Validation of Serpent-SUBCHANFLOW-TRANSURANUS pin-by-pin burnup calculations using experimental data from the Temelín II VVER-1000 reactor

This work deals with the validation of a high-fidelity multiphysics system coupling the Serpent 2 Monte Carlo neutron transport code with SUBCHANFLOW, a subchannel thermalhydraulics code, and TRANSURANUS, a fuel-performance analysis code. The results for a full-core pin-by-pin burnup calculation for the ninth operating cycle of the Temelín II VVER-1000 plant, which starts from a fresh core, are presented and assessed using experimental data. A good agreement is found comparing the critical boron concentration and a set of pin-level neutron flux profiles against measurements. In addition, the calculated axial and radial power distributions match closely the values reported by the core monitoring system. To demonstrate the modeling capabilities of the three-code coupling, pin-level neutronic, thermalhydraulic and thermomechanic results are shown as well. These studies are encompassed in the final phase of the EU Horizon 2020 McSAFE project, during which the Serpent-SUBCHANFLOW-TRANSURANUS system was developed

Finite time and asymptotic behaviour of the maximal excursion of a random walk

Abstract We evaluate the limit distribution of the maximal excursion of a random walk in any dimension for homogeneous environments and for self-similar supports under the assumption of spherical symmetry. This distribution is obtained in closed form and is an approximation of the exact distribution comparable to that obtained by real space renormalization methods. Then we focus on the early time behaviour of this quantity. The instantaneous diffusion exponent ν n exhibits a systematic overshooting of the long time exponent. Exact results are obtained in one dimension up to third order in n −1/2 . In two dimensions, on a regular lattice and on the Sierpiński gasket we find numerically that the analytic scaling ν n ν + An −ν holds. Keywords: random walk, maximal excursion, finite size scaling, enumeration technique, Sierpiński gasket The random walk (RW) on a lattice has long been studied due to its widespread applications in mathematics, physics, chemistry and other research areas. It turns out that despite the huge amount of accomplished work, it still remains a thriving research topic. Lots of results can be obtained in the continuum limit (Brownian motion) but results for RW on a lattice often yield drastically different behaviour -as it is the case for the winding angle distribution [1] -or, at least, unusual finite time convergence properties. In the present work we investigate a central quantity for RW, the maximal excursion from the origin at time n, M n = max(||x m ||, 0 ≤ m ≤ n). This random variable is of great interest in many practical purposes such as the control of pollution spread, propagation ranges of epidemics, tracer displacement in fluids, the radius of gyration of polymer chain

Validation of Serpent-SUBCHANFLOW-TRANSURANUS pin-by-pin burnup calculations using experimental data from the Temelín II VVER-1000 reactor

This work deals with the validation of a high-fidelity multiphysics system coupling the Serpent 2 Monte Carlo neutron transport code with SUBCHANFLOW, a subchannel thermalhydraulics code, and TRANSURANUS, a fuel-performance analysis code. The results for a full-core pin-by-pin burnup calculation for the ninth operating cycle of the Temelín II VVER-1000 plant, which starts from a fresh core, are presented and assessed using experimental data. A good agreement is found comparing the critical boron concentration and a set of pin-level neutron flux profiles against measurements. In addition, the calculated axial and radial power distributions match closely the values reported by the core monitoring system. To demonstrate the modeling capabilities of the three-code coupling, pin-level neutronic, thermalhydraulic and thermomechanic results are shown as well. These studies are encompassed in the final phase of the EU Horizon 2020 McSAFE project, during which the Serpent-SUBCHANFLOW-TRANSURANUS system was developed