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Thursday, Nov. 4, 1999
Kepco cancels hearing on MOX fuel
KYOTO -- Antinuclear groups have raised concerns that data concerning mixed uranium-plutonium (MOX) fuel to be burned in a Fukui Prefecture reactor later this year were falsified and are calling for the utility, Kansai Electric Power Co., to hold a public hearing on the issue.
Kepco officials, claim, however, that their own check of the data indicated there were no safety concerns and, because they have already addressed the issue, there is no need for a hearing.
Late last week, two antinuclear groups, Kyoto-based Green Action Japan and an Osaka-based group that opposes reactors in Fukui, obtained inspection results from Kepco for MOX fuel that was processed by British Nuclear Fuels Ltd. in Sellafield, England, for use in the Takahama No. 4 reactor.
The fuel is pressed into tiny pellets, and then bound into lots. There are 3,000 pellets to a lot. In one of the lots, the groups said they discovered something odd.
"In spite of the fact that the pellets were selected at random, the average diameter value for six pellets in row in one of the lots was exactly the same to three decimal places," said Stephen Ready, a Canadian activist with Green Action Japan.
"The second problem is that it appears data for one of the lots was altered to avoid having more than six pellets fall outside the upper specs," Ready said, explaining that data provided to activists by Kepco officials include figures that appear to have statistical anomalies.
The fuel that will be used in the Takahama No. 4 reactor is divided into 199 lots. Each of the 3,000 pellets in a lot should have a diameter of roughly 8 mm and a length of 13 mm. Normal testing procedures call for two separate checks on the size of the pellets to be carried out by BNFL.
The first inspection, using a laser micrometer, checks the upper, middle and lower section of each pellet in the entire lot. In the second inspection, 200 pellets are removed from the lot and checked, also using a laser micrometer.
One pellet must have a diameter of between 8.179 mm and 8.204 mm. If just one section of the pellet is out of specs, the pellet is discarded. If, during the random sample test, the average value of more than six pellets exceeds the upper limit value, the entire lot must be discarded.
In its inspection of 200 pellets, Kepco found that 66 were slightly large individually. But because their average value was close to the average of one 3,000-pellet lot and within the acceptable range, Kepco concluded there was no need to replace the 66 pellets.
In addition, Kepco said that the same value for six pellets in a row recorded by BNFL is not statistically unusual.
"In our explanation to Green Action Japan, we noted that there were cases where the same value appeared three and four times in a row. The same figure appearing six times in a row is not unusual and is not proof that the data was falsified," said Takeshi Kato, a Kepco spokesman.
Activists are concerned because BNFL has already admitted that data concerning another batch of MOX fuel, currently being processed in Britain for use in Kepco's Takahama No. 3 reactor, was faked when two technicians failed to conduct the second checks properly and simply copied the numbers for the pellet sizes from the first test reportedly in order to save time.
"The fuel for Takahama No. 4 was processed and sent to Japan before revelations about data falsification came to light, which leaves serious questions about the safety of the fuel," said Aileen Smith, another Green Action activist.
A variation in the size of the pellets could cause the fuel to burn unevenly, Kato said. However, he added that there were numerous other safety measures in place to monitor the fuel as it burns, and any deviation in temperature would immediately be noticed.
But antinuclear activists, as well as several members of the Fukui Prefectural Assembly, are calling on Kepco officials to hold a public hearing on the issue and to provide assurances that the fuel is safe.
Kepco officials, however, have so far refused the requests, claiming such questions have already been answered.