Project WAGR: the UK Demonstration Project for Power Reactor Decommissioning

Abstract

The United Kingdom Atomic Energy Authority (UKAEA) has built and operated a wide range of nuclear facilities since the late 1940’s. UKAEA’s mission is to restore the environment of its sites in a safe and secure manner. This restoration includes the decommissioning of a number of redundant research and power reactors.The Windscale Advanced Gas-cooled Reactor (WAGR) was the UK’s prototype Advanced gas cooled reactor and became the forerunner of a family of 14 reactors built to generate cheaper and more efficient electricity in the UK. WAGR was constructed between 1957 and 1961 and was a carbon dioxide cooled, graphite moderated reactor using uranium oxide fuel in stainless steel cans. The reactor consisted of a graphite moderator housed in a cylindrical reactor vessel with hemispherical ends. The reactor and associated heat exchangers were enclosed in the iconic spherical containment building regularly used by the media in the UK as an illustration of the nuclear industry.The reactor first produced power in August 1962 and achieved full design output in 1963. It operated at an electrical output of 33 MW (E) for 18 years (average load factor of 75%). In 1981 the reactor was shut down after satisfactory completion of all the research and development objectives.In anticipation of the UK’s likely nuclear decommissioning needs the UKAEA decided to decommission WAGR to the International Atomic Energy Agency’s (IAEA) stage 3 (restoration of the area occupied by the facility to a condition of unrestricted re-usability) as the national demonstration exercise for power reactor decommissioning.Since 1998 the UKAEA and its contractors have been undertaking the dismantling of the reactor core components and pressure vessel in a series of 10 campaigns. These contain neutron activated components expected to produce dose rates well in excess of 1Sv/hr. To carry out the work UKAEA installed an £8M remote dismantling machine (RDM), a waste recovery and transport system and a shielded waste route through which to move, sort, assay condition and package the waste. The RDM and associated hoist have been used to deploy the numerous tools and end effectors necessary to effect the painstaking dismantling process.Now that the remote operations are reaching a conclusion it is possible to review the success of both these tools and the RDM itself.