No Sign of Resumption of Vitrification at Rokkasho Nuke Info Tokyo No. 124
No chance of completing the plant in May as planned
The final stage of the active tests of the Rokkasho Reprocessing Plant began in February this year, but the high-level liquid waste vitrification facility is still out of action, with no indication of when it will resume operation. According to Japan Nuclear Fuel Ltd. (JNFL), construction and testing of the plant is scheduled to be completed at the end of May, but this is now clearly impossible, so another extension is inevitable.
Never Ending Vitrification Problems
The glass vitrification facility at the Rokkasho Reprocessing Plant has two glass melting furnaces, A and B. In November 2007, the facility began producing high-level glass canisters using furnace A, but production ceased at the end of the year due to problems controlling the temperature of the furnace. Platinum group metals had accumulated at the bottom of the furnace causing the molten glass to take more than twice the normal time to flow down. JNFL cleaned out the glass that remained in the bottom of the furnace and is trying to fix the operating method and the method of controlling the temperature. However, due to the high level of radiation in the furnace, all the work has to be done by remote control. It is a pains-taking process, so the glass was not cleaned out until the middle of April. The operating method, including temperature control, is being reviewed, but it is now clear that the vitrification process developed at the Tokai Reprocessing Facility was immature and that the technology transfer to the Rokkasho Reprocessing Plant was unsuccessful. (See NIT 122 for more details.)
Oil Leak from Shearing Equipment
Meanwhile, on April 14, in the Head End Building in the upstream part of the plant, approximately 60 liters of oil spurted out from the oil pressure control equipment of the shearing machine. Shearing of spent fuel was stopped and at the time this article was being written it had not restarted. Only a few months earlier, on January 1, 750 liters of oil leaked from the same equipment and steps had been taken to prevent a recurrence.
In the January incident, a joint in a 1.5 cm diameter pipe which feeds oil from a tank to the shearing machine’s oil pressure control unit was broken. In April the leak occurred at the connection between a pressure gauge and a pipe. A 2.6 cm diameter fluoride resin support ring to prevent oil from leaking from the joint had come loose. The ring had been refitted during an inspection in February, but it may have been fitted incorrectly. A worker found it on the floor on April 12, but couldn’t locate where it came from. This shoddy failure to prevent the leak from occurring in the first place has led many local residents to believe that there are problems with JNFL’s safety system.
IAEA Seal Broken
The Rokkasho Reprocessing Plant is the world’s largest facility subject to inspection in the context of comprehensive IAEA safeguards. However, on two occasions JNFL broke an IAEA seal on nuclear materials. The supervising authority issued a stern warning in response to these incidents. The polystyrene seal was located on a rail near the entrance to a building for storing uranium recovered during reprocessing. The first incident occurred in March. On that occasion, a worker who accidentally broke the seal was given a verbal reprimand by the office responsible, but in April the seal was broken again by a different worker. A surveillance camera confirmed that no uranium was removed, but the inadequacy of JNFL’s warning to its workers has been strongly criticized.
By Masako Sawai (CNIC)