On August 31 Japan Nuclear Fuel Ltd. (JNFL) announced that it had extended the estimated date of completion of construction and testing of its Rokkasho Reprocessing Plant by fourteen months to October 2010. It was the seventeenth time that the schedule had been extended. Compared to the original schedule, the cumulative delay now amounts to nearly thirteen years. Active tests using spent nuclear fuel started in March 2006, but since then JNFL has gradually extended the schedule in response to numerous problems with the vitrification facility. Testing of the vitrification facility is the final stage before construction of the plant is officially declared to be complete. This time JNFL was forced to concede that it would take a substantial amount of time to restore the plant and complete the tests, so a longer than usual extension was announced.
Testing of the vitrification facility began in November 2007, but the process of mixing glass with highly radioactive liquid waste from the reprocessing of spent fuel and sealing it in canisters has been plagued with problems. Tests were suspended repeatedly, because JNFL was unable to solve the problem of metal particles (platinum group elements) accumulating in the bottom of the vitrification furnace. Last December it was discovered that a fireproof tile had fallen from the inner wall of the furnace. Then in January, while attempts were being made to remove the tile, 150 liters of high-level radioactive liquid waste leaked from a pipe within the vitrification cell.
It seems that most of the leaked fluid evaporated within the cell. The liquid, which contained concentrated nitric acid, formed a mist which adhered to and corroded cables and equipment in the cell. JNFL claims that it will take eleven months to fix these problems and a further three months to complete the tests. However, this schedule assumes that everything will go smoothly from now on.
In practice, JNFL's estimate of fourteen months is unlikely to be achievable. Problems caused by the corrosive nitric acid mist will certainly increase and restoration work in such an environment will be extremely difficult. Furthermore, so far tests have been carried out on only one of the two vitrification furnaces (furnace A). It is possible that furnace B, which is immediately alongside furnace A, has also been affected. It seems unrealistic to allocate just three months to complete tests on both furnaces, considering all the problems that have arisen while testing just one furnace. Under the circumstances, even JNFL was forced to admit that "this is just an estimate" and that "it might take slightly longer".
With test operations suspended, by the end of this year Rokkasho Reprocessing Plant's spent fuel storage pool, which can hold up to 3,000 tons of spent fuel, will reach 95% capacity. Consequently, JNFL has decided not to accept any more spent fuel from utilities during 2010.
Rokkasho's spent fuel storage pool has a maximum holding capacity of 1,500 tons each of BWR and PWR spent fuel. Japan has a similar number of BWR and PWR plants, but the storage capacity in spent fuel pools at BWRs is relatively limited. There is not much space left in the spent fuel pools of some of these plants, in particular at Tokyo Electric Power Company's (TEPCO) Fukushima I and Fukushima II nuclear power stations. In collaboration with Japan Atomic Power Company, TEPCO plans to build an interim spent fuel storage facility with a capacity of 5,000 tons in Mutsu City in Aomori Prefecture, but the facility is still undergoing safety assessments. If operation of the Rokkasho Reprocessing Plant is further delayed, utilities are likely to consider responses to the lack of spent fuel storage capacity such as re-racking of existing pools and additional temporary on-site storage facilities.
Masako Sawai (CNIC)
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See previous articles about he active testing of the Rokkasho Reprocessing Plant.