Design bureau Hydropress is a Russian state construction office which works on the design, analysis, development, and production of nuclear power plant reactors, most notably the VVER range. OKB stands for experimental design bureau. OKB GIDROPRESS is a subsidiary of the state atomic energy corporation Rosatom.
In 1997, the global climate treaty known as the Kyoto Protocol was signed in Kyoto, Japan. This treaty symbolized the fact that the world had finally “warmed up” to the threat of global warming. Countries unanimously pledged to reduce carbon dioxide (CO2) emissions and greenhouse gases in the atmosphere. Coal, the major energy source of CO2 emissions, contributed 25 percent of global energy consumption. Something had to change.
But change was painstakingly slow. In 2017, coal made up 27.6 percent of global energy consumption. Renewables were making progress, but the earth was warming up faster than before.
That same year, the world’s first full startup of a Generation III+ nuclear reactor, the VVER-1200, a water-moderated, watercooled reactor, happened in Novovoronezh in Central Russia.
There is a connection here: the still-persistent reliance on coal and fossil fuels today is a pressing problem. The VVER-1200 is a small yet significant part of the solution.
To combat the growing threat of climate change, the International Energy Agency (IEA) has estimated that by 2040, 84 percent of all energy must come from low-carbon sources. This marks a significant jump from the current value of 35 percent and one that cannot be met by renewables alone. To tackle the looming climate change threat, the scientific community agrees an energy plan inclusive of all carbon-free sources is needed.
Enter the nuclear option. Nuclear energy is still the best available source of continuous, carbon-free electricity and can play a significant role in meeting these aggressive energy targets. To produce one kilowatt hour (KWh) of electricity, the emissions from nuclear power is 40 times less than burning coal for the same amount of electricity. Nuclear energy is also the safest energy source per terawatt hour (TWh) and the most environmentally friendly, contributing the same amount of emissions as offshore wind energy and significantly less than hydro and solar power.
But the nuclear industry is at a crossroads. Most of the current reactors are reaching the end of their 40-year lifecycle and are not economical to operate. More importantly, their safety systems are not up to post-Fukushima standards. Newer technology like small modular reactors (SMR) are incredibly promising but unproven, unlicensed and not yet under construction.
This is where the role of Generation-III+ reactors like the VVER-1200 is amplified in the fight against climate change. Designed with some of the most sophisticated engineering simulation in any industry, the VVER-1200 is a ready answer to the immediate threat of climate change and can help meet the world’s carbon-free energy requirements.
Today, VVER-1200 reactors are operating or under construction in a handful of countries, primed to play an important role in lowering emissions. Better, safer and more economical than Generation III reactors, the Generation III+ reactor comes at a significant time for the nuclear industry.
The VVER-1200, a thermal neutron reactor, is the latest reactor from OKB GIDROPRESS, the Russian state nuclear agency with 70 years of experience in operating and constructing nuclear plants. An update from the popular VVER-1000 design, VVER-1200 reactors address the two main factors hampering nuclear adoption today: safety and economics.
The world’s first Generation III+ reactor, the VVER-1200 is a specialized design of the pressurized water reactors (PWR) and provides improved performance and cost efficiency. Boasting a 20-percent higher power capacity, a 60-year service life, 18-month refueling cycle, complete factory manufacturing and 30 to 40 percent less personnel due to automation, VVER1200 reactors lead to better economics.
But where the reactor really shines is where it really should: safety. The VVER reactor family is already known for their safety with 1,000 reactor years of fail-safe operation. The new VVER-1200 designs are equipped with an extensive combination of active and passive safety systems designed to meet all post-Fukushima safety requirements from the International Atomic Energy Agency (IAEA). The possibility of an emergency failure of a VVER-1200 reactor is about one per few thousand years.
The VVER-1200 reactors can withstand the worst of natural disasters, including earthquakes greater than intensity 8 on the Medvedev-Sponheuer-Karnik (MSK-64) scale, aircraft impacts, flooding and tornadoes. The state-of-the-art safety systems are designed on a “defense-in-depth” concept, providing multiple barriers and isolation systems to confine fission products in case of an accident and minimize damage.
Passive heat removal is the key to this improved safety. The reactors do not depend on external power for the critical safety systems, ensuring protection against a complete blackout. A core catcher under the reactor protects against core meltdown. Double containment with a ventilated gap protects against accidental radioactive release to the environment. All these systems exist in addition to the active safety systems, providing four trains of safety systems. The safety systems offer guaranteed protection delivering termination of nuclear reaction, continuous heat removal and containment of nuclear reaction.
Think of how difficult it is to inspect and test a nuclear reactor in the design stage: the magnitude of the reactor, the components, the operation, and the fission. Once sealed, it is impossible to test and measure the internal operating performance.
With years of extensive reactor design experience, OKB GIDROPRESS knew their best chance to successfully design a new reactor system with improved safety and cost economics relied on a comprehensive digital twin – a “virtual reactor model.” The manufacturer had an established simulation process built in Simcenter™ STAR-CCM+™ software, the computational fluid dynamics (CFD) tool from Siemens Digital Industries Software. The virtual reactor model enabled the engineers at OKB GIDROPRESS to efficiently and accurately model the performance of all aspects of the nuclear reactor’s operation.
The simulations helped the engineers at OKB GIDROPRESS guarantee extreme fuel reliability, higher availability and improved performance. The result is a modern reactor that is safe and economical.
The world’s first Generation III+ nuclear reactor was born together with one of the world’s largest engineering simulation models, created in Simcenter STAR-CCM+.
Vasilii Volkov, design engineer at OKB GIDROPRESS, is one of the chief architects of the simulations behind the VVER-1200. “We do CFD simulations with Simcenter STAR-CCM+ to make the reactors better, cheaper and safer,” says Volkov. “The simulations help us optimize the thermohydraulic behavior, understand failures and design faster.”
Volkov’s team has used Simcenter STARCCM+ for years. For the VVER-1200, OKB GIDROPRESS pushed the code to its limits, modeling different equipment in the reactor. The most important simulation is modeling the first primary circuit of the reactor. The primary circuit is incredibly complex and provides the first line of cooling for the reactor core using water to transfer all heat from the core. The integrity of the primary circuit performance is the most critical aspect of reactor design, one which would be impossible without simulation.
To accurately assess the primary circuit performance, OKB GIDROPRESS developed one of the industry’s largest CFD simulation models. The model included every component of the primary circuit in detail and is the only model in the world to include the real profile of the pumps and the wheel rotation. Approximations and simplifications were kept to a bare minimum. Capturing the reactor geometry accurately for simulation was crucial. The geometry preparation and meshing tools in Simcenter STAR-CCM+ proved more than capable. The incredibly high-fidelity reactor’s comprehensive digital twin clocked in just shy of one billion computational cells and included multiphysics simulation of every aspect of the primary circuit.
“Simcenter STAR-CCM+ is the only CFD code that allows us to create simulations with a mesh size of one billion cells with ease and accuracy,” says Volkov. “Previously, it took us half a year to build a mesh. Now with Simcenter STAR-CCM+, the whole process takes about a week to mesh and analyze.”
The unsteady simulations of the primary circuit showed good agreement with experimental and measured data and significantly reduced the design time for the primary circuit. The steam generator was created based on previous designs, confirmed and improved with CFD simulations.
The reactor’s comprehensive digital twin helped OKB GIDROPRESS to virtually analyze the full performance of the primary circuit. Pressure, temperature and flow of the coolant, mixing efficiency, impact of pumps and steam generator were all confirmed. In addition, simulations also provided performance insights and areas of improvement that would not have been available from experimental data. The ability to virtually visualize and analyze every aspect of the primary circuit performance in detail helped accelerate the reactor design and delivered the safest Generation III+ reactor on the market.
With hundreds of components and personnel working together on a complex reactor design, it was crucial to streamline and manage the process every step of the way to design faster. To deliver on this, OKB GIDROPRESS used Teamcenter® software from Siemens for product lifecycle management (PLM) at every design step. Everything from design to test, 2D sketches to 3D models, and simulations to experiments were managed with a central platform in Teamcenter, allowing information to flow smoothly between different stages of product design. To meet the challenge of better reactor economics, shortening the design cycle plays a key role and the combination of Simcenter and Teamcenter provided OKB GIDROPRESS with the tools to achieve this. Simcenter and Teamcenter are a part of Xcelerator, a comprehensive and integrated portfolio of software and services from Siemens.
The design, construction and commissioning of a new reactor requires extensive digital simulation, both to accelerate the lengthy design process and demonstrate its safety and economic viability. Simulation also helps speed up the lengthy licensing process. Using simulation, OKB GIDROPRESS has delivered the immediate future of nuclear energy with their VVER-1200 reactors.
Extending the VVER-1200 design, OKB GIDROPRESS have also introduced the VVER-TOI (typical optimized with enhanced information) design with the first plant in construction in Russia. Designed with the same simulation process in Simcenter, the VVER-TOI delivers increased power and cooling reliability, lower construction and operating costs, a 72-hour grace period for passive safety systems and 40-month construction time. Together, the VVER-1200 and VVER-TOI are helping reduce CO2 emissions and deliver on our energy future.
“For the last 10 years, CFD simulations have helped OKB GIDROPRESS develop new equipment and maintain our leadership in the nuclear industry,” says Volkov. “With Simcenter and Teamcenter, we can make better, more efficient reactors faster.”