Nuclear Energy and Radiation – Protective Paints and Coatings

What is Nuclear Energy?

Nuclear, derived from the Latin word "Nucleus," literally means "relating to the atomic nucleus." Nuclear Energy refers to the energy produced as a result of reactions occurring within or between atomic nuclei. There are two different types of nuclear reactions: Nuclear Fission and Nuclear Fusion: Nuclear Fission refers to reactions in which an atomic nucleus splits into smaller fragments. During these reactions, nuclear energy is released along with radioactive byproducts. (For example, U-235 uranium isotopes splitting to produce neutrons along with Barium and Krypton isotopes) This article examines nuclear facilities using U.S. technology and associated paints and coatings. Nuclear facilities in other countries may employ different technology and have different design specifications. This may result in differences in the type of paint or coating selected and other physical properties (such as film thickness). 2An isotope is a new atomic arrangement created when atoms of the same element have the same number of protons but different numbers of neutrons. For example, there are three naturally occurring uranium isotopes: U-234, U-235, and U-238. In nuclear fusion reactions, two light atoms combine (fusing) to form larger atoms. (Such as two hydrogen isotopes—Deuterium and Tritium—combining to form a helium atom.) This is actually the energy source of our sun and other stars, but because it requires extremely high temperatures and pressures, it represents a more expensive nuclear technology in terms of investment costs.For more detailed information on Nuclear Fusion Reactions and Reactors, you can access resources on the World Nuclear Association website. 1 The Sun is a massive source of hydrogen. 2 Within the Sun, hydrogen atoms are heated to the point where electrons no longer orbit the protons in the atomic nucleus and instead transform into plasma. The exposed atomic nuclei then combine with each other to form helium atoms and neutrons. This fusion process releases energy. Today, when nuclear energy is discussed, it actually refers to Nuclear "Fission" Energy resulting from nuclear fission reactions in which an atomic nucleus splits into lighter atoms.3Nuclear Fission Energy will hereafter be referred to simply as Nuclear Energy.

History of Nuclear Technology

The history of this technology began in early 1900s Europe (with Antoine Becquerel's discovery of the radioactive properties of uranium in 1896, followed by Ernest Rutherford, Marie Curie, and Enrico Fermi). Significant technological advances in the nuclear industry in the United States emerged before and after World War II due to the need for nuclear weapons development. The world's first known nuclear reactor, Chicago Pile-1, was built by a team led by Enrico Fermi at the University of Chicago in the late 1940s as an experimental nuclear reactor. The world's first commercial nuclear facility was APS-1, located in Obninsk, Russia, commissioned on 26 June 1954 after World War II, with an electrical output of 5 MW.

Paints and Coatings - Why Are They Special and Important?

In the nuclear sector, paints and coatings serve purposes far beyond aesthetics. Their primary function is to prevent any harmful chemical release (particularly radioactive material) from the facility, its systems, structures, and auxiliary components during the worst-case design-basis accidents (DBA) that may occur at a nuclear facility. For this reason, in certain areas of the nuclear facility (to be specified below), testing for DBA compliance is required. During nuclear energy generation, high-energy radiation from the radiation types mentioned above (alpha-beta-gamma radiation, X-rays, etc.) is emitted to the surroundings. The primary characteristic of these types of radiation is that due to their high energy levels, they can break the chemical bonds in the polymers that make up the paint film, thereby damaging the paint and coating film and even penetrating to the underlying surface! As can be seen, the selection of paints and coatings for use in nuclear facilities is critical. For this reason, numerous tests and field studies have been conducted since the 1950s, and many industrial standards have been published. The most important of these standards are: • ANSI N5.12 – Protective Coatings (Paints) for the Nuclear Industry. • ASTM D5144 – Standard Guide for Use of Protective Coatings in Nuclear Power Plants. • ASTM D4537 – Standard Guide for Establishing Safety and Health Practices Associated with Coating, Lining, and Fireproofing Work in Nuclear Power Plants. • ASTM D4538 – Standard Terminology Relating to Protective Coatings and Lining Work for Power Generation Facilities. The standards above specify in detail which paints must be selected according to which criteria and where paint and coating materials can be used. Additionally, the ASTM standards in this area are periodically updated to incorporate experience and knowledge gained in the industry into these standards. Particularly in ASTM D4538, paints and coatings used in nuclear facilities are classified based on their location of use in the facility: • Coating Service Level I – Covers areas inside reactor containment. Coating failure can affect post-accident cooling system operation and therefore may prevent safe shutdown of the nuclear facility (may not prevent radioactive leakage). • Coating Service Level II – Defines areas outside reactor containment. Coating failure may impair normal operation performance of the nuclear facility but does not prevent its operation. The primary function of Level 2 coating materials is to provide corrosion protection and decontamination for areas outside reactor containment that are exposed to radiation and radioactive nuclei. • Coating Service Level III – Defines areas where coating failure outside reactor containment could affect the safety function of a structure, system, or component of the nuclear facility (coatings related to safety). Water vapor, Cooling Tower, Warm Water Inlet, Transformer, Generator, Pump, Cold water basin, Cold water source, Cooling water, Condenser, Turbine, Steam lines, Containment building, Steam generator, Uranium fuel, Reactor vessel, Control rods. Paint selection is made in accordance with this classification and ASTM standards. Without going into details, coatings suitable for these classes can be summarized as follows:   • Coating Service Level I Paints and Coatings Coatings in this classification are divided into two categories: 1. Non-Embedded Steel/Concrete Surfaces: For these surfaces, Inorganic Zinc Silicate, Epoxy, and Epoxy Phenolic paint and coating systems, which are known to have higher radiation resistance than other paints, are recommended. This is because these types of paint and coating materials have higher corrosion resistance due to their highly cross-linked chemical bond structures and are more resistant to chemicals that may be found in nuclear facilities (such as acids, bases, and deionized water) (they have lower permeability coefficients). Prior to these coating systems, surface preparation in accordance with SSPC SP 10/ISO 8501 Sa 2½ must be performed.

2. Embedded Steel/Concrete Surfaces (Pressure-suppression Pools/Tanks)

These pools and tanks serve to cool the reactor during a "loss-of-coolant accident" (LOCA). For this reason, they are constantly filled with water from environmental water sources. Accordingly, paints and coating materials selected for these surfaces must resist continuous water exposure. For this reason, Inorganic Zinc/Epoxy coating systems can be used on these surfaces. • Coating Service Level II Paints and Coatings The coating systems in this area are not safety-related but may be exposed to radiation and may require decontamination. The following types of coating materials can be used in this area: • Solvent-based Epoxies • Water-based Epoxies • Phenolic Epoxies • Siloxanes • Polyurethanes • Phenolic Alkyds • Acrylics

• Coating Service Level III Paints and Coatings

Since coatings in this class are used outside reactor containment, they will not be exposed to radiation or radioactive nuclei. For this reason, the DBA tests mentioned above are not required. However, when used in embedded service areas, they are classified as safety-related because coating failure could affect the performance of safety-related systems and components. The following sections provide general information about where and what types of Level III coating materials can be used: • Auxiliary Water Systems These systems contain water that cools the reactor and, due to continuous water exposure, these areas require lining for corrosion protection. Lining materials can be Cement, Vulcanized Rubber, Epoxy, and Phenolic Epoxy. • Water Tanks Since there will also be continuous water contact here, 100% solids Epoxy or Vulcanized Rubber can be used. Pump internals and impellers can be successfully lined with Ceramic-filled Epoxy. • Storage Tanks These storage tanks for process water, water-treatment chemicals, and ion-exchange resin regeneration must also be lined against chemical attack and liquid penetration. Suitable linings include Epoxy, Novolak Epoxy, Vinyl, Vinyl Ester, and Glass-flake-filled Polyester. Prior to coating applications in this class, abrasive blasting cleaning at the highest surface preparation level ISO 8501-1 Sa 2½ / SSPC SP5 is required in the nuclear industry!

• Paints and Coatings for the Balance of the Nuclear Facility (Balance-of-Plant Coatings-BOP)

Paints and coatings outside of Service Levels I, II, and III are called "Balance-of-Plant Coatings" or BOP for short. In these areas, paints and coatings used in other fossil-fuel power plants, refineries, and industrial production facilities can be used.

Summary

Commercial nuclear energy facilities are subject to very stringent specifications and regulations, and paint and coating selection must be carefully made in accordance with national and international standards and desired test results. Additionally, qualified and certified personnel may be required for the application of these coatings. All of this paint and coating selection and application will be significantly different from other industrial coating projects. During these processes, even a small error can result in both serious economic losses and harm to human and environmental health. For this reason, the points mentioned above contain only summary information. More detailed information can be obtained from the "References" section that I have shared. Until we meet in the next article, wishing you good days and good work. Goodbye… Tolga Dıraz - Chair, Surface Protection Committee (TK-4) / Turkish Structural Steel Association (TUCSA)

References 1. Nuclear power plants, world-wide: https://www.euronuclear.org/info/encyclopedia/n/nuclear-power-plant-world-wide.htm 2. Nuclear Fission and Fusion: https://www.diffen.com/difference/Nuclear_Fission_vs_Nuclear_Fusion 3. The ABC's of Nuclear Coatings – What's So Special? – John R. Cavallo, PE, FASTM, Enercon Services Inc. 4. ASTM D5144 – Standard Guide for Use of Protective Coating Standards in Nuclear Power Plants 5. Corrosion in Power Plants: Operating Conditions and Maintanance Planning – E. Bud Senkowski, KTA-Tator,Inc. – JPCL November 1997 6. Developing a Maintanance Program for a Nuclear Power Plant – Don A.Hill, PE – JPCL November 1996 7. Radiation-induced Degradation of Coatings – Clive H. Hare – JPCL August 2000 8. Coating Program Requirements at Nuclear Power Plants – Daniel E. Cox – JPCL July 2011 9. ASTM D4538 – Standard Terminology Relating to Protective Coating and Lining Work for Power Generation Facilities 10. U.S. Nuclear Regulatory Commission Regulatory Guide 1.54 11. Protective Coatings System For Nuclear Power Plant and Corrosive Environments – S. Guruviah, M.Sundaram, V. Chandrasekaran, P. Jahakrishnan, K. Raghupathy, V. Ganesa Sarma, Bulletin of Electrochemistry, July-August 1986 12. A New Design for Nuclear Power Plants and Its Effect on Coating Requirements – Michael C. Durbin, Kristin Ruth – JPCL June 2014