Code Manual for CONTAIN 2.0 - Federation of American Scientists

—.
The bound water release is calculated by default from an Arrhenius rate law:
and
dG~i
— =
(M~i - G~,~~ exp ~
[)
dt i
dGbi
AG~i
,
= - AtC,
dt
where ~ is the decomposition rate constant and ~ is the activation energy.
A similar equation and similar parameters are used for COZ.
(10-148)
(10-149)
The Arrhenius release model may not be appropriate for complicated situations. For example, the
decomposition of a mixture of MgCO~ and CaCO~, both of which produce CO ~gas, cannot be
represented by a rate equation of the type given by Equation (10-148). The user does, however, have
the freedom to select the rate constant K and the activation energy E so that average parameters for
a mixture can be chosen. A simpler model, identical to the pressure-independent, temperature-range,
evaporable water release model mentioned earlier, can also be used in such situations. This simpler
model is activated through the TRANGE keyword in the OUTGAS input block. It is provided as
an alternative that maybe more appropriate than the Arrhenius model in some cases.
10.6 Couded Heat and Mass Transfer
The heat and mass transfer processes discussed in this chapter generally become coupled at the heat
transfer interface, through the interface energy balance equation. This equation typically is used to
determine the interface temperature Ti~which drives the interface processes. This energy balance
equation and the derivation of the interface temperature are discussed in this section.
To avoid separate discussions for each type of interface in CONTAIN, a general discussion of heat
and mass transfer at an interface is given. This general discussion is directly applicable to the
interface between the gas and a heat transfer structure. Figure 10-11 illustrates the processes that
can occur at this interface. However, the reader should note that the processes considered at an
interface and the manner in which they are taken into account may vary with the interface. Table
10-1 summarizes the processes that are modeled for each type of interface in CONTAIN and
indicates whether or not each process is considered in the interface temperature calculation.
At an interface involving the gas, convective (q,) and condensation heat transfer (~O.~)are in general
taken into account. For gas-structure interfaces the enthalpy conveyed by water aerosol deposition
(q..,) is a.lso taken into account and included in the interface energy conservation equation for the
interface. Although water aerosol deposition and the enthalpy carried by the water aerosols are
modeled at interfaces with respect to pools, lower cell layers, or engineered systems, the aerosol
sensible heat is not taken into account in the interface temperature calculation. Rather, the deposited
water aerosols and the associated enthalpy are simply transfemed to the collecting pool. The inner
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