Mechanism analysis of the contribution of nuclear data to the keff uncertainty in the pebble bed HTR

As one part of IAEA CRP on HTGR UAM, mechanism analysis of the contributions of nuclear data on the keff uncertainty for the pebble bed HTR core has been studied through a “step-by-step comparison scheme” and HTR-10 is chosen as the representative core model. Within this scheme, three main types of HTR-10 core states including initial critical configuration, initial core and equilibrium core, have been established by using the continuous energy module named Tsunami-3D-K6 in SCALE6.2.1 to quantify the uncertainty of keff propagated from nuclear data. Then, the mechanism of the keff uncertainty difference deriving from the core models, temperature distributions, material compositions and different covariance libraries are analyzed in-depth. Meanwhile, some valuable observations have been made through the mechanism analysis and also the most significant contributors to the total keff uncertainty have been figured out for HTR-10.