Possible increase of spent fuel to be reprocessed during active tests
Step 3 of the active tests currently being carried out at the Rokkasho reprocessing plant were completed in April (see NIT 118). On July 19 the Nuclear Fuel Cycle Safety Subcommittee of the Advisory Committee for Natural Resources and Energy approved Japan Nuclear Fuel Ltd’s (JNFL) progress report on step 3. During step 3 (January 29 – April 26) 49.5 tons of BWR and 19.9 tons of PWR spent fuel were reprocessed. JNFL’s main objective for the active tests is to pass the government’s inspections. These inspections will be carried out during steps 4 and 5, so for most of the buildings the step 3 progress report was written in terms of whether the conditions for carrying out these inspections had been met. The report concluded that they had.
However, it is clear that changes will be made to the program for functional testing of the high active liquid waste vitrification building. JNFL says that the radioactivity concentration of the high active liquid waste from steps 1 and 2 was too low to test the high active liquid waste vitrification process, so it will use liquid waste from the high burn-up spent fuel reprocessed from step 3 onwards. The maximum burn-up reprocessed during steps 1 and 2 was 21,000 MWd/t for BWR and 36,000 MWd/t for PWR spent fuel. However, the maximum burn-up during steps 3 and 4 is 36,000 MWd/t for BWR and 47,000 MWd/t for PWR spent fuel. The Nuclear Industrial and Safety Agency (NISA) says that all that is required is for JNFL to produce vitrified waste and pass the tests. It is up to JNFL to decide what liquid waste to use. To ensure that there is sufficient liquid waste to conduct the tests (planned for step 5), NISA says that it will permit JNFL to reprocess more spent fuel.
If the vitrification testing program is changed, some other tests which were planned for step 4 will have to be carried out during step 5 as well. Tests to confirm the quantity of liquid and aerial releases must take into account the increased radioactive releases from the operation of the vitrification facility. NISA says that it will confirm whether the necessary conditions are in place after it receives JNFL’s report on step 4 of the active tests.
JNFL’s real reason for wanting to use liquid waste from higher burn-up fuel for the tests is not clear. The main processes used at the Rokkasho reprocessing plant were imported from France based on the LaHague UP3 plant. However, Rokkasho’s vitrification facility is based on Liquid Fed Ceramic Melter (LFCM) technology developed at the Tokai reprocessing facility. For the melting system, LFCM employs ceramic bricks which are said to be resistant to fire, heat and corrosion. High active liquid waste and glass ingredients are fed and melted continuously. Glass canisters were first produced at Tokai in 1995 and to date 62 have been produced. However, there have been lots of problems and repeated design changes have been necessary during the construction of the Rokkasho facility.
Fault directly beneath Rokkasho reprocessing plant
The government approved design changes to correct earthquake safety design flaws in fuel handling equipment and the channel box shearing machine (see NIT 118). However, after the July 16 earthquake, it was discovered that a fault runs right under the Kashiwazaki-Kariwa nuclear power plant. As a result, the government’s earthquake safety standards are in total disarray. There are also faults running under the Rokkasho reprocessing plant (see map below f-1, f-2) and a short distance away there is a much larger fault (west of Dedo). JNFL says that these are not active faults and the government has accepted this, but after the Kashiwazaki-Kariwa earthquake, who can be sure that a big earthquake will not occur at Rokkasho?
By Masako Sawai (CNIC)