The Swedish Radiation Safety Authority (SSM – Strålsäkerhetsmyndigheten) said on 9 December that it had approved the safety report for dismantling and demolition of Ågestaverket, the Agesta nuclear plant, which operated between 1964 and 1974. The decision means that dismantling and demolition can now begin, but before any dismantling begins, the projects must be reported to SSM.

Ågestaverket, a 10MWe pressurised heavy water reactor located about 4 km south of Farsta in Stockholm County, produced district heating as well as electricity and was also initially used for plutonium production. It is sited in an underground rock cavern. Following its decommissioning all the fuel  and heavy water were removed. Ågestaverket is owned by Vattenfall and In June 2019, Vattenfall, which hold the licence for the plant, applied for approval of the safety report for its dismantling. SSM inspector Patrik Lundell said a comprehensive review of the safety report and other required reports confirmed he plant’s safety. SSM said  Vattenfall AB had taken appropriate measures to enable demolition to take place “in a radiation-safe manner”.

At the end of World War II, Sweden adopted “the Swedish line'”, an ambitious nuclear programme aimed at self-sufficiency. Reactors would be designed and built without external help and fuelled with natural uranium from local mines. Atomenergi, a semi-state company formed in 1947, led the project. In 1956, the company conducted a pilot study of a reactor facility for district heating in the Stockholm area. The project was initially run in partnership with Stockholms Elverk and was called R3. At the same time, Vattenfall was planning the Adam nuclear heating plant in Västerås/

However, there were no resources for two programmes and overall responsibility was given to Atomenergi. Vattenfall's plans were sidelined and in 1958 the two companies agreed to collaborate. The result was R3/Adam, a combined heat and power PHWR located in Ågesta. The Agesta reactor was a unique design - the only plant with a similar design concept is in Argentina (Atucha-1). Ågesta was described as a demonstration plant to be followed by a prototype facility, R4/Eva in Marviken. The R4 reactor was intended for both electricity and plutonium production but it was cancelled in 1970.

The R3 PHWR had a thermal output of 65 MW, which was later increased to 80 MW, with 12 MW of electricity and 68 MW of district heating. Uranium from Atomenergi's uranium mine in Kvarntorp was used as fuel. Construction costs for Ågesta were estimated at SEK50 million ($5.2m), but the final figure was SEK230 million. However, cost was not the primary issue as the goal was to gain expertise about reactor design and operation.

The plant operated reliably except for an accident in 1968 which closed it for seven months. The details were eventually revealed in 1993. According to Karl-Erik Sandstedt, then Assistant Director of the Ågesta reactor, the accident occurred when a technician made an error in a routine change of a valve, releasing 500 tons of water  from a cooling tower 30 metres over the reactor building. On its way down, it knocked out the reactor control system. Short circuits resulted in valves opening and closing at random putting the plant at risk of a meltdown. The public was not notified after officials determined that evacuation of the area at risk could not take place fast enough.

Since its closure in 1974, Agesta has since been in a state of storage with surveillance. This has been exclusively by periodic inspections, without any personnel on site permanently. There had been some pressure to preserve Agesta as a national antiquity. However, Vattenfall said major investments would have been needed to meet increased security requirements. Moreover, Agesta had become obsolete after unit 1 at the Ringhals NPP - a 881MWe boiling water reactor - began commercial operation in 1976. The area is currently used as a training site by Stockholm's fire services. Demolition is now expected to begin in early 2020.