| Popis: |
The important thermal hydraulic limiting phenomena were studied during the natural convection cooling of a proposed irradiated Low Enriched Uranium (LEU) plate’s target. The irradiated LEU targets are used for the production of the medical isotope Molybdenum-99 (Mo-99), whose decay product, Technetium-99 (Tc-99), is used in the majority of medical diagnostic imaging procedures. After finishing the stage of irradiation for the LEU targets, they reach a high level of radioactivity, so the direct handling and maneuvering for these targets at that time becomes quite difficult. The targets should stay for a period of time for decay and cooling either at the reactor core situation or at a special basket inside the reactor main pool. This parametric study was performed to verify the thermal–hydraulic limiting phenomena (Onset of Nucleate Boiling, Pulsed Boiling Power ration, Onset of Net Vapor Generation and Burn-out Power ratio) during the natural convection cooling against the different power ratio of the irradiated plate (plate decay power at the establishment of natural convection regime to the steady state plate operational full power during the irradiation). The study was performed at two different positions, namely inside the reactor core with a long chimney, and in a storage basket. Half load and full load were considered, and both of these possibilities were discussed and analyzed with considering different power ratios. All the limiting phenomena satisfy the safety margins except the ONBR. The ONBR requires certain conditions to satisfy the safety margin. |
Full Text from ScienceDirect