An easy way to carry out 3D uncertainty analyses

In this paper a method is demonstrated which allows the user to carry out uncertainty calculations in arbitrary 3-dimensional radiation transport problems in an easy and straightforward manner. Although 3D uncertainty tools do exist their use is very limited because they are tied to 3D deterministic radiation transport codes, which are not commonly used because of their complexity. The method we present makes use of the 3D Monte Carlo code MCNP, which is world-wide the most commonly used radiation transport code. Using standard options of MCNP we produce a sensitivity profile, which is converted to an uncertainty value. This conversion may be carried out by a suitable uncertainty code. In the current work we used the modular code SUSD. Because of the minimal effort needed to carry out these analyses, 3-D uncertainty calculations may be performed as standard practice. Design calculations for advanced nuclear systems (such as Generation-IV reactors and ADS systems) may greatly benefit from this development. Increased insight may be obtained from neutronics design calculations, as uncertainty bands may be associated to critical design parameters. Note, however, that proper covariance data are an essential ingredient in the analysis. Unfortunately these data are rather scarce. We strongly support the current initiatives to produce high-quality covariance data-libraries for all relevant isotopes. (authors)