Category Archives: Strontium

Radiation and food safety: A story of standards

April 26th marked the 30th anniversary of the 1986 Chernobyl nuclear disaster. The ~2600 sq km (~1000 sq mi) exclusion zone remains in place around the power plant and wildlife are reclaiming the habitat. Just outside the exclusion zone, the Associated Press reports that dairy farms are operating and selling milk and dairy products around Belarus and Russia. The author obtained a milk sample from one of these farms, had it tested, and found it to be contaminated with levels of strontium-90 (90Sr) that are 10 times higher than the nation’s food safety limits. At first I was alarmed that this could make it to market, however, since working for the InFORM project I’ve learned that not all limits are equal. Let’s take a gander at how this milk would fare under standards from around the world.

Continue reading Radiation and food safety: A story of standards

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

Fukushima Radionuclides in Pacific: Doses to Japanese and World Public Unlikely to Cause Health Damage

By Jay T. Cullen

The purpose of this post is to summarize a the most recent, peer reviewed scientific study to examine the likely impact of Fukushima contamination of the North Pacific on human health. The blog is part of a continuing series that seeks to communicate the results of scientific studies aimed at determining the impact of the triple meltdowns at the Fukushima Dai-ichi nuclear power plant (FDNPP) on ecosystem and public health. Povinec and Hirose’s recent paper in Scientific Reports examined the variation in Fukushima derived 90-Strontium (90Sr half life 28.8 years), 134-Cesium (134Cs half life ~2 years) and 137-Cesium (137Cs half life ~30 years) in seawater and biota offshore of the FDNPP and in the northwest Pacific. These isotopes are most likely to represent radiologically health risks to consumers of Pacific seafood given their propensity to concentrate in organisms and, in the case of 90Sr and 137Cs, their longevity in the environment. Doses to the Japanese and world population were estimated and compared to doses attributable to naturally occurring isotopes present in food. Doses from food caught in coastal waters right next to the FDNPP to 20 km offshore were similar to doses from naturally occurring isotopes (primarily 210Po) while doses from the consumption off fish caught in the open northwest Pacific were much lower than natural doses. In each case the individual doses are well below levels where any negative health effects would be measurable in Japan or elsewhere. Continue reading Fukushima Radionuclides in Pacific: Doses to Japanese and World Public Unlikely to Cause Health Damage

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

Comparing the Environmental Impacts of the Chernobyl and Fukushima Disasters

Estimated total atmospheric source term for Fukushima compared to Chernobyl in PBq (PBq = 10^15 Bq). From Steinhauser et al. (2014) SciToTEnviron

By Jay T. Cullen

This post reports on a recently published peer reviewed study by Steinhauser and colleagues in the journal Science of the Total Environment (behind pay wall) comparing the Chernobyl and Fukushima nuclear accidents. The post is part of an ongoing effort to communicate the results of scientific studies into the impact of the Fukushima disaster on the environment. A majority of the radioactivity released from both Chernobyl and Fukushima can be attributed to volatile radionuclides (noble gases, iodine, cesium, tellurium). In contrast, the amounts of more refractory elements (including actinides like plutonium), released by Chernobyl was ~four orders of magnitude (10,000 fold) higher than releases from Fukushima. The most cited source term for Chernobyl is 5300 PBq (excluding noble gases) while a review of published studies of Fukushima carried out by the authors above allow an estimate for the total atmospheric source term of 520 (a range of 340–800) PBq. Monitoring of air, soil and water for radionuclides after the respective accidents indicate that the environmental impact of Chernobyl is likely to be much greater than the Fukushima accident. The post is relatively information dense as I have provided data tables for those who are interested in the estimates and the peer-reviewed studies from which they come. Apologies up front to those who find such information tedious. Continue reading Comparing the Environmental Impacts of the Chernobyl and Fukushima Disasters