Development and improvement of thermodynamic understanding for use in nuclear waste disposal safety case

Development and Improvement of Thermodynamic Understanding for use in nuclear waste disposal Safety Case (DITUSC) is a work package within the Eurad-2 project. This 24-month strategic study aims to enhance scientific knowledge to predict long-term safety-relevant processes in radioactive waste disposal. The work package focuses on several critical aspects, including identifying, evaluating, prioritizing, and defining strategies to fill gaps in safety-related thermodynamic databases. It also aims to advance expertise in thermodynamics, supporting current and future capabilities for using thermodynamics in assessing radioactive waste disposal configurations, conducting safety analyses, and preparing safety cases.

DITUSC program is multifaceted, focusing on several key areas. Firstly, it aims to identify data gaps crucial for understanding the transport behavior of safety-relevant radionuclides and organics. This involves examining existing data and identifying areas where additional information is needed. Secondly, the work package seeks to develop a thermodynamic description of perturbations, such as the effects of temperature and high salinity plumes. These perturbations can significantly impact the behavior of radionuclides and other substances in geological disposal environments, making it essential to understand their thermodynamic implications. Another critical focus area is the thermodynamic description of solid-solutions and their role in radioactive waste management and final disposal. Additionally, the interplay between thermodynamics and kinetics is a key area of study. This includes examining solid phase transformations, relevant redox phenomena, and the illustrative case of spent fuel dissolution. Understanding these processes is essential for developing accurate models of radionuclide behavior over extended periods. The work package also aims to document how thermodynamic approaches are currently implemented in safety cases and to identify and assess potential improvements in line with end-user needs and priorities. This involves reviewing existing practices and developing recommendations for enhancing the use of thermodynamics in safety assessments.

To achieve these objectives, DITUSC will produce two authoritative high-level documents: a Green Paper and a White Paper. The Green Paper will define the scope, framework, and reach of the strategic study, involving key players in the field. The White Paper will provide a consolidated and prioritized list of the current needs of stakeholders within the EURAD-2 colleges. It will focus on specific needs related to the safety analysis of radioactive waste disposal facilities and promote new scientific strategies to support the use of thermodynamics in safety cases.