Experiments on Source Term for Delayed Releases (ESTER) Project
Joint project

CHIP experimental facility to study fission product transport and deposition in the primary circuit. Photo: IRSN

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) 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 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 will 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 will be 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 ongoing and 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. 

ESTER members' area  (password protected | reminder)


Finland, France, Germany, Japan, Korea, Sweden, United States

Project period

September 2020 - August 2024


EUR 3.14 million