Use of the HARPROB program to evaluate the effect of parameter uncertaintyon chemical modelling predictions

This paper describes HARPROB, a computer program developed for Nirex by AEA Technology to allow a quantitative assessment of the impact of uncertainti es in input data on chemical modelling predictions. The program uses a Mont e-Carlo sampling technique to select values from a user-defined probability distribution for input into the HARPHRQ chemical modelling program. The use of the program is illustrated for two specific cases: 1. recalculation of a representative 'in situ' deep groundwater composition for a sample perturbed by degassing on extraction from depth; 2. prediction of the solubility of urainum(VI) in cement-equilibrated water .