Thesis work

We are currently proposing a number of thesis projects. Contact our human resources department, Annika Comstedt, Studsvik Nuclear, email address annika.comstedt@studsvik.se, tel +46 (0)155-22 12 24. You are also very welcome to submit your own proposals.

1. Development of crack growth measurement

Crack growth in construction material in simulated reactor water environments is measured by sending a current through a test specimen and continually measuring the increased resistance of the specimen as a stress corrosion crack is formed and grows. The measurements are very sensitive and growth rates down to 10-9 mm/s or lower are measured, which corresponds to about 0.03 mm/year. The accuracy of measurement is affected by a number of factors, including conductivity in the water around the specimen. The work involves developing better measurement techniques for use in water at temperatures around 300°C with various additives that increase conductivity. Good metrology skills are required.

2. Microscopy analysis of oxides in fuel and system surfaces

The oxide formed on various surfaces that come into contact with the medium (water at high temperature) in power plants is of high significance to the corrosion properties of the surface in question. New advanced microscopic methods give new knowledge of which phases are formed on the surfaces while earlier analysis mainly gave the integral composition of elements. It is assumed that the work in this area will be in cooperation with a higher education institution that has at its disposal advanced electron microscopes such as FEG-SEM, FEG-TEM and FIB. The aim is to survey oxides on system surfaces from power plants and simulated environments in the laboratory. For example, a study could be made of how the hydrogen content in a pressurized water reactor environment affects various oxide phases. The influence of the hydrogen content is now being studied worldwide to optimize conditions with regard to corrosion and activity build up.

3. FEM modelling of tensile samples for corrosion analyses

Tensile samples, which are slowly elongated in the relevant environment, are sometimes used in corrosion tests. The initiation of corrosion attacks depend on material, environment and mechanical parameters, such as stress, strain and strain rate. The samples used can be specially designed to get corrosion attacks in highly resistant material. To detect the initiation of corrosion attacks on-line a current can be put through the sample and continually measure the increased resistance of the sample due to crack formation. There is a need for modelling the local strain and strain rate in such a sample and for calculating how the specimen geometry and its resistance without any initiated crack changes during tensile testing. The work requires knowledge of modelling using finite element methods.

4. Electrochemical measurement at high temperatures

For more than 30 years Studsvik has been carrying out electrochemical measurements in power plant environments. The measurements are used to control certain chemical additives at the power plants and to monitor corrosion experiments in simulated laboratory environments. There are currently some developments in the field to improve the precision and the life time of the electrodes. Thesis projects in this field entail studies of new electrode concepts for measuring in ultra-pure water at about 300°C. The work requires electrochemistry skills and a liking for experimentation.

Do you want to know more about the thesis works above (No 1-4)? Please contact Anders Molander, , phone +46 155 22 14 79

For further information about the thesis work below (no 5) please contact Anna-Maria Alvarez Holston, .

5. The effect of hydrogen in solution on deformation and cracks in fuel cladding

The majority of fuel cladding used in nuclear power plants today is made of Zr alloys. Zirconium has low solubility of hydrogen and hydrides are formed after a period of use in the reactor. Since hydride embrittlement is a well known phenomenon efforts are being made to develop material with as low a hydrogen uptake during reactor operation as possible. In the most recent generation of fuel the hydrogren content is under the solubility limit for hydrogen in Zr, even after a long period of use. Earlier studies of more traditional metal alloys show that hydrogren in solution can affect a number of mechanisms of significance to deformation and cracks. Among other things it has been shown that hydrogen in solid solution affects the cross slip of dislocations, slip localization and slip plane decohesion. This study aims to investigate the effect of hydrogen in solution on the deformation mechanisms in some typical Zr alloys. Conventional methods such as gas phase hydrogen charging, mechanical testing and microscopy will be used. There is access to the latest generation of electron microscopes (FEG-SEM, FEG-TEM and FIB). The work requires experience of mechanical testing and microscopy. Good metallography skills are desirable.

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