The third (and most advanced) option for defining matrix degradation rates in the Source Inventories dialog is to assume that the matrix degrades based on solubility-limited dissolution.
To simulate this, GoldSim identifies the largest single species in the inventory, and treats this as the matrix material. Upon barrier failure, the matrix is then degraded at a rate that keeps the matrix species at its solubility limit within all Inventory Cells (at least until the matrix is completely dissolved).
This method more accurately represents that actual degradation process for many types of systems in which the degradation rate is a function of 1) the matrix material’s solubility; and 2) the rate of transport of dissolved matrix material away from the waste package. For systems that have low flow rates, this process of solubility and transport-limited matrix degradation can represent a significant barrier to release of contaminant species. It would also be difficult, if not impossible, to capture this process accurately using one of the other two matrix degradation methods.
There are requirements that must be met in order to use this option:
•The Inventory Cells must contain Water or some other Fluid. If no Fluid is present, the matrix will not degrade.
•The matrix species must have a non-zero solubility. If the solubility of the matrix species is zero, the matrix will not degrade.
•One species in the inventory should be larger than all of the others combined (in terms of mass), and this species is automatically defined as the matrix material. If this is not the case, GoldSim will select the species with the largest mass, and add a warning message the the Run Log.
•If Inventory Cells inside different Sources are part of the same Cell net, for any Sources that have congruently-dissolved matrices, the same species must represent the waste matrix.
An overview of the solution algorithm is discussed in Appendix E of the Contaminant Transport Module User’s Guide.