Thesis (master's)--University of Michigan, 1973.

Thesis (M.S.)--University of Michigan, 1985. / Includes: Supplement: the time required for complete core meltdown of FNR under LOCA accident.

Thesis (M.S.)--University of Michigan, 1985.

Thesis (M.S.)--University of Michigan, 1964.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1960. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1982. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 498-507).

Thesis (M.S.)--University of Wisconsin--Madison, 1982. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 93-95).

The materials under study are 9–12% Cr ferritic/martensitic steels, alternative candidate materials for application in core components of nuclear power reactors. This work involves: (1) investigation of high temperature fracture mechanism during slow tensile and limited creep testing at 600°C; (2) extensive study of solute element segregation, theoretically using proposed model of combined equilibrium and non-equilibrium mechanisms; and experimentally using field emission gun scanning transmission electron microscopy; (3) investigation of effects by thermal ageing and irradiation on microstructural developments in relation to high temperature mechanical behaviour. Quenching rates, tempering temperature and tensile test temperature variations are included in the thermomechanical treatments.

Advanced gas cooled nuclear reactors (AGRs) contain a range of alloys, selected for their physical and chemical performance in the conditions present. Carbon deposition on boiler and fuel pin heat transfer surfaces affects a reactor's efficiency and may necessitate downrating to maintain safety margins. This is believed to arise from decomposition of some of the coolant gas constituents. Deposition minimisation, while maintaining the structural integrity of the reactor, is technologically and economically important. This study has looked at deposition on a range of transition metal spinels, manganese oxides, uranium oxides and single crystal magnetite samples with a view to furthering knowledge of catalytic reactions that may occur within an AGR. In particular, the effect of mixed valency on deposition rates was studied. The spinels were successfully prepared by solid state reactions between the relevant oxides, oxalates and I or carbonates. A range of elemental and chemical analytical techniques were used to characterise the samples both before and after exposure under controlled gas and radiological conditions. Deposition was induced, to varying extents, on all the samples exposed. No filamentary deposits were observed. The spinels gave quantities of deposition in the order: Manganese spinels gave increasing deposition with increasing manganese content at 650°C, but decreasing deposition at 550°C. Iron-cobalt spinels showed no consistent increase or decrease in carbon deposition with changing composition. Nickel rich spinels were unstable in the reaction gas mixture and generated metallic nickel during exposure. At both temperatures, this gave levels of carbon deposition which increased with increasing nickel content of the original oxide. NiF~04 exposed at 550°C fragmented as it catalysed carbon formation. Manganese oxides converted to MnO during exposure, MnO proving also to be a most effective catalyst. Mn304' an Mn2+ I Mn3+ compound where the manganese ions do not form an electron exchanging octahedrally coordinated pair, did not yield large quantities of deposit. The uranium oxides examined converted to the interacting mixed valence U409' which gave copious carbon deposition. The U4+ I U6+ non interacting mixed valence Ot-U30 S gave the least deposition. Magnetite slices gave laminar carbon deposits, but no filamentary growth. Structured deposit was seen in two cases, including on one face oriented approximately parallel to the [111] plane, the plane previously expected to catalyse deposition most effectively.

A direct digital control algorithm for low power reactors is proposed using logarithmic power level as input. The logarithmic power levels allow the use of fixed point arithmic resulting in faster calculation speeds than are obtainable with algorithms using floating point arithmetic. A stability analysis for various sampled data hold types is shown to have a 25% safety margin. A time optimal control sequence for power increases is derived using switch points. The switch points are determined using simulation techniques, eliminating the use of complex and approximate calculations. A practical demand level controller is developed using machine language programming to minimize the delay from the sampling of the neutron power to the output of control action. The controller is tested with digital and analog simulations of a thermal reactor showing that a successful, near time-optimal, control algorithm with general applications to low power reactors has been developed. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate