NPP SAFETY: HOW THE "DEFENSE-IN-DEPTH" CONCEPT WORKS
2026-01-29 12:00:00 / News
4 Robust Protection Barriers
There are four primary physical barriers positioned between the nuclear fuel and the environment to contain radionuclides:
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Fuel Pellet: A durable pellet made of uranium dioxide that retains the majority of radionuclides generated during the nuclear fission process.
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Fuel Cladding: A hermetic zirconium alloy tube (cladding) for the fuel elements. It prevents fission products from escaping into the primary coolant (water).
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Reactor Pressure Vessel: High-strength steel walls. Before operation, the vessel undergoes hydraulic testing at 250 atmospheres to ensure superior airtightness.
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Containment Building: The outermost concrete shell of the reactor building. It is designed to localize all materials within the building, even in the event of a severe accident.
🚀 Modern Passive and Active Safety Systems
Modern NPP designs (Generation 3+) are equipped with additional safety systems that maintain plant stability even without human intervention:
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Sprinkler System: Designed to reduce pressure inside the containment building and condense steam.
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Core Catcher: In the event of a severe accident involving core melt, this specialized device captures and cools the molten material, preventing it from breaching the foundation.
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Conclusion: Due to these multi-layered safety systems, the radiation background around nuclear power plants remains at natural background levels and does not change.
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Hydrogen Recombination System: Eliminates hydrogen buildup within the building to prevent the risk of explosions.
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Passive Heat Removal System: Enables reactor cooling through natural circulation, even in the event of a total loss of external power supply.