[en] Reactor pressure vessel (RPV) steel undergoes significant changes in brittle to ductile transition temperature shift ΔRT_NDT when irradiated with fast neutrons leaking from the pressurized water reactor (PWR) core. This means that, according to American Society of Mechanical Engineers (ASME) 3-G Code, pressure-temperature limits have to be recalculated periodically. Heatup-cooldown limits require intensive calculations of time-dependent thermal and stress fields, brittle to ductile transition temperature RT_NDT determination, and so forth, and often with highly scattered material properties data. The error induced by those scattered data is then compensated for with introduction of additional safety factors specified by the ASME code. By using sensitivity analysis and performing only moderately complicated calculations, one can not only calculate certain quantities, but also their variance-covariance matrixes, based on a known (either measured or modeled) variance-covariance matrix of input parameters (i.e., material data)