I suspect that 'raw' sandblasted parts would not be allowed on-site until painted. Too much chance for "loose contamination" to stuck on the surfaces if these parts were allowed into the radioactive areas of the plant.
The greater problem would be rust and corrosion from unpainted surfaces cleaned by any means.
Uncleaned sandblasted internals - surfaces or parts with the grit or blast residue and crud left inside - are illegal/out-of-spec, but that's because of the crud potential of the dirt - ANY dirt - not just uncleaned sandblast grit. Many tens of thousand "nuclear parts" in a plant are not connected directly to the primary (radioactive) water, but the corrosion problem and contamination problem of uncleaned parts would be applicable to all.
The paint used in containment can be important. But no restrictions on sandblast to prep prior to coating.
I wonder if someone wrote a spec prohibiting sandblasting because they were worried about sand getting inside the part of interest. For example sand traveling along shaft seal clearance into a bearing.
The blasting operation is done "on the bench" (in a vise, back in the fab shop; sometimes in the laydown area, but not often) rather than "in the field" (already installed in the plant).
I don't know why there would be any issue with sand-blasted brackets, or external piping components. Sandblasting of internal piping or turbine rotors, etc. that could come in contact with the water systems can upset the chemistry balance of the water and have an effect on the steam generators and other components where chemistry limits are strictly maintained.
A high percentage of how a nuclear power plant is rated is based on the cleanliness of the water cycle (water, steam, condensate etc.). If anything can get into the water through any means it is viewed as a potential problem area. So, is there any residue on the brackets? Where are the brackets in the plant? What is the proximity of the brackets to water/steam/condensate etc.?
Sandblasted parts in general are not prohibited. There are pretty strict cleanliness specifications - especially for parts in important systems. You may be dealing with a particular plant/company's reaction to an issue where they found loose blast media in a system or part...
TorsionalStress,
Assuming that the sand blasting occured outdoors instead of in an enclosed space, the potental for achieving a true white metal blast or near white metal blast is decreased due to the potential for flash rusting or other contamination deposited on the surface from the atmosphere/environment.
