Code Manual for CONTAIN 2.0 - Federation of American Scientists

For purposes of the present discussion, two types of interfaces and repositories are defined: internal
and external. Internal interfaces are those that connect internal repositories, which are defined as *’
ones that consistently utilize the CONTAIN set of materials and thermodynamic fimctions. External
interfaces are those that connect an internal repository with either an external source, external
repository, or external boundary condition. A repository is defined as external when it is
incompatible with the internal repositories with respect to the set of materials or thermodynamic
functions used. Such repositories are typically the result of importing codes with similar but
incompatible representations into CONTAIN. In the present scheme, mass and energy accounting
is done only for the internal repositories. The heat and mass fluxes from the external repositories
are treated as if they were external sources applied to the internal repositories.
By design, certain CONTAIN internal interfaces are treated as nonconservative with respect to the
energy loaded into the standard interface arrays (even when the potential energy change is
considered). In general, an internal interface should be conservative unless a good reason exists for
a nonconservative one. One reason for a “nonconservative” interface is to compensate for the effect
of considering the coolant to have a ftite volume in some repositories, such as the pool, but not in
others, such as structures. An example is the interface for coolant film overflow from structures into
pools. Since displacement effects on the atmosphere by a coolant film are ignored, but those of a
pool are considered, the new pressure term in the enthalpy (see Equation (3-3) or (3-8)), which
should in general be present in the liquid water enthalpy transferred from the film to pool on
overflow, is included in the energy added to the pool but omitted from the energy subtracted from
the structure film. This nonconservative treatment gives a more accurate representation of the
thermodynamic state of the film when the work done against the system constraints is considered,
and as a minor side benefit, it also reduces the coding involved in implementing the pressure term.
Interfaces associated with a source table or an external user-specified temperature boundary
condition are examples of external interfaces. An important example of an external interface
connecting two repositories is the interface between CONTAIN and the lower cell layers
representing CORCON. The latter layers are considered to be external repositories because of
representational incompatibilities between the materials and thermodynamic functions used by
CONTAIN and by CORCON. To accommodate this representational incompatibility, the flux of
aerosol materials from VANESA, the aerosol generation module of CORCON, into the CONTAIN
domain is determined by mapping the larger set of VANESA materials onto the smaller set of
CONTAIN materials and the enthalpy flux of released gases is determined by matching
temperatures, not enthalpies, of the released gases across the interface. (These gases are presently
assumed to be ideal, and therefore knowledge of the pressure is not required.)
The decision to exclude external repositories as separate accounting entities in the mass and energy
accounting scheme is based on the observation that energy is in general not formally conserved
across the interface to an external repository but the significance of the lack of conservation cannot
be determined in a simple manner. (It also should be noted that CORCON, the principal external
repository, has its own internal energy accounting scheme.) It is possible that the lack of formal
conservation has little or no impact on the calculated thermodynamic states. For example, if the
same set of materials with the same thermodynamic derivative functions (such as the specific heat)
is used on both sides of such an interface, but the arbitrary zeroes of enthalpies are substantially
different on the two sides, then temperature and pressure matching would lead to the correct ~
Rev O A2 6/30/97