I commend Giovanni Fazio in his letter of Oct. 16 for drawing attention to the fact that Okutama, with some of the highest radiation levels in Tokyo, is also a major source of drinking water for its 13 million people. However, he overstates his case when claiming "Tokyo tap water comes from an area with cesium contamination at levels equivalent to the Chernobyl evacuation zones."
A helicopter survey found most of the mountains around Lake Okutama to be contaminated with between 10,000 and 30,000 Bq/m² of cesium 137. The "permanent control zone" around Chernobyl is defined as 555,000 Bq/m² and more while the evacuated "closed zone" is polluted with 1,480,000 Bq/m² and more.
We would not even be discussing such numbers if Tepco had invested in a scrubber to filter the emergency venting system of its reactors. Thirty years ago Sweden installed the so-called FILTRA system at its boiling water reactors. None of the Japanese nuclear power stations have such external scrubbers, which would have been dirt cheap compared to now trying to decontaminate hundreds of square kilometers of polluted land. Their installation should be mandatory for any reactors allowed to resume power production.
The opinions expressed in this letter to the editor are the writer's own and do not necessarily reflect the policies of The Japan Times.