For about a quarter of a century, Sweden conducted secret scientific research work to create its own nuclear weapons. It began at the very end of WW2, and the last experiments with weapon-graded plutonium were completed by the Swedes in 1972, four years after the Scandinavian country joined the Treaty on the Non-Proliferation of Nuclear Weapons. Swedish scientists stopped literally seconds away from the goal: there was everything necessary to make a nuclear bomb within months in the country.
A conscious need
The Swedish research in the field of nuclear weapons began in 1945, soon after the American atomic bombs fell on Japan. Already in August, literally a few days after the bombing of Hiroshima, Helge Victor Jung, who were that time the 2nd Supreme Commander of the Swedish Armed Forces, demanded to find out all the details about the new weapons. The Swedish National Defense Research Institute (Försvarets forskningsanstalt, FOA) that was created in 1945 by combining three organizations – the Military Physics Institute, the Swedish Armed Forces Chemical Institute, and a part of the Swedish Board of Inventions, was in charge of the issue.
Initially, the scientific researches were held with the aim to find out the way Sweden could protect itself from a nuclear weapon attack. Nevertheless, FOA almost from the very beginning had an interest in creating its own nuclear bomb, the possession of which considered as the best guarantee against a possible attack. So Sweden decided to get the nuclear weapons in its arsenals like many other countries in the world after WW2. Nils Swedlund, Chief of the Defense Staff, who later became the Supreme Commander of the Swedish Armed Forces, stated on this occasion, that without A-bombs, the country was an easy target for any enemy.
The Swedish Government made several attempts to get the access to the American nuclear technologies, including the uranium enrichment technology. And Sweden was not the only country that applied for such assistance and no wonder it got the polite refusal. Under The US President Eisenhower’s “Atoms for Peace” program, the United States offered Sweden access to enriched uranium under the condition that it would be used only for energy production. The right of the US inspectors to exercise control over Swedish power plants was specified separately. The Americans believed that such a small country as Sweden would not be able to makes its own nukes “from the scratch”.
After that, the Swedish Government decided to open the cards and tried simply to buy ready-made nuclear ammunition from the Americans. The Swedes knew that the US legislation prohibited the nuclear weapons export, but they decided to try, considering that the United States were strongly interested in well-protected Sweden as a stronghold against Soviet aggression. In 1955, the Swedes even announced the planned volume of the purchase – 25 nuclear devices.
As expected, and then the Swedes got the negative answer. There was no fundamental refusal – but to obtain a nuke, Sweden had to fulfill two obligatory conditions. The first one was the neutrality refusal and the signing of a defense agreement with the United States and the second one – the US control over the Swedish nuclear weapon usage. Neither of the conditions were acceptable for Social Democratic government of Sweden. The Scandinavians were then even more strengthened in the idea to develop their own atomic bombs.
The secret “Swedish line”
Of course, all the works in the direction went top-secret. A very narrow circle of militaries, scientists and politicians were aware of the program until about the mid-1950s and they were directly involved in its implementation. In 1947-1948, one more organization – civil one this time – joined FOA in its nuclear researches. That was a state company AB Atomenergi (AE), created in May 1947. The main purpose of its work was the development and implementation of the civil nuclear power in Sweden. There was a certain labour division between these two organizations: FOA was involved into the creation and development of a nuclear warhead, and AE was responsible for the technological process organization of receiving of the weapons-grade plutonium from uranium. Between 1949 and 1968, when Sweden signed the Treaty on Non-Proliferation of Nuclear Weapons, AE already finished four major research programs in this area.
No later than 1948, FOA submitted a secret report to the Supreme Commander of the Swedish Armed Forces, which described the necessary conditions of a nuclear warhead obtaining. And by 1954, when the Supreme Commander Nils Swedlund in public expressed for the first time that it would be good to create their own nuke, the Swedes in fact already had a good technological basis for the practical realization of the idea. Moreover, in all the necessary directions – from the weapons-grade plutonium production and the serial production of the nuclear ammunition to the creation of various means of delivery, including cruise missiles, aircrafts and submarines.
From the very beginning, the Swedes did not plan to create strategic nuclear weapons. It was planned to be tactical things and first of all play the role of a deterrent. According to the 1956 project Swedish plutonium bombs were supposed to weight 400-500 kg and have a diameter of 35 cm, which would allow to use new (at that time) SAAB 32 Lansen jet planes as carriers.
In general as the result of their nuclear program execution, that was named “Swedish line”, the Swedes planned to produce 100 warheads with a capacity of about 20 kilotons each.
The process started
Sweden had several advantages in comparison to many other countries that in various times desired to enter the Nuclear Powers Club. The country had well-developed industry and qualified scientific personnel. Above all, Sweden had (and still has) significant reserves of natural uranium, contained in black shale in the central part of the country. These deposits are among the largest in the world. Having faced the difficulties with self-mastering of uranium enrichment technologies, the Swedes decided to use a heavy-water nuclear reactor for the production of weapons-grade plutonium, using heavy water as a coolant and moderator. The additional difficulties, connected with the complexity and the high cost of heavy water production in the right quantities were compensated by the fact that in this type reactor it was possible to use unenriched natural uranium, which was available in abundance in Sweden.
Shortly after the War, FOA developed a uranium extracting method from the shale by burning its carbon component and washing out the radioactive metal from the resulting ash. The first uranium was produced at the old Nobel’s plant for the sulfuric acid production in Stockholm. Plants were built later in Kvarntorp (with the capacity of 5 tons of uranium per year) and in Ranstad (120 tons of uranium per year). A pilot plant for heavy water production was also erected near the Kvarntorp plant. However, the plant did not reach the planned capacity and Sweden imported the heavy water from Norway. Around that time, Norway launched its own nuclear program, but there was no uranium in the country and under the veil of secrecy, the Scandinavian kingdoms exchanged nuclear “precursors” with each other.
In 1951 in Stockholm, the Swedes started to construct and in 1954 they launched the first Swedish heavy-water nuclear reactor R1. It was not big and had a power of 0.3MW (later increased to 1 MW), and it was able to produce about half a gram of weapons-grade isotope plutonium-239 per day. Its first loading was done with three tons of French metallic uranium (the first Swedish specialized plant in Kvarntorp was launched only in 1953 and it did not have enough time to produce the necessary amount if radioactive metal) and 5 tons of Norwegian heavy water.
Around the same time, the Swedes made up their minds with the ammunition type, which they decided to make according to the implosive scheme. The nuclear explosion was supposed to occur as the result of plutonium charge compression to a critical density by means of an explosion of the charge of conventional explosive (CE). Both the “Fat Man” bomb, dropped by the Americans on Nagasaki, and the first Soviet A-bomb RDS-1 were implosive.
In 1956 a series of super-powerful explosions, using CE began in Jokkmokk, Swedish Lapland, in order to obtain experimental data about an explosive wave impact. The first experiment under the code-name “Sirius” included three explosions with the capacity of 0.36, 3.6 and 36 tons in TNT equivalent, the second, in 1957 – under the name of “Vega” – consisted of two explosions with the capacity of 3 and 21.6 tons.
In 1956, Sweden also bought the second nuclear reactor in the United States – R2. This happened after the signing of a bilateral cooperation agreement in the field of civil nuclear energy use within the framework of the above-mentioned American program “Atoms for peace”. Moreover, Sweden got the access to results of US researches in the nuclear energy areas. The country also could receive the necessary materials from the USA, including a little amount of the enriched uranium and heavy water on less than Norwegian prices. At the same time, the agreement separately stipulated that Sweden undertook not to use the obtained information and materials for nuclear weapons production and any other military purposes.
In order to carry out the design calculations, necessary for the creation of atomic weapons in the early 60s FOA bought one of the most powerful transistor computers at that time – IBM 7090.
One more reactor, «Ågesta» (launched in 1964), the Swedes built independently. «Ågesta» was the first Swedish commercial nuclear reactor that supplied the Stockholm suburb Farsta with heat (68 MW) and a small amount of electricity (12 MW). At the same time, the reactor fulfilled the military orders, making from 0.5 to 1 kg weapons-grade plutonium per week. Those capacities were clearly not enough for the creation of a hundred planned nuclear warheads, and the military gave a special role to the more powerful fourth nuclear reactor that was built in Marviken. In addition to the generation of 130 MW of electricity, it was supposed to meet fully the Swedish military demands in weapons-grade plutonium.
R4 reactor in Marviken that played a core part in the Swedish program was almost built, when the Swedish government officially abandoned the design and creation of their own nuclear weapons in the late 1960s – early 1970s.
By 1965, the Swedes had almost everything for the nuke production, except for a political solution and 10 kilos of weapons-grade plutonium. In addition, in order to create a charge suitable for combat use, practical tests with detonation of charges were to be carried out, but in 1963, Sweden joined the Moscow Treaty Banning Nuclear Weapon Tests in the Atmosphere, in Outer space and Underwater.
The Treaty did not prohibit underground tests and FOA prepared plans for their implementation in Lapland in the Nausta river basin, where super-power CE charges were already detonated. But the scientists assured that there would be no requirement in practical nuclear tests. They had so much confidence in their scheme that they were ready to launch the bomb into the production without any tests at all!
Since the late 50s, such events began to take place both in Sweden and abroad that eventually buried the Swedish nuclear program. Outwardly, they were expressed in the fact that the Swedish society, which initially approved the government plan to build nuclear weapons, later began to treat the national military nuclear program critically. For example, the petition against A-bombs creation was signed by 95 000 Swedish citizens.
The politicians could not help spotting the protest mood growth – in the same 1957, Sweden as a member of UN Security Council put forward a proposal for nuclear tests moratorium. In 1968, Sweden joined the Treaty on the Non-Proliferation of Nuclear Weapons, which was formally supposed to put the end of the national nuclear program, although in fact, the work on it was completely curtailed only in 1972.
However, there is one more version of the fall of the Swedish militaries interest for their own bomb possession. It has a slight conspiracy spirit but it is quite widespread in the Swedish media. Its essence is that around 1964, when the United States faced the fact Sweden was about to build its own nuclear weapons, the Americans were compelled by the fact to protect Sweden in case of nuclear war and took the only “non-NATO” Scandinavian country under their nuclear umbrella.
The Swedish media also find indirect confirmations for the existence of this hypothetic top-secret agreement between the UN authorities and neutral Sweden. For instance, about the same time the runways on the Swedish Air force bases were expanded so, that from that moment they could receive US strategic bombers. And the Swedish tanker aircraft nozzles were adapted to the NATO standards.
After the complete Swedish nuclear program closure, most of the weapons-grade plutonium that had been developed in the country was exported to the UK, although a small amount of it was still in the country. On the 2nd of February 2012, the Scandinavian Kingdom government decided to send 3.3 kg of plutonium and about 9 kg of uranium to the United States for disposal. But nevertheless, Sweden together Japan, Germany, South Korea and several other countries, is still among the states, that are able to produce their own nuclear weapons within just a few months.
- Jonter, Thomas, dr. Nuclear Weapons Research in Sweden. The Co-operation between Civilian and Military Research, 1947 – 1972. Uppsala University, Department of History, S:t Larsgatan 2, SE-753 10 Uppsala, Sweden, May, 2002;
- Jonter, Thomas (1999), Sverige, USA och kärnenergin – Framväxten av en svensk kärnämneskontroll 1945–1995, Uppsala: Historiska institutionen Uppsala universitet;
- Den svenska atombomben nyteknik.se;
- The Swedish Nuclear Weapons beforeitsnews.com;
- Swedish plutonium to the United States stralsakerhetsmyndigheten.se.