This article examines the specific features of roofing works on buildings and structures of nuclear power plants. It provides a comparative analysis of the two main types of roof coverings: membrane (polymer) roofing and torch-applied (bitumen-polymer) roofing. It analyzes the regulatory requirements of NP-041-22, SP 17.13330.2017, fire-safety rules, and criteria for selecting a roofing system for different responsibility classes. The technological stages of roofing installation, quality-control requirements, and service lives are presented.
The roof is one of the most critical building elements, protecting building structures and interior spaces from atmospheric exposure. At facilities using nuclear energy (FUNE), roofing works are subject to increased requirements: reliability, durability (at least 30-50 years), maintainability, and, for strict-regime zones, decontaminability.
Nuclear power plants and related enterprises operate buildings of different safety classes, from the main reactor-building structure (class 1-2) to auxiliary administrative and amenity buildings (class 4). Depending on the safety class, structural features, and operating conditions, the roofing system is selected: membrane (polymer) or torch-applied (rolled bitumen-polymer). Each technology has its own advantages, limitations, and production requirements.
Regulatory Framework for Roofing Works at NPPs
Roofing works at facilities using nuclear energy are governed by the following documents:
• NP-041-22, Safety Requirements for Building Structures of Nuclear Power Plant Buildings and Structures, establishes safety classes for building structures, including roof coverings, and requirements for their durability and resistance to impacts.
• SP 17.13330.2017, Roofs (updated version of SNiP II-26-76), is the main document regulating the design and installation of all types of roofs.
• SP 118.13330.2022, Public Buildings and Structures, applies to roof requirements for administrative buildings.
• Fire Safety Rules in the Russian Federation (Resolution No. 1479) set requirements for the use of open flame when torch-applying rolled materials, which is especially relevant at controlled-access facilities.
• GOST R 51102-97 (for roofs in strict-regime zones) establishes decontaminability requirements for coatings if the roof may be subject to radioactive contamination.
NPP sites also have internal industry regulations that prohibit or restrict the use of open flame on operating power units. In such cases, preference is given to membrane roofing with mechanical or ballast fastening.
Comparative Analysis of Roofing Systems
Membrane (Polymer) Roofing
Membrane roofs are made of polyvinyl chloride (PVC), thermoplastic polyolefins (TPO), or ethylene-propylene-diene monomer rubber (EPDM). Installation is performed without open flame: sheets are welded with hot air (PVC, TPO) or bonded (EPDM).
Advantages of membrane roofing:
• High elasticity and resistance to temperature deformation and vibration.
• Durability: service life of 30-50 years (up to 50 years is claimed for TPO).
• Installation without open flame: possible to perform work on operating power units.
• High maintainability: local repair by welding.
• Low weight (1.2-2.0 kg/m²), with no need to strengthen structures.
• Resistance to aggressive media (boric acid, decontamination solutions).
Limitations:
• Higher cost (materials and labor) compared with two-layer bitumen systems.
• Requirement for a flat and strong substrate.
• PVC membranes are sensitive to bitumen, so compatibility with the substrate must be checked.
Torch-Applied (Bitumen-Polymer) Roofing
Torch-applied roofing is a multilayer system of rolled materials based on bitumen modified with polymers (styrene-butadiene-styrene, atactic polypropylene). Installation is carried out using gas burners (open flame).
Advantages of torch-applied roofing:
• Lower cost compared with membrane roofing.
• A technology proven over decades, with a wide selection of materials.
• High mechanical strength in two- or three-layer systems.
• Resistance to point loads and personnel traffic.
Limitations:
• Use of open flame: at operating NPPs this is often restricted or requires a work permit and fire-prevention measures.
• Shorter service life: 15-25 years for high-quality bitumen-polymer systems, compared with 30-50 years for membranes.
• Higher weight (5-10 kg/m²), requiring verification of the load-bearing capacity of floors.
• More complex repair (local torch application while maintaining overlaps).
The roof is one of the most critical building elements, protecting building structures and interior spaces from atmospheric exposure. At facilities using nuclear energy (FUNE), roofing works are subject to increased requirements: reliability, durability (at least 30-50 years), maintainability, and, for strict-regime zones, decontaminability.
Nuclear power plants and related enterprises operate buildings of different safety classes, from the main reactor-building structure (class 1-2) to auxiliary administrative and amenity buildings (class 4). Depending on the safety class, structural features, and operating conditions, the roofing system is selected: membrane (polymer) or torch-applied (rolled bitumen-polymer). Each technology has its own advantages, limitations, and production requirements.
Regulatory Framework for Roofing Works at NPPs
Roofing works at facilities using nuclear energy are governed by the following documents:
• NP-041-22, Safety Requirements for Building Structures of Nuclear Power Plant Buildings and Structures, establishes safety classes for building structures, including roof coverings, and requirements for their durability and resistance to impacts.
• SP 17.13330.2017, Roofs (updated version of SNiP II-26-76), is the main document regulating the design and installation of all types of roofs.
• SP 118.13330.2022, Public Buildings and Structures, applies to roof requirements for administrative buildings.
• Fire Safety Rules in the Russian Federation (Resolution No. 1479) set requirements for the use of open flame when torch-applying rolled materials, which is especially relevant at controlled-access facilities.
• GOST R 51102-97 (for roofs in strict-regime zones) establishes decontaminability requirements for coatings if the roof may be subject to radioactive contamination.
NPP sites also have internal industry regulations that prohibit or restrict the use of open flame on operating power units. In such cases, preference is given to membrane roofing with mechanical or ballast fastening.
Comparative Analysis of Roofing Systems
Membrane (Polymer) Roofing
Membrane roofs are made of polyvinyl chloride (PVC), thermoplastic polyolefins (TPO), or ethylene-propylene-diene monomer rubber (EPDM). Installation is performed without open flame: sheets are welded with hot air (PVC, TPO) or bonded (EPDM).
Advantages of membrane roofing:
• High elasticity and resistance to temperature deformation and vibration.
• Durability: service life of 30-50 years (up to 50 years is claimed for TPO).
• Installation without open flame: possible to perform work on operating power units.
• High maintainability: local repair by welding.
• Low weight (1.2-2.0 kg/m²), with no need to strengthen structures.
• Resistance to aggressive media (boric acid, decontamination solutions).
Limitations:
• Higher cost (materials and labor) compared with two-layer bitumen systems.
• Requirement for a flat and strong substrate.
• PVC membranes are sensitive to bitumen, so compatibility with the substrate must be checked.
Torch-Applied (Bitumen-Polymer) Roofing
Torch-applied roofing is a multilayer system of rolled materials based on bitumen modified with polymers (styrene-butadiene-styrene, atactic polypropylene). Installation is carried out using gas burners (open flame).
Advantages of torch-applied roofing:
• Lower cost compared with membrane roofing.
• A technology proven over decades, with a wide selection of materials.
• High mechanical strength in two- or three-layer systems.
• Resistance to point loads and personnel traffic.
Limitations:
• Use of open flame: at operating NPPs this is often restricted or requires a work permit and fire-prevention measures.
• Shorter service life: 15-25 years for high-quality bitumen-polymer systems, compared with 30-50 years for membranes.
• Higher weight (5-10 kg/m²), requiring verification of the load-bearing capacity of floors.
• More complex repair (local torch application while maintaining overlaps).
Selection of the Roofing System for NPP Buildings
When selecting a roof type for buildings and structures of a nuclear power plant, the following factors are considered:
1. Safety class of the building under NP-041-22: for class 1-2 buildings that affect safety, membrane roofing with a service life of at least 40 years confirmed by testing is recommended.
2. Operating mode: flame-free technologies (membrane roofing) are preferred on operating power units.
3. Floor/slab structure: where load-bearing capacity is limited (wooden or light-metal coverings), membrane roofing is safer.
4. Budget and planned service life: for temporary or auxiliary buildings (class 4, service life 15-20 years), torch-applied roofing may be economically justified.
5. Fire-safety requirements: for category A, B, and C rooms (explosion and fire hazardous) and zones where hydrogen systems are located nearby, the use of open flame is prohibited, making membrane roofing the only acceptable option.
Roofing Installation Technology
Membrane Roofing (Using Mechanical Fastening as an Example)
1. Substrate preparation: cleaning, leveling, and priming if necessary. Permissible deviations are not more than 10 mm over 2 meters.
2. Installation of vapor barrier (polyethylene film or bitumen-polymer vapor barrier) with taped seams.
3. Installation of thermal insulation (high-density mineral-wool boards) in two layers with staggered joints. Fastening with telescopic fasteners (2-4 pieces per board).
4. Installation of a separation layer (glass mat, geotextile) to protect the membrane from contact with bitumen if a bitumen vapor barrier is used.
5. Rolling out and welding the membrane: sheets are welded with hot air with a 50-80 mm overlap. Weld quality is checked visually and with a spatula/probe.
6. Mechanical fastening of the membrane to the insulation and substrate using telescopic fasteners with enlarged washers at junctions and along the perimeter.
7. Arrangement of junctions to parapets, drains, and pipes: special profile elements, PVC collars, and sealing.
8. Drainage funnels: the membrane is led into the funnel bowl and sealed.
9. Roof testing (water flooding or spray testing) with preparation of a certificate.
Torch-Applied Bitumen-Polymer Roofing
1. Substrate preparation: cleaning, dust removal, and priming with bitumen primer. Primer drying time is 1-2 hours.
2. Installation of vapor barrier (torch-applied bitumen vapor barrier).
3. Installation of thermal insulation (high-density mineral-wool boards) by mechanical fastening or bonding with bitumen mastic.
4. Torch application of the lower layer of rolled material: the underside of the roll and the substrate are heated with a burner; the roll is unrolled and pressed with a roller. The overlap must be at least 80 mm.
5. Torch application of the upper layer with seams offset by 300 mm relative to the lower layer.
6. Arrangement of junctions: application of additional layers extending 250-300 mm onto vertical surfaces, with seams bonded using bitumen mastic.
7. Installation of funnels and water-collection gutters.
8. Fire-prevention measures during work at NPPs: fire extinguishers, fire blankets, work permit, and supervision.
Quality Control of Roofing Works
• Incoming inspection of materials (certificates, passports, marking, and compliance with the design).
• Operational control: continuity and tightness of welded seams (probe, visual inspection, and for membranes also peel or air-pressure testing), thickness of torch-applied layers, and flatness of the substrate.
• Acceptance control: hydraulic or rain test certificate (water flooding for 2 hours, no leaks). For membrane roofs, additional measurement of coating thickness and checking of adhesion to the substrate are performed.
• For nuclear-industry facilities, control is carried out with construction-control participation and documented in concealed-work certificates (certificates for vapor barrier, thermal insulation, and each roof layer).
Conclusions and Recommendations
When selecting and installing roofing on buildings and structures of nuclear power plants, it is recommended to:
1. For safety class 1-2 buildings and operating power units, use membrane roofing (PVC, TPO) with a service life of 40-50 years, since it is installed without open flame and is more maintainable.
2. For auxiliary buildings (class 4) and new construction on non-operating industrial sites, torch-applied bitumen-polymer roofing with a service life of 15-25 years may be used when the budget is limited.
3. Ensure substrate preparation with control of screed moisture (not more than 4% for bitumen materials and not more than 8% for membranes).
4. Comply with thermal-insulation requirements: for roofs over dry rooms, one layer is sufficient; over humid/heated rooms, vapor barrier and a ventilated air gap may be required.
5. Perform roof tests and prepare as-built documentation in accordance with Rostechnadzor requirements.
To obtain a commercial proposal for roofing works (installation of membrane or torch-applied roofing) at your facility, including substrate preparation, thermal insulation, vapor barrier, drainage systems, quality control, and documentation handover, send a technical specification indicating the building type, its safety class under NP-041-22, roof area, and service-life requirements to the commercial department of TechAtomStroy LLC via the feedback form on the website. A cost estimate, work schedule, and recommendations for selecting the optimal roofing system will be prepared.
*This material was prepared on the basis of NP-041-22, SP 17.13330.2017, fire-safety rules, and GOST R 51102-97.*
When selecting a roof type for buildings and structures of a nuclear power plant, the following factors are considered:
1. Safety class of the building under NP-041-22: for class 1-2 buildings that affect safety, membrane roofing with a service life of at least 40 years confirmed by testing is recommended.
2. Operating mode: flame-free technologies (membrane roofing) are preferred on operating power units.
3. Floor/slab structure: where load-bearing capacity is limited (wooden or light-metal coverings), membrane roofing is safer.
4. Budget and planned service life: for temporary or auxiliary buildings (class 4, service life 15-20 years), torch-applied roofing may be economically justified.
5. Fire-safety requirements: for category A, B, and C rooms (explosion and fire hazardous) and zones where hydrogen systems are located nearby, the use of open flame is prohibited, making membrane roofing the only acceptable option.
Roofing Installation Technology
Membrane Roofing (Using Mechanical Fastening as an Example)
1. Substrate preparation: cleaning, leveling, and priming if necessary. Permissible deviations are not more than 10 mm over 2 meters.
2. Installation of vapor barrier (polyethylene film or bitumen-polymer vapor barrier) with taped seams.
3. Installation of thermal insulation (high-density mineral-wool boards) in two layers with staggered joints. Fastening with telescopic fasteners (2-4 pieces per board).
4. Installation of a separation layer (glass mat, geotextile) to protect the membrane from contact with bitumen if a bitumen vapor barrier is used.
5. Rolling out and welding the membrane: sheets are welded with hot air with a 50-80 mm overlap. Weld quality is checked visually and with a spatula/probe.
6. Mechanical fastening of the membrane to the insulation and substrate using telescopic fasteners with enlarged washers at junctions and along the perimeter.
7. Arrangement of junctions to parapets, drains, and pipes: special profile elements, PVC collars, and sealing.
8. Drainage funnels: the membrane is led into the funnel bowl and sealed.
9. Roof testing (water flooding or spray testing) with preparation of a certificate.
Torch-Applied Bitumen-Polymer Roofing
1. Substrate preparation: cleaning, dust removal, and priming with bitumen primer. Primer drying time is 1-2 hours.
2. Installation of vapor barrier (torch-applied bitumen vapor barrier).
3. Installation of thermal insulation (high-density mineral-wool boards) by mechanical fastening or bonding with bitumen mastic.
4. Torch application of the lower layer of rolled material: the underside of the roll and the substrate are heated with a burner; the roll is unrolled and pressed with a roller. The overlap must be at least 80 mm.
5. Torch application of the upper layer with seams offset by 300 mm relative to the lower layer.
6. Arrangement of junctions: application of additional layers extending 250-300 mm onto vertical surfaces, with seams bonded using bitumen mastic.
7. Installation of funnels and water-collection gutters.
8. Fire-prevention measures during work at NPPs: fire extinguishers, fire blankets, work permit, and supervision.
Quality Control of Roofing Works
• Incoming inspection of materials (certificates, passports, marking, and compliance with the design).
• Operational control: continuity and tightness of welded seams (probe, visual inspection, and for membranes also peel or air-pressure testing), thickness of torch-applied layers, and flatness of the substrate.
• Acceptance control: hydraulic or rain test certificate (water flooding for 2 hours, no leaks). For membrane roofs, additional measurement of coating thickness and checking of adhesion to the substrate are performed.
• For nuclear-industry facilities, control is carried out with construction-control participation and documented in concealed-work certificates (certificates for vapor barrier, thermal insulation, and each roof layer).
Conclusions and Recommendations
When selecting and installing roofing on buildings and structures of nuclear power plants, it is recommended to:
1. For safety class 1-2 buildings and operating power units, use membrane roofing (PVC, TPO) with a service life of 40-50 years, since it is installed without open flame and is more maintainable.
2. For auxiliary buildings (class 4) and new construction on non-operating industrial sites, torch-applied bitumen-polymer roofing with a service life of 15-25 years may be used when the budget is limited.
3. Ensure substrate preparation with control of screed moisture (not more than 4% for bitumen materials and not more than 8% for membranes).
4. Comply with thermal-insulation requirements: for roofs over dry rooms, one layer is sufficient; over humid/heated rooms, vapor barrier and a ventilated air gap may be required.
5. Perform roof tests and prepare as-built documentation in accordance with Rostechnadzor requirements.
To obtain a commercial proposal for roofing works (installation of membrane or torch-applied roofing) at your facility, including substrate preparation, thermal insulation, vapor barrier, drainage systems, quality control, and documentation handover, send a technical specification indicating the building type, its safety class under NP-041-22, roof area, and service-life requirements to the commercial department of TechAtomStroy LLC via the feedback form on the website. A cost estimate, work schedule, and recommendations for selecting the optimal roofing system will be prepared.
*This material was prepared on the basis of NP-041-22, SP 17.13330.2017, fire-safety rules, and GOST R 51102-97.*