Between Stalin and radiation

"Vinca was the first realization of the dreams of our revolutionaries to build something new and significant. After Hiroshima, nothing was more recent and significant than nuclear energy", writes one of the initiators of nuclear research in Vinča, Milorad Mlađenović. Born in 1920 in Sarajevo, he studied metallurgy in France, then spent the war in Great Britain and North Africa as a member of the Yugoslav Air Force, and then, at the insistence of Pavle Savić, he was returned to the country where he finished physics and came to Vinča.

Mlađenović was in charge of nuclear physics in Vinci from the very beginning, and his graduation thesis from 1948 on electron trajectories in a magnetic lens, as well as Wallen's suggestion on the use of a hodoscope, was the beginning of the development of beta spectrometry. After his stay in Stockholm, he founded a group that dealt with spectroscopy and worked on detection systems, especially Wilson chambers, then nuclear emulsions, gas and scintillation detectors. A whole series of memoirs talks about these first experiments and the first researchers who are systematically sent to European scientific centers to be educated and return to the country. In this, knowledge is sought both in the East and in the West.

Tito's Yugoslavia, as a community of six republics held together by an unusual mixture of ideology and post-war enthusiasm, was going through dramatic social and economic changes at that time. The country is rebuilding after the war, but the wounds of severe internal conflicts and crimes are alive, while the majority of the population lives in great poverty. Although the Red Army, after participating in the liberation of Belgrade, soon left the territory of the country, immediately after the Second World War, Yugoslavia was part of the Eastern Bloc and an important ally of the Soviet Union.

However, Tito, as a world-renowned leader of the national liberation movement that broke free from the Nazis, entered into conflict with Stalin. Because of this, the international organization of communist parties, Informbiro, which succeeded the Comintern dissolved during the war, in 1948 condemned and expelled Yugoslavia from the then communist community. The conflict grows into a major crisis - on the brink of war with the communist empire, Yugoslavia is now looking for friends in the West, while at the same time investing in its own military capabilities.

In these circumstances, Vinča is at the center of the Yugoslav dream of independence. It is believed that, during the first five years, at the same time as the persecution of the Informbiro people was going on, and Soviet tanks were on the borders of Yugoslavia, the amount that could have been used to build a subway in Belgrade was invested in Vinč, i.e. 1,75 billion dinars, which at that time amounted to about 35 million dollars, which would be worth 4,5 billion dollars today.

HUNGARIAN REVOLUTION

It is not unknown that, in addition to the French leftists, Yugoslavia also collaborated with Norway for a long time on the development of the nuclear program. The director of the institute, Stevan Dedier, established relations with Norwegian scientists, many of whom stayed in Vinci. King Olaf V of Norway also came to Yugoslavia on that occasion. Thanks to such international contacts and the growth of local knowledge, after the construction of the first facilities, the construction of laboratories for physics, physical chemistry, biology and electronics began in Vinci in the early fifties. The first, a small accelerator called V02, which accelerates protons and deuterons, is launched. It will later operate at an energy of 200 keV.

After the first accelerator, a building is being erected for the Cockroft Walton accelerator, a 1,5 MeV named V15. This plant was put into operation in 1952 by Josip Broz himself, together with his close associate Edvard Kardelj. At this time, two accelerators are intensively used - they work for several thousand working hours per year. They are an attraction for physicists and represent equipment that at that time could only be found in leading scientific institutions in the world. In the meantime, at the turn of 1953 and 1954, a crisis arose at the top - Milovan Đilas fell from power and numerous lower managers changed in waves throughout Yugoslavia, which would also affect the situation in Vinča. Wallen and Dedier leave, but the research continues.

The most significant instrument arrived in Vinča after that, right after the Hungarian Revolution - it is the RA research reactor, the first nuclear reactor in Serbia and Yugoslavia. The reactor, together with the fuel, was purchased as a finished product from the Institute for Theoretical and Experimental Physics in Moscow, at a time when, after Stalin's death, relations between Yugoslavia and the USSR were thawing. The first elements arrived by wagon through Hungary in 1956, while the revolution against the Soviet government was raging there.

The Hungarian revolution began with a student protest on October 23, 1956 against the unpopular communist government of Macaš Rakosi, whose secret police were terrorizing the population. The Hungarian revolutionaries, led by Imre Nagy, modeled themselves on socialist Yugoslavia and Tito's policy of independence. In a revolt that is rapidly spreading across the country, the people's soviets take power from the Rakosi people, and Imre Nagy declares Hungary's exit from the Vásravsk Pact. The USSR reacts with an invasion and on November 4, the Soviet army enters and occupies Hungary. The Western powers are preoccupied with the Suez crisis and the revolutionaries in Hungary are left alone.

Their only friend, Josip Broz, strongly opposes the Soviet intervention in Hungary, but still meets with Nikita Khrushchev in Brioni. The revolution was crushed, and Imre Nag took refuge in the Yugoslav embassy in Budapest, where he sought asylum. However, Tito makes the decision to hand him over to the Soviet soldiers anyway. There are views that this decision and the concession to the USSR were part of the trade between the Soviet and Yugoslav leaders - that they were made in exchange for a nuclear reactor that would then arrive in Yugoslavia. The railway composition with the first parts of the reactor travels through Hungary, visiting the intersections where the hanged Rakosi people hang and Red Army tanks are on duty.

REACTOR

The researchers state in their memoirs how the installation of the reactor changed the life of the institute. The reactor was named RA and had a power of 6,5 MW. It consisted of 54 vertical channels, used low-enriched uranium as fuel and was moderated by heavy water. However, it took almost four years to install the new reactor. SKNE adopted an investment plan and the so-called "Vinca-project" was launched for the construction of a new reactor building and supporting facilities, new isotope laboratories and a high-activity laboratory. The Yugoslav People's Army and numerous Yugoslav companies are involved in the project.

While the new building was being built, seven tons of heavy water were delivered to Vinci for RA's future needs. When four tons of uranium in the form of rods were procured, the physicists decided on an unusual venture - to wait for the installation of the Soviet reactor in Vinci to build a smaller, simple zero-power reactor and, before installing the RA, use their own ingenuity to achieve the first controlled fission in Yugoslavia.

This reactor will be known as RB. It was made as a very simple system with uranium rods and heavy water as a moderator, with the aim of training personnel and starting the first experiments. The reactor was located in a container that was raised 4 meters from the floor (the reasons are experimental because the reactor did not use reflection). The aluminum construction carried 15 tons, and the entire plant was placed in a pool of 8x8 meters, 1,5 meters deep.

The venture was successful - the so-called criticality was reached at the RB reactor at the end of April 1958 - the physicists in Vinci were justifiably elated, they achieved the first controlled chain reaction in Yugoslavia and this part of Europe. Two weeks later, on May 17, 1958, Tito, together with Aleksandar Ranković and Edvard Kardelja, officially put the RB reactor into operation in Vinci, while the construction work on the building of the large RA reactor was still ongoing.

ACCIDENT

Just a few months later, on October 15, 1958, an accident occurred at this very "trial" reactor RB. Long hidden from the public, it will be the biggest nuclear incident that happened on the territory of Serbia and the former Yugoslavia. During the experiment, radioactive material was released and six young researchers were irradiated - Radojko Maksić, Roksanda Dangubić, Draško Grujić, Stjepko Hajduković, Živorad Bogojević and Života Vranić. And although they will be criticized for negligence in the later investigation, Pavle Savić manages to get the researchers from Belgrade transferred to the Curie Institute in Paris the very next day, since it was not possible to cure them otherwise. In Paris, five of them, all except Bogojević, were subjected to experimental therapy and the first bone marrow transplant procedure in history. The pioneering operation will prove to be successful - everyone survived except Vranić, who died from an overdose of radiation.

The RB reactor will be shut down for a year and a half after the accident. In the meantime, the Yugoslav press reports very sparingly about this incident, so the event is covered up, but there is no doubt that the whole case cast a shadow on Vinca. The event takes place in the immediate aftermath of the Mayak plant accident and the Windscale fire, as we have seen - at a time when nuclear power is beginning to be viewed with much greater caution around the world. It is possible that with the disaster at RB, Tito's original dream of developing nuclear weapons was actually extinguished.

However, work on the new RA reactor building will continue. Thus, a year later, the installation of the RA reactor will finally be completed, so that the first chain reaction will be realized on it as well. On December 29, 1959, Josip Broz, together with Pavlo Savić and the most respected physicists, attends the ceremony in Vinča where the RA reactor is started and of which a rich photo and written documentation remains.