Following two previous nuclear reactor accidents involving light water reactors, there is a renewed interest in accident tolerant fuels. These accident tolerant fuels should not oxidise in a steam atmosphere during loss of coolant accidents. One such accident tolerant fuel that has been suggested is the use of ceramic composite cladding material as a replacement for the current zircaloy cladding. The high temperature stability of silicon carbide, together with its high resistance to corrosion may make it preferable to zircaloy during accident conditions. Furthermore, if the neutron absorption cross section of the cladding is less than the current zircaloy, extended life might be available when compared with current fuels. One of the main difficulties in using ceramic cladding materials as nuclear fuels is the lack of a reliable joining process to manufacture end caps for the cladding tubes. A manufacturing method would need to be developed to produce ceramic joint that is able to withstand a PWR environment.Two methods of ceramic joining have been proposed. Firstly, silicon carbide deposition process that is used to infill the gap between two ceramic components and secondly a ceramic soldering technique. A silicon carbide deposition process has been developed. The deposit was confirmed to be 3C silicon carbide which has preferable irradiation response to the other polytypes. The deposit was found to be carbon rich which was largely removed through the use of a thermal treatment step. The deposit was used to coat metallic surfaces for increased hardness, reduced sliding wear and corrosion resistance. Silicon carbide joints were produced using an oxide powder frit of silicon dioxide, yttrium oxide and aluminium oxide. Tubular samples were joined, however they contained circumferential cracking resulting in a join that was not hermetically sealed. The thermal conductivity of each joint varied from sample to sample. X-ray computed tomography showed there were large inconsistencies in the volume of joined material present in each sample giving rise to the large variation in thermal conductivity.
|Date of Award||1 Aug 2017|
- The University of Manchester
|Supervisor||Timothy Abram (Supervisor)|