CHIP experimental facility to study fission product transport and deposition in the primary circuit. Photo: ASNR
Following several years of experimental research in the field of source terms analysis in the LOFT, BIP, STEM and THAI joint projects but also other research activities (2015 Iodine Workshop), the NEA Working Group on the Analysis and Management of Accidents (WGAMA) organised in January 2019 a Source Term Workshop to discuss the achievements in this area and to identify research priorities for future projects (2019 Source Term Workshop). The outcome of the 2019 workshop served as a basis for the French Institute for Radiological Protection and Nuclear Safety (IRSN), now the French Nuclear Safety and Radioprotection Authority (ASNR), to propose together with its partner, the French Alternative Energies and Atomic Energy Commission (CEA), and the interested community the Experiments on Source Term for Delayed Releases (ESTER) project.
The experiments in ESTER project focus on two of the four identified thematic areas of the workshop. As first topic, the investigations address remobilisation of fission product deposits that might occur during a severe nuclear accident and contribute significantly to delayed releases. The importance of fission product remobilisation, in particular that of Cs, was evidenced through the Fukushima Daiichi accident analysis performed in the BSAF and ARC-F projects. Separate effect remobilisation tests, semi integral tests for studying coupled effects in the CHIP facility at IRSN, as well as confirmatory tests on deposits obtained in the VERDON facility at CEA in release tests from real fuel are performed. As second topic, the ESTER project plans to achieve an improved understanding of the processes involved in the formation of organic iodides in the containment. The related experiments continue the work done during the STEM project on organic iodide formation and are conducted in the EPICUR facility at IRSN. The investigations in ESTER are complementary to investigations performed in the THEMIS project by Becker Technologies.
The results of the ESTER experiments are to be used to support evaluations of source term and of accident management strategies. The information will serve as a basis for the improvement and validation of source term predictive models. A part of this work is being done in an analytical working group (AWG) composed of the project members where experience of the application and enhancement of simulation tools is shared. The ESTER project has strong links with other concluded joint projects in this field: the LOFT, BIP, STEM, THAI and THEMIS projects. It is also related to post-Fukushima Daiichi projects addressing analysis of fission product behaviour such as BSAF, ARC-F, TCOFF and FACE projects.
In 2024, all planned experiments were completed, with tests in the EPICUR and CHIP facility at the ASNR and with experiments at CEA with prototypical radionuclide deposit samples from the VERDON release tests done with actual fuel pellets. Related to radionuclides remobilisation, ESTER provides investigations that are complementary to the THEMIS project operated by Becker Technologies. The ASNR completed all tests in the EPICUR facility investigating the influence of methane (CH4) on the formation of organic iodides and small-scale remobilisation tests in the dedicated ATMIRE experimental device. Three semi-integral remobilisation tests were performed in the CHIP facility with the aim of studying the remobilisation of representative deposits involving major fission products such as caesium, iodine and molybdenum. The CEA performed the two planned tests with deposit samples from real fuel. The project was extended until the end of March 2025 to allow completing the final reporting.
Discussions took place in 2024 on a new source term-related project, called FORESEEN, to address knowledge gaps to reduce uncertainties on source term evaluation with ATFs (Cr-doped fuels, Cr-coated and Fe-Cr-Al claddings). The project would span five years, be led by the ASNR and INL, and provide data on the effect of chromium dopant on fission product release kinetics and on the effect of Cr on FP (Cs, Mo, I) transport and containment chemistry. The FORESEEN proposal was endorsed by the CSNI at its December 2024 meeting.
ESTER members' area (password protected | reminder)
Finland, France, Germany, Japan, Korea, Sweden, the United States
September 2020 - March 2025
EUR 3.144 million