Code Manual for CONTAIN 2.0 - Federation of American Scientists

diffusion of water and the released gases within the concrete. Nevertheless, it is a simple and
efficient model that has been verified for certain concrete types.
The heat and mass transfer processes described above ~e for the most part controlled by the interface
temperature, which must be determined self-consistently from the heat and mass transfer rate for
each process. A discussion of the interface energy balance equation, which is solved to obtain the
interface temperature, is given in Section 10.6. Finally, Section 10.7 discusses control options
available to the user for activating or deactivating heat and mass transfer processes at specific
interfaces.
2.11 Boilirw Water Reactor and Related Models
CONTAIN treats a number of processes in which the partitioning of enthalpy and mass flows
between pool and atmosphere is important. These are commonly associated with the design of
boiling water reactors (BWRS) but not restricted to them. They include suppression pool vent
clearing, gas-pool equilibration and scrubbing for gas mixtures injected under the surface of a pool,
and coolant phase separation modeling for low-quality two-phase flow that is injected into the
atmosphere. This modeling is discussed in the context of(1) BWR suppression pool vent models
and (2) safety relief valve (SRV) discharge models.
Within the generalized treatment of pool flooding implemented in the pool tracking modifications,
modeling of the above types of processes should occur automatically on the basis of a flooded
geometry. For example, suppression pool vents are, in principle, no more than submerged flow paths
and thus the vent clearing process should be modeled automatically in such a geometry. Within the <
limitations of the pool tracking modifications, this is the case. Thus, two ways of modeling
suppression pool vent systems are discussed in Chapter 11 for a Mark III BWR: through a collection
of ordinary gas and pool flow paths and through the dedicated suppression pool vent model
originally developed to treat the BWR vent system. An approach using ordinary flow paths could
presumably be developed for Mark I’s and II’s, but this configuration would involve water-solid
cells, an aspect of the pool tracking modifications that has not been fully tested. Thus, only the
dedicated model is currently recommended for the last two designs.
It should be noted that the ordinary flow path model and the dedicated model have their own
advantages and disadvantages with respect to modeling gas-pool equilibration and aerosol scrubbing.
The user may specify the gas-pool equilibration length for a gas flow path, but, for simplicity, all
aerosols are assumed to be removed by scrubbing for a submerged gas flow path. In contrast, gaspool
equilibration is always assumed to be complete for the dedicated model in forward submerged
flow but is ignored in reverse submerged flow. However, two different mechanistic aerosol
scrubbing models are available in conjunction with the dedicated model.
Although intended originally to describe the SRV discharge of gases, aerosols, and fission products
through lines leading to the bottom of the suppression pool in a BWR, the SRV discharge model may
also be used in other situations in which the discharged materials are equilibrated and scrubbed by
a pool before being introduced into the atmosphere. A submerged discharge is treated in a manner
similar to that from the dedicated suppression pool vent model in forward submerged flow.
Rev O 222 6/30/97