Sensitivity analysis in the migration of radionuclides: differential MonteCarlo versus double randomization

We address in this paper the efficient estimation of sensitivity coefficien ts by Monte Carlo simulations. In the context of geological performance for the risk assessment of radioactive waste repositories, a recent non-analog Monte Carlo simulation [1] based on an integral equation for the transport of radionuclides in porous media is examined in the view of sensitivity an alysis. Two methods are compared: Differential Monte Carlo which requires s pecial care when the integral kernel of the integral equation vanishes; and Double Randomization technique which is used to evaluate an effective sens itivity coefficient. Numerical results illustrate the methods for radionucl ide migration and focus on the fraction reaching the upper surface of the m edium. (C) 2001 IMACS. Published by Elsevier Science B.V. All rights reserv ed.