Code Manual for CONTAIN 2.0 - Federation of American Scientists

compartment. Hence it was judged that including the insulation from the upper part of the vessel
would be overly conservative.
Debris TransDort and Trt_iDD@. The representation of debris-gas slip in CONTAIN is highly
simplified; Section 6.2.1 maybe consulted for additional information. The standard prescription
consists of specifying the slip parameters = 5 for all airborne fields in the cavity and in the chute
volume connecting the cavity to the subcompartments, and specifying s = 1 elsewhere. This
prescription gave good results for the Zion- and Surry-geometry IET experiments, and AP and
hydrogen production were found to be insensitive to variations in s in either the cavity or the
subcompartments. For the less prototypic geometries of the SNULFP experiments, the standard
prescription overpredicted debris transport to the dome and hence overpredicted AP. Specifying a
higher slip factor (s = 5) in the subcompartment gave more realistic results for the SNLJLFP
experiments but underpredicted debris transport to the dome in the IET experiments. If cavity
pressurization is of interest, the standard prescription was found to underpredict the extent of cavity
pressurization relative to the dome (i.e., the difference PC,vi,Y- P~Om~) by factors of 2 to 4;
considerably more realistic results were obtained assuming no slip (s = 1) in the cavity and chute.
However, the no-slip assumption overestimates debris velocities exiting the cavity and is believed
to be physically unrealistic. Compensating errors may be involved in the cavity pressurization
calculation when no slip is assumed and caution is therefore warranted in using the s = 1
specification in order to estimate the extent of cavity pressurization.
In the standard prescription, trapping in the cavity cell and chute is not modeled because the effects
of any trapping in these regions is already taken into account in the value of fti,pused to define the
airborne debris sources. The time-of-flight/Kutateladze number (TOF/KU) trapping model with the ~
options indicated in Table 13-1 is recommended as the standard prescription, although other options
may be considered for the dome as noted below. In Table 13-1, the parameter LI refers to length of
the debris flight path to the fwst structure impacted by debris, and ~ refers to the path length from
the fust to the second structure impacted, respectively. ~ is the distance from the second structure
to the final collection surface of debris that does not de-entrain on either the fmt or second impacts,
and Ldt is the gravitational fall height, which is normally set equal to the cell height. The option
RHODG = MIX specifies that the momentum flux of debris as well as that of the gas is credited in
evaluating the Kutateladze number for the sticking criterion. The option VNOST = GFT specifies
that, if debris does not stick on either the first or second structure impact, the gravitational fall
velocity is used to estimate the flight time to the final collection surface. Section 6.3.6 should be
consulted for more detailed deftitions of the trapping parameters listed in Table 13-1, and Section
14.3.2.11 provides the instructions for the relevant code input.
In the TOF/KU model, the first trapping length (LI) is intended to represent the flight path length
from the cell entrance point to the point of impact with the first major structure. If this distance
cannot be estimated unarnbiguously, the generic estimate 6V@,U maybe used, where V~is the cell
gas volume and S,mis the total unsubmerged surface area of structures in the cell. This generic
estimate is generally recommended for the second trapping length (Q because the debris trajectories
are expected to undergo considerable randomization following the first structure impact; different
values may be used if the generic value is believed to be inappropriate for the specific cell of interest.
In setting the trapping lengths, it is probably best not to take into account fine-scale structure such
Rev O 13-36 6/30/97