Contact

Ronald Lehnigk

r.lehnigkAthzdr.de
Phone: +49 351 260 3157

Dr. Dirk Lucas

Head Computational Fluid Dynamics
d.lucasAthzdr.de
Phone: +49 351 260 2047

Safety of storage pools for spent nuclear fuel (SINABEL)

The collaborative project "SINABEL", funded by the Federal Ministry of Education and Research within the framework of the R&D program "Grundlagenforschung Energie 2020+" and worked on jointly by the Technical University of Dresden (TUD), the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and the University of Applied Sciences Zittau/Görlitz (HSZG), was directed at the investigation of the safety of storage pools for spent fuel elements. With the accident at the Fukushima Daiichi nuclear power plant in March 2011, this topic has again moved into the focus of nuclear safety research. The wet storage of fuel assemblies is necessary to reliably remove the heat resulting from radioactive decay. After removal of the fuel elements from the reactor pressure vessel, it decreases exponentially and typically lies between 5 and 200 watts per fuel rod, depending on the duration of storage. A failure of the pool cooling system, e.g. due to a failure of the plants power supply, can lead to an exposure of the fuel assemblies within days. Within the HZDR part of the project, possible problems regarding the sufficient cooling of the fuel assemblies were investigated by means of numerical flow simulation. The focus was on the flow in the pool atmosphere in case of a partial exposure of the fuel assemblies, whereby the heat transport by free convection along the fuel assembly is interrupted. The simulations show that the flow characteristics are independent of the spatial distribution of the decay heat in the pool and that a typical flow path as illustrated in the figure below develops. Detailed simulations at the fuel assembly level by the Institute of Fluid Mechanics of the Technical University of Dresden however show that the intensity of the convective heat exchange between the atmosphere and the fuel assemblies interior depends on its spatial position in the pool. The results suggest that in the case of partial exposure, a storage of fuel assemblies of higher decay heat close to the wall leads to a favorable cooling situation. An additional local cooling effect can be achieved by a checkerboard-like distribution according to the decay heat.

(a) Snapshot of the temperature and velocity field in a vertical plane through the pool center; (b) Illustration of the prevailing flow characteristic in the pool atmosphere. ©Copyright: Lehnigk, Ronald

Figure: (a) Snapshot of the temperature and velocity field in a vertical plane through the pool center; (b) Illustration of the prevailing flow characteristic in the pool atmosphere. (Oertel et. al, 2019)


Acknowledgment

This work is carried out in the frame of a current research project funded by the German Federal Ministry of Education and Research, project number 02NUK027C.

sponsored by BMBF ©Copyright: BMBF


Publications

Oertel, R.; Hanisch, T.; Krepper, E.; Lucas, D.; Rüdiger, F.; Fröhlich, J.;
Two-scale CFD analysis of a spent fuel pool involving partially uncovered fuel storage racks
Nuclear Engineering and Design 341(2019), 432-450

Oertel, R.; Krepper, E.; Lucas, D.;
CFD Simulation of Spent Fuel Pool Accidents resulting in partially uncovered Fuel Assemblies
47th Annual Meeting on Nuclear Technology (AMNT 2016), 10.-12.05.2016, Hamburg, Deutschland

Oertel, R.; Krepper, E.; Lucas, D.;
Application of CFD towards the thermo-hydraulic analysis of Spent Fuel Pool accidents
The 16th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-16), 30.09.-04.10.2015, Chicago, USA

Oertel, R.; Krepper, E.; Lucas, D.;
Large Scale CFD Simulations of Spent Fuel Pool Accident Scenarios Using a Porous Body Approach
46th Annual Meeting on Nuclear Technology (AMNT 2015), 05.-07.05.2015, Berlin, Deutschland


Contact

Ronald Lehnigk

r.lehnigkAthzdr.de
Phone: +49 351 260 3157

Dr. Dirk Lucas

Head Computational Fluid Dynamics
d.lucasAthzdr.de
Phone: +49 351 260 2047