Trial production of vitrified waste at one of the two melting furnaces at the Rokkasho reprocessing plant has been successfully completed, Japan Nuclear Fuel Ltd (JNFL) announced.
The company said that 30 batches of vitrified waste were produced from liquid high-level waste (HLW) during pre-operational testing of the 'B' furnace at Rokkasho between 19 November 2012 and 3 January 2013.
Five of these were produced between 7 and 19 December in a test to confirm the relationship between the power being fed into the furnace and the temperature of the glass being produced. A further 20 blocks were produced during a subsequent test to confirm that temperatures within the furnace were being maintained at the correct levels. An additional test between 31 December and 3 January confirmed that the furnace was capable of vitrifying at the design capacity of 70 litres of HLW per hour.
The successful tests at the B Furnace follow earlier ones in July 2012, which produced ten batches of vitrified HLW. Pre-operational testing of furnace 'A' at Rokkasho will resume in March or April, JNFL said.
The Rokkasho-mura reprocessing plant was due to start commercial operation in November 2008, following a 28-month test phase plus some delay at the end of 13 years construction. However, 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 delayed its start up.
Active testing at the vitrification plant began in November 2007, with separated HLW being combined with borosilicate glass. The plant takes wastes after uranium and plutonium are recovered from used fuel for recycle, leaving 4% of the used fuel as HLW. However, the furnaces have proved unable to cope with impurities in the wastes, and commissioning was repeatedly delayed. Finally in 2010 JNFL decided to redesign the unit to better control temperature of the molten glass. It is now expected to be commissioned in October 2013.
Once operational, the maximum reprocessing capacity of the Rokkasho plant should be 800 tonnes per year, according to JNFL.
Researched and written
by World Nuclear News