Markus Iseli

Preliminary Safety Analysis of ITER

Abstract In order to support the licensing application for the ITER facility at Cadarache, a preliminary safety case has been prepared and submitted to the French nuclear safety authorities. This paper provides an overview of technical aspects of this case, which is based on an evolution of the safety approach developed and applied in earlier phases of the ITER project. The basis of the safety of ITER derives from the fundamental safety characteristics of fusion. The potential radiological hazards that arise are related to the tritium fuel and material activated by neutrons. The confinement of these materials is therefore the principal safety function, and it is reliably provided by robust barriers inherent in the design together with filtering and detritiation as a secondary level of confinement provision. A Defense in Depth approach is taken to ensure that off-normal events are minimized in their frequency, and that the consequences of accidents, even though extremely unlikely, are limited. A comprehensive set of analyses of postulated event sequences provides the demonstration that the consequences of enveloping scenarios are well within acceptable limits, and that even for hypothetical events involving two or more independent failures, the public and environmental impacts remain limited. An ALARA approach is taken to minimizing occupational radiation exposure, as well as other potential impacts of normal operation such as routine releases. Other hazards arising from internal and external risks are also considered, with design provisions, for example the Tokamak building is built on seismic isolation pads to minimise the effect of an earthquake.

Sensitivity Studies on the Accidental Impact of 1 G of Tritium for ITER Site Specific Characteristics

Abstract One of the safety issues related to ITER concerns the potential impact of Tritium that could be released to the environment in a postulated accident. As the final site located at the vicinity of Cadarache nuclear facilities in France is known, some calculations have been made to assess the effect of the nominal release of 1 g of tritium for ITER site specific characteristics. Sensitivity studies have been performed according to these characteristics, but also to assumptions related on the way the tritium could be accidentally released (chemical form, height of the releases...). The results being used for demonstrating the low impact of tritium accident releases, care has been considered on the selection of the most penalizing assumptions in terms of results. The results have shown that, whatever are the assumptions, the consequences of 1 g of tritium that could be accidentally released into the environment is extremely low, in the domain of low doses. In spite of this very low impact, many safety provisions are undertaken with regards to defence in depth principles in order to further reduce both the likelihood of an accident involving tritium and its consequences.

Creation of ISO Standards Related to the Confinement Systems in Tritium Facilities

Abstract This paper gives the rationale for creating through International Standard Organization a standard for confinement systems in Tritium facilities under the frame of the working group dealing with confinement, ventilation and shielding issues in the radiation protection subcommittee of the nuclear energy technical committee (ISO TC85/SC2/WG23).

The Role of Operational Feedback and R&D in ITER Safety

This paper presents an overview of the safety-related operating feedback taken into account in the ITER baseline design and of the previously completed and ongoing research and development (R&D) activities in support of ITER safety analyses. Operating feedback relevant to ITER mostly comes from previous and currently existing fusion devices and from the operation of tritium laboratories. Regarding the safety-related R&D, since the early times of the ITER project, an extensive program has been devoted to understanding the issues, gathering data on source terms, modeling underlying phenomena, and developing analytical tools for safety analysis.

Safety related R&D for the ITER baseline design

This paper presents an overview of the safety related operating feedback taken into account in the ITER baseline design, and of the previously completed and ongoing Research and Development (R&D) activities in support of ITER safety analyses. Operating feedback relevant to ITER mostly comes from previous and currently existing fusion devices, and from the operation of tritium laboratories. Regarding the safety related R&D, since the early times of the ITER project, an extensive program has been devoted to understanding the issues, gathering data on source terms, modeling underlying phenomena, and developing analytical tools for safety analysis.