UAM (Uncertainty Analysis in Modelling)

OECD/NEA UAM - LWR (Light Water Reactor Uncertainty Analysis in Modelling Benchmark)

The OECD/NEA Light Water Reactor (LWR) - Uncertainty Analysis in Modeling (UAM) (LWR-UAM) benchmark is an international high-visibility benchmark for uncertainty analysis in best-estimate coupled code calculations for design, operation, and safety analysis of LWRs. The benchmark activities are coordinated by the NCSU faculty: Dr. Maria Avramova and Dr. Kostadin Ivanov in cooperation with Dr. Eric Royer from CEA, France. More information could be found at:
Reference systems and scenarios for coupled code analysis are defined to study the uncertainty effects for all stages of the system calculations. Uncertainty propagation is being estimated through the whole simulation process – the benchmark builds a unified framework, which can be used and followed in the future. The chain of uncertainty propagation from basic data, and engineering uncertainties, across different scales (multi-scale), and physics phenomena (multi-physics) is tested on a number of benchmark exercises for which experimental data is available and for which the power plant details have been released. The experimental and numerical test problems are representative of the three major types of LWRs – Pressurized Water Reactors (PWRs), Boiling Water Reactors (BWRs), and the Russian designed VVER reactors. The benchmark activities are organized in three phases – Phase I (standalone neutronics phase where uncertainty quantification and propagation is performed through multi-scale steady state reactor physics calculations without taking into account feedback effects); Phase II (core phase where the other physics phenomena in LWR cores and time-dependent effects are introduced); and Phase III (system phase where multi-physics coupling in LWR cores is modeled and simulated as well as the coupling between reactor core and reactor system). There are annual benchmark workshops which are attended by many experts in industry, research institutes, national laboratories, academia, and government agencies.

The workshop at BEPU2020 Conference will be the 14th workshop of LWR-UAM activities – LWR-UAM-14.


UAM - SFR (Sodium-cooled Fast Reactors Uncertainty Analysis in Modelling Benchmark)

One of the tasks of the OECD/NEA sub-group on Uncertainty Analysis in Modelling (UAM) of Sodium-cooled Fast Reactors (SFR-UAM) under the NSC/WPRS/EGUAM is to perform a code-to-code comparison on neutronic feedback coefficients and associated uncertainties calculated for transient analyses. G. Rimpault from CEA, France lead the benchmark activities in cooperation with ANL.

This benchmark exercise benefits from the results of a previous Sodium Fast Reactor core Feed-back and Transient response (SFR-FT) Task Force work under the NSC/WPRS/EGRPANS. Two SFR cores have been selected for the SFR-UAM benchmark, the 3600MWth oxide and the 1000MWth metallic SFR cores. Results from four and seven participating international institutes were received for respectively, the metallic and oxide SFR cores, using a wide range of calculation methodologies. The preliminary results display good agreement in the reactivity coefficients estimated, with remaining discrepancies explained by different nuclear data libraries, modeling approximations for deterministic solutions, and statistical convergence for stochastic evaluations on small perturbations. Nuclear data uncertainty evaluations on the reactivity coefficients are compared and display consistent results.

The benchmark has also neutronics and thermal-hydraulic phases each consisting of several exercises. The neutronic phase, which is coordinated of GRS, and NCSU consists of:
o Exercise I-1: Pin cell
o Exercise I-2: Fuel assembly
o Exercise I-3: Super-cell
o Exercise I-4: Heterogeneous reactor core

The thermal-hydraulic phase, which is coordinated from ORNL and NCSU, consists of:
o Exercise 1: Model development and single phase pressure drop simulations;
o Exercise 2: Solid component modelling and temperature fields computations;
o Exercise 3: UQ analysis and Hi2Lo methodology development.

The workshop at BEPU2020 Conference will be the 6th workshop of UAM-SFR




2000 BEST ESTIMATE Washington DC USA
2004 BEST ESTIMATE Washington DC USA
2018 BEPU 2018 Lucca ITALY