Photo : The Inside of Reactor 2 in June, 2021 by Tepco [Link]
Tepco and the government of Japan are planning to discharge the filtered contaminated water to the Pacific from 2023. The filtered contaminated water officially only contains radioactive water, Tritium.
However, Tepco actually revised the definition of the filtered contaminated water on the 27th of April, 2021. In the new definition, the filtered contaminated water is changed to be the filtered contaminated water “etc”.
Et cetera is added because 70% of such water to be discharged to the Pacific, still contains a significant amount of radionuclides other than radioactive water, Tritium due to the insufficient filtration.
Rhetorically, the discharged water will primarily contain only Tritium. However, according to Tepco’s technical papers issued on the 12th of July, 2021, the filtered water is going to be mixed with insufficiently filtered water before the discharge. Only in cases when the radionuclide density (other than Tritium) is higher than the safety level, the mixed contaminated water is to be sent back to ALPS (Advanced Liquid Processing System).
The unfiltered water, which has 70% share of all the contaminated water, is estimated to contain 9 (Cs-134/137,Sr-90,Co-60,Sb-125,Ru-106, I-129, C-14,Tc-99) to 56 sorts of radionuclides more than the safety limit (60,000,000 Bq/m3) in total. The filtered water contains these nuclides at lower density than the safety limit though this safety limit is approximately 667 times higher than WHO’s guideline for Drinking-water quality.
Based on Tepco’s report, at the time of the end of March, 2021, around 33% of all the stored contaminated water in Fukushima nuclear plant has 1 to 5 times higher levels of these radionuclides than the safety limit. 5% of the stored contaminated water contains 100 to 19,909 times higher levels than the safety limit.
As a result of mixing, the discharged water will contain both filtered and unfiltered water. Even though the water will be diluted, as the nature of the water remains the same, the total amount of contamination to be discharged will not be reduced.