1. External radiation exposure
The highly active solutions and materials produce dose rates that would be immediately lethal without shielding. Workers cannot enter hot cells containing active process equipment.
2. Maintenance dose
Although the plant is designed for remote operation, maintenance activities can result in significant occupational dose. Workers performing maintenance on equipment outside the hot cells, or on contaminated systems, receive the majority of the collective dose at reprocessing plants.
3. Liquid discharges
Reprocessing produces various liquid waste streams of different activity levels. Historically, medium-active liquid wastes from Sellafield were discharged to the sea after a period of storage. Radioactive discharges from Sellafield peaked in 1974 and have been dramatically reduced since through the introduction of new treatment plants (SIXEP in 1985, EARP in 1993).
4. Gaseous discharges
Volatile fission products released during dissolution include krypton-85, iodine-129, carbon-14, tritium, and xenon. These are treated by scrubbing and filtering before controlled discharge to the environment. The off-gas treatment removes >99.99% of radioactivity.
5. Criticality risk
Reprocessing plants are particularly vulnerable to unplanned criticality because:
- Fissile materials are present in liquid form (easier to accumulate than solids).
- Both uranium and plutonium are present.
- The process involves moving fissile liquors between organic and aqueous phases.
- Concentration can occur unexpectedly (e.g., in evaporators or settling tanks).