Regulator approves safety upgrades at Japanese MOX plant

Following the March 2011 accident at the Fukushima-Daiichi nuclear power plant, new safety standards for power plants were introduced by the NRA in July 2013. In December of that year, new standards came into force that apply to the country's fuel fabrication plants and its reprocessing facilities. Used fuel and radioactive waste storage and disposal facilities are also subject to the revised rules, as are research reactors and nuclear fuel research centres.

The requirements vary from facility to facility, but generally include reinforcement measures against natural threats such as earthquakes and tsunamis, and in some cases tornadoes, volcanoes and forest fires. The standards require that fuel fabrication plants are able to contain radioactive material in the event of an accident, and have measures in place to prevent accidental criticality events. Reprocessing plants need to demonstrate these as well as countermeasures specifically for terrorist attacks, hydrogen explosions, fires resulting from solvent leaks and vaporisation of liquid waste.

At the J-MOX fuel fabrication plant, work has been carried out to enhance the earthquake resistance of structures in operations rooms. Equipment to counter internal fires has also been installed. The plant floor space has been expanded in order to accommodate both these measures.

JNFL applied to the NRA in January 2014 for the modification of safety measures for at its J-MOX fuel fabrication plant in compliance with revised regulatory standards. In October this year, the NRA approved a draft report on the modification of safety measures at the facility.

At a meeting today, the five NRA commissioners gave the final approval for the safety measures taken at the plant.

"This regulation is said to have institutionalised the highest level of safety requirements in the world," JNFL said in a statement. "We believe today's permission is a big step towards the completion and subsequent safe operation of the MOX fuel fabrication plant."

On 29 July, JNFL received permission from the NRA for the modification of safety measures at its reprocessing plant, also under construction at Rokkasho. Additional equipment and systems are being installed for the recovery of radioactivity in the event of a severe accident. Additional safety-related countermeasures are also being put in place, such as internal flood protection, strengthening of the seismic resistance of pipework and improving measures against internal fires.

Construction of the Rokkasho reprocessing plant began in 1993 and was originally expected to be completed by 1997. The facility is based on the same technology as Orano's La Hague plant in France. Once operational, the maximum reprocessing capacity of the Rokkasho plant will be 800 tonnes per year, according to JNFL.

Construction of the J-MOX plant at Rokkasho began in late 2010. Construction of the 130 tonne per year plant had been delayed by three years from the planned 2007 start by revision of seismic criteria following on from the powerful Niigata-Chuetsu-Oki earthquake.

Completion of both the reprocessing plant and the MOX fuel fabrication plant has faced several delays. Under the latest schedule, completion of the reprocessing plant has been put back to the first-half of FY2022 (ending March 2023), owing to the implementation of safety measures at the plant, including construction of a new cooling tower. Completion of the MOX plant is now expected in the first-half of FY2022.