The industry ministry will investigate the distribution routes of crushed stone with possible high radioactive levels shipped by 17 quarry operators and stone crushers in Fukushima Prefecture.
The industry ministry will investigate the distribution routes of crushed stone with possible high radioactive levels shipped by 17 quarry operators and stone crushers in Fukushima Prefecture.
The decision came after the revelation on Jan. 15 that concrete contaminated with radioactive substances was likely used to build an apartment building in Nihonmatsu, Fukushima Prefecture.
The Ministry of Economy, Trade and Industry said the crushed stone in the concrete that was used to build the apartment house came from a quarry in Namie, Fukushima Prefecture, operated by stone crusher Futaba Saiseki Kogyo, located within the planned evacuation zone.
Six other stone businesses also operate in the same zone.
The industry ministry has decided it was necessary to investigate crushed stone shipped by those companies, as well as from 10 additional businesses that operate in the vicinity of areas recommended for evacuation.
The 17 businesses include five stone crushers, which manufacture gravel for use in concrete and other materials. All five are thought to have been operational in March and April after the onset of the accident at the Fukushima No. 1 nuclear power plant, which was set off by the Great East Japan Earthquake.
Four of them, except for Futaba Saiseki Kogyo, are currently operating. The industry ministry plans to measure radiation levels of crushed stone from those businesses first, and to call for a suspension of shipments if high radiation levels are detected.
The Fukushima prefectural government is also considering measuring indoor radiation levels in new houses in the prefecture where construction began after the March 11 disaster.
Meanwhile on Jan. 17, the Nihonmatsu city government began measuring radiation levels at all public works project sites where crushed stone from the Futaba Saiseki Kogyo quarry in Namie was used. The survey will cover more than 100 locations, most of them being sites of road repairs.
The latest concerns involving contaminated concrete is strongly reminiscent of a similar development last summer over radioactive contamination of rice straw.
Radioactive cesium was detected in a succession of beef samples from cattle fed with rice straw that had been contaminated after the rice straw was left outdoors.
In the latest incident, the stones were also likely contaminated when they were left outdoors after the nuclear disaster.
"The damage could have been forestalled to a certain degree if we had taken notice during the disturbance over the rice straw," said an official at the Japan Crushed Stone Association.
The problem created concerns on Jan. 16 at the Asahi Elementary School in Nihonmatsu, after the revelation that crushed stone from the Futaba Saiseki Kogyo quarry had been used to pave a road that leads up to the school gate.
"It never occurred to me that road repair material could be contaminated," said Mitsuhiro Tsuchiya, the 51-year-old principal of the school.
The "Slope of Greetings," as the gently sloping road is known to the community, suffered numerous surface cracks during the March 11 quake. Repairs were made at three locations in April over a stretch of about 100 meters.
Tsuchiya and other school officials on Jan. 16 measured radiation levels at the pavement work sites and recorded a reading of 0.52 microsieverts per hour at a height of 1 meter above the ground, which was similar to readings in surrounding areas.
Although Tsuchiya said he felt relieved at the results, he used the school's public-address system around the time the children returned home to tell them to walk along the opposite side of the road from where the repairs were made.