In some situations, after defining decay rates and daughter products for your species, you may want to carry out some simulations in which the species do not decay (i.e., decay is deactivated). This is particularly useful in the early stages of your modeling effort when you are testing and debugging your model. Temporarily deactivating decay makes it much easier to interpret results and assure yourself that the model has been correctly implemented.
GoldSim provides for this on the Contaminant Transport tab of the Options dialog (accessed via Model | Options):
If you check the Disable decay of species box, decay will be disabled (all decay rates will be ignored and assumed to be equal to 0).