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Active Tests at the Rokkasho Reprocessing Plant

As reported in NIT 112, active testing ("hot tests") of the Rokkasho reprocessing plant commenced on 31 March 2006. The tests are scheduled to continue for 16 months until July 2007, during which time 430 tons of spent nuclear fuel will be reprocessed. Construction of the Rokkasho reprocessing plant was virtually complete in 2001. Chemical tests were carried out from September 2002 and uranium tests using depleted uranium were conducted from December 2004. During these hot tests, plutonium will be recovered for the first time and the release of radiation has begun.

Circumstances surrounding start of active tests
In order to start the tests, the electric power companies, Japan Nuclear Fuel Ltd (JNFL), Aomori Prefecture, the Atomic Energy Commission and the Nuclear and Industrial Safety Agency (NISA) banded together to force matter through the political procedures. Their priority was to meet the schedule to commence operations in August 2007. The plan for the hot tests was submitted to the government and approved even before the report on the uranium tests had been completed. The results of the uranium tests were only confirmed afterwards. The Nuclear Safety Commission's (NSC) policy was to carry out the tests in stages, proceeding to the next stage only after the results of the previous stage had been confirmed, but this process was completely ignored.

One major reason for the rush was that by starting hot tests JNFL could begin to receive payments for reprocessing. Japan's fiscal year runs from April 1st to March 31st, so by commencing the tests on March 31st JNFL became eligible for a portion of the 2005 fiscal year payments after doing just one day's work. All JNFL did on that day was move one PWR fuel assembly from the storage rack in the spent fuel pool to a position before the shearing machine. For this JNFL received 52.9 billion yen. If JNFL continues to extract plutonium at Rokkasho, it will receive the sum of 280 billion yen per year from the electric power companies.

There is a lot of opposition to the hot tests, not just within Aomori Prefecture, but also in Iwate Prefecture immediately to the south. Liquid radioactive waste from the Rokkasho reprocessing plant is released into the Pacific Ocean from a pipe 3 kilometers out to sea. At this point the current flows from north to south, so there have been strong expressions of concern from the governor of Iwate Prefecture and from the fishing industry that the radioactivity released will affect the fishing industry (see NIT 108 Group Introduction). JNFL therefore held two explanatory meetings in Iwate Prefecture in Kuji City and Miyako City, but participation was restricted to members of the local councils and fishermen. In an extraordinary move, the general public was excluded from these meetings. In the end, JNFL provided only formula explanations and questions were cut short on the grounds that time had run out. The process was criticized by both participants and residents alike.

Outline of the tests
According to JNFL's "Hot Test Plan (Comprehensive Tests Using Spent Fuel)", a total of 430 tons of spent fuel (approximately 210 tons of PWR type spent fuel and 220 tons of BWR type spent fuel) will be processed over a period of 16 months. The whole process will be broken up into 5 steps as follows:

Step 1, approximately 30 tons of PWR fuel in 2 months;
Step 2, approximately 50 tons of PWR fuel and 10 tons of BWR fuel in 4 months;
Step 3, approximately 20 tons of PWR fuel and 50 tons of BWR fuel in 5 months;
Step 4, approximately 110 tons of PWR fuel in 3 months;
Step 5, approximately 160 tons of BWR fuel in 3 months.

Steps 1 to 3 make up the first stage of the process. This stage will begin with small quantities of less radioactive low burn-up fuel that has been cooled for a long time. It will test whether individual machines and equipment perform within design parameters. Steps 4 and 5 make up the second stage. The plan for this stage is to test spent fuel close to real conditions (burn-up of 45,000 MWd/t1). The plant will be operated continuously at near real operating conditions to confirm whether or not it is capable of processing 800 tons per year.

One important issue is the quantity of radioactivity released into the environment. In particular, the amount of radioactivity released on a daily basis, in the form of aerial releases and liquid releases, will be measured. The Rokkasho reprocessing plant's benchmarks for annual radioactive releases assume that all krypton and tritium will be released. This is a problem in itself. However, in regard to the other radionuclides, it is unclear whether they will be held within their allocated benchmarks. There are also problems with the evaluation of the test results. There are "hold points" after Step 1 and Step 2 to assess the amount of radioactivity released. However, there are no hold points after the later steps. On the basis of the evaluation of the tests up to the end of Step 2, which involve low amounts of radioactivity, the go sign will be given to reprocess the remaining 340 tons. This reveals that there are major problems with the intentions of the government and JNFL.

Step 1 was completed on June 26th. Naturally, the amount of radioactivity released so far is low, because of the 30 tons of PWR spent fuel which has been reprocessed, 16 tons had a burn-up ranging from 12,000 to 17,000 MWd/t (cooling period of about 20 years), and 14 tons had a burn-up ranging from 30,000 to 33,000 MWd/t (cooling period of 10-18 years). When compared to the benchmarks, there don't appear to be major problems. However, it should be pointed out that there is a tendency for Iodine-129 (3.8 x 107 Bq) to be higher than it should be at this stage in the tests.

Plutonium in rice?
JNFL has published estimates of the impact that the radioactivity released from the Rokkasho reprocessing plant will have on the surrounding environment in the future. For example:

  • 1 kilogram of rice produced in the surrounding area will contain 90 becquerels of carbon-14, 100 becquerels of tritium, 0.05 becquerels of ruthenium-106 and 0.0003 becquerels of plutonium;
  • seaweeds such as kelp and wakame will contain 0.02 becquerels of plutonium and 0.08 becquerels of ruthenium-106;
  • fish will contain 0.005 becquerels of plutonium and 300 becquerels of tritium;
  • shell fish will contain 0.01 becquerels of plutonium; and so on.

However, this estimate is based on calculations which are very advantageous to JNFL. The estimate assumes that radioactivity released will be dispersed and diluted in accordance with these calculations and that radioactivity will not accumulate. It is inconceivable that contamination of the surrounding environment will be held within these levels. Apparently JNFL thought that by publishing these figures it could suppress future civil unrest, but in fact these figures have given rise to serious concerns among consumers living in other regions. It is quite conceivable that in future questions will be raised in the marketplace about radioactive contamination of agricultural products and seafood from Rokkasho.

Internal exposure to plutonium

Internal exposure to plutonium was one major issue to arise during Step 1 of the hot tests. Already two such cases have occurred, both in the Analysis Laboratory Building. Liquid containing uranium and plutonium is sent from the whole reprocessing plant to the Analysis Laboratory Building. There the constituents and concentration of the liquid are analyzed and calculated. The two cases of radiation exposure occurred during continuous processes related to the analysis of plutonium-containing liquid waste.

Cartoon by Shoji Takagi

The first case occurred on May 20th. A 35 year-old subcontractor worker was exposed to radiation while handling an analysis sample under a "hood"2. The worker was not wearing a mask at the time and was internally exposed by inhaling alpha emitting radioactivity including plutonium by nose and mouth. JNFL announced that the committed effective dose (dose received over a 50 year period) was 0.014 milli-sieverts. The radiation exposure was not detected when the worker left the area where the exposure occurred. It was not until two days later that the radiation exposure was recognized.

The second case occurred on June 24th. A 19 year-old subcontractor worker was exposed to radiation while carrying out analysis in the room next door to the room where the first incident occurred. On this occasion radioactivity was detected on both gloves and on the right leg when the worker left the room. Again the worker was not wearing a mask. A smear test of the nose membrane was carried out immediately and alpha emitters including plutonium were measured at 0.7 becquerels. Tests were carried out on the worker's urine and feces for the next 5 days, but no radioactivity was detected. JNFL pronounced that there had been no internal exposure. However, plutonium had already been detected on the worker's nose. If plutonium was inhaled deep into the lungs, it would not have shown up in JNFL's tests. The plutonium particles would not dissolve and be carried away in the blood. They would lodge in the lungs and continue to irradiate the worker until, if ever, they are expelled from the body.

As a result of these problems and other factors the hot tests are currently running one month behind schedule.

Masako Sawai (CNIC)

1. Burn-up is measured in megawatt days per ton.
2. A "hood" is a ventilated box-like structure, which is used to prevent dispersal of radioactive materials and chemicals during handling.

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