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Sphere hazard removal gets green light

March 06, 2009

Members of the DFR project team

Dounreay is another step closer to destroying one of the largest single hazards left over from the fast reactor research and development programme.

The first batches of liquid metal from the coolant system of the Dounreay Fast Reactor have been destroyed following a five-month pause while modifications were made to the chemical treatment plants.

The sodium-potassium alloy, known as NaK, is heavily contaminated with radioactive caesium, and the major challenge for the active commissioning of the plants has been to reconfigure the ion exchange clean-up process to improve its performance.

The clean-up plants have so far processed fourteen batches of primary NaK and during routine work last September the project team observed a couple of small leaks in the ion exchange drip trays. Rigorous safety procedures were followed, work was immediately suspended and following a thorough investigation a recovery plan was put in place.

The commissioning team worked closely with our regulators throughout the independent investigation and subsequent review to examine the findings of the reports in order to share valuable lessons learned. Management shared their experiences to fully understand the cause of the leaks, which was mainly attributed to incompatibility between sealing threads and materials with ageing pipework.

“The DFR NaK represents one of the highest hazards on the Nuclear Decommissioning Authority’s sites and we must ensure we meet the necessary safety and environmental standards,” explained Mike Brown, fast reactors decommissioning unit manager.

“When working with complex plants built to strip-out a fifty year old nuclear facility you have to be prepared for challenges of this nature and I can’t commend the team enough for embracing the lessons we have learned and developing an ongoing improvement programme which is clearly working given this achievement.

“Dounreay Site Restoration Ltd and its contractors have worked tirelessly to prepare for this day, demonstrating forward thinking and commitment to a project which is one of the major decommissioning milestones DFR has to manage.”

With all work now safely accomplished and the recovery plan complete, the improved and more robust ion exchange plant was declared ready to commence operation and DFR has today successfully restarted the destruction of Dounreay’s highest hazard.

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