Quantitative comparability of heavy ion and in-pile irradiations on UMo fuel systems

Irradiation with heavy ions is an increasingly often used tool to quickly reproduce and simulate certain effects of irradiation tests in nuclear reactors (in-pile irradiations). Using SRIM/TRIM, a dataset for the deposition of energy and the creation of vacancies in UMo/Al fuels by in-pile fission products as well as out-of-pile Iodine-127 ions (80 Mev) has been created, that allows for a proportional conversion of ion flux and fluency in the corresponding fission rate and burn-up equivalents. The conversion factor depends on the irradiated geometry, i. e. order of the layers and thickness of the top layer, as well as on the point of interest in the sample. To verify the calculations, a comparison of thicknesses and growth dynamics of out-of-pile produced interdiffusion layers (IDL) with predictions based on in-pile data has been made. The IDL is mainly composed of UAl_x and forms during irradiation at the UMo-Al-interface. The observed thicknesses match within 10%, which is well inside the uncertainties of both methods. This demonstrates the applicability of the presented conversion approach as well as the reliability of heavy ion irradiations. The data from two I-127 irradiation experiments furthermore support the current understanding of the Arrhenius-like in-pile IDL growth, i. e. its forth-root dependency on fission rate (or ion flux), the square-root dependency on the irradiation time and the exponential temperature dependency.