Analysis of Core Equipment for Air Purification in Nuclear Power Plants: Selection and Application of Air Filters
As a high-safety-level energy facility, the air purification system of a nuclear power plant is directly related to nuclear safety, the stable operation of equipment, and the health of personnel. It is necessary to adopt a combined solution of “multi-stage filtration + functional segmentation” to address complex pollutants, including radioactive aerosols, harmful gases, and dust particles. The following are the types, functions, and application scenarios of core air filters in nuclear power plant air purification, which are explained in combination with industry standards and technical characteristics:
I. Pre-treatment filters: Coarse/medium efficiency filtration, the first line of defense
Coarse filter (G1-G4 grade, EN 779 standard)
Core function: Intercept large particles of dust (≥5μm), hair, fibers, and other impurities in the air, prevent premature clogging of subsequent high-precision filters, extend their service life, and reduce system operating costs.
Filter materials: Commonly used are polyester fibers, non-woven fabrics, metal meshes, etc. In some working conditions, flame-retardant materials are selected (to meet the fire protection requirements of nuclear power plants).
Scénarios d'application
Pre-treatment of intake air for the ventilation system in conventional areas of nuclear power plants (such as offices and auxiliary workshops);
Primary filtration for the ventilation and air conditioning (HVAC) systems of the nuclear island and conventional island, protecting equipment such as fans and heat exchangers.
Transitioning from pre-treatment, the next crucial step in air purification is medium efficiency filtration. Medium efficiency filters (F5-F9 grade, EN 779 standard) play a specific role in this process:
Filter materials: superfine glass fiber, polyester-coated fiber, etc. Some adopt a folded structure to increase the filtration area.
Scénarios d'application
Intermediate filtration for ventilation in areas such as the auxiliary plant of the nuclear island and the steam turbine room of the conventional island;
The pretreatment stage of the ventilation system in the nuclear power plant laboratory and control room is used to prevent fine dust from affecting precision instruments.
After medium efficiency filtration, high-precision core filtration becomes vital for nuclear safety. This next section details high-efficiency and ultra-high-efficiency filters, which are the key to radioactive protection:
High-efficiency filters (HEPA, H10-H14 grades, EN 1822 standard)
Core functions: Intercepting sub-micron particles (≥0.3μm), with a filtration efficiency of ≥99.9% for radioactive aerosols (such as nuclear fission products, radioactive dust) (H13 grade), it is the core equipment for radioactive protection in nuclear power plants.
Filter material: Superfine glass fiber filter paper (such as borosilicate glass fiber), with a folded structure, combined with a frame (aluminum alloy, stainless steel) with excellent sealing performance to prevent air leakage.
Scénarios d'application
Nuclear island containment ventilation system (filtering radioactive aerosols and preventing their diffusion under normal operation and accident conditions);
Exhaust air filtration in radioactive waste treatment workshops and nuclear fuel operation areas;
The “purification air shower room” at the personnel entrance and exit is equipped with air supply filtration to prevent people from carrying radioactive particles outside.
2. Ultra-high efficiency filters (ULPA, U15-U17 grade, EN 1822 standard)
Core function: Filtration efficiency for extremely fine particles (≥0.12μm) is ≥99.9995% (U15 grade), suitable for scenarios with extremely high requirements for cleanliness and radioactive protection, further enhancing filtration accuracy.
Filter material: Finer glass fiber filter paper, combined with high-efficiency sealant (such as silicone sealant), and the frame is made of stainless steel (corrosion-resistant and radiation-proof).
Scénarios d'application
Air supply filtration for the main control room of the nuclear power plant and the control room of nuclear safety-level equipment (to ensure that precision instruments are not contaminated by dust and radioactivity);
Local purification of key equipment areas such as nuclear reactor coolant pumps and steam generators;
Ventilation and filtration in the radioactive sample analysis laboratory (to protect laboratory personnel and equipment).
Iii. Special Function Filters: Specifically designed for treating harmful pollutants
Activated carbon filter (Chemical adsorption type)
Core function: Adsorb harmful gases in the air (such as radioactive iodine, chlorine, formaldehyde, acidic gases, etc.), especially for radioactive iodine isotopes (such as I-131) that may be released under nuclear power plant accident conditions. It is a key device for chemical protection.
Filter material: Impregnated activated carbon (such as activated carbon impregnated with potassium iodide and triethylenediamine), enhancing the adsorption capacity for specific gases; Some parts adopt a honeycomb structure to enhance adsorption efficiency and service life.
Scénarios d'application
Nuclear island containment exhaust system (in accident conditions, adsorbs radioactive iodine to prevent it from being discharged into the atmosphere)
Ventilation and filtration in radioactive laboratories and nuclear fuel storage areas;
Nuclear power plant exhaust gas treatment system (used in combination with HEPA filters to achieve dual filtration of “particles + gas”).
2. Metal fiber filter (High-temperature resistant/corrosion-resistant type
Core functions: Resistant to high temperatures (up to over 400℃), high pressures, and corrosive gases, intercepting dust and radioactive particles in high-temperature flue gas, suitable for extreme working conditions.
Filter material: Stainless steel fibers (such as 316L, 304 stainless steel), processed by sintering, featuring excellent air permeability and mechanical strength, and can be repeatedly cleaned and reused.
Scénarios d'application
Exhaust filtration of the reactor containment spray system in nuclear power plants (particle filtration in high-temperature and high-pressure environments under accident conditions);
High-temperature flue gas filtration in the nuclear waste incineration treatment workshop;
Pre-treatment filtration of the flue of the conventional island boiler (intercepting high-temperature dust to protect subsequent equipment).
3. Iodine adsorber (Special radioactive gas filtration)
Core function: Specifically designed for the adsorption of radioactive iodine and its compounds (elemental iodine, organic iodine), with a filtration efficiency of ≥99.97%, it is a core device for the protection of radioactive gases in nuclear power plants (often combined with HEPA filters to form a “HEPA + iodine adsorber” unit).
Filter material: Impregnated activated carbon (such as activated carbon impregnated with silver nitrate or potassium iodide), which fixes radioactive iodine through chemical reactions to prevent its desorption.
Scénarios d'application
Nuclear island containment exhaust system (iodine adsorption under normal operation and accident conditions)
Ventilation and filtration for nuclear fuel reprocessing workshops and radioactive iodine laboratories;
Terminal filtration at the atmospheric emission outlet of nuclear power plants (to ensure that the emitted gas complies with national standards such as GB 6249).
Iv. Core Selection Principles for Nuclear Power Plant Filters
Safety grade matching: Nuclear safety grade filters (such as HEPA and iodine adsorbers used in containment) need to be certified by international nuclear safety standards (such as ASME AG-1, ISO 16890) to ensure reliability under accident conditions;
Filtration efficiency classification: Select the appropriate grade based on the degree of regional pollution (for example, G4/F8 for conventional areas and H13/U15 for radioactive areas) to avoid energy waste caused by excessive filtration.
Environmental resistance performance: It needs to withstand the high temperature, high humidity, radiation, and corrosive environment of nuclear power plants. Stainless steel and flame-retardant materials are preferred for the frame and materials.
Sealing and leak detection: All filters must have excellent sealing performance. After installation, they must pass the PAO leak detection test (EN 1822 standard) to prevent radioactive particle leakage.
Lifespan and maintenance: Prioritize filters with replaceable filter materials to reduce replacement costs. At the same time, it should have an online monitoring function (such as differential pressure monitoring) to promptly warn of filter blockage.
Résumé
The selection of filters for the air purification system of nuclear power plants should focus on the three core demands of “particle filtration + gas adsorption + adaptation to extreme working conditions”, forming a multi-level combination scheme of “coarse efficiency → medium efficiency →HEPA/ULPA→ activated carbon/iodine adsorber”. Among them, the HEPA filter is the core of radioactive particle protection, and the iodine adsorber is the key to radioactive gas protection. Together with the pretreatment filter and the special function filter, they jointly build the air safety barrier of the nuclear power plant, ensuring the safety of personnel, equipment, and the environment.
As a high-safety-level energy facility, the air purification system of a nuclear power plant is directly related to nuclear safety, the stable operation of equipment, and the health of personnel. It is necessary to adopt a combined solution of “multi-stage filtration + functional segmentation” to address complex pollutants, including radioactive aerosols, harmful gases, and dust particles. The following are the types, functions, and application scenarios of core air filters in nuclear power plant air purification, which are explained in combination with industry standards and technical characteristics:
I. Pre-treatment filters: Coarse/medium efficiency filtration, the first line of defense
Coarse filter (G1-G4 grade, EN 779 standard)
Core function: Intercept large particles of dust (≥5μm), hair, fibers, and other impurities in the air, prevent premature clogging of subsequent high-precision filters, extend their service life, and reduce system operating costs.
Filter materials: Commonly used are polyester fibers, non-woven fabrics, metal meshes, etc. In some working conditions, flame-retardant materials are selected (to meet the fire protection requirements of nuclear power plants).
Scénarios d'application
Pre-treatment of intake air for the ventilation system in conventional areas of nuclear power plants (such as offices and auxiliary workshops);
Primary filtration for the ventilation and air conditioning (HVAC) systems of the nuclear island and conventional island, protecting equipment such as fans and heat exchangers.
Transitioning from pre-treatment, the next crucial step in air purification is medium efficiency filtration. Medium efficiency filters (F5-F9 grade, EN 779 standard) play a specific role in this process:
Filter materials: superfine glass fiber, polyester-coated fiber, etc. Some adopt a folded structure to increase the filtration area.
Scénarios d'application
Intermediate filtration for ventilation in areas such as the auxiliary plant of the nuclear island and the steam turbine room of the conventional island;
The pretreatment stage of the ventilation system in the nuclear power plant laboratory and control room is used to prevent fine dust from affecting precision instruments.
After medium efficiency filtration, high-precision core filtration becomes vital for nuclear safety. This next section details high-efficiency and ultra-high-efficiency filters, which are the key to radioactive protection:
High-efficiency filters (HEPA, H10-H14 grades, EN 1822 standard)
Core functions: Intercepting sub-micron particles (≥0.3μm), with a filtration efficiency of ≥99.9% for radioactive aerosols (such as nuclear fission products, radioactive dust) (H13 grade), it is the core equipment for radioactive protection in nuclear power plants.
Filter material: Superfine glass fiber filter paper (such as borosilicate glass fiber), with a folded structure, combined with a frame (aluminum alloy, stainless steel) with excellent sealing performance to prevent air leakage.
Scénarios d'application
Nuclear island containment ventilation system (filtering radioactive aerosols and preventing their diffusion under normal operation and accident conditions);
Exhaust air filtration in radioactive waste treatment workshops and nuclear fuel operation areas;
The “purification air shower room” at the personnel entrance and exit is equipped with air supply filtration to prevent people from carrying radioactive particles outside.
2. Ultra-high efficiency filters (ULPA, U15-U17 grade, EN 1822 standard)
Core function: Filtration efficiency for extremely fine particles (≥0.12μm) is ≥99.9995% (U15 grade), suitable for scenarios with extremely high requirements for cleanliness and radioactive protection, further enhancing filtration accuracy.
Filter material: Finer glass fiber filter paper, combined with high-efficiency sealant (such as silicone sealant), and the frame is made of stainless steel (corrosion-resistant and radiation-proof).
Scénarios d'application
Air supply filtration for the main control room of the nuclear power plant and the control room of nuclear safety-level equipment (to ensure that precision instruments are not contaminated by dust and radioactivity);
Local purification of key equipment areas such as nuclear reactor coolant pumps and steam generators;
Ventilation and filtration in the radioactive sample analysis laboratory (to protect laboratory personnel and equipment).
Iii. Special Function Filters: Specifically designed for treating harmful pollutants
Activated carbon filter (Chemical adsorption type)
Core function: Adsorb harmful gases in the air (such as radioactive iodine, chlorine, formaldehyde, acidic gases, etc.), especially for radioactive iodine isotopes (such as I-131) that may be released under nuclear power plant accident conditions. It is a key device for chemical protection.
Filter material: Impregnated activated carbon (such as activated carbon impregnated with potassium iodide and triethylenediamine), enhancing the adsorption capacity for specific gases; Some parts adopt a honeycomb structure to enhance adsorption efficiency and service life.
Scénarios d'application
Nuclear island containment exhaust system (in accident conditions, adsorbs radioactive iodine to prevent it from being discharged into the atmosphere)
Ventilation and filtration in radioactive laboratories and nuclear fuel storage areas;
Nuclear power plant exhaust gas treatment system (used in combination with HEPA filters to achieve dual filtration of “particles + gas”).
2. Metal fiber filter (High-temperature resistant/corrosion-resistant type
Core functions: Resistant to high temperatures (up to over 400℃), high pressures, and corrosive gases, intercepting dust and radioactive particles in high-temperature flue gas, suitable for extreme working conditions.
Filter material: Stainless steel fibers (such as 316L, 304 stainless steel), processed by sintering, featuring excellent air permeability and mechanical strength, and can be repeatedly cleaned and reused.
Scénarios d'application
Exhaust filtration of the reactor containment spray system in nuclear power plants (particle filtration in high-temperature and high-pressure environments under accident conditions);
High-temperature flue gas filtration in the nuclear waste incineration treatment workshop;
Pre-treatment filtration of the flue of the conventional island boiler (intercepting high-temperature dust to protect subsequent equipment).
3. Iodine adsorber (Special radioactive gas filtration)
Core function: Specifically designed for the adsorption of radioactive iodine and its compounds (elemental iodine, organic iodine), with a filtration efficiency of ≥99.97%, it is a core device for the protection of radioactive gases in nuclear power plants (often combined with HEPA filters to form a “HEPA + iodine adsorber” unit).
Filter material: Impregnated activated carbon (such as activated carbon impregnated with silver nitrate or potassium iodide), which fixes radioactive iodine through chemical reactions to prevent its desorption.
Scénarios d'application
Nuclear island containment exhaust system (iodine adsorption under normal operation and accident conditions)
Ventilation and filtration for nuclear fuel reprocessing workshops and radioactive iodine laboratories;
Terminal filtration at the atmospheric emission outlet of nuclear power plants (to ensure that the emitted gas complies with national standards such as GB 6249).
Iv. Core Selection Principles for Nuclear Power Plant Filters
Safety grade matching: Nuclear safety grade filters (such as HEPA and iodine adsorbers used in containment) need to be certified by international nuclear safety standards (such as ASME AG-1, ISO 16890) to ensure reliability under accident conditions;
Filtration efficiency classification: Select the appropriate grade based on the degree of regional pollution (for example, G4/F8 for conventional areas and H13/U15 for radioactive areas) to avoid energy waste caused by excessive filtration.
Environmental resistance performance: It needs to withstand the high temperature, high humidity, radiation, and corrosive environment of nuclear power plants. Stainless steel and flame-retardant materials are preferred for the frame and materials.
Sealing and leak detection: All filters must have excellent sealing performance. After installation, they must pass the PAO leak detection test (EN 1822 standard) to prevent radioactive particle leakage.
Lifespan and maintenance: Prioritize filters with replaceable filter materials to reduce replacement costs. At the same time, it should have an online monitoring function (such as differential pressure monitoring) to promptly warn of filter blockage.
Résumé
The selection of filters for the air purification system of nuclear power plants should focus on the three core demands of “particle filtration + gas adsorption + adaptation to extreme working conditions”, forming a multi-level combination scheme of “coarse efficiency → medium efficiency →HEPA/ULPA→ activated carbon/iodine adsorber”. Among them, the HEPA filter is the core of radioactive particle protection, and the iodine adsorber is the key to radioactive gas protection. Together with the pretreatment filter and the special function filter, they jointly build the air safety barrier of the nuclear power plant, ensuring the safety of personnel, equipment, and the environment.
