AMPP Nuclear Coatings cheat sheet

Service Level I coatings are applied to structures, systems, and components whose failure could prevent safe shutdown or mitigate accident consequences; they require qualification by radiation exposure and simulated design basis accident testing before use.

Service Level II coatings are those not classified Level I, but whose degradation or released debris could adversely affect safety-related systems; they do not require DBA qualification but must not impair Level I coating performance.

Service Level III coatings are all coatings that are neither Level I nor Level II; only general industrial good practice and normal quality requirements apply to them.

Qualification sequence rule: specimens are first exposed to gamma radiation per ASTM D4082 to a plant-specified total integrated dose, then the same specimens are exposed to the simulated DBA per ASTM D3911.

ASTM D3911 simulates loss-of-coolant accident conditions, typically combining elevated temperature and pressure with a chemical spray, and evaluates blistering, cracking, softening, and film loss afterward.

ASTM D4256 evaluates how readily a coating surface can be decontaminated; coatings in radiologically controlled areas are assessed for ease of removing contamination.

Zinc-rich primers are generally prohibited or restricted inside PWR containment because zinc reacts with boric acid spray, producing deposits and potentially generating hydrogen.

ASTM D5144 gives guidance on selecting and applying the family of protective coating standards for light-water nuclear power plants; ASTM D3843 defines the associated quality assurance requirements.

In-service monitoring follows ASTM D5163: periodic visual inspection, condition rating, trending of degradation, and documented corrective action for Level I and Level II coatings.

SSPC-SP 5/NACE No. 1 (white metal) or SSPC-SP 10/NACE No. 2 (near-white) is the typical minimum blast cleanliness for nuclear coating work; the product data sheet and specification govern which applies.

SSPC-SP 1 solvent cleaning must precede abrasive blasting so that oil and grease are not driven into the steel surface or the anchor profile by the abrasive.

Concrete is prepared to SSPC-SP 13/NACE No. 6, removing laitance, form release agents, curing compounds, and contaminants; new concrete must be adequately cured before coating.

Surface profile is measured after blasting by ASTM D4417 Method B (depth micrometer), Method C (replica tape), or Method D (comparator disc) and compared with the product data sheet requirement.

Soluble salt loading is determined by the Bresle patch method (ISO 8502-6 extraction, ISO 8502-9 conductivity) or by ASTM D4940 abrasive conductivity testing; limits are commonly 3 micrograms per square centimetre for immersion service.

Surface temperature must be at least 3 degrees Celsius (5 degrees Fahrenheit) above the dew point during both surface preparation and coating application.

Sharp edges, weld spatter, slag, laminations, and weld porosities are removed or smoothed before coating because they cause thin spots and holidays that fail continuity testing.

Abrasive must be clean, dry, and free of chlorides and other contaminants; nonmetallic or metallic abrasives are recycled only after verification that contamination has not accumulated.

Blasted steel must be coated within the time limit stated in the specification; visible rust bloom or surface oxidation requires reblasting before the primer is applied.

Ambient and substrate temperatures must fall within the manufacturer's range, commonly 10 to 35 degrees Celsius for amine-cured epoxies, with relative humidity typically at or below 85 percent.

Inorganic zinc silicates cure by reacting with atmospheric moisture and generally require relative humidity above about 50 percent; dry, cold air can leave the film uncured and poorly adhered.

Two-component materials require recording of batch numbers, the exact mix ratio, the induction time, and the pot life; material beyond pot life is discarded rather than thinned.

Wet film thickness is calculated as dry film thickness divided by the volume solids fraction, and is verified during application with a comb or wheel gauge.

When the recoat window is exceeded, the cured film is abraded and cleaned per the manufacturer's instructions before the next coat to restore intercoat adhesion.

Stripe coats are brush-applied to edges, welds, bolt heads, and back-to-back members before the full coat, often in a contrasting color for verification.

Amine blush, a carbamate film forming on amine epoxies under cool or damp conditions, is removed with warm water or a solvent wipe before recoating.

Ventilation and dehumidification control solvent concentration, humidity, and surface temperature during application and cure; airflow is maintained until the film is set.

Metallic pigments other than those approved for the area are avoided in Level I coatings; the plant specification controls acceptable products and pigment types.

Dry film thickness is measured per SSPC-PA 2: each spot is the average of five gauge readings, magnetic gauge tolerance is about plus or minus 3 percent, and spot averages must fall within 80 to 120 percent of the specified thickness.

Under SSPC-PA 2, when the specification states only a minimum thickness and no maximum, the maximum acceptance limit is three times the specified minimum.

Low-voltage wet sponge holiday testing per NACE SP0188 is used for films up to roughly 500 micrometres (20 mils); high-voltage spark testing per NACE SP0274 is used for thicker films, with voltage set by film thickness.

Adhesion is assessed by ASTM D3359 tape test after a cross-cut or X-cut for classification, or quantitatively by ASTM D4541 pull-off testing; concrete pull-off uses ASTM D7234.

Inspection personnel are qualified and certified under ASTM D4537; nuclear coatings specialists are qualified under ASTM D7108; applicators are qualified under ASTM D4227 for concrete and ASTM D4228 for steel.

Hold points are defined in the inspection and test plan, typically before blasting, after blasting and before priming, after stripe coating, after each full coat, and at final acceptance; work cannot continue until the hold point is released.

Environmental records are made at the start and end of each shift and include air temperature, relative humidity, steel or concrete surface temperature, and dew point.

The coating log records product identity, batch and lot numbers, mix ratio, application method, environmental conditions, and measured film thickness for each coat and area.

A nonconformance report documents any failure to meet specification, such as low thickness, a holiday, or an adhesion failure, together with disposition, corrective action, and re-inspection results; records are retained under the plant quality assurance program.