Early history

Sweden began research into nuclear energy in 1947 with the establishment of the Atomic Energy Company, AB Atomenergi, which originated in the ongoing military research and development at the Defence Institute FOA.^[5] In 1954, the country built its first small research heavy water reactor, the R1 nuclear reactor. The R1 was dismantled in 1970. It was followed by two heavy water reactors: Ågesta or R3 nuclear reactor, a small heat and power reactor in 1964, and Marviken or R4 nuclear reactor which was finished but never operated (was never loaded with nuclear fuel), due to several safety issues.^[6] The R3 reactor stopped operations in 1974 and is to be demolished with work beginning in 2020 and ending 2025. The R4 project was cancelled in 1970, with the site being used in non-nuclear capacity since. Also a reactor named the R2 nuclear reactor, the second nuclear reactor in Sweden, was built in Studsvik, east of Nyköping. Studsvik also hosted a reactor named R2-0 nuclear reactor. Both R2 and R2-0 were small research reactors, and both were decommissioned in 2005. Furthermore there was also a third research reactor in Studsvik called FR-0 nuclear reactor which was a zero-power fast reactor with low power output. It was operated 1964–1971 and was then dismantled.

On 1 May 1969, the prototype nuclear cogeneration plant Ågestaverket (R3) suffered an incident in which secondary cooling water flooded through a broken valve and caused a number of electrical problems in the plant, resulting in a 4-day shutdown.^[7]

R1, R3, and particularly the never finished R4 project at Marviken were heavy water reactors, motivated by the option to use Swedish uranium without isotope enrichment and by the possibility to use the reactors to produce weapons grade plutonium for Swedish nuclear warheads. The Swedish nuclear weapons program was eventually shut down, however, and Sweden signed the nuclear non-proliferation treaty in 1968.^[8]

Six nuclear reactors began commercial service in the 1970s, and another six through 1985. Nine of the reactors were designed by Allmänna Svenska Elektriska Aktiebolaget (ASEA), and three supplied by Westinghouse.

Plans for nuclear phase-out

After the Three Mile Island accident in 1979, there was a national referendum in Sweden about the future of nuclear power. As a result of this, the Riksdag decided in 1980 that no further nuclear power plants should be built, and that a nuclear power phase-out should be completed by 2010. Some observers have condemned the referendum as flawed because people could only vote "NO to nuclear", although three options were basically a harder or a softer "NO".^[9][10]

After the 1986 Chernobyl accident in USSR, the question of security of nuclear energy was again raised. In July 1992 an incident at Barsebäck 2 showed that the five older boiling water reactors had had potentially reduced capacity in their emergency core cooling systems since they started operation. Mineral wool was dislodged and ended up in the suppression pool where it clogged the suction strainers.^[11] It was classified as a grade 2 incident in the IAEA INES scale, due to the degradation of defence-in-depth. All five reactors were ordered down by the Nuclear Inspectorate for remedial action where backwash and additional strainers were installed. Most of the reactors were back in operation by next Spring, but Oskarshamn 1 remained down until January 1996 due to other work being carried out.

During the late 1990s a unique capacity tax on nuclear power (effektskatten) was introduced. It was initially set at 5514 SEK per MWth per month, and only applied to nuclear power plants, thus penalizing them relative to other energy sources. In January 2006 it was almost doubled (at 10,200 SEK per MWth per month).^[12] An agreement struck in June 2016 among other things meant the capacity tax would be phased out by 2019. By then the tax constituted about one third of the cost of operating a nuclear reactor.^[13]

In 1997 the Riksdag decided to shut down one of the reactors at Barsebäck nuclear power plant by 1 July 1998 and the second before 1 July 2001, although under the condition that their energy production would be compensated.^[14] The next conservative government tried to cancel the phase-out, but, after protests, decided instead to extend the time limit to 2010. At Barsebäck, block 1 was shut down on 30 November 1999 and block 2 on 1 June 2005.

In August 2006 three of Sweden's ten nuclear reactors were shut down due to safety concerns following an incident at Forsmark Nuclear Power Plant, in which two out of four emergency power generators failed causing a power shortage. It was classified as a grade 2 incident in the INES scale, due to the degradation of defence-in-depth.

In 2006 the Centre Party of Sweden, an opposition party that until then had supported the phase-out, announced that it was dropping its opposition to nuclear power, at least for the time being, claiming that it is unrealistic to expect the phase-out in the short term. It said it would now support the stance of the other opposition parties in Alliance for Sweden, which were considerably more pro-nuclear than the then Social Democratic government.^[15]

Phase-out abandoned

On 17 June 2010, the Riksdag adopted a decision allowing the replacement of the existing reactors with new nuclear reactors, starting from 1 January 2011.^[16]

In June 2016, the coalition government decided to abolish the nuclear power output tax in 2019 and to successively replace the existing reactors with new ones.^[17] In October 2022, the new Swedish governing decided to have Ringhals 1 and 2 reactors restarted and the construction of further reactors examined.^[18]

Nuclear revival

In June 2023, the new Kristersson Cabinet established after the country's 2022 election voted to switch the national energy target from 100% renewable electricity by 2045 to 100% fossil fuel-free electricity by 2045, a move seen as supporting and extending the ongoing use of nuclear power in the country.^[19] At the time, hydro, nuclear, and wind power already produced 98% of Sweden's electricity, with the government aiming to increase electricity production from carbon-free sources to meet an estimated doubling of national electricity consumption by 2040.^[20]

In November 2023, more details about the new nuclear policy, which is to enter into force on 1 January 2024, were revealed. The current 10 reactor cap will be dropped, permitting process will be shortened and new nuclear reactors will be allowed also on new sites and not just existing ones. A target of 2500MWe of nuclear power by 2035 was announced, as electricity consumption is expected to rise to 300TWh by 2045.^[21]