• Nuclear

Core inspection expertise

James Fisher Nuclear has won the contract to manufacture highly specialised inspection tools for EDF Energy's fleet of nuclear reactors.

Since 2012 EDF Energy (EDF) has been using special ‘eddy current inspection tools’ which were specially developed by James Fisher Nuclear (JFN) to help assess the health of the graphite blocks that make up the reactor core of many of its nuclear energy sites.

It is vital to regularly monitor the graphite that is critical to the safe generation of electricity and so ensure the continued safe operation of EDF’s nuclear reactors. But an increasing desire to extend the safe life of existing nuclear plants has stimulated the need for ever more advanced inspection technology.

The multinational electricity generator has been working closely with JFN in recent years to ensure the inspection technology is as sophisticated as possible. When EDF was given a ten-year extension on Dungeness B it asked JFN to upgrade its inspection system and ensure it was fully compatible with the specifics of the Dungeness B reactors.

The teams worked in collaboration with Serco (now AMEC), Bloodworth Consultancy and Manchester University to design a new highly sophisticated evolution, called ECIT. The system is undergoing final tests, and JFN has been given the go-ahead to manufacture three ECIT core inspection units at its modern engineering facility in Malton, Yorkshire, with a view to delivering the final tools and all their equipment by the middle of 2019.

The new system has been further developed to be robust and adaptable enough to provide reliable and accurate data in the hostile and highly radioactive environment of the reactor cores of EDF’s fleet of operating advance gas cooled (AGR) nuclear power stations. The data from each inspection is relayed to operators on the charge face – on top of the nuclear reactor - to enable rapid assessment of the condition of the core by the EDF Energy inspection team.

The EDF commission is for three tools, each of which having a control console, a calibration unit and a storage unit to allow safe handling and transportation of the tool once it’s been in the core.

‘The recent product development has combined all the good design of our previous system along with operational experience from the field to significantly improve it,’

Explains project lead for JFN, Sarah Town.

‘We were asked to modify the tool specifically for use in Dungeness B nuclear power station, which has much tighter size restrictions, and this added to the engineering challenge,’

Sarah adds.

The increased understanding of changes to the status of these cores will enable energy companies to improve the assessment of station lifetimes to help keep costs down and reduce downtime. EDF Energy owns and operates 15 nuclear plants at eight nuclear power stations in the UK. These stations have an approximate combined capacity of just under 8.8 million kilowatts (kW): a significant proportion of the UK's total installed electricity generation capacity.

How it works:

ECIT works by applying an electromagnetic field to the graphite bricks which make up the reactor core. Because graphite is electrically conductive, eddy currents are induced in the material. This electrical conductivity can be measured to give an indication of graphite density and stability. The eddy current generates data and highlights heat spots and any weaknesses or changes in density or cracks in the graphite which could have a significant impact on the reactor.

The ECIT control console has been improved, making it more ergonomic and easier to work with as well as to clean and decontaminate. This will make ECIT safe to handle and transport once it’s been in the core.