The editorial staff of Neptune 911 is frequently asked about radioactivity released into the Pacific Ocean from the Fukushima accident in 2011. Neptune 911 tries to use reliable news sources when it comes to reporting news about our seas. And, frankly, much of what comes thru our news feeds in regards to radioactivity is either vague or from unreliable sources.
A recent report in The Guardian, “US sailors prepare for fresh legal challenge over Fukushima radiation,” appears to confirm radioactive releases that were not originally reported by the nuclear power plant’s owners. Similar stories give fair rise to concerns about subsequent radioactive pollution in the ocean.
Another recent report, “Fukushima radioactive water ‘ice plug’ plan fails,” from the August 20, 2014 The Telegraph, incites additional queries about exactly how much radioactive water has been released.
Meanwhile, citizen scientists and scientists in California (Our Radioactive Ocean, a non-profit) report:
August 14, 2014
Using the most sensitive methods to measure your water samples, we have detected only cesium-137, the “legacy” cesium that remains from 1960s atmospheric weapons testing. This isotope is still in all ocean basins because of its relatively long 30-year half-life, which means it takes a long time to decay away. Levels of cesium-137 in all 43 samples analyzed thus far average 1.5 Bequerels per cubic meter of water, which is equivalent to one-and-a-half decay events per second per metric ton of water. This is a very small number if we compare it to the 7,400 Bq/m3 used by US EPA as the drinking water limit, and the millions of Bq/m3 of cesium detected in the ocean off Japan in 2011 at the peak of the accident, which at that level are of considerable concern for direct negative impacts on marine biota and human health.
The Fukushima reactors also released cesium-134 into the ocean and because it has a shorter half-life (2 years) any cesium-134 detected in the ocean today must have come from Fukushima. Though we do detect this isotope in abundance off Japan, cesium-134 is not YET present in any of the sample collected by citizen scientists along the North American west coast and Hawaii. Our instruments are capable of detecting as little as 0.2 Bq/m3 so the concentration of cesium-134 is below this level.
We emphasize that cesium-134 has not been detected “YET” as it has been detected offshore of North America by Canadian oceanographers. It’s difficult to predict when these radionuclides will arrive onshore because the mixing of offshore and onshore waters is complicated, and not represented in the simple models that predicted the arrival onshore of Fukushima radionuclides this year. The uncertainty in the predictions by these ocean models only emphasizes the importance of collecting samples from along the shores. Remember too that while those models predict increasing levels of both cesium isotopes for the next 2-3 years, the highest published prediction is for 20-30 Bq/m3, or well below what is thought to be of human health or fisheries concern. But it’s important to continue making observations with real data!
–By Charmaine Coimbra