Uncertainty quantification method for RELAP5-3D© using RAVEN and application on NACIE experiments

Abstract

The best estimate plus uncertainty (BEPU) method plays a key role in the development of the innovative Generation IV nuclear reactors, for the improvement of knowledge and the good evaluation of the safety margins for new phenomena. The aim of this paper is to validate an uncertainty quantification (UQ) approach using RAVEN code. RAVEN, developed at the Idaho National Laboratory, is a multipurpose probabilistic and uncertainty quantification framework, capable to communicate with any system code, implemented with an integrated validation methodology involving several different metrics. In this activity, a coupled calculation RELAP5-3D/RAVEN has been performed to assess the validity of the embedded UQ approach. The simulations have concerned two tests conducted on NACIE (NAtural CIrculation Experiment) facility, a nonnuclear loop-type system using Lead-Bismuth Eutectic (LBE) as coolant, realized at the ENEA Brasimone Research Centre (Italy) to support the development of the GEN-IV reactors. The experimental tests are aimed to investigate the phenomena related to the natural and gas enhanced circulation flow regimes of heavy liquid metals (HLM), and to test and validate the main components in a LBE environment. A numerical 1D model of NACIE facility has been realized and the post-test analysis has been carried out using RELAP5-3D © ver. 4.3.4. Based on these results, a statistical analysis has been performed using RAVEN computer code, investigating the capability of three probabilistic comparison metrics fully integrated in the code.

Overview on Lead-Cooled Fast Reactor Design and Related Technologies Development in ENEA

“…Experimental data have been used to evaluate the reliability of the code results and, to some extents, also the accuracies of the predictions. Simulations of the separate effect test facility data, based on NACIE tests [56][57][58][59][60] (see also Section 4.2), were aimed at validating the core related thermalhydraulic phenomena (e.g., heat transfer, wall to fluid friction, transition from forced to natural circulation, and single-phase natural circulation) occurring in normal operation and accidental conditions (e.g., flow blockage). Other phenomena, such as pool thermalhydraulics phenomena, thermal mixing, multidimensional coolant temperatures and flow distributions, and heat transfer in prototypical steam generators have been assessed, together with the overall performances of the code at a system level, using integral test facility data based on CIRCE [13,61,62] experiments (Figure 9) and, in some cases, using sodium fast reactor [63,64] data (Figure 8), released in the framework of international benchmarks (i.e., EBR-II and PHENIX, Figure 10).…”

Preliminary sensitivity analysis for an ex-vessel LOCA without plasma shutdown for the EU DEMO WCLL blanket concept

“…Nowadays RAVEN is a multi-purpose probabilistic and uncertainty quantification platform, capable to be coupled with any system code. The software tool can be employed for several types of applications, such as uncertainty quantification [7], sensitivity analysis and probabilistic risk assessment [8]. A new Python code interface has been developed by Sapienza University of Rome to couple the MELCOR code with the RAVEN tool.…”

Post-test simulations for the NACIE-UP benchmark by STH codes

“…The scheme of the nodalization (Figure 11) is obtained improving the previous NACIE model (Narcisi et al, 2019) and it consists in a one-dimensional model of several pipes and junctions connected to each other in such a way to build a truthful simulation of the different parts of the loop. The model is composed by 186 hydrodynamic volumes and 184 junctions with a mesh size comprised in a range between 0.09 m and 0.18 m. The NACIE-UP model is composed by the following parts: the FPS (PIPE 001, active length represented in red), its outlet pipe (PIPE 003), the riser (PIPE 005), the expansion tank (PIPE 103 and PIPE 007), the HX primary side (PIPE 011), the HX low and high power secondary side (PIPE 203 and PIPE 208, respectively), the downcomer (PIPE 013) and the two horizontal legs (PIPE 009 and PIPE 015).…”