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Analysis and management of nuclear accidents


Specific Objectives:
1. SEVERE ACCIDENTS to integrate the necessary knowledge on severe accident phenomenology into common databases and common reference analytical computer tools and to support common conclusions for accident management measures;
1.1 Assistance in the management of the international integral in-pile PHEBUS programme: deputy project manager, Steering Committee (chair/co-chair), Scientific Analysis WG, PHEBUS-2K (16mm);
1.2 Organisation and Co-ordination of three PHEBUS networks including benchmark-exercises with international partners for the application of computer codes for core degradation, FP release and transport in the circuit and aerosol behaviour in the containment (18mm);
1.3 Specific Benchmark-Studies for the FP transport in the circuit, aerosol behaviour and chemistry in the containment for model/code improvements and recommendations for code application (16mm);
1.4 Source Term calculations for representative PWR accident sequences with conclusions for the impact on plant safety and Severe Accident Management (SAM) strategies (4 mm);
1.5 Validation of the European Integral Severe Accident code ASTEC using PHEBUS data and validation of specific modules on separate test effects as well as application of other models for benchmarking (10mm);
1.6 Validation of different integral codes, application of detailed codes, code requirements for plant assessment, guidelines for code application and co- ordination of European working group (5mm);
1.7 Model improvements to reaction kinetics model for new species and its application to Phebus tests using reactor-specific boundary conditions and to full reactor geometry (2mm);
1.8 Co-ordination of the experimental and analytical work performed in co- operation with RIAR and IBRAE (Russian Academy of Science) on simultaneous dissolution of UO2 and ZrO2 (1mm);
1.9 Application of the dissolution and oxidation models (implemented in the Russian SVECHA code) to PHEBUS tests (3mm);
1.10 Web-based preservation and dissemination of existing and new severe accident data used for the assessment of severe accident mitigation and code performance (5mm);
1.11 Validation of models, criteria and codes to predict hydrogen combustion behaviour and corresponding pressure loads in multi-compartment geometry using the JRC code REACFLOW, comparison calculations with CFX in co- operation with GRS (18mm);
2. DESIGN BASIS ACCIDENTS (DBA) to support the transfer and exchange of knowledge, data and tools in some key issues of VVER-DBA safety and as a contribution to European next-generation tools based on JRC previous programs and expertise;
2.1 Transfer and dissemination of JRC's LOBI experimental data and expertise to VVER-specific Loss-of-Coolant Accidents (LOCA) - PSB test facility of EREC/Russia (2mm);
2.2 Advanced 3D Two-Phase Flow Module for application to safety analyses (ASTAR): high resolution upwind schemes, stiff source terms, efficient implicit numerical schemes (10mm);
3. PROBABILISTIC AND RISK ASSESSMENT METHODOLOGIES / SYSTEM RELIABILITY / SAFETY PRACTICES to give scientific/technical contributions and support to the harmonisation of the scientific basis of probabilistic methodologies with risk-informed approaches and to provide scientific & technical underpinning for safety questions arising from related DG Working Groups METHODOLOGICAL DEVELOPMENTS:
3.1 Refinement and application of probabilistic accident progression analysis for identification of research needs and relevance in the mechanistic analysis of accidents (link to A) - (4mm);
3.2 Basic principles in quantification of sensitivity and uncertainty in severe accident analysis, impact on safety margins (OECD WG) - (4mm);
3.3 Characterisation and structuring of the impact of ageing aspects in PSA (5mm) KNOWLEDGE DISSEMINATION:;
3.4 Contribute to scientific networks and information systems in the area of safety research and information dissemination (VVER network, Risk Regulation TU-Delft) - (3mm);
3.5 Systematic collection and dissemination of past and on-going research results in the area, including basic methodologies and generic data via a web- based Information System containing standard problems and benchmark exercises for training and education (12mm) HARMONISATION EFFORTS:;
3.6 Basic methodical and probabilistic principles in the application of risk informed methods (e.g. for risk-informed inspection) - (3mm);
3.7 Comparison of probabilistic versus deterministic approaches, identification of application fields, PSA quality criteria and limits (IAEA WG on PSA quality guide) - (6mm);
3.8 Contribute to establishing a European Guidance on Accident Investigation across different industry sectors (ESReDA's Accident Investigation Working Group) - (3mm);
3.9 Support to harmonisation and contribution to improvement of basic safety methodologies and practices on selected safety issues in line with existing and emerging demands from customer DGs by running benchmark exercises, e.g. on Safety Evaluation of Computer-Based Systems (12mm);
3.10 Collaboration with Horizontal Activity H3.3 by extracting generic principles, approaches, tools and methodologies from the nuclear reactor safety field for the development of a risk assessment platform (2mm);
4. COMMITTEES / WORKING GROUPS Participation, follow-up of international activities and Community programmes and studies: especially OECD/NEA/Committee for the Safety of Nuclear Installations and its Principal Working Groups (WGRisk, WG on the Analysis and Management of Accidents), IAEA, WGs of DG TREN (NRWG, ENIS-G) - (6mm) Anticipated milestones and schedule 1. PHEBUS steering committee - June 2003 PHEBUS network meetings - April+Oct 2003 FPT0 final interpretation report/part I - Feb 2003 FPT1 intermediate interpretation report - Dec 2003 FPT3 test - Feb 2004 End of SCA EVITA (part of A.5) - July 2003 H2 final reports within HYCOM - Sept 2003 2. Final reports within ASTAR - Sept 2003 3. Mostly on-going (some activities start second half 2003) Connected to NRWG schedules of DG TREN, to OECD/NEA and IAEA WGs - see D 4. NRWG meeting - Spring/autumn ESReDA seminar in Petten - May 2003 OECD/WG Risk/GAMA and sub-groups, IAEA WG on PSA quality guide - open.
Planned Deliverables:
1.1 ongoing project management, 1 Steering Committee, 2 SAWG, 1 PH-2K, minutes of the meetings
1.2 2x3 meetings, meeting documentation (6), FPT0 Final Interpretation Reports (2), FPT1 Intermediate Interpretation Reports (2)
1.3 Progress Reports (2), Technical Reports (2)
1.4 Input deck
1.5 contr. to common Progress Reports (2), Final Report (1), Technical Reports (3)
1.6 meeting minutes (2), progress reports (2), Working report on Code Assessment Criteria
1.7 contr. to common Tech.Reports (2) and to FPT1 Intermediate Interpretation Report (draft)
1.8 final data report and final model report on UO2/ZrO2 dissolution
1.9 Technical Report on fuel and cladding behaviour in PHEBUS tests
1.10 update of ODIN (on-line data & information network)
1.11 Final Report 2.1 counter part test definition/discussion, 1 meeting
2.2 Final reports 3.1/2/7 Draft position paper
3.3 First overview(activity starts autumn 2003)
3.5 Continuous implementation into the web-based information system (ODIN)
3.6 First position paper
3.8 Common JRC-ESReDA work-shop spring 2003
3.9 cross-function with the NRWG task forces of DG TREN (SCA BE-SECBS, RMPS)
3.10 Participation in meetings, contribution to common position paper.
Summary of the Action:
The objective of AMA is to contribute at a European level to ensure commonly validated and accepted computer code applications for the analysis of nuclear reactor accidents and to develop commonly accepted risk assessment approaches and safety principles, and to be able to draw adequate conclusions for accident management measures. This is done by: the analysis of accidents by test interpretation, code verification and validation, selected bench-mark exercises on code applications (PHEBUS FP and PHEBUS2K, hydrogen deflagration/detonation, VVER-specific issues) the development and inter-comparison of probabilistic and risk assessment methodologies (initiating events and accident progression analysis, risk- informed methodologies, modelling aspects, influence of aging, PSA quality assurance, etc.) the support in the harmonisation of more general basic safety methodologies and practices on selected safety issues (expert judgement, safety critical software, reliability of passive functions). AMA will provide a strong integration of the Candidate Countries within these activities. The dissemination and analysis of the performed research will be transferred into a web-based inter-active application (DMD project).

Together with workshops and benchmark-exercises remote and physical training and knowledge acquisition will be enabled. Rationale Nuclear incidents and accidents could potentially lead to serious consequences for the plant concerned - or worse, for the public and the environment. Even if in nuclear reactor technology a high level of safety has been achieved, there exists a strong need to maintain and further optimise the safety features of the plants. With the enlargement of the EU and nuclear reactors of Eastern design these aspects become even more important. The prevention of serious incidents and accidents in any of these plants has first priority. But it cannot be excluded that prevention fails. In this case engineered safety systems and features are foreseen and accident management measures have to be planned.

A thorough understanding of the transient behaviour of potential incidents and accidents, of the underlying physico-chemical phenomena and sufficiently validated computer tools for the prediction of the course of the accident and the efficiency of counter-measures are a necessary pre-requisite to limit their potential consequences and to prevent any evolution to more serious conditions. Risk and probabilistic assessment methodologies are an essential element together with the more mechanistic oriented safety considerations to have a better understanding of the importance and impact of the influencing parameter in accident progression and the safety margins existing. The AMA programme is fully coherent with the areas of Euratom competence, as clarified in the Court of Justice Judgement of 10 December 2002 in Case C-29/99. It furthermore supports the Commission proposal of November 2002 for a Directive setting out basic obligations and general principles on safety in nuclear installations in the enlarged EU.


Institute for Energy
P.o. Box 2
1755 Zg Petten