Japanese reprocessing plant delayed by another year
25 August 2020
The expected completion of the reprocessing plant at Rokkasho in Japan's Aomori Prefecture has been put back again, 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, Japan Nuclear Fuel Limited (JNFL) has announced.
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The Rokkasho used fuel reprocessing plant (Image: JNFL)
Following the March 2011 accident at the Fukushima Daiichi nuclear power plant, new safety standards for nuclear fuel cycle facilities came into force in December 2013. 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. Reprocessing plants need to demonstrate these as well as countermeasures specifically against terrorist attacks, hydrogen explosions, fires resulting from solvent leaks and vaporisation of liquid waste.
Since August 2019, steel protective nets are required to be installed to the two outdoor cooling towers at the Rokkasho reprocessing plant to protect them from tornados with a maximum wind speed 100 meters per second. One of these towers is on the roof of the used fuel shredding building. JNFL said that if a steel protecting net was installed there, the seismic capacity of the building would be affected because of the weight increase. It therefore decided to construct a new cooling tower equipped with a steel protective net on the ground.
On 29 July, JNFL received permission from the Nuclear Regulation Authority (NRA) for the modification of safety measures at its reprocessing plant. 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.
"It takes time to design, manufacture and construct [the new cooling tower]," JNFL noted on 21 August. "Also, there will be the final self-inspection by JNFL to confirm whether the plant design complies with new regulatory requirements, and confirmation of the inspection result by the NRA." The company has therefore changed the expected completion of the required safety measures from the first-half of FY2021 to the first-half of FY2022.
Construction of the Rokkasho reprocessing plant began in 1993 and was originally expected to be completed by 1997. However, its construction and commissioning have faced several delays. Problems in the locally-designed vitrification plant - where dried out and powdered high-level radioactive waste is mixed with molten glass for permanent storage - have contributed to these delays. JNFL designed the vitrification unit to go with the reprocessing section supplied by Areva. The Rokkasho reprocessing 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.
Researched and written by World Nuclear News