Thermo-hydraulic Analyses

NRG has over 40 years of experience in performing and reviewing safety analyses for pressurised and boiling water reactors (PWR and BWR), both for Design Base Accidents (DBA) and Severe Accidents (SA). In addition, NRG is leading when it comes to analysing phenomena unique to gas-cooled, graphite moderated reactors, including the transport and deposition of radioactive (graphite) dust and aerosols.

We use validated commercial computer codes such as RELAP5/MOD3.3, TRACE V50P3, MELCOR 2.1, and the in-house developed code SPECTRA 3.6 which is suitable for advanced reactor types.

Thermal-hydraulic safety analyses can contribute to safety in other fields besides nuclear, for example in the chemical industry. Originally designed for nuclear applications, the computer codes used by NRG can be applied to any installation with a water/steam based cooling system. Safety analyses provide insight into the (time dependent) system response in the case of a disturbances or accidents.

SPECTRA (Sophisticated Plant Evaluation Code for Thermal-hydraulic Response Assessment) is a computer program designed by NRG for thermal-hydraulic analyses. SPECTRA has been extensively validated using benchmarks from the nuclear industry.

Thanks to its flexible design and generic models, SPECTRA can be applied to both nuclear and conventional power plants and installations. The code has been successfully used for safety and design analyses of light water reactors (LWR), High Temperature Reactors (HTR), Pebble Bed Modular Reactor (PBMR), Gas-Cooled Fast Reactor (GCFR), liquid metal reactors (lead, sodium) and chemical reactors.

What makes SPECTRA unique is its applicability for 4th Generation (Gen-4) reactors such as HTR, PBMR and GCFR. SPECTRA is the only code capable of modelling in detail the transport, deposition and resuspension of (graphite) dust. It also calculates the dispersion, absorption, adsorption and desorption of fission product.