Nuclear inspection equipment features electric linear actuator

Inspections of nuclear reactor cores are essential to the safe and efficient operation of a nuclear power station. To perform this inspection a specialist machine with a camera and bore measuring sensors is used. This machine is lowered to engage with the reactor standpipes by means of an electric linear actuator supplied by Power Jacks.

Known as the NICIE (New In-Core Inspection Equipment), the machine was developed by BNS Nuclear Services with which Power Jacks worked closely to design and manufacture the main linear actuation unit that engages the machine with the reactor standpipe. Four additional jacks act as stabilisers when the machine is coupled to the standpipe.

The NICIE inspects nuclear reactors by lowering a camera down into the reactor fuel channel to provide measurement and maintenance checks. The main body of the machine is raised and lowered to engage it with the reactor stand pipes. A specially designed electric linear actuator from Power Jacks performs this actuation.

Custom actuator

A 20kN load must be raised and lowered over a distance of 525mm, with the end of travel signalled by electromechanical limit switches installed in the actuator. The linear movement is produced by a precision worm gear set matched to a trapezoidal machine screw and nut mounted in a ram-style housing. It is important that the rigidity of the ram is maintained over its stroke, hence there are two internal guidance mechanisms for the ram; one guides the outer diameter of the ram and the other guides the internal bore of the ram. This, combined with the screw and nut drive connections, provides a very stable actuation column. As a safety feature the ram is fitted with a proprietary clutch to act as a mechanical fail safe, thereby preventing an overload condition should the external control systems fail. Powering the actuator is a three-phase, 0.75kW AC motor with an integral brake for position holding, plus there is an auxiliary hand drive shaft should manual operation be required.

The machine itself is mounted on wheels for easy transportation. However, when in use its position must be held firm. For this purpose four E-Series machine screw jacks are mounted on the base of the machine; when extended, these take the weight off the wheels in a similar way to stabiliser jacks on mobile cranes.

Hinckley Point Power Station will be operating the hoist, which is currently being tested by BNS Nuclear Services at Whetstone in England. Hinkley Point is a nuclear power station near Bridgwater, Somerset, on the Bristol Channel coast of south west England. It is an advanced gas-cooled reactor (AGR), which was designed to generate 1250MW of electricity.

Nuclear industry experience

Power Jacks has a longstanding working relationship of over 38 years with BNS Nuclear Services, now operating under the Babcock Group. Alex MacMillan, Leading Design Engineer of BNS Nuclear Services, says that the products from Power Jacks for the NICIE hoist were delivered on time and on budget and are now fitted to the first of two machines.

Frank Shinn, Power Jacks Area Sales Manager for the East Midlands, adds: "This is a typical application from BNS Nuclear Services - two of our products on one machine, one of which has been engineered specifically to suit, the other is a standard unit. As usual, the selection process was an enjoyable and interesting experience, dealing with engineers who are specialists in the business".

Power Jacks expertise in providing an engineered solution for a customer's linear actuation application continues to meet the exacting requirements of the nuclear industry whether at the stage of development, decommissioning or new build.

Follow the links to find out more about electric linear actuators and E-Series machine screw jacks.