Advertisement
Science
ChinaScience

Fukushima power plant: as Japan discharges treated waste water, nuclear radiation readings don’t add up

  • Discharge data logs indicate a reoccurring difference in incoming seawater and outgoing diluted waste water
  • An environmental science professor says they would be expected to be about the same

Reading Time:5 minutes
Why you can trust SCMP
67
Treated water has been released from the Fukushima power plant in Japan. Photo: Kyodo
Victoria Bela

The numbers were within safety limits, but they did not add up.

Earlier this month at the Fukushima Daiichi nuclear power plant in Japan, as seawater was pumped into and diluted treated waste water released from the facility, some readings of gamma radiation varied when they should have been roughly the same.

The seawater pumped into the plant accounts for most of the water being released. For every 20 tonnes of treated waste water discharged per hour, about 15,000 tonnes of fresh water is pumped in from the sea to dilute it.

09:16

What is tritium? The radioactive element that caused controversy during the Fukushima water release

What is tritium? The radioactive element that caused controversy during the Fukushima water release
But at about 2pm on a rainy September 4, live data from Tokyo Electric Power Company (Tepco) indicated that the seawater being pumped in had a reading of 11 counts per second (cps) – a measure of radioactive disintegration by a detector – while the treated water and the diluted mixture heading for discharge both had a radiation level of 5.3 cps.

Jim Smith, a professor of environmental science at the University of Portsmouth, said the background gamma radiation level in natural seawater was expected to be at about 10 cps.

For the seawater pumped in and diluted water discharged, “you would expect the two readings to be about the same – the gamma radiation added from gamma emitting radionuclides discharged with the waste water is unlikely to change the seawater radiation levels”, he said.

This discrepancy persisted throughout the first round of release that ended last week. The radiation level of the diluted mixture was always lower than the radiation level of the seawater being pumped in, according to Tepco data logs and their tracker on the International Atomic Energy Agency’s (IAEA) website.

Advertisement