Safety systems of manufactured reactors
III+ generation
An unrivaled reactor with III+ generation safety system was launched, for the first time, at the Novovoronezh NPP in 2017
Safety
Gravity- and convection-type systems ensure safety without operator intervention and power supply
Reliability
Redundant emergency systems provide double protection
Environmental compatibility
Multiple cooling circuits prevent leaks even in case of severe accidents
Core safety factor
Emergency systems ensuring safety without power supply and human intervention.
Developed on the basis of 50 years of experience and key achievements of the Soviet and Russian nuclear power industry.
01
Instant stop
Rapid termination of a chain reaction using one of two redundant systems.
02
Autonomous cooling
Prevention of reactor overheating without power supply and human intervention.
03
72 h time reserve
Reactor plant resistance to fatal losses in unmanned conditions
Emergency protection system
0 sec
Detection of leak from the main coolant pipelines (MCP).
1 sec
Disabling of electromagnetic grips of absorbing rods. Gravity drop of absorbing rods into the core, chain reaction termination
10 sec
Automatic valve opening in the primary circuit due to a pressure drop. Boric acid solution supply from ECCS accumulators to the reactor core, rapid cooling.
20 sec
Activation of the emergency boron injection system to reduce pressure and/or terminate the chain reaction in case of a failure in rods drop into the core (provided power supply is available).
2 min
Gravity and atmospheric pressure supply of boric acid solution from PCFS accumulators No.1 and No.2 to the primary circuit (up to 1.5 hours).
1,5 h
Supply of solution from PCFS accumulators No.3 and No.4 (up to 3 hours).
3 h
Supply of solution from PCFS accumulators No.5 and No.6 (up to 8 hours).
8 h
Supply of solution from PCFS accumulators No.7 and No.8 (up to 24 hours).
24 h
- Supply of solution from accumulators of the third stage - PCFS equivalents in the VVER-TOI project (up to 72 hours).
- Operation of the hydrogen recombination system. Hydrogen afterburning within the power unit scope when hydrogen concentration sensors are triggered.
- When the sensors are triggered, the sprinkler system is activated. Aqueous solution spraying facilitates pressure drop and steam cooling within the power unit scope.
0 sec
1 sec
10 sec
20 sec
2 min
1,5 h
3 h
8 h
24 h
Severe accident core catcher
A core catcher is an optional component of the nuclear reactor containment, one of the passive nuclear safety systems. This structure is designed for confinement of the reactor molten core. In case of severe accidents, it prevents melt release outside the containment.
The core catcher was developed by Russian nuclear scientists and is one of the most important safety systems for cases of beyond design basis accidents. The core catcher vessel weighs over 160 tons. For its installation, a special equipment is used including a super-heavy lifting crane.
Autonomous reator cooling during three days
Autonomous core cooling systems serve to replenish the reactor with coolant during cooldown after shutdown, when feed water stops flowing into the core according to the standard procedure. Turbo-pumps ensure circulation by driving the steam released in the reactor itself. The system operates at any pressure.
Physical safety systems
Successive barriers to an accident and leakage of radioactive substances into environment make a multilayer reactor protection. The barriers are duplicated, have alternatives and are isolated from each other.
Barrier 1 - fuel pellet
A fuel pellet is manufactured at 100℃ to take on ceramic properties. Due to its absorbing ability, it reduces the excess reactivity margin in the reactor core.
Barrier 2 - fuel element cladding
The fuel element cladding is made of nuclear grade zirconium, has increased corrosion resistance, and prevents fission products release from zirconium tubes.
Barrier 3 - primary circuit
The primary circuit includes a reactor pressure vessel, headers and tubes of the steam generator primary circuit, pressurizerr, main coolant pipeline, RCPS spherical housing, etc. The design of this equipment prevents fission products release from the primary circuit.
Barrier 4 - containment
The containment consists of internal and external walls. The internal wall ensures tightness of the internal space.
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1 m
thickness of external reinforced concrete wall
60 years
resistance to corrosion and radiation exposure
Protection from external influences such as:
- earthquake of magnitude 8 points;
- floods;
- hurricanes and tornadoes with wind speeds up to 56 m/s;
- fall of an aircraft weighing up to 5 t;
- shock wave with a pressure of 30 kPa.
Sprinkler system
In the event of primary coolant leakage and pressure increase inside the containment, the system automatically sprays the boric acid solution, condenses the steam and reduces the pressure inside the containment.
Passive heat removal system
The system removes excess heat from the containment in case of beyond design basis accidents with loss of primary coolant; it operates in case of failure of emergency safety systems.
Hydrogen removal system
The system provides a high safety level during design basis and beyond design basis accidents at NPPs. The system equipment includes a series of passive autocatalytic hydrogen recombiners.
Core catcher
The core catcher is built under the reactor at its cavity bottom. It confines the reactor molten core.
Emergency core cooling system
The system consists of special accumulators with boric acid. In the event of maximum design basis accident, the chain reaction is suppressed by a large amount of boron-containing substance which absorbs neutrons very well.
Active safety systems
The systems are driven by power sources. They are triggered when one of the reactor parameters reaches normal values. Among the parameters, there are temperature, pressure, coolant flow rate, level and rate of power increase.
The active safety systems begin their operation long before development of an accident and serve as a preventive measure. When the active systems may not be triggered, the passive systems start their operation.
