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
When cold emergency cooling water is injected into the main coolant line of a nuclear reactor, locally high thermomechanical stresses occur due to temperature differences. In an experimental study, heat and phase-change transfer processes were analyzed and provided as numerical validation data.
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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.
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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.
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Single-effect studies on steam condensation in an inclined pipe
A drop in the water level in the reactor pressure vessel caused by accident scenarios is to be counteracted by a passive emergency condensation system. The flow regimes and phase distributions occurring in the slightly inclined condensation pipes were investigated using an imaging tomography system, and heat transfer was measured with a specially developed probe.
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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.
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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.
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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.
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Counter-current flow limitation during reflux condenser in the hot leg of a PWR nuclear reactor
During emergency cooling scenarios, countercurrent flow of steam and condensate can occur in the hot leg of pressurized water reactors. To simulate instabilities of such flows, fundamental experiments on countercurrent flow limitation were conducted at HZDR.
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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.
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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.
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