Radioactive hot spots found in seabed as far away as Miyagi

by Tomohiro Osaki

Staff Writer

A research team led by the University of Tokyo has found more than 30 concentrations of radioactive cesium in the first full-fledged study of the isotope’s accumulation on the seabed near the crippled Fukushima No. 1 nuclear plant, scientists said Wednesday.

The research, spearheaded by the university’s Institute of Industrial Science, found that cesium-137, which has a half-life of 30 years, tends to get absorbed by clayish soil and concentrate in seabed depressions.

For example, a hot spot 70 meters wide was discovered 32 meters below the ocean surface 5.9 km from the plant.

The team said it found soil there containing radioactive cesium concentrations of 651 becquerels per kilogram.

The research, conducted from last August to July, covered the ocean within 20 km of the nuclear station. In the past scientists had only conducted sporadic samplings for cesium near the plant.

The team found relatively high levels of cesium-137 near the mouth of the Abukuma River in Miyagi Prefecture, 70 km north of the plant.

For example, 1.6 km east of the Abukuma River estuary, the research team found a hot spot with average concentrations of 1,029 becquerels per kilogram of mud. The river runs through both Fukushima and Miyagi prefectures, and the research team believes radioactive cesium was carried by the river to the hot spots in the sea.

It has also been reported that contractors doing decomtamination work have dumped their debris in rivers.

Blair Thornton, a special associate professor at the university, told reporters that the findings will be shared with fishery researchers, who hope it will shed light on the possible effect of radioactive contamination on marine life.

Experts also hope the findings will lead to better contamination mechanisms and the ability to predict the movement of cesium-137 near coastal areas.

University of Tokyo professor Toyoji Kaneko, an expert on maritime creatures, said he doesn’t believe all fish caught at or near the seafloor hot spots is dangerous to eat.

Fish swimming near the sea bottom may eat sand worms that have taken in mud contaminated with radioactive cesium, but fish eventually excrete most of the cesium and little would penetrate from the bowels into the muscle of the fish, Kaneko said.

“Although I can’t guarantee 100 percent safety, it’s not the like (meat from) fish will get immediately contaminated” with radioactive cesium, he said.

Thornton also said most of the cesium now detected in fish off Fukushima is believed to have come from tainted seawater near the plant, not from seabed mud.

National Maritime Research Institute of Tokyo and Kyushu Institute of Technology also participated in the survey.

  • piglet25

    These “hot spots” have lower concentrations of radiocesium than those I
    measured throughout the Clyde Sea area in the mid `70s – and levels in the
    Irish Sea were similar or higher. This was due to operational releases from the
    Windscale reprocessing plant which disposed to sea a similar inventory of
    Cs-137 EACH YEAR as was released in total from Fukushima Daiichi. Despite such
    widespread contamination, there were no indications of any health effects to
    local communities.

    • Beppe

      As far as I know local communities in Sellafield think otherwise

      • piglet25

        You clearly don’t know! This was almost 40 years ago and the area has been intensively studied since then. There were concerns, but these focused on Ru-106 and actinides – see eg https://en.wikipedia.org/wiki/Sellafield . Cs-137 was never considered as a concern then!

    • thedudeabidez

      “there were no indications of any health effects to local communities.”

      As if anyone was looking for them.

  • Eric

    By those classifications my garden is a hot spot.
    I wonder if the 651 Bq/Kg soil samples were of wet or dry soil.

  • Beppe

    “Although I can’t guarantee 100 percent safety, it’s not the like (meat from) fish will get immediately contaminated”

    No immediate danger for health?? Again? Who is this? Edano’s twin brother? and how about Strontium, which has a much longer biological half life than Cesium and accumulates in the bones?

    Also, these University of Tokyo researchers have found sea bed hot spots higher than 40,000 bq/kq (wet) whereas the maximum Tepco could detect was 2,700 (dry) (source: Asahi TV)? Anything above 8,000 bq/kg needs to be disposed as radioactive waste, according to the current Japanese law.

  • Noborry

    651 becquerels per kilogram?
    *gasp*
    That is almost as radioactive as brazil nuts!
    Fully *four time* as dangerous as bananas!
    +runs around in blind panic+

    • thedudeabidez

      Not the banana argument again. The potassium in bananas will be processed from your system within a matter of hours, a day or two max. Compare that to strontium which will lodge in your bones, or cesium which has a biological half-life of several months. The comparison is not a valid one in the least.

      According to the US Environmental Protection Agency:
      “The human body is born with potassium-40 in its tissues and it is the most common radionuclide in human tissues and in food. We evolved in the presence of potassium-40 and our bodies have well-developed repair mechanisms to respond to its effects. The concentration of potassium-40 in the human body is constant and not affected by concentrations in the environment.”
      None of the above can be said of the man-made, non-naturally occurring isotopes being released from Fukushima Daiichi.