Within the framework of the BALDER project, the Paul Scherrer Institute (PSI), in collaboration with the Danish start-up company Copenhagen Atomics, is planning to test a Molten-Salt Reactor (MSR). This is a new Small Modular Reactor (SMR) concept in the form of a freight container that is to be installed and tested on the PSI’s premises in Villigen.

For testing purposes, PSI intends to operate the installation over a limited period of one month at a reduced power of one megawatt (thermal). According to its information, the risk potential of the planned test reactor will be proven to be low. Based on this, PSI intends to submit an application for approval for a nuclear installation with low hazard potential pursuant to Article 22 para. 1 of the Nuclear Energy Ordinance.

In accordance with the Nuclear Energy Act, no general licence is necessary for a nuclear installation with low hazard potential.

In contrast, however, a construction and operating licence from the Federal Department of the Environment, Transport, Energy and Communications (DETEC) as well as a series of technical approvals from ENSI are required. The application for approval and the necessary documents must be submitted to the Swiss Federal Office of Energy (SFOE). ENSI’s role in the licensing process is to examine and assess the nuclear safety and security aspects and to approve them.

Other authorities, e.g. the Federal Office for the Environment (FOEN) or the Federal Office for Spatial Development (ARE) are responsible for other approval-relevant aspects such as environmental protection or spatial planning. Currently, PSI is working in collaboration with Copenhagen Atomics to draft the documents needed for the approval process. Based on ENSI’s current knowledge, PSI intends to submit the application documents in the second half of 2026 at the earliest.