Antibacterial Putties for Cleanrooms at Radioactive-Waste Management Facilities: From Regulatory Requirements to Confirmation of Biological Resistance

Abstract. This article examines the problem of biological damage to surfaces in cleanrooms at radioactive-waste (RAW) management facilities. It shows the limitations of using stainless steel under high humidity and vibration. An engineering solution is presented: epoxy-based antibacterial putty with silver nanoparticles. Test results under GOST 9.049-91, the application technology for gypsum-board substrates, and an economic comparison with periodic replacement of sandwich panels are provided.



Regulatory Requirements and the Operating Problem

At facilities using nuclear energy (FUNE), especially plants for processing, conditioning, and storing radioactive waste, strict standards apply to air and surface cleanliness (SP 137.13330.2012 and industry rules). The traditional solution is the use of stainless steel as a corrosion-resistant material that is easy to decontaminate. However, operating practice reveals a systemic problem.



Condensate forms at vertical joints of sandwich panels under high-humidity conditions, creating an environment for microorganism growth. Studies show that even stainless steel develops biofilm over time - a stable community of bacteria and fungi attached to the surface and tolerant of ordinary disinfectants.


For facilities such as cementation and bituminization units and temporary RAW storage points, the problem is aggravated by:



• high humidity caused by technological processes;

• difficulty of regular wet cleaning in radiation-controlled zones;

• vibrations from pumping and ventilation equipment.



An additional risk factor is the possibility of growth of radiotrophic fungi on irradiated surfaces, for example mold of the Cladosporium genus. These microorganisms not only cause biocorrosion but can also damage sealing layers of coatings, leading to impairment of barrier functions.



Engineering Solution: Epoxy-Based Antibacterial Putty with Nanosilver

As an alternative to traditional finishing materials, a specialized epoxy-based antibacterial putty modified with silver nanoparticles is proposed.



Mechanism of action: silver nanoparticles release Ag+ ions, which interact with thiol groups of bacterial enzymes, disrupt the respiratory chain, and cause oxidative stress leading to cell death. This mechanism has been confirmed by laboratory studies and remains active throughout the coating's service life.



Key characteristics:



Prolonged antibacterial and fungicidal action, preventing growth of mold and fungi after repeated cleaning cycles.



Low modulus of elasticity - the coating remains elastic under dynamic loads. Unlike conventional putties, which crack under vibration, the nanosilver composition damps oscillations and preserves integrity.



Resistance to decontamination solutions, with certification under GOST R 51102-97 and GOST 26825-86.



Application Technology on Gypsum-Board Substrates

Use of antibacterial putty on gypsum-board sheets requires compliance with special conditions. The critical parameter is spraying pressure: it must not exceed atmospheric pressure (0 MPa gauge) in order to avoid destruction of the fragile gypsum-board core.



Technological cycle, step by step:



1. Deep-penetration priming - 1-2 layers with intermediate drying.



2. Joint reinforcement - taping of seams with fiberglass mesh and application of starter putty.



3. Application of the antibacterial compound - layer thickness from 0.5 to 2.0 mm depending on requirements for smoothness and mechanical strength.



4. Intermediate sanding and dedusting - removal of irregularities and dust before finishing.



5. Finish coating, if necessary - polymerization at +20°C for 24 hours.



Results of Fungal-Resistance Testing

The material passed a full cycle of industrial tests under GOST 9.049-91, the method for determining fungal resistance of paint coatings. The essence of the method is that coated specimens are infected with spores of mold fungi (Aspergillus niger, Penicillium, etc.) and held under conditions optimal for their development (temperature 28-30°C, humidity 95-98%), followed by assessment of mold-growth intensity.



Result: after six months of continuous exposure under cyclic wetting and temperature variations from +5 to +40°C, there were no signs of fungal damage. Biofilm did not form and no mold foci were present.



In addition, the coating is certified for use in the strict-regime zone (SRZ) of NPPs under GOST R 51102-97, Decontaminable Protective Polymer Coatings. It retains adhesion to the substrate after three decontamination cycles (alkaline and acidic solutions) and does not change its properties after treatment with the formulations specified in GOST 26825-86.



Economic Comparison with Alternative Solutions

Use of antibacterial putty with nanosilver provides not only microbiological cleanliness but also significant savings compared with the traditional scheme of periodic sandwich-panel replacement, which is required every 3-5 years due to biological damage.

Economic effect: in the long term, over 10 years and more, total costs are reduced by 70-80% compared with periodic panel replacement.



Application Areas and Recommendations

Epoxy-based antibacterial putty with nanosilver is recommended for use at nuclear-industry facilities where long-term biological cleanliness of surfaces is required:



safety class 4 and 5 zones under NP-041-22;



rooms for processing and conditioning low- and intermediate-level waste;



temporary RAW storage points;



cleanrooms with a regulated level of microbiological contamination.



TechAtomStroy LLC undertakes projects for anti-corrosion treatment, fire protection, and installation of specialized coatings at nuclear power plants. To calculate the cost and schedule for construction and installation works, send the facility specification and bill of quantities through the feedback form on the website.

*This material was prepared on the basis of GOST 9.049-91, GOST R 51102-97, GOST 26825-86, and SP 137.13330.2012.*