Question

Estimate the current source strength of Cesium-137 at Fukushima based on the amount of Cs-137 released to the environment at the time of the accident.

Answer 1

Dear Student,

Among the radioactive elements released during the Fukushima disaster were cesium-134 and cesium-137, both of which occur on earth only as a result of human activity.

Because of its long half life, much of the cesium-137 detected in the environment actually originates with nuclear tests conducted decades ago. Cesium-134, in contrast, has a half-life of only two years.

That means any cesium-134 in the environment (especially when detected at large distances from likely sources of nuclear contamination, such as power plants, dumps or weapons factories) stems from the Fukushima meltdowns.

The Woods Hole researchers tested water samples collected from various locations off the coast of Ucluelet, British Columbia, a small town on Vancouver Island.

They detected cesium-134 at levels of 1.4 Becquerel per cubic meter, and cesium-137 at levels of 5.8 Becquerel per cubic meter.

A Becquerel is a unit of radioactivity.

According to Canada’s Department of Fisheries and Oceans, the Pacific Ocean typically contains cesium-137 levels of “only” about one Becquerel per cubic meter, making the levels near Ucluelet nearly six times higher.

The Current Source Strength of Cesium-137 at Fukushima:

Almost any seawater sample from the Pacific will show traces of cesium-137, an isotope of cesium with a 30-year half-life, some of which is left over from nuclear weapons testing carried out in the 1950s to 1970s.

The isotope cesium-134 is the "fingerprint" of Fukushima, but, with a 2-year half-life, it decays much quicker than cesium-137.

Scientists back calculate traces of cesium-134 to determine how much was actually released from Fukushima in 2011 and add to it an equal amount of cesium-137 that would have been released at the same time.

Experts have found very high levels of cesium-137 in plankton living in the waters of the Pacific Ocean between Hawaii and the west coast.

Back in 2012, the Vancouver Sun reported that cesium-137 was being found in a very high percentage of the fish that Japan was selling to Canada

Canadian authorities are finding extremely high levels of nuclear radiation in certain fish samples

Some experts believe that they could see very high levels of cancer along the west coast just from people eating contaminated fish.

An EU-funded study concluded that Fukushima released up to 210 quadrillion becquerels of cesium-137 into the atmosphere.

It is being projected that significant levels of cesium-137 will reach every corner of the Pacific Ocean by the year 2020.

Cesium-137 from Fukushima has been found in fish caught as far away as California. It spreads throughout the body, but tends to accumulate in the muscles.

The Iodine-131, Cesium-137 and Strontium-90 that are constantly coming from Fukushima are going to affect the health of those living in the northern hemisphere for a very long time.