmentalized geometries, the most important debris transport issue is often the fraction of
the debris transported to the dome (f~O..). This transport fraction is governed by the relative rate at
which airborne debris is transported by gas flow to downstream cells versus the rate the debris is
removed from the cell atmosphere by trapping. Hence high trapping rates in the subcompartment
cells tend to reduce f~O~..The TOF/KU model, when used as suggested here, is thought to be either
reasonably best-estimate or else tend toward conservatism in terms calculating fd~~..However, it iS
not bounding; for example, it underestimated fdO~~by 20-40% in the Surry JET experiments. If it is
thought that f~O~. is being overpredicted for the case at hand, and that this is significantly affecting
the calculation, sensitivity calculations may be run with sd>1 in the subcompartments and/or with
the defaults used for RHODG and./or VNOST. In the TOF/KU model, variations in the critical
Kutateladze numbers for de-entrainment Nfi,~,land Nfi,~J (see Sections 6.3.6 ~d Section 14.3.2.11)
may be used to assess the effects of uncertainties in the de-entrainment criteria. For any trapping
model, the TRAPMUL parameter may be used to vary trapping rates in either direction by an
arbitrary user-specified factor. Sensitivity calculations such as these can help determine whether
loads are sensitive to debris transport and trapping uncertainties, but we cannot offer defensible
uncertainty ranges for these parameters that would be generally applicable to all problems.
In the dome, debris flight paths are typically long and the TOF/KU model often predicts the debris
will stick on fmt impact, which may not be fully realistic; hence the model maybe nonconservative
if dome carryover is large. A sensitivity calculation with the critical Kutateladze number for sticking
on the fmt impact (Nfi,~,l)set to a very small value can be performed to investigate the importance
of this question. Alternatively, gravitational fall time trapping may be specified for the dome. These
sensitivity studies may be unnecessary if fd~~~.