Cell Decommissioning Program Set to Start at Dounreay

The successful repair of the active filter change mechanism means that D1206 can proceed with its program of cell clean-up work

During a routine filter change operation the team found a mechanism on one of the filters had seized and they were unable to change the filter. The ventilation system has been operating at a reduced capacity since 2009 as a result. This is not suitable for the programme of decommissioning work. It was not easy to gain access to the repair area. The components are situated in a heavily shielded chamber with no designed access arrangements. Due to the high radiation and contamination, the team made the decision to carry out the repair by semi-remote means. The team used a mock-up of the AFC to create and trial the tools needed for the repair. It also ensured the workers received minimal dose.

Gordon Tait, senior project manager said, “This is another excellent demonstration of the b e n e f i t s o f m o c k u p s i n decommissioning and also highlights the engineering talent and team work existing within the DSRL workforce”.

Before the active repairs to the filter cell could start, the work area had to be opened up. The redundant dissolver cell 3 c o n t r o l  p a n e l  a n d o f f i c e enclosure were removed.

A section of a dividing wall between the cell and the inactive feed area was also removed to improve access. Using the techniques developed on the mock-up, the team cored a hole into the cell shielding, and identified the cause of the problem. They found that a bush, made from mild steel instead of stainless steel, had corroded and seized the clamp. They replicated the fault on the mock up and trialled ways to repair it, before completing the work. The alternative to the repair would have been to install a new v e n t i l a t i o n  s y s t e m  a t  a n approximate cost of £10 million. This would have had significant safety, cost and time implications o n t h e d e c o m m i s s i o n i n g  program.

The team will now be able to change all filters.  This will allow the  active filter cell to operate at full capacity and reduces any risk t o t h e d e c o m m i s s i o n i n g program.

Steve Beckitt, FCA Project Director said, “This is an excellent example of the use of mock-ups and innovation. “Its success has resulted in significant  savings of over £10 million.