Design rules to simplfy running of fusion reactors

Designing a reactor with the simplest structure possible can reduce maintenance periods, as well as building expenses and overhead costs.

Since 1995, VTT Technical Research Centre of Finland has participated in two international projects aimed at building a full-scale fusion reactor and commercialising fusion as an energy source.

ITER and DEMO (DEMOnstration Power Plant) are international programmes targeting the harnessing of fusion energy for energy production and VTT has developed remote handling systems for critical reactor parts. The research organisation says remote handling and virtual technologies are crucial in fusion reactor maintenance because of radiation and limited space in the interior sections of a reactor. These restrict accessibility and render remote handling the single viable maintenance option.

ITER is an experimental nuclear fusion reactor currently being built to test various technologies and materials for use in fusion reactors. DEMO, the first prototype of a commercial fusion power plant, will be built if ITER is successful.

Together with the European Fusion Development Agreement (EFDA), VTT has studied how to apply the maintenance and equipment designed during ITER, and avoid the problems encountered during the programme in a DEMO reactor.

The resulting concept plan provides for the planning of fusion reactor maintenance alongside other structural design work at a sufficiently early stage. VTT say designing remote handling and reactor structure in parallel would prevent major errors that hamper compatibility. This would mean fewer alterations during the building process and minimised downtime in the finished power plant, resulting in lower construction and overhead costs.

Several maintenance issues have been encountered during the ITER experiment. Installation of service equipment and the required maintenance ports sizes were not considered sufficiently in the original plans, limiting the opportunity for remote maintenance.

Because the objective of DEMO is to build a commercially viable reactor, the maintenance requirements are significantly stricter than for ITER. Problems discovered during ITER would mean extended downtime periods and considerable additional costs if encountered in DEMO. The basic premise of DEMO design has been to minimise maintenance periods through modular design and simple module structure.

ITER’s objective is to build a full-scale experimental reactor to demonstrate the technical and scientific viability of fusion energy and achieve high efficiency fusion. This project was initiated in the 1980s and includes input from the EU, Russia, Japan, China, India, South Korea and the United States.

An ITER reactor is currently under construction in Cadarache, France and is due for completion in 2020. VTT Technical Research Centre of Finland and the Tampere University of Technology (TUT) participated by developing the maintenance of the most critical parts of the facility.