Providing for the nuclear 'family'
30 March 2009
Nuclear reactor core inspection is an essential maintenance function that all nuclear power stations must undertake in order to achieve continuity of power generation and the highest levels of plant safety and efficiency. To perform this operation, a special machine is employed, complete with TV inspection and bore measuring equipment. In operation, the main body of the machine is lowered to engage with the reactor standpipes by means of an electric linear actuator. Dubbed NICIE (New In-Core Inspection Equipment), the machine was developed by BNS Nuclear Services, with whom Power Jacks worked in close partnership to design and manufacture the main linear actuation unit.
Once it is lowered and engaged with the standpipe, four additional screw jacks are deployed to ensure stability of the rig, and the camera is lowered into the reactor fuel channel to carry out the necessary measurement and maintenance checks. The actuator is sized to lift and lower the 20kN load over a stroke of 525mm, with the end of travel signalled by proximity sensors located within the actuator itself.
To maintain a rigid column over the stroke, the actuator has two internal guidance mechanisms for the ram. For safety reasons, the ram is fitted with a proprietary clutch to provide a mechanical fail safe and prevent an overload condition, should the external control systems fail. The actuator is powered by a 0.75kW motor with integral brake for position holding. An auxiliary hand drive shaft is also fitted, should manual operation be required. The machine itself is mounted on wheels for easy transportation; however, when positioned for use, the four screw jacks at the base of the machine take the weight off the wheels, rather like the hydraulic stabiliser jacks on a mobile crane.
Currently under test at the BNS Nuclear Services facility at Whetstone, the first of two machines will undertake inspections at the 1,250MW Hinckley Point nuclear power plant near Bridgwater, Somerset, which operates an advanced gas-cooled reactor.
Power Jacks has a long standing working relationship of over 38 years with BNS Nuclear Services, now part of the Babcock Group. While BNS lead design engineer, Alex MacMillan pays tribute to his supplier for delivering the NICIE hoist products on time and on budget, Power Jacks’ East Midlands area sales manager, Frank Shinn expresses his enthusiasm for a relationship that, while demanding, is always stimulating.
"This is a typical application from BNS Nuclear Services,” he says. “Two of our products on one machine - one of which has been engineered specifically to suit, the other being a standard unit – and, as usual, the selection process was an enjoyable and interesting experience, dealing with engineers who are specialists in the business".
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