Radioactive nuclear waste is treated in

ANS:C - pulsed column extractor

Radioactive nuclear waste is typically treated using various methods, including those you mentioned. Each of these methods has its own advantages and applications:

1. Mixer-settler extractor: This method involves mixing the waste with a solvent or extractant in a mixer, allowing the desired components to transfer from the waste to the solvent. The mixture is then allowed to settle, separating the phases, and the solvent containing the desired components is extracted.
2. Rotating-disc contactor: In this method, the waste and the solvent are brought into contact on rotating discs or plates. The rotation enhances the mixing and mass transfer between the phases, facilitating the extraction process.
3. Pulsed column extractor: This technique involves periodically pulsing the solvent and waste mixture through a column containing packing material. The pulsing action helps improve the contact between the phases and enhances the extraction efficiency.
4. Bollman extractor: The Bollman extractor is a type of liquid-liquid extractor that utilizes a series of perforated plates or trays to facilitate the contact between the waste and solvent phases. The extractor operates based on the principle of counter-current extraction, where the phases flow in opposite directions, promoting efficient mass transfer.