Assessment of safety aspects of first rod-type fuel irradiation at Tehran research reactor, Part I: Neutronic analysis

Following domestic fabrication of nuclear fuels in Iran, the need to investigate fuel behavior at different burnup with regard to fission gas release, fuel swelling, cladding material behavior and fuel integrity necessitates in-pile tests irradiation in research reactors. Currently, Tehran research reactor is the sole operating research reactor which can be used for fuel irradiation experiments in the country. This is Part I of the articles describing the details of Tehran research reactor core performance during a fuel irradiation experiment. This first part of the article series is aimed at evaluating the potential capability of Tehran research reactor core to conduct nuclear fuel test during irradiation from the neutronic point of view. A neutronic study on the feasibility of irradiating a rod-type fuel assembly of natural UO2 pellets in the Tehran research reactor core, which itself contains 20% enriched plate-type U3O8-Al fuels, is presented in this paper. The feasibility study is performed by calculating safety related neutronic parameters of the core, i.e., excess reactivity, shutdown margin, reactivity worth of the test fuel, safety reactivity factor and power peaking factors, during irradiation experiment using MCNPX nuclear code. Comparing obtained results to the permissible limits reported in the final safety analysis report of the reactor indicates that this irradiation experiment will not induce any reduction of the reactor safety.