A team of experts from the National Centre for Nuclear Research, based on the experience of the MARIA research reactor operating in Świerk for 50 years and the Japanese High Temperature Engineering Test Reactor (HTTR), developed a concept for the Polish research and demonstration high-temperature reactor HTGR-POLA (POLish Atomic). The project is currently at a high level of technological readiness, including the basic design with a significant part of the so-called Preliminary  Safety Report (PSR) necessary for its licensing and further design work, commencement of construction and commisioning. This reactor will become the basis for commercial reactors to be used in Polish industry.

Since the 2015 Paris Agreement, there has been growing public pressure to reduce global warming by limiting greenhouse gas emissions. This means changing the approach to generating electricity and heat, which has so far been mostly generated using fossil fuels. One solution to this problem is the nuclear industry, which does not emit greenhouse gases into the atmosphere except for water vapor, which circulates in the atmosphere in a closed cycle anyway. Nuclear fuel for HTGR reactors is extremely efficient and consequently generates small amounts of waste, which is currently safely stored in appropriate places or processed for reuse. For example, all the waste from all the nuclear power plants in France would fit on the surface of one football pitch.

According to the Polish Nuclear Power Program (PNPP), by 2043, 4-6 so-called light-water nuclear units should be built in our country, producing 6-9 GW of electric power, which provides about 25% of the current demand. However, decarbonization of the energy sector must include not only electricity production, but also other sectors, such as heat for home heating and high-temperature steam necessary in industrial processes. Achieving it also requires the implementation of smaller nuclear units (so-called small modular reactors - SMR). While municipal heat can be produced by modular light-water reactors, high-temperature steam requires the use of high-temperature gas-cooled reactors (HTGR).

The production of high-temperature steam for Polish industry is currently burdened with a very high carbon footprint. The fifteen largest Polish chemical plants require at least 6.5 GW of thermal power in the form of steam at a temperature of 400-550 degrees Celsius in a continuous and controllable manner. The Polish energy system employs over 60 of 200 MW class units built in the 1970s, of which 47 are still operating after modernization: 38 for hard coal and 9 for lignate. The average age of these units is over 50 years and they will soon reach their technological limit. In accordance with Poland's commitments to reduce greenhouse gas emissions and due to the age of these units, they should be replaced by more ecological solutions by 2035.

According to PNPP, the introduction of large nuclear power plants with light water reactors will mean strengthening energy security, as it will effectively diversify the fuel base and directions of energy supply and replace the aging fleet of high-emission coal units. The authors of the program also emphasize that nuclear power plants are the cheapest sources of energy when taking into account the full cost calculation (investor, system, network, environmental, health, etc.) and the factor of long operating time after the depreciation period. This applies to both individual and business recipients, and in particular secures the development of energy-intensive enterprises, including plants from the chemical and petrochemical industry requiring high steam temperatures, i.e. HTGR reactors.

Polish scientists and engineers from the National Centre for Nuclear Research (NCBJ) began research and design work more than ten years ago on the concept of a small high-temperature research reactor with a capacity of 30 MW thermal, which could serve as a technology demonstrator. Such a reactor, after conducting appropriate operational and safety tests, would be scaled up to a capacity of approx. 180 MW thermal and built in series, meeting the needs of local industry. This stage is crucial because there is currently no unit in Poland that would allow for gaining experience in operating commercial reactors. It is also necessary because the only currently operating commercial high-temperature reactor HTR-PM with an electrical capacity of 210 MW is located in China and was launched only in December 2023, although units of this type operated in the 1970s and 1980s in the USA and Germany.

In order to develop a new concept of a Polish high-temperature reactor, NCBJ implemented the HTR-PL research and development project in 2012-2015, which prepared the initial assumptions of the reactor project. In 2016, the Minister of Energy appointed the "Team for Analysis and Preparation of Conditions for the Implementation of High-Temperature Nuclear Reactors", which in 2018 presented a report estimating the demand of our industry for a fleet of several reactors with an average thermal power of 180 MW in the form of 230 tons/hour of steam at a temperature of 540 degrees Celsius and a pressure of 13.4 MPa. These results were independently confirmed by the European Gemini+ project coordinated by NCBJ in 2017-21 and by the National Strategic Program GOSPOSTRATEG-HTR co-financed by the National Center for Research and Development in 2019-2022. The subject of this last project was the preparation of legal, organizational and technical instruments for the use of high-temperature reactors in Poland. As a result, a so-called pre-concept of a research reactor project with a thermal power of 40 MW and a road map for the construction of prototype and serial commercial reactors were created.

The next step in the development of this concept was an agreement between the National Centre for Nuclear Research and the Ministry of Education and Science to implement a project in 2021-2024 devoted to creating a technical description of a high-temperature research reactor. The aim of this project, which will be completed in the autumn of 2024, is to prepare a basic design of the reactor and a PSR, which will become the basis for a future application to the Polish Atomic Energy Agency for a license for its construction, commisioning and operation. The next planned phases of activities are: preparation of a detailed (technical) design of the reactor (2 years), licensing (minimum 1 year), construction (4 years) and commisioning (6-12 months). As a stage of the implementation of the agreement, a conceptual design of the reactor was also prepared by the end of 2022, which specifies the principle of its operation, the assumptions of the construction of its core, the primary and secondary cooling circuits based on approximate calculations and technical analyses, as well as the research potential necessary to assess the materials used in the construction. The basic elements of this project were published by the NCBJ team in the prestigious nuclear energy journal "Nuclear Engineering and Design" in early 2024 and also entered into a special bulletin of the Nuclear Energy Agency (OECD agenda) and bulletins of the International Atomic Energy Agency.

High-temperature reactors use a chemically inert gas, helium, to collect heat from the core, which circulates at high pressure in a closed circuit through the reactor and steam generator. Uranium dioxide enriched from a few to a dozen or so percent in the fissile isotope U235 is used as fuel, and graphite is used as a moderator, i.e. a material for slowing down neutrons. All of these materials are resistant to high temperatures, which allows the production of steam at a temperature of even 950 degrees Celsius. This heat, as mentioned previously, can be used in chemical and petrochemical processes, as well as for highly efficient production of electricity in typical power generators and high-efficiency production of hydrogen. In addition, the high-temperature reactor has large safety margins ensured by the much higher resistance of the structure used to high temperatures, by a decrease in fuel reactivity with increasing temperature and by the minimal risk of penetration of decay products into the reactor systems. The latter is ensured, among others, by the use of special TRISO fuel in the form of a ball covered with, among others, a layer of porous pyrolytic carbon that retains these products and constitutes the so-called first safety barrier of the reactor. What is extremely important in industry, the reactor design allows for smooth regulation of its power. This also facilitates the system's operation in cooperation with renewable energy sources.

As part of the work, using simulations performed, among others, using the computational cluster available at the Świerk Computer Center (CIŚ), the thermal and radiological characteristics of the reactor components were determined, including fuel, structural components, radiation control systems and appropriate instrumentation. The work on the reactor components drew on the experience of Japanese teams under the cooperation agreement signed by the National Center for Nuclear Research with the Japan Atomic Energy Agency (JAEA) in November 2022. The prepared study includes a concept for using the reactor's power in conventional processes carried out by turbines, pumps, heat exchangers, reboilers (devices used to evaporate a liquid substance at the expense of heat transferred to it from another fluid), compressors and heat removal systems to the environment. These devices will not only allow for the production of industrial heat for the test chemical installation assumed in the project, but would also be able to provide electricity generation and office space heating for the campus of the National Center for Nuclear Research in Świerk. The implementation of the developed concept may also open up research opportunities in the production of new radioisotopes for medical purposes, materials research or industrial technologies.

The PSR report prepared as part of the project includes, in addition to a description of the nuclear facility itself, the assumptions of the integrated management system, a summary and assessment of the results of safety analyses, the scope of emergency operations, aspects of the facility's impact on the environment, waste management and the strategy and conditions for decommissioning the reactor.

The HTGR-POLA research reactor project is the first step towards the use of high-temperature reactors in the Polish chemical and petrochemical industry, which will significantly contribute to reducing domestic greenhouse gas emissions. Thanks to the expert knowledge and experience gathered at the National Centre for Nuclear Research in Świerk and the strategic agreement with the Japanese Atomic Energy Agency, which has an operating HTTR research reactor, a stable basis has been created for further steps in the reactor construction process and the implementation of this technology in the economy. Due to the significant intellectual contribution of up to 50% to the HTGR-POLA project by Polish scientists and designers and the involvement of Polish companies in its design and construction, the HTGR-POLA reactor may constitute a breakthrough in the Polish energy and chemical industry as well as become an export product for our country.