In November 1945, the Government established the independent Atomic Energy Committee with the mandate to advise the Government in all civilian and military matters dealing with nuclear energy. On 18 March 1957, Parliament ratified the Statute of the IAEA, which entered into force on 29 July 1957. In 1969, Switzerland signed the Treaty on the Non-Proliferation of Nuclear Weapons, which Parliament ratified on 9 March 1977.

As early as 1946, Brown, Boveri & Cie (BBC, now ABB Group) took the first steps to build a team of physicists and to launch a development programme. BBC was later joined by Sulzer Brothers and Escher Wyss. Initial studies dealt with graphite–carbon dioxide reactor concepts, but from 1952 on, the development concentrated on heavy water moderated reactors, with subsequent planning of the research reactor DIORIT. In 1955, more than 150 private companies joined forces and formed Reactor Ltd to build and operate the new, privately owned research centre in Würenlingen, with the two reactors on the site SAPHIR and DIORIT. In 1960, the Government took over the research centre, known by its abbreviation EIR (Eidgenössisches Institut für Reaktorforschung). In 1988, the merger of EIR and SIN (Schweizerisches Institut für Nuklearphysik) led to the creation of the Paul Scherrer Institute (PSI).

In Switzerland, the nuclear age began on 30 April 1957, when the SAPHIR research reactor went critical under the responsibility of Swiss scientists and engineers. This pool reactor had been purchased in 1955 from the Government of the United States of America, after being exhibited in Geneva during the First International Conference on the Peaceful Uses of Atomic Energy. SAPHIR was shut down permanently at the end of 1993.

DIORIT, the first reactor designed and constructed in Switzerland, reached criticality on 15 August 1960. It was moderated and cooled by heavy water; the fuel was initially natural uranium; a special loop allowed for the testing of power reactor fuel elements. DIORIT was shut down permanently in 1977. At the end of 2003, all radioactive material was removed from the reactor building.

In 1962, construction began on the experimental nuclear power reactor in Lucens, a 30 MW(th), 6 MW(e), heavy water moderated, carbon dioxide cooled reactor located in an underground cavern. Criticality was reached in late 1966 and commissioning in early 1968. In spite of numerous difficulties, the supply consortium led by Sulzer Brothers had demonstrated that Swiss industry was capable of building nuclear plants. The goal was the development of a small to medium sized power reactor fuelled with natural uranium within a massive containment system. As enriched uranium became readily available during the mid-1960s, the unit size of commercially offered light water reactor (LWR) NPPs increased drastically and Swiss utilities started construction of such plants very early on. Interest in the Lucens reactor type decreased, however, and further large expenses for such a development could not be justified. The decision was taken to operate the reactor until the end of 1969. However, on 21 January 1969, the plant was abruptly put out of service by a partial core meltdown that destroyed the integrity of the primary system and released radioactivity into the cavern. After decontamination, decommissioning and termination of intermediate storage of radioactive material, the entire site was prepared for unrestricted reuse in 2003.

In August 1965, a turnkey contract was awarded by Nordostschweizerische Kraftwerke AG (NOK) to a consortium made up of Westinghouse International Atomic Power Company and BC for the supply of a 350 MW(e) plant equipped with a pressurized water reactor (PWR) and two turbo generators (Beznau). In late 1967, NOK took the option to order a duplicate of the first unit. Beznau I reached criticality by the end of June 1969, and Beznau II in October 1972.

Also in 1965, Bernische Kraftwerke AG (BKW) chose a 306 MW(e) plant equipped with a boiling water reactor (BWR) manufactured by General Electric and twin turbo generators from BBC (Mühleberg). In July 1971, full power was achieved, but on 28 July 1971 a turbine fire broke out. Sixteen months later the plant was officially handed to the owner.

In 1973, a supply contract was signed by a consortium of Swiss utilities with Kraftwerk Union (Siemens) for the delivery of a 900 MW(e) PWR and turbogenerator (Gösgen). Construction of the plant went very smoothly until the first connection to the grid in February and an 80% power test in March 1979. However, the accident at Three Mile Island on 28 March 1979 led to an eight month delay in its commissioning.

In December 1973, a consortium of Swiss utilities and one German utility awarded a turnkey contract to General Electric Technical Services Overseas (GETSCO) and BBC for the supply of a 940 MW(e) NPP equipped with a BWR (Leibstadt). Construction began in 1974 and the plant was commissioned in December 1984.

The nuclear controversy began in Switzerland in 1969 with the first signs of local opposition to a nuclear plant project at Kaiseraugst, near Basel. For 20 years, the Kaiseraugst project was to remain centre stage in the nuclear controversy: site permit, local referendums, legal battles, site occupation by opponents in 1975, parliamentary vote in favour of construction in 1985, and finally a parliamentary decision in 1989 to end the project definitively. Further, the accident at the Chernobyl nuclear power plant had a dramatic impact on the political climate. Although some of the necessary permits had already been issued for two planned NPPs at Kaiseraugst and Graben, their construction was subsequently abandoned, as well as other projects in Verbois, Inwil and Rüthi.

The nuclear controversy led to several anti-nuclear initiatives at the federal level:

1. An attempt to forbid all nuclear plants, both new and those already in operation — rejected by 51.2% of the vote in February 1979.

2. Aimed at forbidding future nuclear plants, leaving untouched the plants in operation, two initiatives differing only in the treatment to be applied to Leibstadt, then under construction — rejected by 55% of the vote in September 1984.

3. Nuclear phase out — rejected by 52.9% of the vote in September 1990.

4. A ten year moratorium on the construction of new NPPs — accepted by 54.6% of the vote in September 1990.

5. In 1999, two new initiatives were organized aiming at the ban of the construction of new NPPs until 2010 and the closure of all NPPs after a 30 year lifespan — both initiatives were rejected in May 2003 by 58.4% and 66.3%, respectively.

A new Nuclear Energy Act came into force on 1 February 2005 in addition to the new Nuclear Energy Ordinance. It allowed the possibility of building new reactors, with the possibility of a referendum against their construction. There is no time limit to the lifetime of existing NPPs. The general licence is still in place. It introduced a ten year moratorium on the export of nuclear fuel for reprocessing from 2006 to 2016. It also includes provisions for decommissioning, simplifies licensing procedures and introduces the general right of appeal.

During the ten year moratorium on reprocessing, which began in July 2006, spent fuel was stored in Switzerland. Plutonium and uranium gained from reprocessing of spent fuel that was sent abroad before July 2006 is recycled in Swiss NPPs. The radioactive waste arising from reprocessing of spent fuel was returned to Switzerland.

Following the accident in Fukushima, the head of the Federal Department of the Environment, Transport, Energy and Communications (DETEC) announced in mid-March 2011 that the pending procedures for handling applications for general licences for new NPPs had been suspended. Then, in the course of 2011, with their decision to withdraw from the use of nuclear energy on a step by step basis the Federal Council and Parliament laid the foundations for a new energy policy, the Energy Strategy 2050. The intention is to decommission Switzerland’s five NPPs when they reach the end of their service life and not to replace them with new ones. According to the Energy Strategy 2050 and the amended Nuclear Energy Act, reprocessing is forbidden indefinitely.

The public consultation on the Energy Strategy 2050 took place from 28 September 2012 to 31 January 2013. The Federal Council presented its message to Parliament in September 2013 in the new Energy Act. A final vote of Parliament took place in September 2016. A public referendum in May 2017 confirmed the new amended provisions of the Energy Act. On 1 January 2018 the new amended act entered into force.

The safe disposal of radioactive waste is the responsibility of those parties that produce it, namely the following NPP operators: BKW FMB Energie AG (Mühleberg), KKW Gösgen–Däniken AG, KKW Leibstadt AG, Nordostschweizerische Kraftwerke Baden — now Axpo (Beznau I and II), Energie Ouest Suisse — now Alpiq. In 1972, these operators established the National Cooperative for the Disposal of Radioactive Waste (Nagra) together with the Government, which is responsible for the disposal of radioactive waste from the health care sector, industry and research and is represented by the Federal Department of Home Affairs.

So far, there are no deep geological repositories in Switzerland. For both low and intermediate level waste (LILW) and high level waste (HLW) repositories, a site selection process is defined in a sectoral plan within the framework of the spatial planning legislation. The Federal Council adopted the conceptual part of the Sectoral Plan for Deep Geological Repositories in April 2008, thus initiating a three stage procedure that will result in the designation of suitable sites for deep geological repositories.

The selection — based on safety criteria — of siting regions for geological repositories for HLW and for LILW was the goal of the first stage. Nagra proposed six potential siting regions in October 2008. ENSI, considering the input of a number of expert organizations, approved the six proposals. Following this review process, the SFOE carried out a broad consultation on the first stage at the end of 2010 and submitted a report to the Federal Council. The Federal Council approved all six potential siting regions on 30 November 2011, thus concluding the first stage of the site selection process and initiating the second stage (see Section 2.7).

The goal of PSI’s energy research is the development of technologies for a sustainable use of energy. This includes environmentally friendly energy production, the application of renewable energy sources, and low loss energy storage. In addition, technologies are investigated which will contribute to the safe use of nuclear energy. Environmental research is concentrated on the study of processes taking place in the atmosphere. Comprehensive assessment of the economic, ecological and environmental performance of current and future energy supply technologies provides support for decision making.

To cope with the increasing fluctuating energy production (i.e. solar and wind), development of new energy storage methods is critical. In order to test, further develop and optimize different energy storage methods, the PSI operates the Energy System Integration (ESI) Platform. This facility offers research and industry an experimental platform where promising approaches can be tested in all their complex connections and interrelations. New ideas for energy conversion can be tested on a small scale, and their potential for industrial use can be realistically evaluated.

About 8% of PSI’s annual government funding of CHF 280 million is dedicated to nuclear energy research (budget 2017 data). PSI’s government funded nuclear energy research activities have been strongly reduced over the past two decades. This reduction was partly compensated by increasing external funding. The current staffing quota per year of about 155 person-years (plus about 25 postdoctoral and 40 PhD students). More than 57% of the overall direct costs of nuclear energy research are externally funded by Swiss NPP operators, Nagra, ENSI, SNF and other national and, in particular, international agencies (including the European Union and the Organisation for Economic Co-operation and Development (OECD) Overview Committee on the Safety of Nuclear Installations). A large part of this support is for long term research contracts. About 50% of the nuclear energy research at the PSI concentrates on reactor safety and safety related operational aspects of Swiss NPPs and on nuclear waste disposal. Nearly 15% of the resources are dedicated to future reactor concepts and their safety features, which rely on inherent safety mechanisms and on passive system layouts which are investigated (to a limited extent through an active partnership of the PSI in the Generation IV International Forum).

The main objectives of nuclear energy research carried out in the Nuclear Energy and Safety (NES) research division at the PSI are as follows:

• To foster nuclear education by substantially contributing to the Swiss Nuclear Master Programme and other programmes (PSI/EPFL/ETHZ);

• To contribute to the safe and economic operation of the existing NPPs in Switzerland and to the safe geological storage of radioactive waste by reinforcing the scientific bases of the technologies in the appropriate areas;

• To secure standby functionality in key areas, particularly those requiring the services of a Hot Lab;

• To provide inputs to stakeholders for decision making purposes;

• To look for opportunities to apply NES expertise in sectors other than nuclear, and in its role as an international technical safety organization;

• To train young nuclear specialists over a broad spectrum of disciplines, including those with experience of other energy systems.

The NES department is structured into six research laboratories according to their specific scientific and technical areas of competence; an additional department operates the only Hot Lab in the country.

In addition, the PSI academy, which includes the Reactor School and the Radioprotection School offers education and training programmes for present and future reactor operators as well as for radioprotection experts or scientists and technicians working with radioisotopes.

The following sections provides a brief description of the programmes currently carried out within the NES department.

(a) Reactor technology

The STARS programme is a long standing project aimed at the development, maintenance and application of a complex code and database system to be used for investigations into the behaviour of the Swiss nuclear reactors. Focus areas include combined system transient and uncertainty analysis, fuel modelling and neutronics.

The main focus in the Human Reliability Assessment (HRA, risk and human reliability) concerns resolution of current and emerging issues associated with the treatment of human factors in the context of a probabilistic safety assessment. Examples of currently investigated topics include: development of HRA methods, quantification of errors of commission, application of simulator data and a technical basis for seismic HRA.

The Nuclear Fuels programme involves microstructural/micromechanical examination of the ageing of core internals (fuel rods and structural materials), and the development of associated theoretical models. In particular, fuel rod behaviour under service but also under long dry storage conditions are investigated and possible causes of failure are evaluated. Novel methods for production of Generation IV fuels, and their associated fuel cycles, are also under consideration.

The Component Safety programme (INTEGER) involves the experimental characterization of important ageing mechanisms (stress corrosion cracking, thermal fatigue and irradiation embrittlement) in primary pressure boundary components, the development and validation of advanced mechanistic material ageing models and probabilistic methods for improved integrity assessments and lifetime predictions, as well as the evaluation of advanced non-destructive techniques for the early detection of fatigue and stress corrosion crack initiation and for the characterization of the actual degree of embrittlement in components.

The containment phenomenology during postulated severe accidents is further carried out by participation in the project Hydrogen Mitigation Experiments for Reactor Safety (HYMERES) Project Phase 2 (OECD Nuclear Energy Agency (OECD/NEA)). Its main objective is to improve basic understanding of the complex thermohydraulic processes and to extend the experimental database to phenomenology not investigated previously. The experiments are carried out at the PSI in the PANDA facility (a large scale, multicompartmental thermal hydraulic facility suited for investigations related to the safety of current and advanced LWRs).

The Source-Term Evaluation programme activities are centred on the AeRosol Trapping in the Steam generator (ARTIST) test facility which reproduces (at reduced scale), aerosol deposition behaviour during a severe accident following a postulated steam generator tube rupture. General considerations of iodine chemistry are being investigated, with specific application to NPPs. The experimental programme is balanced by the development and validation of numerical models, the overall theme being aimed at replacing the existing empirical models by mechanistic modelling using computational fluid dynamics (CFD). All activities are directed towards source term evaluation relevant to the Swiss NPPs.

(b) Waste management

The programme is an ongoing commitment, overseen by the Government, to ensure the safe disposal of radioactive waste from the medical and nuclear industries and also various research facilities. The activities cover fundamental waste disposal chemistry, the physics and chemistry of radionuclides, and investigation of the geological barriers for radionuclide transport. Results will ultimately find use in the comprehensive application of safety criteria. This R&D programme is carried out in close cooperation with Nagra.

(c) Energy systems analysis

These activities are carried out within the Laboratory for Energy System Analysis (LEA) which is an interdisciplinary laboratory supporting both the NES and the Energy and Environment Division (ENE). The laboratory aims to contribute to effective decision making on long term technology strategies in energy supply and demand by ensuring the full integration of major environmental, economic and social factors. The LEA also develops methodologies, and carries out the associated risk analyses, with a focus on HRA.

The Technology Assessment programme involves comprehensive analyses of environmental, economic and risk performance of fossil, nuclear and renewable energy technologies as well as of a wide spectrum of mobility options. It is based on an interdisciplinary framework, thus enabling consistent comparisons to be made between current and future options for the electricity, heating and transport sectors.

In the Energy Economics programme, energy system models are developed and quantitative analyses are carried out on the Swiss, European and global levels to improve the understanding of the interactions among energy, economics, the environment and technology. The generated long term scenarios of energy systems enable examination of the associated energy-technology strategies and the impact of related policy instruments

(d) Hot Laboratory

The Hot Laboratory (Hot Lab) is the largest nuclear research facility in Switzerland, under the supervision of ENSI, and the only Swiss research facility capable of examining large quantities of radioactive material. The two main tasks of the Hot Laboratory Division (AHL), the operating organization unit, are to ensure the safe and efficient operation of the Hot Lab infrastructure and to conduct state of the art service work for the Swiss nuclear industry. Accordingly, AHL offers Hot Lab users (i.e. research groups from other units) modern analytical tools for the manipulation and investigation of radioactive material. In particular, the laboratory is well equipped for structural and chemical analyses of the materials used in NPPs and accelerator facilities.

The ALPHA programme provides confirmation of the characteristics of passive safety systems for advanced LWRs, and is centred on the large scale, integral test facility PANDA. More recently, the experimental base was broadened to incorporate investigations of fundamental phenomena in both the primary circuit and containment, and include the study of two phase flow phenomena (such as bubbly flows), the prediction of critical heat flux, and mixture/stratification phenomena. A number of additional small and medium scale, single effect test facilities are now also included under the project heading. At all three scales, experimentation is accompanied by the development and application of novel instrumentation techniques able to measure the distributed parameters characteristic of 3-D flow fields. In parallel, there is an ongoing development and validation programme for the accompanying numerical tools, particularly CFD, but also including multiscale modelling approaches to basic phenomena, such as boiling.

In the appropriately named FAST programme (fast spectrum core and safety analysis with emphasis on generic developments and Generation IV systems), activities are aimed at the development and implementation of a code system representing state of the art safety analyses of nuclear systems incorporating fast neutron spectra.

The High-Temperature Materials programme activities involve characterization of materials to be used in future Generation IV reactors (particularly gas cooled reactors), which will operate at significantly higher temperatures, and are subject to a more intense radiation environment than current Generation II reactors. Mechanistic models are being developed for the prediction of material behaviour, from the atomic level up to the scale of the continuum. Experimental validation of the models is also undertaken using advanced spectroscopic methods and, in particular, synchrotron radiation.

Switzerland has participated in international projects in the field of plasma physics and controlled nuclear fusion for the past 25 years, primarily in a European context. In participating in the research programmes of the European Atomic Energy Community (Euratom), Swiss research on fusion has focused on its primary skills and is seen as an important partner at the European level. Switzerland participates indirectly in the international organization International Thermonuclear Experimental Reactor (ITER, which also means a path or journey in Latin), which has been tasked with conducting a decisive experiment for determining the viability of nuclear fusion as a clean and safe source of energy. Switzerland is a member of Fusion for Energy, the common European company established to provide Europe’s contribution to the ITER project.

The Laboratory of Radiochemistry (LRC) focuses on fundamental research and on education in the field of radiochemistry. The topics studied within LRC cover a wide and diverse range of radiochemical research, including studies on the chemistry of heavy elements, harvesting exotic radionuclides from irradiated accelerator components for use in fundamental research, developing innovative radiopharmaceuticals and the chemical behaviour of radionuclides in liquid metals proposed as target material or coolant in future nuclear facilities.

A new laboratory concentrating different groups that are active in the modelling of complex, multiscale processes was created in the NES division. The main goal of this laboratory is to offer a centre of competence for the development of high end tools for numerical simulations and visualization of complex physical phenomena using the High Performance Computers available in Switzerland. In particular, the further development of computational fluid dynamics and the simulation of advanced nuclear systems will ideally be realized in this lab.

The Federal Council is the authority that grants general licences. DETEC grants construction licences and operating licences for nuclear facilities. SFOE is responsible for coordinating the licensing procedures and issuing licences for the handling of nuclear material and radioactive waste.

ENSI is the national regulatory authority in Switzerland with responsibility for nuclear energy. It is supervised by an independent board, which is elected by the Federal Council and reports directly to it.

ENSI is responsible for the supervision of Swiss nuclear facilities (i.e. the NPPs, the interim storage facility for radioactive waste, the nuclear research facilities at the PSI, in Villigen, the EPF Lausanne and the University of Basel). Its regulatory remit covers the entire life of a facility (i.e. from initial planning through operation to final decommissioning, including the disposal of radioactive waste). It also includes the safety of staff and the public and their protection from radiation, sabotage and terrorism. In addition, ENSI is involved in the transport of radioactive material to and from nuclear facilities and in the continuing geoscientific investigations to identify a suitable location for the deep geological disposal of radioactive waste.

ENSI monitors the operation of nuclear facilities:

• ENSI reviews reporting by the operators, holds regular supervisory discussions and monitors the nuclear facilities (including their organization and operation) by means of more than 400 on-site inspections each year.

• Each summer, every NPP carries out an inspection, lasting several weeks, during which maintenance work and repairs are undertaken in the plant.

• In order to protect staff, the population and the environment, ENSI monitors compliance with the radiation protection regulations and dose limits.

• ENSI collates all the data obtained during the year into one comprehensive safety assessment, from which it derives any measures that may be required as well as its future supervision plans.

ENSI assesses nuclear facilities:

• The assessment and monitoring of nuclear facilities are based on laws, guidelines and underlying technical and scientific documentation, which transparently set out the safety requirements and criteria that ENSI applies for its assessments. ENSI continues to develop the underlying documentation and guidelines in accordance with the latest status of science and technology.

• ENSI draws up safety assessments when operators of nuclear facilities submit applications which go beyond the scope of their existing operation.

• Applications for modifications to nuclear facilities that are covered by existing operating licences are dealt with by ENSI, which issues a permit if the decision is positive.

The NSC is designated as an advisory committee to the Federal Council and DETEC. It is involved in the licensing process as it reviews and comments on the safety evaluation reports prepared by the supervisory authorities.

In the nuclear field, the supervisory authority with respect to nuclear safety and radiation protection is ENSI. In the non-nuclear field, the supervisory authorities are the Federal Office of Public Health (FOPH) and the public sector insurer SUVA (formerly Swiss National Accident Insurance Fund). The FOPH manages the licensing procedures in the non-nuclear field according to the radiological protection legislation. It is responsible for waste produced from the health care sector, industry and research.

The National Emergency Operations Centre (part of the Federal Office of Civil Protection in the Federal Department of Defence, Civil Protection and Sport) oversees all emergency situations, including those arising from events at NPPs and relating to the protection of the public and the environment.

Several advisory committees to the Government or governmental departments covering aspects of radiological protection, emergency planning and waste disposal have responsibilities associated with the operation of NPPs. However, they are not involved in the licensing process and have no authority over the plants.