Nuclear reactor safety
The assessment of accident scenarios in nuclear power plants and the validation of thermal hydraulics codes require experimental studies under realistic thermal hydraulic conditions. Such experiments are being carried out at our TOPFLOW test facility. Furthermore we work on answers to questions on the functionality and safety of innovative passive cooling systems as well as on advanced instrumentation for monitoring of nuclear reactors and waste containers.
Thermal fluid dynamics of pressurized thermal shock
During a loss-of-coolant-accident in a nuclear reactor circuit, the emergency core cooling system injects water of approximately 9°C temperature into a partially filled cold leg in order to maintain safe cooling of the reactor core. This event may result in high thermal loads to the reactor pressure vessel wall and thus affect the reactor pressure vessel's integrity.
Core thermal hydraulics, wall boiling and critical heat flux
Together with the other project partners the transient process from nucleate boiling to film boiling is studied both by means of experimental and numerical tools. Numerical method development includes the modelling of the development of gas fraction, bubble size and distribution and heat transfer in the Euler-Euler two-phase framework near or at CHF.
Passive cooling systems
The storage of spent fuel elements in actively cooled water pools, e.g. by pumps, is common practice in nuclear power plants. A promising approach to enhance the reliability of power plants is a two-phase, passive heat transfer system.
Behavior of zink borate species in loss-of-coolant accidents
Measures to ensure the long-term core coolability after design-basis accidents are integral part of the safety concept of nuclear power stations in the whole world. In case of loss-of-coolant accidents in pressurized water reactors, the cooling water spilling out of the leak in the primary cooling circuit is collected in the reactor sump and recirculated into the primary cooling circuit by emergency cooling pumps during sump recirculation operation.
Safety of spent fuel pools
The objective of the project is the experimental investigation and modelling of the thermal hydraulics in a mock-up of a boiling water reactor fuel element to gain a better understanding of the underlying processes and to assess the time course of such an accident scenario.
Gas entrainment into pumps and valves
The project deals with the analysis and prediction of the behavior of safety related components in light water reactors under critical operation conditions. One issue is the potential gas entrainment into emergency cooling pumps.
Counter-current flow limitation in the hot leg of a PWR nuclear reactor
If accidents occur on Nuclear Power Plants (NPP), the safe reactor core cooling always has to be guaranteed, even in case of additional failure of components. One of the considered accident scenarios is a little leakage at the primary loop of a Pressurized Water Reactor (PWR) with simultaneous failure of the high-pressure emergency core cooling system after the shut-down of the main coolant pumps.
Monitoring of nuclear reactors state in severe accidents
Accidents with multiple security system failures in light water nuclear reactors can lead to a coolant level decrease inside the reactor and may cause the core to heat up and eventually melt. Initiation of emergency measures in such an accident requires knowledge of the filling level decrease and the beginning of the meltdown.
Long-term monitoring methods for spent fuel
Without a long-term storage for highly-active nuclear waste a prolonged intermediate storage of spent fuel in dry storage casks at the power plant sites is required. Therefore, it is of public interest to find and potentially implement methods which can provide information about the condition of the storage container inventory.