Radioactive cesium levels exceeding 100,000 becquerels per kilogram were measured in mud accumulated at the bottom of swimming pools at two high schools in and around Fukushima city.
Mud in the pool of a third high school in Minami-Soma, which is closer to the crippled Fukushima No. 1 nuclear plant, showed at least 8,000 becquerels per kilogram.
Under a special measures law, the central government must remove mud and other substances with radioactivity levels of more than 8,000 becquerels caused by the meltdowns at the plant.
The three high schools have not discharged the water from their swimming pools since the nuclear crisis started on March 11, 2011. The water has apparently blocked the spread of contamination from the mud; air radiation levels near the three school pools are almost the same as those of other locations.
“Mud under the water, even if highly contaminated, would not become an issue unless it was taken out of the water,” said Kunikazu Noguchi, an associate professor of radiation protection at Nihon University.
However, 63 of the 70 public high schools in Fukushima Prefecture that have swimming pools have already released the water, often into rivers and irrigation canals, according to the Fukushima prefectural board of education.
The central and local governments will likely have to conduct surveys to check whether mud released from school pools has polluted rivers and canals beyond government safety levels.
The Asahi Shimbun obtained the mud with the help of the three schools and teachers, and had the Citizen's Radioactivity Measuring Station (CRMS), a Fukushima-based nonprofit group, measure the radioactivity levels.
In March 2012, the CRMS tested mud collected from the pool of the high school in Fukushima. The radioactive cesium level was 65,900 becquerels, according to the results released on April 1 this year.
The prefectural government has measured radioactivity levels of water in the school pool, but not the mud. The latest results for mud from the high school swimming pool in Fukushima showed 104,100 becquerels per kilogram.
“We have concentrated on decontamination of the pools and not thought about the mud,” said a senior Fukushima prefectural government official in charge of decontamination efforts.
The Asahi Shimbun also obtained mud from the two schools with the consent of principals and vice principals. The test results showed 119,461 becquerels for the high school pool outside the prefectural capital and 8,468 becquerels for the pool in Minami-Soma.
“We are conducting verification experiments to find practical decontamination measures,” said an official of the prefectural government. “We will inform the Environment Ministry and discuss possible measures after reviewing the results of the experiment.”
The CRMS was established in July 2011 amid complaints the central and local governments were not offering sufficient monitoring systems.
The CRMS has measured radioactivity levels of 15,000 food and other items, which citizens brought to its 10 affiliated measuring stations in Fukushima Prefecture, Tokyo and elsewhere. The test results were released on April 1.
By MASAKAZU HONDA/ Staff Writer
SIted from Asahi Shinbun, April 22, 2013