TEPCO has revised the readings on the radioactivity levels at the Fukushima No. 1 nuclear plant well to 5 million becquerels of strontium per liter – both a record, and nearly five times higher than the original reading of 900,000 becquerels per liter.
Strontium-90 is a radioactive isotope of strontium produced by nuclear fission with a half-life of 28.8 years. The legal standard for strontium emissions is 30 becquerels per liter. Exposure to strontium-90 can cause bone cancer, cancer of nearby tissues, and leukemia.
Tokyo Electric Power Co. originally said that the said 900,000 becquerels of beta-ray sources per liter, including strontium – were measured in the water sampled on July 5 last year.
However, the company noted on Friday that the previous radioactivity levels had been wrong, meaning that it was also likely reading taken from the other wells at the disaster-struck plant prior to September were also likely to have been inaccurate, the Asahi Shimbum newspaper reported.