On August 28, the American company NuScale Power received approval from the US Nuclear Regulatory Commission for the design of the first small modular reactor. The current model is designed for 50 megawatts of power, and already in 2022 an application for a 60 megawatt reactor will be considered.
Startup NuScale Power calls for abandoning large reactors, the basis of modern nuclear power plants. Instead, developers are proposing small modular reactors that can be manufactured in a factory and then transported to a power plant construction site. A typical nuclear power plant of this type will consist of 12 small reactors. According to the developers, small reactors are much safer than conventional ones. In addition, they can be used in small towns, industrial facilities and submarines.
Any modern nuclear power plant is not only reactors, a power unit, but also the corresponding infrastructure: shops and production facilities serving the station. The total number of NPP personnel reaches 1000 people. If on the territory of the station there is also a complex for the processing of radioactive waste, storage of spent fuel, etc., then the staff may be larger.
The disadvantages of large NPP-type facilities are the high cost of construction and maintenance, the inability to promptly change something in the design, the complexity of operation and technical support. Mini reactors can make a difference for the better.
The NuScale Power reactor is a steel cylinder 23 meters high and 5 meters wide. Inside are uranium fuel rods that use a nuclear chain reaction to heat the water in the internal circuit. The heated water transfers the temperature to the external steam circuit through a heat exchanger. The steam drives a turbine that generates electricity. During operation, the steam cools down and the water droplets again fall back into the internal circuit.
The small reactor is designed with a passive cooling system. The hot water rises through the heat exchange coils, cools and sinks back to the fuel rods. This approach saved the design of the reactor from pumps and additional moving elements that could fail.
In the event of an emergency, the reactor itself will drown out the nuclear reaction using control rods. The exchange of neutrons stops and the nuclear chain reaction stops. If the supply of electricity suddenly stops, the control rods are automatically triggered by gravity.
To improve safety, small modular reactors will be installed in special cooling pools, which are planned to be placed below ground level in NPP buildings. In case of an emergency, the pools will cool down the reactors and remove excess heat. Since the reactors are small in size, less heat will need to be removed than in a large reactor. The developers believe that their products will generate no more than 1/8 of the amount of heat of standard reactors.
The company said: the application for the design of a small modular reactor was submitted to the US Nuclear Regulatory Commission on December 31, 2016, which is true . The actual consideration of the document began in March 2017. The regulatory body had to sendover 2 million pages of documentation. The next step after obtaining regulatory approval is to request a combined license for the construction and operation of the nuclear power plant.
And this is where a problem can arise. The fact is that a group of experts on the reactor safety advisory board of the US Nuclear Regulatory Commission discovered a potential problem in the NuScale Power reactors. For cooling, boron is added to the water, which absorbs neutrons. However, during the transition to the vaporous state, the concentration of the substance decreases significantly. When boron-poor condensate enters the core, it can provoke an acceleration of the nuclear reaction. In addition, the experts considered the weak link in the steam generator located inside the reactor vessel. According to scientists, the mechanism can be subjected to dangerous vibrations that can destroy the structure of the steam generator.
Nevertheless, these issues can be solved, and NuScale Power already has its first commercial customer. Utah Associated Municipal Power System is poised to build a nuclear power plant with NuScale Power reactors at Idaho National Laboratory. The $ 6.1 billion project has 12 small modular reactors and is due for completion in 2030. A site of 13 hectares was prepared for construction.
