ICONE12-49300 DEVELOPMENT OF THE METHODOLOGY OF THE SAFETY ANALYSIS PERFORMED BY THE COUPLED KIKO3D/ATHLET CODE SYSTEM IN VVER-440 TYPE NPP

ABSTRACT In the deterministic safety analysis codes are required in order to provide evaluations of potential nuclear plant accidents. In the fields of the core transient behaviour, the computer codes have achieved a high degree of realistic modelling. Nevertheless, some further tools for the investigations of the wide range of physical phenomena in the whole plant transient, such as modeling the ex-core detector signals and the malfunctioning of the emergency control system are unavoidable, too. The programs and methods used in KFKI-AEKI for safety analysis of VVER-440 NPP are presented. The accident analysis methodology for a boron dilution scenario, in which an inactive coolant loop is started, is shown

BEMUSE Programme. Phase 2 report : re-analysis of the ISP-13 exercise, post test analysis of the LOFT L2-5 test calculation

The BEMUSE [1] (Best Estimate Methods - Uncertainty and Sensitivity Evaluation) Programme has been promoted by the Working Group on Accident Management and Analysis (GAMA) and endorsed by the Committee on the Safety of Nuclear Installations (CSNI). The high-level objectives of the work are: • To evaluate the practicability, the quality and the reliability of Best-Estimate (BE) methods including uncertainty evaluation in applications relevant to nuclear reactor safety; • To promote the use of BE-Methods by the regulatory bodies and the industry. Operational objectives include an assessment of the applicability of best-estimate and uncertainty methods to integral tests and their use in reactor applications. The scope of the Programme is to perform Large Break Loss-Of-Coolant Accident (LBLOCA) analyses making reference to experimental data and to a Nuclear Power Plant (NPP) in order to address the issue of the capabilities of computational tools including scaling/uncertainty analysis. The justification for such an activity comes from the consideration that a wide spectrum of uncertainty methods applied to BE codes exists and is used in research laboratories, but their practicability and/or validity is not sufficiently established to support general use of the codes and acceptance by industry and safety authorities. The consideration of the BE codes and uncertainty evaluation for Design Basis Accident (DBA), by itself, shows the safety significance of the proposed activity. End users of the results are expected to be the industry, the safety authorities and the research laboratories. The Phase II of BEMUSE Programme is connected with the re-analysis of the Experiment L2-5 performed in the LOFT (Loss Of Fluid Test) facility in June 1982. Fourteen participants coming from the following thirteen organizations have taken part in the Phase II of the Programme