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TÜV SÜD conducts continuous monitoring and testing of all systems and facilities with special emphasis placed on the key component: the reactor pressure vessel, its fuel assemblies and related systems.

Our assessments and advisory services span:

• Reactor physics
• Thermodynamics and fluid dynamics
• Fuel assemblies and core components

Reactor physics

Highly specialised computer codes such as CASMO/SIMULATE, DYN3D, SCALE or MCNP are used to examine and determine the nuclear design and safe operation of fuel assemblies and core configuration for light water and research reactors. Issues involving the reactor dynamics of the core are as much a part of our business as core monitoring (power density distribution, burn up, shut down margin) and evaluating nuclear measurements. Furthermore, we calculate the critical safety and activity inventory of core fuels.

Thermodynamics and fluid dynamics

In the nuclear regulatory and licensing procedure, various operational transients and failures are analysed, especially after performing process engineering modifications.

These studies are used to verify conformance to design requirements after plant modifications have been made and to define minimum system demands for maintaining these requirements in terms of safety case studies and PSAs. To this end, we analyse design and beyond design transients and failures (e.g. LOCA-accidents, turbine trip, PTS, station black out) regarding time-dependent behavior of pressure, temperature and mass flow. In conjunction with these transients, we also investigate the behaviour of piping systems and valves towards dynamic loads forced by condensation phenomena, breaks of pipes or rapid closing / opening of valves.

For simulating the plant dynamics, TÜV SÜD uses internationally validated codes like RELAP, ATHLET or ANSYS-CFX. Computational Fluid Dynamics (CFD) is the most detailed method in use to calculate fluid flow problems. It solves the 2D/3D flow equations even on complex geometry. This method has established itself in all areas of industrial application, providing insight into flow patterns where experiments are too costly or even impossible. Physical phenomena such as turbulence, 2-phase flow or combustion are captured by modeling

Fuel Assemblies and Core Components

We examine and assess every core component during its entire service life: from the planning stage to the manufacturing stage, from its deployment through to its behaviour during operation, to its disposal. During design, we validate the fuel rod behaviour with codes like Transuranus or MSC Marc. In the course of monitoring, complex strength tests are performed, specifications and drawings are verified, inspection schedules are written up jointly with the licensees, on-site inspections are carried out both at the manufacturing plant and at the nuclear power plants, and the results are analysed and assessed.