Readings of tritium in seawater taken from the bay near the crippled Fukushima nuclear plant has shown 4700 becquerels per liter, a TEPCO report stated, according to Nikkei newspaper. It marks the highest tritium level in the measurement history.

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Tokyo Electric Power Company (TEPCO) has detected the highest radiation level in seawater collected in the harbor of the crippled nuclear plant in the past 15 days, Nikkei reports.

TEPCO said the highest radiation level was detected near reactor 1. Previous measurements showed tritium levels at 3800 becquerels per liter near reactor 1, and 2600 becquerels per liter near reactor 2. The concentration of tritium in the harbor’s seawater has been continuously rising since May, according to Nikkei.

Tritium is a radioactive isotope of hydrogen which is produced by nuclear reactors. It is potentially dangerous if inhaled or ingested. The legal limits for Tritium in terms of becquerels per liter vary from country to country. The World Health Organization has a limit of 10,000 Bq/l, but the European Union’s limit is much lower, at 150 Bq/l.



Also on Monday, a leak of highly contaminated water was discovered from a drain valve of a tank dike located on the premises of the nuclear plant, according to Fukushima’s operator responsible for the clean-up.



The level of radiation at the site was estimated at 100 millisieverts per hour, while the safe level of radiation is 1-13 millisieverts per year, according to ITAR-TASS news agency. The plant’s operator is currently investigating reasons for the leak, TEPCO said in a statement.



Earlier, Tepco admitted that an estimated 20 to 40 trillion becquerel’s of tritium may have flowed into the Pacific Ocean since the nuclear disaster.



Three of the plant’s reactors suffered a nuclear meltdown in March 2011 after a massive earthquake struck the area, triggering a tsunami. The plant has been accumulating radioactive water ever since, as groundwater passing through the premises becomes contaminated.



Protective barriers installed to prevent the flow of toxic water into the ocean have failed to do so. The level of contaminated water has already risen to 60cm above the barriers, which has been a major cause of the daily leak of toxic substances, TEPCO admitted.



Japan’s Ministry of Industry recently estimated that around 300 tons of contaminated groundwater has been seeping into the Pacific Ocean on a daily basis. TEPCO has promised to reinforce protective shields to keep radioactive leaks at bay.

