National Nuclear Laboratory


Sunday 25 May 2014

The right amount of innovation

For Nexia Solutions, tailored technology means applying the right amount of innovation to add value for customers at the lowest possible cost.

A key process area on the Sellafield site, the Highly Active Liquor Evaporation and Storage (HALES) plants are of fundamental importance. Continued operations remain a high priority for the site operator British Nuclear Group – a major customer for Nexia Solutions.

The management of highly active liquid waste from the reprocessing of used nuclear fuel is one of the most challenging areas in the industry. High level waste is concentrated by evaporation prior to storage and eventual waste treatment in the Sellafield Waste Vitrification Plant. To support continued operation on behalf of customers, Nexia Solutions offers services ranging from innovative approaches to investigation, diagnosis and resolution of plant issues through to the underwriting of safety cases in areas such as corrosion in storage tanks.

Within the HALES complex, the highly active Evaporators make a primary contribution to the waste management process. Three evaporators underpin continued storage operations at Sellafield. The first, Evaporator A came on line in 1970 followed by Evaporator B in 1984. The latest, Evaporator C, began operation in 1990. It is very important that these key items of plant are operated in a safe manner.

The condition of each evaporator is regularly monitored to meet safety and operational requirements. In the past, this was been achieved via often complex experimentation. With plant thickness measurements so fundamental, it is very important that detailed data is provided to confirm evaporator life expectancy. With that in mind, an inspection unit with much greater flexibility and capable of providing data about the condition of the evaporator was required.

The Nexia Solutions Materials Team developed and prepared a novel inspection device for deployment in the evaporators. The system consists of an integrated CCTV system and ultrasonic capability. This enables the device to provide visual assessment of pipe condition and determine wall thickness of heating/cooling coils in strategic areas in the evaporator.

To deploy effectively, the unit was required to enter the evaporator pipe system and negotiate numerous, often tight, bends. It was vital that the device could be retrieved in a simple manner with no part having the potential to block, lodge or become detached within the cooling/heating coils. The Nexia Solutions team worked within this fundamental requirement when developing the unit. In addition, the team factored in a capability to withstand high radiation and heat related environments and the necessity to make the equipment reusable.

A successful development and testing programme means that the HALES complex is able to inspect the HA Evaporator coils on a regular basis. Remnant life of the evaporator can be calculated with greater accuracy to determine the condition of the plant and how this might affect the customer’s business in terms of safety and production.

Since its introduction, more work has been being carried out to further improve inspection unit manoeuvrability and overall quality. The programme has continued to make progress and a major milestone was achieved during April 2007.

The latest Nexia Solutions bottom coil inspection device, which has been designed and built over the past three months, has successfully completed its stakeholder demonstration to the Nuclear Decommissioning Authority (NDA) and customer British Nuclear Group. This latest unit has already been deployed in HALES Evaporator C to provide information on wall thickness of the bottom outer coil. Again, information gained will be used to refine corrosion estimates and evaporator remnant life.

Ongoing development work is continuing at the Nexia Solutions facility at Workington. Operational since 2004, the Workington facility carries out non radioactive test rig activities on behalf of customers. The latest inspection unit technology is being developed at Workington and has been deployed on a test rig that duplicates the internal structure of the Evaporator coils at Sellafield. Once this work has been successfully concluded, the unit will be prepared and delivered to Sellafield for use on the actual HALES Evaporators.

Nexia Solutions continues to support its customer at Sellafield in this important operational area by resolving technical challenge and maintaining continuous effective operation.