Casper Versteylen

• PhD
• TNO

Pressurized thermal shock (PTS) in a reactor pressure vessel could lead to a sudden brittle and catastrophic cleavage fracture. The combination of radiation embrittlement, the thermal stresses, and low temperatures can cause severe conditions for the structures. Particularly thick-walled reactor pressure vessels, which contain weak spots such as we...

This paper presents the probabilistic study for Leak Before Break (LBB) assessments. The research has been carried out with an in-house developed software that allows to perform both probabilistic and deterministic leak before break analyses for pressurized pipes. The study is based on the UK procedure for the assessment of the integrity of structu...

Most standard surveillance programs for pressurized water reactors (PWR), do not contain enough surveillance specimens for their long-term operation (LTO) beyond the original design life of 40 years. The use of testing methods based on small/sub-sized specimen such as mini-CT (0.16 CT, 4 mm thickness) is considered a promising approach to overcome...

In 2020, the CFD analyses have been performed on a whole reactor vessel model. The action of accumulators during the PTS transient was considered. Using these data, an attempt to the efficient use of sub-modelling is carried out in order to obtain a strong reduction in the computational costs compared to a full 3D analysis. The analyses were given...

In a nuclear power plant, the integrity of the pressure vessel which contains the primary water is paramount. In case of an accident involving the guillotine break of primary system piping there can be a sudden loss-of-coolant accident (LOCA). During such an incident, the reactor core needs to be cooled for some period after its shut-down (residual...

When metals are mechanically loaded at elevated temperatures for extended periods of time, creep damage will occur in the form of cavities at grain boundaries. In the present experiments it is demonstrated that in binary iron-tungsten alloys creep damage can be self healed by selective precipitation of a W-rich phase inside these cavities. Using sy...

A self-consistent model is applied to predict the creep cavity growth and strain rates in metals from the perspective of self-healing. In this model, the creep cavity growth rate is intricately linked to the strain rate. The self-healing process causes precipitates to grow inside creep cavities. Due to the Kirkendall effect, a diffusional flux of v...

In recently discovered self healing creep steels, open-volume creep cavities are filled by the precipitation of supersaturated solute. These creep cavities form on the grain boundaries oriented perpendicular to the applied stress. The presence of a free surface triggers a flux of solute from the matrix, over the grain boundaries towards the creep c...

The diffusivities of substitutional impurity elements in iron have been computed with ab inito electronic density functional techniques, using exchange-correlation functional PW91. Excess entropies and the attempt frequency for a jump were determined by calculating phonon frequencies in the harmonic approximation. The influence of the degree of spo...

The autonomous filling of creep-loading induced grain-boundary cavities by gold-rich precipitates at a temperature of 550 C has been studied as a function of the applied load for Fe-Au alloys using synchrotron X-ray nano-tomography. The alloy serves as a model alloy for future self-healing creep resistant steels. The size, shape and spatial distrib...

In this work, the effect of fluctuations in a disordered square lattice on diffusion of a test particle is studied using kinetic Monte Carlo simulations. Diffusion is relevant to a wide variety of problems, both within physics and outside of physics. Kinetic effects in diffusion are often hidden in a thermodynamical description of the problem. In t...