Release of safety relevant radionuclides from spent nuclear fuel under deep disposal conditions (SAREC)

Objectives

Improved quantification and mechanistic understanding of the release of safety relevant radionuclides covering most representative types of spent nuclear fuel (SNF) and of the fuel evolution both prior and posterior to contact with ground water to better predict the radionuclide source term for post-closure safety assessment.

Major highlights (October 2024 - March 2025)

• The WP had its kick-off meeting in conjunction with the EURAD -2 kick-off in October 2024. The kick-off was well attended by participants of the different tasks, as well as End Users and PMO. 
• The Initial State-of-the-Art report (D8.1) has been submitted to the PMO  who approved it
• Workshops and meetings have taken place within the tasks to discuss and establish sample & data availability. This fulfills the achievement of Milestone 29.

Forward look

• During the coming year materials will be produced and some experiments in Tasks 3,4, & 5 will start 
• In May, the WP will be presented as a poster at the Euradwaste 2025 conference 
• The modelling task will initiate model development and define first set of in-put parameters 

Description of the WP

The aim of this WP is to close knowledge gaps outlined in for example the EURAD State of Knowledge Report Spent Nuclear Fuel Domain 3.1.1 (K. Spahiu 2021) and the WP is built on the experiences gained in the FIRST Nuclides and DisCo projects.

The aim is to provide data that allows re-evaluation of the current approaches to release of safety relevant radionuclides in post closure safety assessments. This will clarify what approaches are overly pessimistic and what approaches need to be adjusted to better represent expected radionuclide release in the repository environment.

In order to do this an improved mechanistic understanding is required, as well as quantification of the radionuclide source term for different fuel types. Carefully designed experiments with advanced experimental set-ups and improved analytical methods for activation- and fission products will increase the system understanding and give confidence in the proposed release values and models.

The studies shall be focused on representative fuel, operated at representative reactor conditions, relevant for WMOs at a European level. 

Efforts shall be made to adapt the experimental protocols to allow for comparison between studies performed at different laboratories whilst still utilizing the strengths at the individual laboratories. 

For Knowledge Management there is a need to synthesize information from past projects.

Outcomes

• Implementing Safety: Radionuclide release data that allows the needed re-evaluation of the current approaches to release of safety relevant radionuclides in post closure safety assessments. 
• Scientific Insight: Data for deriving an updated and improved mechanistic understanding of radionuclide release processes.
• Knowledge management: Completion of SNF dissolution database, thus enhancing knowledge management and transfer between the participating organisations (and beyond).