Neutronic coupling of feedback effects

The currently applied feedback methodology has been extended by explicitly treating the coupling effect which exists between the various feedback components and by improving the description of the temperature dependence of the Doppler feedback. The Doppler and sodium void feedback and coupling coefficients are presented as a first comparison of the improved and the currently applied methods. Further, the energy release which results from hypothetical disassembly accidents is simulated with a special response surface (based upon VENUS-II results) in the parametric safety evaluation code PARSEC. Additionally, the probability distribution for available work-energy, which results from the statistical uncertainty of the Doppler coefficient, is calculated. The improved feedback methodology yields about a 16 percent higher average value for the work-energy. A substantially larger increase is found on the high-yield end of the spectrum: the probability for work-energy above 500 MJ is increased by about a factor of ten