Fusion power plant

In DEMO, the pulsating nature of the plasma operating mode adds complexity to the balance of plant (BoP) design development, since the consequent pulsating operation of the primary heat transfer systems (PHTS) is transmitted to the interfaced power conversion systems (PCS) with a potential adverse impact on its components, such as turbine and steam generators. Hence, integrated dynamic BoP analyses play a vital role in reaching a safe and commercially viable option of a tokamak-based demonstration fusion power plant. The use of Apros continues in the conceptual development phase with integrated analyses of plant models for both the water-cooled lithium lead (WCLL) and the helium-cooled pebble bed (HCPB) concepts. The design process is based on close co-operation with other EUROfusion BoP partners.

Finland is currently designing, constructing, operating and decommissioning nuclear facilities, including the construction of a nuclear waste repository for spent fuel as the first country in the world. This gives nuclear operators (utilities, waste management organisations and VTT as the licensee of the FiR 1 research reactor) an exceptional perspective to decommissioning and waste management planning over the lifecycle of a nuclear facility.

Efficient handling and treatment of the DEMO waste (reduction of waste, Waste Acceptance Criteria) are important and nontrivial issues to clarify. In particular, fusion materials can impact the disposal by interacting with other waste streams. We aim to initiate and enhance the involvement of Finnish companies in the field of nuclear decommissioning and radwaste management in the analysis of DEMO decommissioning and waste management requirements.

In licensing, the licensee must prove to the safety authority that all safety aspects have been acknowledged and the safety requirements are fulfilled. A significant part of licensing is the steering of safety design and the safety analyses substantiating the fulfilment of safety criteria, and the communication of these issues with the safety authority.

Platom’s goal is to develop tools and procedures for licensing that enable smooth, predictable, and efficient nuclear projects. Platom sees that licensing could take a more supportive role in the engineering and project management. Platom focuses on innovating a new model that brings together international nuclear regulatory requirements, legislation, and the needs of the various nuclear ecosystem actors as well as valuable experience that has been gained on the recent nuclear new builds.

VTT’s goal is to support the licensing and safety design of the DEMO reactor and supporting facilities, such as IFMIF-DONES. This is achieved through the application of best practices from fission safety on how to implement balanced safety designs by combining the deterministic and probabilistic safety assessments, human factors engineering and good safety culture practices.

VTT has developed different techniques together with DIARC-Technology Oy (presently Oerlikon Balzers Coating Finland) for cleaning the inner surfaces of fusion reactors from material accumulated on them during plasma operations in the reactors. The aim is to produce a solution for reducing the amounts of radioactive tritium in the surface layers. The most promising methods are based on using arc-discharge plasma pulses or glow-discharge plasma beams to remove the deposited layers in a controlled way in just a few minutes. The composition of the surface is spectroscopically monitored in real time, to give the necessary information when the cleaning process can be stopped.

In fire accident analyses of fusion power plants, fire hazards are identified and fire consequences are assessed. Most importantly, the analyses should show that any releases remain within the plant limits and no conditions for cliff-edge effects occur. In addition, the protection of personnel and property is evaluated. Fires occurring simultaneously with other external hazards are also considered. High-risk areas, such as those including critical equipment, radioactive material inventories, or large fire loads, are of primary interest.

To support fire consequence analysis, computational fluid dynamics (CFD) simulations are made. The simulations enable analysing the possible propagation mechanisms of the fire, the effects of the fire on its surroundings and the possibility of the release of dangerous materials to the environment. As an outcome, it is demonstrated that acceptable fire safety levels can be obtained with the designed fire protection systems.