This article examines the main approaches to anti-corrosion protection of construction facilities and steel structures operated at nuclear power plants and other facilities using nuclear energy (FUNE). It analyzes the requirements of NP-041-22 for protective coatings of different safety classes, the types of paint-and-varnish materials used at NPPs, and methods for quality control of application. Recommendations are provided for selecting a coating system depending on environmental aggressiveness and radiation load.
Corrosion damage to steel structures is one of the main factors reducing the reliability and assigned service life of buildings and structures. At facilities using nuclear energy, corrosion becomes especially significant because nuclear and radiation safety depend on the integrity of load-bearing and enclosing structures.
Anti-corrosion protection of NPP steel structures must ensure preservation of the material throughout the entire design operating life, typically 50-60 years, taking into account exposure to ionizing radiation, elevated temperatures, aggressive chemical media (boric acid and decontamination solutions), and dynamic loads.
Regulatory Framework for Anti-Corrosion Protection at FUNE
The fundamental document for building structures of nuclear power plants is NP-041-22, Safety Requirements for Building Structures of Nuclear Power Plant Buildings and Facilities. In accordance with it, all steel structures are categorized by safety class:
• Class 1 - structures whose failure leads to an accident with release of radioactive substances.
• Class 2 - structures whose failure complicates accident mitigation.
• Class 3 - structures that do not affect safety but require protection to perform their assigned functions.
Requirements for corrosion protection of steel structures are established for each class. The strictest requirements apply to coatings for classes 1 and 2: they must retain integrity during a design-basis earthquake, thermal shocks, and exposure to decontamination solutions.
Additional regulatory documents include:
• GOST 9.401-2018, Unified System of Corrosion and Ageing Protection. Paint Coatings. General Requirements and Methods for Accelerated Climatic-Resistance Testing.
• GOST R 51102-97, Decontaminable Protective Polymer Coatings. General Technical Requirements.
• GOST 26825-86, Paint Coatings for Strict-Regime Zones of NPPs.
Classification of Anti-Corrosion Protection Systems
Depending on operating conditions and the required service life, the following types of coatings are used:
Corrosion damage to steel structures is one of the main factors reducing the reliability and assigned service life of buildings and structures. At facilities using nuclear energy, corrosion becomes especially significant because nuclear and radiation safety depend on the integrity of load-bearing and enclosing structures.
Anti-corrosion protection of NPP steel structures must ensure preservation of the material throughout the entire design operating life, typically 50-60 years, taking into account exposure to ionizing radiation, elevated temperatures, aggressive chemical media (boric acid and decontamination solutions), and dynamic loads.
Regulatory Framework for Anti-Corrosion Protection at FUNE
The fundamental document for building structures of nuclear power plants is NP-041-22, Safety Requirements for Building Structures of Nuclear Power Plant Buildings and Facilities. In accordance with it, all steel structures are categorized by safety class:
• Class 1 - structures whose failure leads to an accident with release of radioactive substances.
• Class 2 - structures whose failure complicates accident mitigation.
• Class 3 - structures that do not affect safety but require protection to perform their assigned functions.
Requirements for corrosion protection of steel structures are established for each class. The strictest requirements apply to coatings for classes 1 and 2: they must retain integrity during a design-basis earthquake, thermal shocks, and exposure to decontamination solutions.
Additional regulatory documents include:
• GOST 9.401-2018, Unified System of Corrosion and Ageing Protection. Paint Coatings. General Requirements and Methods for Accelerated Climatic-Resistance Testing.
• GOST R 51102-97, Decontaminable Protective Polymer Coatings. General Technical Requirements.
• GOST 26825-86, Paint Coatings for Strict-Regime Zones of NPPs.
Classification of Anti-Corrosion Protection Systems
Depending on operating conditions and the required service life, the following types of coatings are used:
High-build compounds deserve special attention: they make it possible to form a coating up to 600 microns thick in one cycle of airless spraying, reducing work duration and eliminating intercoat drying. Such materials are especially in demand during repair work performed in scheduled-maintenance windows.
Surface-Preparation Requirements
The effectiveness of anti-corrosion treatment of NPP steel structures is determined 70-80% by the quality of surface preparation. According to ISO 8501-1, for critical structures (safety class 2), a cleaning grade not lower than Sa 2.5 is required - abrasive blasting to completely remove mill scale, rust, and contamination, leaving a visually clean metal surface.
The following are additionally controlled:
For rooms in the strict-regime zone, radiometric surface control is additionally performed before coating application.
Application Quality Control
During anti-corrosion protection works, operational control of the following parameters is mandatory:
All results are recorded in non-destructive testing reports, which form part of the as-built documentation submitted to Rostechnadzor construction control.
Features of Anti-Corrosion Protection in Zones Exposed to Radiation
For coatings operated in controlled access zones (CAZ) and strict-regime zones (SRZ), the following are additionally verified:
Organic coatings such as epoxy and polyurethane have limited radiation resistance; their use in zones with intense irradiation requires experimental confirmation of service life. In such cases, preference is given to inorganic zinc-rich compounds or hybrid liquid-glass systems.
Economic Efficiency of Selecting a Durable Anti-Corrosion System
Investment in high-quality anti-corrosion protection for steel structures of buildings and facilities pays back by reducing repair frequency and downtime. A comparison for a typical aggressive workshop with 2000 m² of structures is shown below:
Surface-Preparation Requirements
The effectiveness of anti-corrosion treatment of NPP steel structures is determined 70-80% by the quality of surface preparation. According to ISO 8501-1, for critical structures (safety class 2), a cleaning grade not lower than Sa 2.5 is required - abrasive blasting to completely remove mill scale, rust, and contamination, leaving a visually clean metal surface.
The following are additionally controlled:
- Roughness profile, usually 40-85 microns for epoxy systems.
- Presence of soluble salts (chlorides, sulfates), with a limit of no more than 20-30 mg/m² depending on project requirements.
- Degree of degreasing - absence of oils and greases is checked with a UV lamp or water-break test.
For rooms in the strict-regime zone, radiometric surface control is additionally performed before coating application.
Application Quality Control
During anti-corrosion protection works, operational control of the following parameters is mandatory:
- Wet- and dry-film thickness - step-by-step measurement on every square meter using calibrated thickness gauges (magnetometric method).
- Adhesion - by cross-cut or pull-off method in accordance with GOST 28574-2019.
- Continuity, meaning absence of pores and missed areas - using a spark holiday detector for high-build compounds.
- Color and gloss - visually against reference samples to identify repair zones.
All results are recorded in non-destructive testing reports, which form part of the as-built documentation submitted to Rostechnadzor construction control.
Features of Anti-Corrosion Protection in Zones Exposed to Radiation
For coatings operated in controlled access zones (CAZ) and strict-regime zones (SRZ), the following are additionally verified:
- Radiation resistance - the ability to retain adhesion and protective properties after accumulated radiation dose, from 10^5 to 10^6 Gy depending on location.
- Decontaminability - the ability to be washed free of radioactive contamination with standard solutions without coating destruction (under GOST R 51102-97, decontamination coefficient not lower than 0.8).
- Resistance to decontamination formulations, both alkaline and acidic, without swelling, cracking, or color change.
Organic coatings such as epoxy and polyurethane have limited radiation resistance; their use in zones with intense irradiation requires experimental confirmation of service life. In such cases, preference is given to inorganic zinc-rich compounds or hybrid liquid-glass systems.
Economic Efficiency of Selecting a Durable Anti-Corrosion System
Investment in high-quality anti-corrosion protection for steel structures of buildings and facilities pays back by reducing repair frequency and downtime. A comparison for a typical aggressive workshop with 2000 m² of structures is shown below:
In addition, durable coatings reduce radiation risks by minimizing maintenance interventions and make it possible to increase the capital class of the building in accordance with NP-041-22.
Conclusions and Recommendations
To ensure reliable and long-term anti-corrosion protection of steel structures at facilities using nuclear energy, it is recommended to:
To obtain a commercial proposal for anti-corrosion protection of steel structures at your facility, including surface preparation, application of high-build epoxy, polyurea, or zinc-rich systems, quality control, and preparation of as-built documentation, send a technical specification indicating the safety class, structure area, and operating conditions to the commercial department of TechAtomStroy LLC through the feedback form on the website. A cost estimate, work schedule, and feasibility study for selecting the coating type will be prepared.
*This material was prepared on the basis of NP-041-22, GOST 9.401-2018, GOST R 51102-97, GOST 26825-86, and ISO 8501-1.*
Conclusions and Recommendations
To ensure reliable and long-term anti-corrosion protection of steel structures at facilities using nuclear energy, it is recommended to:
- At the design stage, determine the safety class of structures under NP-041-22 and the corresponding coating service life.
- Select the coating type with regard to environmental aggressiveness, radiation load, and decontaminability requirements under GOST R 51102-97 and GOST 26825-86.
- Ensure surface preparation to at least Sa 2.5 with control of salt cleanliness and roughness.
- Use high-build compounds to accelerate work while maintaining the design thickness in one pass.
- Perform a complete cycle of non-destructive testing with reports prepared for construction control.
- For radiation-exposed zones, confirm coating resistance by decontaminability and radiation-resistance tests.
To obtain a commercial proposal for anti-corrosion protection of steel structures at your facility, including surface preparation, application of high-build epoxy, polyurea, or zinc-rich systems, quality control, and preparation of as-built documentation, send a technical specification indicating the safety class, structure area, and operating conditions to the commercial department of TechAtomStroy LLC through the feedback form on the website. A cost estimate, work schedule, and feasibility study for selecting the coating type will be prepared.
*This material was prepared on the basis of NP-041-22, GOST 9.401-2018, GOST R 51102-97, GOST 26825-86, and ISO 8501-1.*