silicon transmutation doping facility Research Project
As a capstone project for my undergraduate degree in mechanical engineering (with a nuclear engineering minor), I lead a team of five students in developing a neutron transmutation doping facility as an addition to the KSU TRIGA research reactor. This facility operated by acquiring high purity silicon ingots and exposing them to a thermalized neutron flux to transmute some of the silicon atoms into other elements via neutron absorption. This silicon, which now contains trace amounts of phosphorous, has a slightly altered conductivity, which makes it useful for manufacture of certain types of electronic hardware, such as solar panels. The primary result of the study was a complete MCNP model of the reactor and analysis of the flux profile for two selected irradiation sites.
Simulating the expected flux profile
Some nice looking charts of thermal neutron flux are depicted here, along with a visual representation of the MCNP model geometry which indicates the location of the two proposed irradiation sites considered for the study in relation to the core of the TRIGA reactor.
Although it was deemed to be physically possible to perform the doping process using the KSU TRIGA reactor, the flux gradient was too strong to allow for even irradiation along the axis of the silicon ingot. The containment for this potential issue was to develop a silicon ingot handling system that would rotate and flip the ingot to ensure all portions of the ingot were evenly irradiated. This proved to be a difficult undertaking, as one of the irradiation sites was located adjacent to the reactor core, inside the spent fuel pool, and the other site was located on the opposite side of the core, behind a heavy concrete door which served as a radiation shield.
Ultimately, the project was too costly an undertaking for a university-based reactor to support. The risk was high and the cost of fuel and labor to operate the reactor overnight during irradiation sessions meant the margin for profit was very narrow. Although the financial feasibility lead to the project being cancelled, the technical feasibility was proven with the simulations we performed and initial design work we completed. The educational value of the project was high, as all the participants learned strategies for project management, data-driven analysis, and business integration that are valuable for future work in research-related fields.