The role of the EUROCORE concerted action is to obtain a much clearer view of the state of the art of European actual reactor corium recovery concepts and to better identify research and development needs, taking into account current technical knowledge and reactor situations. A prioritisation of R&D actions coming from the synthesis of real users needs should hopefully result from this action, which involves public and private, research organisations, but also utilities and nuclear reactors vendors. In order to be successful, it will be paid a great attention to the fact that debates are based on technical objectivity and a strong consensus finally emerges, because a weak consensus makes no sense for handling suvh an important problem.
The project has been concluded in july 2002 with a four months late delay by the approval and the delivery of the final report. This report has been completed five months after the last meeting in Chamrousse (end of January 2002) as a lot of discussions and e-mails have been necessary to get the final consensus and to achieve the final report and distribute it to all participants and the Commission.. Let us recall that the first meeting has been hosted by KTH/RIT (Prof. Sehgal) in Stockholm on May 25, 26th 2000 and it has dealt with the analysis of in vessel corium recovery concepts. The second one has been hosted by AEA-T (Dr Brian Turland) in London on Nov.6,7th, 2000, it has been devoted to corium quenching in the reactor cavity and to corium concrete interaction with water addition. The third technical and mid term meeting took place in Lanzarote (Spain, March,13, 14th, 2001) and it has been devoted as initially planned to approval of the first two consensus reports and to the Ex-Vessel Core-Catcher, spreading concept and the evaluation of corium cooling by top flooding.
The fourth meeting has been organised in Karlsruhe by FZK September 20th and 21st, 2001 on the water injection concepts for ex vessel core catcher concepts. The final meeting took place January 28,29th, 2002 in Chamrousse, near Grenoble. The CEA had invited a Russian specialist to present the Tien Wan core catcher (Dr Yuri Leontiev from Saint Petersbourg nuclear institute) and the rest of the meeting has been devoted to the review of the preceeding meetings syntheses in order to draft the final report. In brief, it can be summarized that all retention concepts differ in focusing on different aspects. Rapid cooling requires large surfaces and water addition; this relaxes requirements to enclose the melt. Slower cooling relaxes requirements of surface enlargement but has to deal with assurance of enclosing still molten material, by structural means (vessel, sacrificial and refractory layers) and external cooling devices. More or less the concepts are affected by scenario uncertainties, especially with respect to melt release history and water addition. It is generally required that the concepts should tolerate various possibilities of melt formation and melt release. R&D needs related to the various core-catcher designs are addressed in detail in the final report.
The role of the EUROCORE concerted action is to obtain a much clearer view of the state of the art of European actual reactor corium recovery concepts and to better identify Research and Development needs, taking into account current technical knowledge and reactor situations. A prioritisation of R&D actions coming from the synthesis of real users needs should result from this action which involves public and private research organisations, but also utilities and nuclear reactors vendors. In order to be successful, it will be paid a great attention to the fact that debates are based on technical objectivity and a strong consensus finally emerges, because a weak consensus makes no sense for handling such an important problem.
To meet the action objectives, the following methodology is proposed:
First, the requirements attached to the considered retention concepts have, to be clearly defined and relevant physical criteria for the concept to be efficient have to be derived, based on the requirements. Second, analyses of reactor scenarios have to be conducted in order to identify the generic situations of interest for the considered retention concepts. Realistic initial and boundary conditions for these situations have to be defined. Third, these situations have to be analysed with the actual technical knowledge, a synthesis has to be written, including the identification of remaining unknowns and phenomena and the estimated ranking of these phenomena considering their relative importance and causality. The final step is to propose a set of research and development actions (modelling & experiments) with associated priorities and a tentative timetable for issuing these actions in close connection with the end users needs. The proposed work programme of the concerted action is structured by the different existing or innovative reactor corium recovery concepts which are or might be studied in Europe. Five different classes of concepts have been distinguished, 1eading to five different workpackages (WP2 to WP6). An additional workpackage is related to the project management and the organisation of the workshops. For each technical workpackage, three major tasks are conducted
-Collection and synthesis of most recent results
-Highlights over related open problems
-Recommendations for further research and development needs and ranking of the priorities.
The issues are:
•requirements attached to the corium considered retention concepts,
•analyses of reactor scenarios (Top-Down and Bottom-Up),
•a set of research and development actions (modelling & experiments),
•recommendations for calculation methodologies and physical models.
Measurable objectives of this project are:
•the production of consensus reports on the four dominant corium recovery concepts
•the production of consensus reports on alternative concepts
•the identification of further R&D needs for assessing, these concepts
•the identification of practical measures for severe accident management
Funding SchemeTHN - Thematic network contracts
DT2 8DH Dorchester - Dorset
08970 Sant Joan Despi
100 44 Stockholm
92084 Paris La Défense