Sellafield Ltd has emptied some of the oldest tanks in its Highly Active Liquor Evaporation and Storage (HALES) facility after transferring legacy radioactive liquid into newer storage equipment. The operation removes material held for decades from ageing infrastructure, reducing the heat load on the original vessels while the waste awaits further treatment by vitrification.
The liquid, known as BUTEX liquor, originated as a waste product during some of the site’s first spent fuel reprocessing operations in the 1950s. It had remained in the oldest HALES tanks for decades, partly because other storage space was difficult to identify within the complex industrial site. Sellafield estimates that around 110 cubic metres of material needed to be relocated, requiring a controlled programme of engineering modifications, plant checks and repeated transfer operations.
After almost 20 years without transfers from the oldest tanks, engineers needed to establish whether the existing equipment could operate dependably. Valves, controls and other components had to be assessed before liquid could be moved safely into the newer storage system. Specialists from operations, engineering and nuclear safety developed a controlled method that could be used while HALES continued its other activities.
Preparations included updating the ventilation arrangements and reviewing the proposed method through Sellafield’s nuclear safety processes. The company also engaged with the Office for Nuclear Regulation and the Environment Agency to obtain the necessary permissions. Plant modifications and authorised operating procedures had to be coordinated so that transfer equipment could function within the facility’s established safety limits.
Initial tests used the existing valves and controls to transfer small quantities rather than moving the main inventory immediately. These operations revealed how the equipment behaved after its long period without transfers and allowed the team to refine the sequence of checks and control actions. The evidence obtained through those movements supported a more repeatable process for handling the remaining liquor.
As confidence in the method increased, shift teams carried out repeated controlled transfers within the approved operating arrangements. Operators had to maintain the required checks across successive movements and coordinate their work with HALES activities elsewhere in the facility. Sellafield completed the programme within months, considerably faster than the earlier expectation of more than a year.
The care required during these transfers reflects the properties of highly active liquor, which continues generating heat through radioactive decay while it is held in storage. Containment, cooling and monitoring arrangements must therefore remain effective throughout handling and subsequent storage. Moving the inventory reduces the thermal burden on the oldest tanks, while the radioactive waste and its associated heat generation remain subject to controlled management.
HALES connects the evaporation, movement and storage of highly active liquid waste from Sellafield’s historical reprocessing operations, so a change to the transfer route affects more than an individual vessel. The revised arrangements had to account for interactions between equipment and for the continuing requirement to contain the liquor as it passed through the plant. Operational checks were consequently incorporated into the complete transfer sequence.
Valves and control systems that have seen little use over an extended period need to be assessed through successive operating movements, because their response under repeated use can differ from their initial behaviour. Mechanical condition, instrument feedback and the coordination of connected equipment all influence whether operators can continue transfers consistently. These checks supported the gradual progression from limited movements to the full operating programme.
As the operating method was refined, shift teams could apply the same sequence of control steps and assess plant behaviour against agreed conditions. The transfer process therefore rested on evidence collected during the earlier movements, supported by the necessary plant modifications and permissions. Maintaining that consistency across successive shifts was essential to completing the work within the approved operating arrangements.
Because HALES remained operational throughout the work, engineering modifications and liquor movements had to be coordinated with existing plant duties. The transfer programme also extended across shift changes, making consistent procedures and communication essential. Its completion within months reflected the progress made after the equipment and operating method had been prepared and the necessary permissions secured.
The relocated liquor is now held in newer vessels pending treatment through Sellafield’s vitrification process. That process incorporates radioactive constituents into a solid glass matrix for subsequent handling and long term storage. Until the treatment is completed, the material remains liquid and continues to require appropriate containment, cooling and monitoring arrangements in its new location.
During vitrification, appropriately prepared waste is combined with glass forming materials and heated to produce a molten mixture that can solidify in engineered containers. The process must account for the chemical composition and radioactivity of the material, together with the operating limits of the treatment equipment. The resulting solid waste form can then be managed within the storage arrangements established for vitrified material.
Further work on the emptied tanks will depend on their condition, any residual material and the wider decommissioning programme. Residual hazards and the state of the connected infrastructure must be assessed before equipment can be modified or dismantled, even after the principal liquor inventory has been transferred. Decisions on subsequent work will remain subject to the site’s nuclear safety arrangements.
Removing the legacy liquor has reduced the decay heat carried by some of the oldest HALES equipment, while moving the waste into storage better suited to its continued management. The remaining treatment stage is vitrification, followed by storage of the resulting solid waste under the appropriate arrangements.
