Assessment and improvements of thermal-hydraulic correlations and methods for the analysis of the Jules Horowitz Reactor
Doktorsavhandling, 2017

Nuclear research reactors are used to test materials for current and future nuclear technologies, and to produce radioisotopes for medical purposes. Most of the existing Material Testing Reactors in Europe have operated for more than 50 years and new ones are needed. Therefore the Jules Horowitz Reactor (JHR) is under construction at the French Alternative Energies and Atomic Energy Commission (CEA), on the Cadarache site. The JHR will allow irradiation experiments with high neutron fluxes, at fast and thermal energies. In order to cope with the considerable heat fluxes generated during operations, the core configuration consists of fuel assemblies with parallel narrow channels, where coolant flows at high velocity. Such a design is unique and specific simulation capabilities have to be developed for the analysis. This doctoral research investigates possible improvements of the thermal-hydraulic modeling of the JHR, and is arranged in three parts. In the first part, correlations for the single-phase turbulent friction and heat transfer, for the fully developed boiling heat transfer, and for the critical heat flux, respectively, are assessed and their accuracy is quantified, against the SULTAN-JHR experiments. These experiments were carried out in heated narrow channels comparable to the JHR ones. It is shown that the single-phase turbulent correlations valid for standard nuclear systems, can perform poorly when applied to the typical conditions of the JHR. Thus, new best-fitting relationships are derived. For fully developed boiling in narrow channels, the Forster-Greif correlation can be considered a reliable option. As regards the modeling of the critical heat flux, the Sudo correlation can provide satisfactory predictions. These results are then used to modify the thermal-hydraulic system code CATHARE for the purpose of a more realistic analysis of the JHR. The second part is focused on the onset of flow instability, which is a primary concern in systems with parallel channels as the JHR, since it can lead to undesirable boiling crisis. In view of this, several criteria are evaluated with experiments in narrow channels from both the SULTAN-JHR program and the literature. Conservative predictions can be obtained with Saha-Zuber KIT correlation. Furthermore, some criteria are optimized with respect to the available experimental data for narrow channels. In the third part, the analysis of a postulated accident in the JHR, namely a station black-out, is performed with a best-estimate plus uncertainty approach, combined with the CATHARE code as modified in the first part of the thesis. As a result, the impact of different input and modeling uncertainties on the simulation is estimated, and the most influential uncertain parameters are identified.

Flow instability

Uncertainty

Narrow channels

Jules Horowitz Reactor

Safety analysis

Critical heat flux

Thermal-hydraulic correlations

Heat transfer

Best-Estimate

Material Testing Reactor

PJ lecture hall, Origo, Kemigården 1, Chalmers
Opponent: Dr. Dominique Bestion, Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Grenoble, France

Författare

Alberto Ghione

Chalmers, Fysik, Subatomär fysik och plasmafysik

Assessment of Critical Heat Flux correlations in narrow rectangular channels

Proceedings of the 11th International Topical Meeting on Nuclear Thermal Hydraulics, Operation and Safety (NUTHOS-11), Gyeongju, Korea, Oct. 9-13 2016,; (2016)

Paper i proceeding

Assessment of thermal–hydraulic correlations for narrow rectangular channels with high heat flux and coolant velocity

International Journal of Heat and Mass Transfer,; Vol. 99(2016)p. 344-356

Artikel i vetenskaplig tidskrift

Criteria for onset of flow instability in heated vertical narrow rectangular channels at low pressure: an assessment study

International Journal of Heat and Mass Transfer,; Vol. 105(2017)p. 464-478

Artikel i vetenskaplig tidskrift

Ghione A., Noel B., Vinai P., Demazière C., Uncertainty and sensitivity analysis for the simulation of a station blackout scenario in the Jules Horowitz Reactor

The Jules Horowitz Reactor (JHR) is a new material testing reactor under construction at the French Alternative Energies and Atomic Energy Commission (CEA) on the Cadarache site. In this research facility, different types of experiments are planned for the development of materials and technologies for current and future nuclear applications, and for the production of radioisotopes for medical purposes.

Although the JHR core is small, the performances are rather extreme. In fact the experiments require large neutron fluxes to develop irradiation effects typical of nuclear power plants, over short time periods. Therefore significant heat fluxes are generated in the core, and the cooling is achieved with water at high velocity through narrow channels.

When operating a nuclear reactor, a sufficient level of safety have to be assured in order to minimize the potential for radioactivity releases to the environment. The safety analysis relies on computational methods developed for the simulation of the system behavior. In particular, a thermal-hydraulic modeling is needed to study the cooling of the reactor under a variety of scenarios.

In this doctoral thesis possible improvements of the thermal-hydraulic modeling of the JHR are proposed. From the investigation of proper experiments, heat transfer correlations and criteria of flow instability and boiling crisis are recommended for the specific case of the JHR. Moreover, a more realistic approach is tested for the safety analysis of the JHR, where the correlations optimized for the reactor are combined with an evaluation of the input and modeling uncertainties.

Ämneskategorier

Materialteknik

Subatomär fysik

ISBN

978-91-7597-520-7

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4201

Utgivare

Chalmers tekniska högskola

PJ lecture hall, Origo, Kemigården 1, Chalmers

Opponent: Dr. Dominique Bestion, Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Grenoble, France