Since April, at around 7am every morning, TEPCO has sampled sea water just near the plant, in front of the sea-water intakes for the four stricken reactors. These coolant-water intakes are behind two breakwaters, in an inner port. Every day, TEPCO also samples the ‘shallow draft quay’, or the dock in the outer part of the port (a diagram is below). From this sampling they have announced only two leaks of radioactive water to the ocean, in April and May.
I have transcribed this sampling data from over one hundred TEPCO press releases and put it in an interactive database here . (Disclaimer: there could have been some data-entry errors entering 5000 samples, it was very boring! This dataset is NOT official, but it is the best you will get online at the moment).
The image below shows the inner port,also known as the ‘intake canal’ or ‘open water channel’, with reactors #1-4 running north to south. TEPCO says it is aware of only two leaks of radioactive material into the port, in April and May, from units #2 and #3. After the first leak, TEPCO installed silt fences, to ‘prevent’ or slow down the spreading of radioactive materials in any water that might leak from the reactor buildings. Silt fences are designed to stop sand and dirt, but to let water and small particles through.
The data seems to indicate that there have been ongoing leaks of radiation, and that the silt fences are not effective at slowing the spread of tiny radioactive particles.
The inner port is about 7 metres deep, and the water goes up and down with the tides, between about 0.5 metres and 1.5 metres, twice a day.
Unit 3 is of particular interest… it’s ‘intake screen’ saw the second major spill – and the last leak according to the official story – in May. After that TEPCO promised to ‘purify’ the water in the intake screen with:
4) installation of circulating water purification equipment. We will install circulation water purification equipment in the screen area. By circulating the water in the intake, we will remove radioactive cesium (commencement of operation: early June).
5) We will continue monitoring of sea water inside and outside of the harbor to check whether there is any significant difference in radioactive doses.
TEPCO press release May 21
The ‘circulating purification system’ (picture here) takes port-water from inside the silt fences of the intake canal, forces it up through a clay called zeolite (which absorbs much of the radioactive Caesium particles), and dumps the water back into the intake canal. It started purifying the water inside the silt fences of Unit 2 and Unit 3 in early June. My visualisation tool allows an assessment of the effectiveness of this purification: