UK-based Cavendish Nuclear announced on 27 August that it had been awarded   a contract by Japan Atomic Energy Agency (JAEA) to support decommissioning of the fast reactor at Monju, Japan

The contract builds on experience of decommissioning fast reactors in the UK, passing on the lessons learned to save time and cost in decommissioning in Japan and ensure the highest levels of safety and environmental protection. Cavendish Nuclear is part of a UK team working with JAEA that will use the skills and experience gained during the ongoing decommissioning of the fast reactors at Dounreay, which are at an advanced stage of clean-out and dismantling. The main elements of the contract with JAEA involve the technical support for creating a lifetime plan for the decommissioning of Monju and a feasibility study into the treatment of sodium coolant from the Monju site.

Mark Rouse, president of Cavendish Nuclear in Japan said: “This is a great opportunity to showcase the talent and experience developed over many years in the UK and demonstrates how Cavendish Nuclear can support other countries to decommission their sites in a safe manner.”

The 280 MWe Monju FBR in Tsuruga City, Fukui Prefecture, began operating in 1994 but was shut down after four months when about 700 kilograms of liquid sodium leaked from the secondary cooling loop. Although there were no injuries or radioactive contamination of the site, JAEA did not reveal the scale of the damage.  The reactor was restarted in May 2010 but was stopped again later that year after  refuelling equipment fell into the reactor vessel during a refuelling outage. The equipment was subsequently retrieved and replaced but the Nuclear Regulatory Authority (NRA) refused permission to restart the reactor.

In November 2015, in the wake of concerns over equipment inspections, NRA determined JAEA was not competent to operate the reactor and, in December 2016, the government formally announced that it would be decommissioned.

The government estimates that decommissioning   will take 30 years and cost more than JPY375 billion ($3.5 billion) including  JPY225 billion for maintenance, JPY135 billion for dismantling   and JPY15 billion for defuelling and decommissioning preparations.