Lead-Bismuth Eutectic Cooled Experimental Accelerator Driven System: Windowless Target Unit Thermal-Hydraulic Analysis

A main concern related to the peaceful use of nuclear energy is the safe management of nuclear wastes, with particular attention to long-lived fission products. An increasing attention has recently been addressed to transmutation systems (Accelerator Driven System: ADS) able to 'burn' the actinides and some of the long-lived fission products (High-Level Waste: HL W), transforming them in short or medium-lived wastes that may be easier managed and stored in the geological disposal, with the consequent easier acceptability by population. An ADS consists of a subcritical-core coupled with an accelerator by means of a target. This paper deals with the thermal-hydraulic analysis, performed with STAR-CD and RELAP5 codes far the windowless target unit of Lead-Bismuth Eutectic (LBE) cooled experimental ADS (XADS), both to assess its behaviour during operational and accident sequences and to provide input data far the thermal-mechanical analyses. It also reports a description of modifications properly implemented in the codes used far the assessment of this kind of plants.