Reactor demolition takes another step forward at Dounreay

10th February 2014

A pioneering Dounreay innovation has allowed the team taking apart the Prototype Fast Reactor to complete one of the final phases ready for demolition.

The centre guide tube - which once housed the reactor's control and shutoff rods - was successfully raised from the reactor core, demonstrating that internal fixtures can be safely removed. This supports plans for taking apart the remainder of the former electricity generating plant.

The original equipment to remove and replace reactor core components was designed to operate while immersed in molten sodium at temperatures above 350°C. Now the reactor is drained of sodium and the temperature is below 100°C, this equipment no longer works.

The reactor dismantling team set to work and identified an alternative method to remove the reactor core items via existing access points.

Led by Calder Bain, who has been at Dounreay for 50 years, a design team proposed a long grab, capable of reaching down approximately 10 metres from the reactor top to latch onto the guide tube, with a chain block connected to the building crane which carefully raised the tube from the reactor depths.

Manufacture of the extraction and sampling equipment was undertaken by local contractors and subsequently assembled and trialled at JGC's T3UK Facility.

The equipment was then transferred to the reactor where further trials were undertaken before the final lift took place.

PFR reactor dismantling project manager Rob Hibbert said: “This was a complex and technical challenge for the team and a significant achievement to carry out the remote operations safely in a hazardous environment. During this project, readings were recorded from the depths of the reactor in excess of 1000Sv/hr, which is valuable data for carrying out the remainder of the reactor decommissioning plans.”

The final reactor component extraction and characterisation will be completed during 2014.

Photograph:
Top, preparations take place to remove the centre guide tube

Contractors:
JGC Engineering and Technical Services Ltd,
Precision Machining
Service Ltd

Article from the NDA newsletter for February - INSIGHT.