Title:	Computational Research on Nuclear Thermal Hydraulics and Severe Accident
DNr:	NAISS 2025/5-37
Project Type:	NAISS Medium Compute
Principal Investigator:	Pavel Kudinov <pkudinov@kth.se>
Affiliation:	Kungliga Tekniska högskolan
Duration:	2025-01-30 – 2026-02-01
Classification:	20306 20399
Homepage:	https://www.physics.kth.se/ne/sunrise
Keywords:

Abstract

In this proposal we would like to extend the previous project, and include one more compuational project for severe accident analysis. The three computational projects are listed as follow, 1. We are continuing our research on CFD modelling of the flow accelerated corrosion/erosion process for the next generation nuclear reactor in Sweden under the umbrella of the SUNRISE project, which is funded by the Swedish Foundation for Strategic Research (SSF). We continue our research with wall-modeled LES in the SEFACE facility to obtain flow statistics. We will also investigate the effect of flow-induced dissolution-induced roughness pattern via LES at different frictional Reynolds number using interval-coupling appraoch to understand their impact to flow and mass transfer statistics. In view of the recent operation of ECO-Rig erosion test rig, transient RANS and LES modelling of the ECO-Rig with erosion model is envisaged. The project aims to provide fundamental insight on the inteplay between turbulence and flow-assisted material damage. 2. We are continuing our research within several OECD/NEA projects. The motivation is to provide analytical support to experimental activities OECD/NEA PANDA, SSM ASOP, NKS PAS-SMR. The goal is to develop, validate and apply numerical methods for prediction of thermal-hydraulic phenomena of safety importance relevant to (i) the Pressure Suppression Pool (PSP), spray and mixing nozzles of the ultimate heat sink, etc.; (ii) transients in Small Modular Reactors (SMRs). The work will provide analytical support to the experiments in a large scale PANDA facility at PSI, Switzerland, HWAT facility at KTH, SEF-POOL and PPOOLEX facilities at the LUT, Finland. The project work will provide pre-test analysis to define test conditions and carry out post-test development and validation of the new models to improve predictive capabilities of the numerical tools used in safety analysis for Swedish nuclear power plants and different designs of SMRs. 3. As part of NKS-STATUS project, KTH is working on source term and uncertainty quantification in Nordic BWRs. Focusing on LOCA and SBO accident scenarios, KTH has performed large scale sensitivity and uncertainty analysis using MELCOR during phase 1,2,3. New pathways for source term release were identified, vis-a-vis basemat meltthrough. Quantification of uncertainties is ongoing, and requires computational resources. As part of the EU-SASPAM project, we are working on modelling severe accident progression in SMRs. We aim to conduct the EPZ assessment, incorporating advanced modelling of uncertainties, including both best-estimate and conservative analyses using MELCOR and MACCS system codes. Because MELCOR and MACCS modelling parameters contribute to uncertainties, accident scenarios add to splinters, sensitivity studies number in hundreds of MELCOR cases. The project intends to provide a safety analysis for SMRs in EU region, helping regulators, utilities and vendors in their decision making.