Rokkasho Reprocessing Plant Fallen brick retrieved at last! Nuke Info Tokyo No. 137
October date for full operations definitely won’t be met
The vitrification furnace at Japan Nuclear Fuel Ltd’s (JNFL) Rokkasho Reprocessing Plant is being restored. However, this only means that the prospects of resuming active tests have improved. The chances of actually passing those tests are by no means good.
Photo of brick retrieved from vitrification furnace
Active testing of the vitrification furnace began in November 2007. However, numerous problems have arisen, including the accumulation of platinum group elements at the bottom of the furnace, which prevented the molten glass from flowing through. While JNFL was trying to fix this problem, a brick fell from the ceiling of the furnace. In addition, in January 2009 about 150 liters of high-level radioactive liquid waste leaked within the vitrification cell. Fixing this problem took one year and four months. (See NIT 129 for a more detailed account of these problems.)
Attempts to recover the fallen brick commenced in April this year, after completion of responses to the leak and the contamination that it caused. The operators were unable to see inside the furnace, so they had to hunt around for the brick with a mechanical arm. The first time they managed to grab the brick it fell back again (see NIT 136). JNFL made adjustments to the crane, introduced a new device with a stronger grip and finally succeeded in retrieving the brick on the 18th attempt on June 17. It then began draining the remaining 1,500 liters (10 glass canisters’ worth) of molten glass. Draining was completed on July 2 and JNFL is now attempting to remove the remaining sediment at the bottom of the vitrification furnace. When that is finished it will finally be able to resume pre-commissioning tests.
Although the brick has been recovered, the fundamental problems with the vitrification furnace have not been solved. It is therefore uncertain whether it can pass the tests.
In the first place, it has not yet established the reason why the brick fell from the ceiling. In the absence of an explanation, JNFL is unable to develop a response. It has simply concluded that the brick “fell naturally”, but if that is the case, it cannot refute the possibility that bricks will fall again in future.
Concerning the biggest problem, the accumulation of platinum group elements at the bottom of the vitrification furnace, JNFL says, “This can be overcome with strict temperature control.” However, it is simply relying on operators perfecting their technical skills. This does not guarantee success.
Regarding production of glass canisters, the required performance is 70 liters flow through of molten glass per hour and the production of 1,000 glass canisters per year at a stable rate of operation. The current performance is a far cry from that.
JNFL has not changed its official schedule for commencing full operations in October. However, no one believes this schedule is achievable. President Yoshihiko Kawai himself admits that it is a “tough situation”. There is no doubt that a new schedule will be announced soon. We must conclude that the future of the Rokkasho Reprocessing Plant remains as uncertain as ever.
Masako Sawai (CNIC)