Rosatom scientists have completed a key stage of reactor tests on laboratory fuel samples for a high-temperature gas-cooled reactor (HTGR). Russia views HTGRs as important to future plans for the production of hydrogen. An engineering nuclear power station (AETS -Atomnoi EnregoTekhnologicheskoi Stantsii) based on HTGRs is being developed by nuclear utility Rosenergoatom (part of Rosatom) as part of an investment project to create domestic technologies for the large-scale production and consumption of hydrogen and hydrogen-containing products.
Reactor tests of laboratory samples of HTGR fuel, which started in early 2022, were conducted in parallel at the experimental facilities of two key research centres – at the SM-3 reactor on the site of the Scientific Research Institute of Atomic Reactors (NIIAR) in Dimitrovgrad (Ulyanovsk region) and at the IVV-2M research reactor of the Institute of Reactor Materials (Sverdlovsk branch of the NN Dollezhal Research & Development Institute of Power Engineering – NIKIET)
By the end of 2023, in the IVV-2M reactor, one of the batches of laboratory samples developed and manufactured by the AA Bochvar Research Institute of Inorganic Materials (VNIINM - part of Rosatom fuel company TVEL) and fuel components developed and manufactured by JSC Luch (scientific division of Rosatom), achieved a burnout of 11-12% of heavy atoms. This effectively corresponded to the design values of burnout for HTGR fuel. During the entire long irradiation cycle of the laboratory samples, the temperature conditions of fuel were maintained in the range of 1000-1200° C, which met the requirements for HTGR fuel from the main designer of the reactor unit, OKBM Africantov (part of Rosatom’s engineering division).
The first one was a Soviet-designed experimental reactor ABTU-15 and a pilot plant ABTU-ts-50 with a VGR-50 reactor. It was designed for power generation and radiation-induced modification of materials (polyethylene, wood, and others). In the 1970s, a pilot high-temperature gas-cooled reactor VG-400 was developed to generate electricity and high heat energy. This was followed by the development of modular HTGRs, such as the VGM-200 pebble-bed reactor and MVGR-GT power unit with a closed-cycle gas turbine. That was the time when Soviet engineers developed the conceptual design of a VTGR-10 small power reactor and principles of combining nuclear and hydrogen technologies, which implied the use of hydrogen produced with nuclear power as a source of energy for industry, transport and households.
As to the AETS, it has a long history. In the 1980s, the Soviet government adopted a national hydrogen economy programme that provided for the development of HTGRs for energy and industrial processes. For example, the VG-400 reactor design was modified for the production of ammonia fertilisers. It was planned to build five plants with HTGRs but the plans were disrupted by the Soviet collapse. However, the idea to build a high-temperature gas-cooled reactor persisted to evolve into the development of a 600 MW reactor with a direct gas turbine cycle, which was underway from 1998 to 2012. General Atomics (US), Framatome (France) and Fuji Electric (Japan) participated in its development.
Today, development of an advanced AETS with a high-temperature helium-cooled reactor and a hydrogen plant has reached the front end engineering design phase, and site selection is underway. The principal difference of the current design compared with the earlier ones is that a hydrogen production plant is an integral part of the nuclear station. The final product of the station will be not heat but hydrogen, which can be stored, transported and sold to customers.
Rosatom said engineers had to make several tough choices. For example, they decided not to use any foreign technology and to use exclusively Russian technology. For this reason, a carbon-free steam methane reforming (SMR) process was chosen instead of electrolysis as a preferred hydrogen production method. The SMR process has long been mastered in Russia, which also has plenty of both methane and water.
Another choice was whether to use an intermediate circuit for transferring heat to the hydrogen plant. It was decided for safety reasons to physically separate the hydrogen-producing and reactor circuits with an intermediate helium circuit. One of the next questions was how far apart the reactor and hydrogen-producing circuits should be to ensure that no accident at the hydrogen plant could damage the reactor.
It is assumed that the HTGR will have a thermal capacity of 200 MW. The hydrogen plant will be capable of producing 110,000 tonnes of hydrogen a year. Since the AETS will have four HTGRs and, accordingly, four hydrogen plants, the station’s total capacity will be 800 MW of thermal energy and 440,000 tonnes of hydrogen a year.
The temperature of the helium will be 330° ? at the reactor inlet and 850° ? at the outlet. Fuel elements are being designed to meet inherent safety requirements: the reactor must be capable of shutting down without triggering shutdown systems, and residual heat removal from the shut-down reactor needs no external energy source or staff involvement. Another requirement is to make the reactor more powerful given the existing reactor vessel fabrication capabilities. As a result, the developers chose to use block-type fuel assemblies as fuel.
The project is expected to be brought to the investment stage in 2024 as the technical design of the reactor unit, declaration of intent and other documents will be prepared by then. The design and licensing stages of the project are scheduled to be completed in 2028, followed by construction of the first unit, which is expected to be completed in 2032. The remaining units are planned to be built in 2035.
Image: High-temperature gas-cooled reactor (HTGR)
