Red oil is defined as a substance of varying composition formed when an organic solution, typically tri-n-butyl phosphate (TBP, an agent used for extracting heavy metals in nuclear reprocessing plants) and its diluent, comes in contact with concentrated nitric acid at a temperature above 120 °C.
Generic types of equipment capable of producing red oil in the complex are categorized as evaporators, acid concentrators, and denitrators.
Sufficient venting serves to keep pressure from destroying the process vessel, while also providing the means for evaporative cooling to keep red oil from reaching the runaway temperature.
Mass controls utilize decanters or hydrocyclones to remove organics from feedstreams entering process equipment capable of producing red oil.
A U.S. government study concluded that none of the controls should be used alone; rather, they should be used together to provide effective defense in depth for prevention of a red oil explosion.