Tag Archives: 90-Sr

Radioactive Strontium and Cesium in Fish From the Harbor at the Fukushima Dai-ichi Nuclear Plant

By Jay T. Cullen

The purpose of this post is to report on a recent peer-reviewed study that investigated the radionuclide content of fish caught in the harbor of the Fukushima Dai-ichi Nuclear Powerplant (FDNPP) in 2012 and 2013. The post is also written in part to address questions like:

Why don’t you measure 90Sr in fish you catch off of North America?

This post is part of an ongoing series dedicated to summarizing results from scientific research into the impact of the FDNPP disaster on the environment. Fujimoto and colleagues measured the activity of Cesium-134 (134Cs half life ~2 years), Cesium-137 (137Cs half life ~30 years) and Strontium-90 (90Sr half life ~29 years) in fish collected from the FDNPP harbor and just outside the port in 2012 and 2013. Fish were most contaminated in the harbor and had radiocesium activity concentrations (in whole body without internal organs, Bq kg-1 – wet weight) that were ~200-330 times higher than measured 90Sr levels. The much lower 90Sr levels compared to radiocesium in the fish is consistent with much lower releases of 90Sr to the Pacific Ocean compared to radiocesium in the aftermath of the meltdowns at FDNPP (see here, here and here for example). The activity of radiocesium in fish diminishes dramatically with distance from the harbor and as of April-June 2015 none of the fish caught in Fukushima prefecture waters exceeded the stringent 100 Bq kg-1 Japanese safety standard. Across the Pacific, we have yet to detect Fukushima derived radiocesium in salmon and steelhead trout caught in British Columbian waters as part of the Fukushima InFORM monitoring effort. 90Sr is much more difficult and costly to analyze in environmental samples than are the cesium isotopes. The results of the Fujimoto study suggest that 90Sr from Fukushima is unlikely to be found at detectable levels in marine organisms in the northeast Pacific and that resources to monitor the impact of the disaster on our marine environment should focus on the detection of the cesium isotopes. Continue reading Radioactive Strontium and Cesium in Fish From the Harbor at the Fukushima Dai-ichi Nuclear Plant

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Dramatic Decrease of Fukushima Derived Radionuclides in the Northwest Pacific Ocean 2011-2012

By Jay T. Cullen

A schematic view of the formation and subduction of mode waters in the North Pacific

The purpose of this diary is to report on a recently published (Jan 2015) open-access, peer reviewed study which examined the activities of 137Cs (half life 30.2 yr), 134Cs (half life ~2.1 yr) and 90Sr (half life ~28.8 yr) in the northwest Pacific off the coasts of Japan and China. The diary is part of a ongoing effort to communicate the results of scientific research into the impact of the Fukushima Dai-ichi nuclear disaster on environmental and public health. Men and colleagues report on how activities of these fission produced isotopes changed between three research expeditions in June 2011, December 2011 and June 2012. Activities in seawater decreased dramatically through time for all three isotopes consistent with very high release rates measured from the Fukushima site in March-April 2011 followed by ongoing but many orders of magnitude (10,000 – 100,000 fold) lower releases from the site thereafter. By 2012 the impact of the Fukushima releases could be still be detected in most samples for Cs isotopes however 90Sr distributions were much more uniform with the highest measured activity only slightly above the pre-Fukushima background. These results are consistent with:

  1. the relatively small source term for 90Sr from compared with the Cs isotopes from Fukushima as determined by measurements of air, soil and water after the disaster
  2. the much lower Fukushima derived activities for these isotopes in the eastern Pacific off of North America being measured given decay and mixing of the contamination as it is transported by ocean currents

Continue reading Dramatic Decrease of Fukushima Derived Radionuclides in the Northwest Pacific Ocean 2011-2012

Release, Dispersion and Fate of Radioactive Strontium From Fukushima in the Northwest Pacific Ocean

By Jay T. Cullen

The purpose of this diary is to summarize recent models and measurements of the release of strontium-90 (90-Sr, half life 28.8 yr) to the ocean resulting from the triple meltdowns at the Fukushima-Daiichi nuclear power plant in March 2011. This post is part of an ongoing series aimed at understanding the impact of the disaster on the North Pacific Ocean and residents of the west coast of North America. 90-Sr is a beta-emitting element that is a radiological health concern given its relatively long half life and similar chemistry to the nutrient calcium (Ca). Previous peer-reviewed work indicate that releases of 90-Sr were about 30-10,000 fold less than 137-Cs and similar to the release of 90-Sr from the Chernobyl disaster in 1986 and about 600-fold lower than the releases from atmospheric weapons tests that peaked in the mid-1960’s. Given maximal release rates after the disaster, modeled activities of 90-Sr in the marine foodweb and in fish that accounts for bioconcentration and accumulation predict maximal dose rates from Fukushima to human consumers three orders of magnitude less than doses owing to the presence of 137-Cs in marine products and thus well below maximum dose limits thought to be detrimental to public health. Continue reading Release, Dispersion and Fate of Radioactive Strontium From Fukushima in the Northwest Pacific Ocean

Comparing 20th Century Strontium and Cesium Isotopes From Atmospheric Weapons Testing in the Pacific to Fukushima Sources

by Jay T. Cullen

The purpose of this post is to compare the concentrations of Sr-90 and Cs-137 in the North Pacific Ocean over the last 50 years to the concentrations predicted to arrive on the west coast associated with waters affected by release of radionuclides from the Fukushima-Daiichi Nuclear Power Plant. Given present levels that are being measured in the eastern Pacific and barring release rates that significantly exceed past rates in March-April 2011, when release rates were 10,000-100,000 times greater than ongoing releases at the plant, the impact on marine organisms and the marine environment is likely to be less significant than impacts owing to radioactivity in the 20th century. What follows is a comparison of the concentrations measured and predicted over much of the Pacific owing to Fukushima to the concentrations that were present in the mid-1960s from the fallout of atmospheric weapons testing that is free from any discussion of safe doses or models of radiation exposure to organisms.

Continue reading Comparing 20th Century Strontium and Cesium Isotopes From Atmospheric Weapons Testing in the Pacific to Fukushima Sources