Cavendish to assist in decommissioning Monju

28 August 2019

British nuclear services company Cavendish Nuclear has been awarded a contract by Japan Atomic Energy Agency (JAEA) to support decommissioning of the Monju prototype fast breeder reactor. Cavendish, a subsidiary of Babcock International Group, has been involved in the ongoing decommissioning of the fast reactors at the UK's Dounreay site.

The Monju FBR (Image: Nuclear Fuel and Power Reactor Development Corporation / IAEA)

Cavendish will provide 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.

Cavendish said 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".

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."

A key part of Japan's nuclear energy programme, the 280 MWe Monju FBR in Tsuruga City, Fukui Prefecture, initially started in 1994. However, it was shut down after just four months when about 700 kilograms of liquid sodium leaked from the secondary cooling loop. Although there were no injuries and no radioactivity escaped plant buildings, the operator tried to conceal the scale of the damage. It eventually restarted in May 2010 but has not operated since refuelling equipment fell into the reactor vessel during a refuelling outage later that year. The equipment was subsequently retrieved and replaced but the Nuclear Regulatory Authority (NRA) did not permit the reactor to restart.

In November 2015, following concerns over equipment inspections, the NRA determined JAEA was not competent to operate the idled reactor and, in December 2016, the government formally announced its decision to decommission it

The decommissioning of Monju will take 30 years and cost more than JPY375 billion (USD3.5 billion), the government estimates. This includes JPY225 billion for maintenance, JPY135 billion for dismantling the plant and JPY15 billion for defuelling and preparations for decommissioning.

Researched and written by World Nuclear News