四十年前蘇聯核爆輻射持續污染環境

Recently the Yomiuri News on-line reported the following:
ロシアの有力紙イズベスチヤは１４日、１９７１年に地下核爆破が実施された同国中部イワノボ州で、今日もなお放射性物質セシウム１３７の汚染が深刻であることが判明したと報じた。
　汚染の実態は国営原子力企業ロスアトムが２０１１年、同州で大規模調査を行った結果、分かった。場所によっては土壌１キロ・グラム当たり、最悪で１０万ベクレルのセシウム１３７が検出されたという。この値は日本でコメの作付け制限が発動される基準値（昨年時点）の２０倍という高いものだ。同社は除染に乗り出すことを決めた。
　汚染地域はモスクワの北東約３４０キロ・メートル。当時、ソ連では資源探査や大規模な土木工事で、破壊力が大きい核爆弾を使用した。軍事的な核実験とは区別し、「平和的核爆発」と呼ばれた。
　イワノボ州の核爆破は「地質調査のため」で、地下約６２０メートルで実施された。だが、爆破の後、放射性物質を含む地下水が間欠泉のように噴き出し、地表を汚染した。その面積は「１ヘクタール未満」とされ、表土は除去されていた。
　その４０年後の調査で汚染が確認された地域は住民の生活圏にも近く、最も近い村までは４キロ・メートルしか離れていない。
（2012年3月15日16時18分 読売新聞）

(試譯文)
   The influential newspaper Izvestiya in Russia reported on the 14th that in the Ivanove state which was at the centre of the country where underground blasting was carried out in 1971, it became clear today that contamination by radioactive material cesium 137 was serious.
 
   The actual condition of contamination was found as a result of the large-scale investigation in the state conducted in 2011 by the national atomic power company "Loss Atom". Cesium 137 per 1 kg of soil at different location was detected, and it was said that the worst location was with 100,000-Bq cesium 137. This value was 20 times higher than the standard value (the time was last year) restrictions set for rice production advocated in Japan. The company decided to carry out decontamination.
 
   The contaminated zone was the about 340-km northeast of Moscow. In those days the Soviet Union used the large nuclear bomb destructive power for resource investigation or large-scale public works. Making distinction from the military nuclear test, it was called "peaceful nuclear explosion."

   Nuclear blasting was carried out in the State of Ivanovo "for a geological survey" at about 620 meters below the ground. But after blasting, groundwater containing radioactive material blew out like a geyser and polluted the top soil. This area was "less than 1 ha", and the topsoil was removed.

   The investigation conducted after 40 years showed that the area that had confirmed contamination was near the a neighborhood with residents living; the separation with the nearest village was merely 4 km.

It is a costly project to remove cesium 137 from the contaminated area.