József Bánáti arrives at the Paks II project with knowledge established in Hungary and acquired in Scandinavia

József Bánáti was already fascinated by the Paks Nuclear Power Plant in his high school years: the student, who was equally interested in all natural science subjects, decided to study Heat and Nuclear Energy at the University of Technology and later at its Faculty of Mechanical Engineering. During his student years, he became more and more involved in the use of nuclear energy: as a fourth-year student, he had the opportunity to participate in internships in the former Soviet Union (Moscow, Leningrad and Voronezh) and at the Paks Nuclear Power Plant.

Already in 1985 he did his thesis on a computer

"At that time, I was already thinking about a possible topic for my thesis"," he says, "and the young team of engineers I met in Paks suggested a topic. So I did my thesis on the numerical simulation and tuning of the water level control of a steam generator."Computer simulation is a common thing in today's world, but when József Bánáti was writing his thesis, it was far from being so: "While the others had to make appointments for punched tape, room-sized computers, I was working on one of the first personal computer types, a Sinclair Spectrum with a Junosty TV monitor."

During the defence of his thesis, Ernő Petz, one of the managers of the Paks power plant (who also became the CEO of the Paks Nuclear Power Plant after the regime change), was his opponent, and József Bánáti was immediately offered a job. However, due to his family circumstances - he had to look after his elderly parents living near the capital - he was unable to take up the opportunity.

He worked on zone monitoring at the Chillebérc research centre

His first job was at the Central Institute for Physical Research (KFKI) of the Hungarian Academy of Sciences in Csillebérc, the country's largest independent scientific centre, where more than 4000 researchers worked in particle and nuclear physics, reactor physics, informatics and much more. It was here at KFKI that he was introduced to and worked on the development of the VVER On-Line Analysis (VERONA) system, the first zone monitoring and data visualisation system at the Paks power plant. On this system, the operator could already see summary diagrams and zone maps with complete data series, and could immediately detect which parameter was at which value in which range. An improved version of the system is still in operation today in the Paks I block controllers.

"After working on VERONA, I started thinking that I would prefer to focus on thermohydraulics. (Thermohydraulics is basically the science of flow, the study of multiphase flows, pressure, temperature and heat transfer and their relationships - editor's note)So I transferred from Reactor Physics - in-house at AEKI - to the Department of Thermohydraulics."

Safety experiments on a 1:2070 scale model of the Paks Nuclear Power Plant

It was here that József Bánáti first worked on one of the scalable models of particular importance for his DSA career, a scaled-down model of Paks I (1:2070) on a device called PMK (Paks Model Experiment) . "It's basic that we don't experiment in a nuclear power plant! The safety risks of postulated malfunctions must be evaluated in advance by analytical (computer) and laboratory experimental methods carried out under non-nuclear conditions. This is similar to the way in which, in medicine, experiments are not carried out directly on humans, but the effects of drugs can be studied by "stalking", e.g. on experimental mice. In a similar way, we can model real nuclear power plant processes on a miniaturised device, where, for example, nuclear heating is replaced by an electric heat source. Once the laws of similarity have been obeyed, the whole thermohydraulic process is now the same. Our now very advanced computer codes (software) allow us to simulate the process modelled on the miniaturised plant and then to "scale up" the geometric data to calculate in advance the consequences of the malfunctions that can be assumed in the real reactor. As a check, we can "validate" the code by comparing the results of the model experiment with the computer data, to make sure that the preliminary calculation for a real power plant pipe rupture accident, for example, is accurate.

Finland was the next stop

Meanwhile, the winds of change are blowing, and we are approaching the years of regime change in the interview. "While I was working on these tasks at KFKI AEKI in Csillebérce, an opportunity to move on came up. In the late 1980s, the International Atomic Energy Agency (IAEA) supported Hungary with grants for young researchers to work for a short period of time in various Western research institutes. I won one of these scholarships in 1990 and ended up at Lappeenranta University of Technology, a nice little Finnish university town on the shores of Lake Saimmaa, not far from the Russian border.

Here, too, I was working on a power plant model experiment similar to the PMK: the PACTEL (Parallel Channel Test Loop). This facility, like the Paks I, is a scaled-down 1:305 scale model of a Russian-designed VVER 440 reactor (the Loviisa nuclear power plant). The material summarising the experimental results obtained here later became the subject of my PhD."

What was originally supposed to be a six-month period continued in an adventurous way. "At the end of my IAEA fellowship, when my wife and I were packing up to go home, my Finnish professor handed me a work contract. In the meantime, the first freely elected government had already been formed in Hungary, we were over the taxi blockade, economic uncertainty, unemployment and inflation were on the rise. My original workplace, KFKI, was also undergoing major changes. So my stay in Finland was a little longer, 11 years in total. During the 1990s, the eastern markets that had benefited Finland collapsed. The Finnish parliament twice voted against the construction of a new nuclear power plant. Reflecting on this, I accepted an appointment as a visiting researcher in Halden, Norway, where, as a Hungarian, I was able to participate as a Finnish delegate in the large OECD collaborative research project Halden Reactor Project for nearly four years."

The research centres of Norway and Sweden were next

In the small town of Halden, south of the Norwegian-Swedish border, József Bánáti and his research team have developed a code called TEMPO (the acronym stands for Thermal Performance Monitoring and Optimization.) This software is not only suitable for simulating nuclear power plants, but also for visualizing data and thermal optimization of any other power plant process.

In his life story, he says: "Meanwhile it was 2004 and my second fixed-term mandate was coming to an end. The youngest of our three sons was already in school in Norway, so moving back to Finland was not an easy option. Then, at a conference, I met again Professor Imre Pázsit, whom I knew from KFKI. He had previously done research at Studsvik near Stockholm and was later appointed professor at Chalmers University of Technology in Gothenburg. Imre had already invited me to join him for a project - although I was still at the beginning of my secondment in Halden and had to say no. But by 2004 things had changed. After careful consideration of the fact that Swedish and Norwegian are similar, people understand each other, and the children would not be too upset by the language change, I was happy to accept. As part of a multi-year project, we carried out the safety analyses needed to increase the output of units 3 and 4 of the Ringhals power plant, 60 kilometres from Gothenburg, with a research team from Chalmers University of Technology. As a result, these two units have survived the closure and are still in operation today, with an increased capacity of more than 14%."

Once again, political change has presented the researcher with a difficult decision

"Like the Germans, after a few years, unfortunately, the Swedes also started to turn green, or even 'dark green' - this is 2015-16 - after a change of government, when the Greens joined the coalition. As a result of the machinations of the radicals (of whom Greta Thunberg is now a prominent representative), the idea of building any new nuclear power plants was swept off the table, and they even decided to close the ones that were still in operation." He recalls with reflection: "In education and research, nuclear energy has become almost a buzzword. Even the word nuclear had to be removed from the name of the department. Instead, we were merged with particle and plasma physics. The students changed direction, the education of nuclear engineers and the funding of research projects was reduced to almost zero. Today, seven of the twelve Swedish nuclear power units that were once in operation have been closed down.

"This situation has presented me with a serious dilemma. Is it worth continuing to fight in a country that has turned its back on nuclear power, or is it worth changing careers at the age of 57? Or would it be better to use the knowledge I had acquired in Hungary and gained in Scandinavia for the benefit of my own country? So the idea of returning home and getting involved in the development of Paks II logically came up. The problem was that my family - my wife and our sons, who were in their twenties by then - had put down roots in Sweden, and it was not realistic for them to come with me. Now I feel very comfortable professionally in Paks and, looking back, I made a difficult but good decision in 2017. However, I miss the family very much. Although I commute 2000 km between 'home' and 'here at home' several times a year, my fate proves that there is always a way home, even if it is sometimes long and sometimes bumpy..."

József Bánáti's scientific work is marked by nearly 80 scientific papers, conference proceedings and research reports. In addition, there are over 40 publications in which other researchers cite his achievements.

But what is Deterministic Safety Assessment?

Following this, József Bánáti will explain in more detail what the work of the team he leads in the Paks II project involves. "My position is the DSA area manager. In Deterministic Safety Assessment, the word 'safety' is clear what it means, but I would expand the word 'deterministic' with a counter-definition: what is deterministic is not probabilistic, i.e. not probabilistic. That would be Probabilistic Safety Assessment (PSA) - it's another existing discipline, it tells you what the frequency of occurrence of an event is, so what the probability of a consequence happening in the end is."

"In contrast, the DSA does not look at the odds, it says: if an initial event occurs, what will be the effects. This is where process modelling and running computer simulations come in. This means that, by applying the laws of physics in mathematical form and using numerical methods, we can predict the outcome, course and safety impact of any initial event for which we have enough information and which occurs in a system that we know exactly. In our case, this is the thermo-hydraulic and control system of VVER-type units, of which I have had the opportunity to study different versions several times in my career. Our task consists, to a large extent, in creating models of the main VVER 1200 equipment used in the Paks II reactors, designed by the designer, GIDROPRESS, the Podolsk institute of Roszatom, and in simulating the processes on the computer on the basis of the preliminary documentation and in carrying out safety analyses independent of the designer."

As József Bánáti says, GIDROPRESS has documented in its preliminary safety report how the system will react to all the emergency situations foreseen in the Hungarian Nuclear Safety Code, with a very wide safety margin. He says: "the key to the approach is that if several plants were to fail at the same time, how the redundant safety systems can handle the whole process and whether the criteria parameters (pressure, temperature, fuel cladding temperature, even dose rate) reach some limit or whether any physical barriers are breached."

An international summit was held in Hungary in May 2023

Finally, he concludes by talking with no secret pride about how the CAMP (Code Application and Maintenance Program) annual meeting of a major international collaboration was held in Budapest. "In the 1970s, under the coordination of the US Nuclear Regulatory Commission (US NRC), various thermohydraulic and neutron kinetic codes for modelling power plant processes were developed. Later, international institutions became involved in the development and application. Hungary joined the CAMP Convention in the 1990s. Currently, the code systems provided by CAMP are used worldwide, and we are using them for the analysis of the planned Paks II VVER 1200 units. The developers and users of the codes meet annually in different parts of the world to exchange experiences. It was therefore timely that our country should host such a conference. As a result of a real team effort, and with the sponsorship of Paks II, we finally managed to make it happen in Budapest this spring. Many thanks to the management and staff of Paks II for their enthusiastic work in organising this event. Nearly a hundred researchers, engineers, physicists and IT specialists attended the highly successful meeting, which included a number of presentations and ended with a visit to Unit 4 of the operating plant and a tour of the construction site of the new units in Paks."