Radioactive hot particles still afloat throughout Japan six years after Fukushima meltdowns — BuzzFlash

” Radioactive particles of uranium, thorium, radium, cesium, strontium, polonium, tellurium and americium are still afloat throughout Northern Japan more than six years after a tsunami slammed into the Fukushima Daiichi Power Plant causing three full-blown nuclear meltdowns. That was the conclusion reached by two of the world’s leading radiation experts after conducting an extensive five-year monitoring project.

Arnie Gundersen and Marco Kaltofen authored the peer reviewed study titled, Radioactively-hot particles detected in dusts and soils from Northern Japan by combination of gamma spectrometry, autoradiography, and SEM/EDS analysis and implications in radiation risk assessment, published July 27, 2017, in Science of the Total Environment (STOLEN).

Gundersen represents Fairewinds Associates and is a nuclear engineer, former power plant operator and industry executive, turned whistleblower, and was CNN’s play-by-play on-air expert during the 2011 meltdowns. Kaltofen, of the Worcester Polytechnic Institute (WPI), is a licensed civil engineer and is renowned as a leading experts on radioactive contamination in the environment.

415 samples of “dust and surface soil” were “analyzed sequentially by gamma spectrometry, autoradiography, and scanning electron microscopy with energy dispersive X-ray analysis” between 2011 and 2016. 180 of the samples came from Japan while another 235 were taken from the United States and Canada. The study further clarifies, “Of these 180 Japanese particulate matter samples, 57 were automobile or home air filters, 59 were surface dust samples, 29 were street dusts (accumulated surface soils and dusts) and 33 were vacuum cleaner bag or other dust samples.”

108 of the Japanese samples were taken in 2016, while the other 72 were gathered in 2011 after the meltdowns. Gundersen and Kaltofen tapped 15 volunteer scientists to help collect the dust and soil — mostly from Fukushima Prefecture and Minamisoma City. “A majority of these samples were collected from locations in decontaminated zones cleared for habitation by the National Government of Japan,” the study revealed. For the 108 samples taken in 2016, an “International Medcom Inspector Alert surface contamination monitor (radiation survey meter) was used to identify samples from within low lying areas and on contaminated outdoor surfaces.”

Fairewinds Associates’ video from 2012 features Gundersen collecting five samples of surface soil from random places throughout Tokyo — places including a sidewalk crack, a rooftop garden, and a previously decontaminated children’s playground. The samples were bagged, declared through Customs, and brought back to the U.S. for testing. All five samples were so radioactive that according to Gundersen, they “qualified as radioactive waste here in the United States and would have to be sent to Texas to be disposed of.” Those five examples were not included as part of the recently released study, but Gundersen went back to Tokyo for samples in 2016. Those samples were included, and were radioactive, and according to Gundersen were “similar to what I found in Tokyo in [2012].”

Furthermore, 142 of the 180 samples (about 80 percent) contained cesium 134 and cesium 137. Cesium 134 and 137, two of the most widespread byproducts of the nuclear fission process from uranium-fueled reactors, are released in large quantities in nuclear accidents. Cesium emits intense beta radiation as it decays away to other isotopes, and is very dangerous if ingested or inhaled. On a mildly positive note, the study shows that only four of the 235 dust samples tested in the United States and Canada had detectable levels of cesium from Fukushima.

Cesium, due to its molecular structure, mimics potassium once inside the body, and is often transported to the heart where it can become lodged, thereafter mutating and burning heart tissue which can lead to cardiovascular disease. Other isotopes imitate nutritive substances once inside the body as well. Strontium 90 for example mimics calcium, and is absorbed by bones and teeth.

“Different parts of the human body (nerves, bones, stomach, lung) are impacted differently,” Kaltofen told EnviroNews in an email. “Different cells have radio-sensitivities that vary over many orders of magnitude. The body reacts differently to the same dose received over a short time or a long time; the same as acute or chronic doses in chemical toxicity.”

In contrast to external X-rays, gamma, beta or alpha rays, hot particles are small mobile pieces of radioactive elements that can be breathed in, drunk or eaten in food. The fragments can then become lodged in bodily tissue where they will emanate high-intensity ionizing radiation for months or years, damaging and twisting cells, potentially causing myriad diseases and cancer. The study points out, “Contaminated environmental dusts can accumulate in indoor spaces, potentially causing radiation exposures to humans via inhalation, dermal contact, and ingestion.”

The study also explains, “Given the wide variability in hot particle sizes, activities, and occurrence; some individuals may experience a hot particle dose that is higher or lower than the dose calculated by using averaged environmental data.” For example, a person living in a contaminated area might use a leaf blower or sweep a floor containing a hefty amount of hot particle-laden dust and receive a large does in a short time, whereas other people in the same area, exposed to the same background radiation and environmental averages, may not take as heavy a hit as the housekeeper that sweeps floors for a living. People exposed to more dust on the job, or who simply have bad luck and haphazardly breathe in hot radioactive dust, are at an increased risk for cancer and disease. High winds can also randomly pick up radioactive surface soil, rendering it airborne and endangering any unsuspecting subject unlucky enough to breath it in.

Hot particles, or “internal particle emitters” as they are sometimes called, also carry unique epidemiological risks as compared to a chest X-ray by contrast. The dangers from radiation are calculated by the dose a subject receives, but the manner in which that dose is received can also play a critical factor in the amount of damage to a person’s health.

“Comparing external radiation to hot particles inside the body is an inappropriate analogy,” Gundersen toldEnviroNewsin an email. “Hot particles deliver a lot of energy to a very localized group of cells that surround them and can therefore cause significant localized cell damage. External radiation is diffuse. For example, the weight from a stiletto high heal shoe is the same as the weight while wearing loafers, but the high heal is damaging because its force is localized.”

Kaltofen elaborated with an analogy of his own in a followup email with EnviroNews saying:

Dose is the amount of energy in joules absorbed by tissue. Imagine Fred with a one joule gamma dose to the whole body from living in a dentist’s office over a lifetime, versus Rhonda with exactly the same dose as alpha absorbed by the lung from a hot particle. Standard health physics theory says that Fred will almost certainly be fine, but Rhonda has about a 10 percent chance of dying from lung cancer — even though the doses are the same.

External radiation and internal hot particles both follow exactly the same health physics rules, even though they cause different kinds of biological damage. Our data simply shows that you can’t understand radiation risk without measuring both.

Some isotopes, like plutonium, only pose danger to an organism inside the body. As an alpha emitter, plutonium’s rays are blocked by the skin and not strong enough to penetrate deep into bodily tissue. However, when inhaled or ingested, plutonium’s ionizing alpha rays twist and shred cells, making it one of the most carcinogenic and mutagenic substances on the planet.

“Measuring radioactive dust exposures can be like sitting by a fireplace,” Dr. Kaltofen explained in a press release. “Near the fire you get a little warm, but once in a while the fire throws off a spark that can actually burn you.”

“We weren’t trying to see just somebody’s theoretical average result,” Kaltofen continued in the press release. “We looked at how people actually encounter radioactive dust in their real lives. [By] combining microanalytical methods with traditional health physics models… we found that some people were breathing or ingesting enough radioactive dust to have a real increase in their risk of suffering a future health problem. This was especially true of children and younger people, who inhale or ingest proportionately more dust than adults.”

“Individuals in the contaminated zone, and potentially well outside of the mapped contaminated zone, may receive a dose that is higher than the mean dose calculated from average environmental data, due to inhalation or ingestion of radioactively-hot dust and soil particles,” the study says in summation. “Accurate radiation risk assessments therefore require data for hot particle exposure as well as for exposure to more uniform environmental radioactivity levels.” ”

source with video by Arnie Gundersen

Radioactively-hot particles detected in dusts and soils from Northern Japan by combination of gamma spectrometry, autoradiography, and SEM/EDS analysis — Marco Kaltofen, Arnie Gundersen, ScienceDirect


After the March 11, 2011, nuclear reactor meltdowns at Fukushima Dai-ichi, 180 samples of Japanese particulate matter (dusts and surface soils) and 235 similar U.S. and Canadian samples were collected and analyzed sequentially by gamma spectrometry, autoradiography, and scanning electron microscopy with energy dispersive X-ray analysis. Samples were collected and analyzed over a five-year period, from 2011 to 2016. Detectable levels of 134Cs and 137Cs were found in 142 of 180 (80%) Japanese particulate matter samples. The median radio-cesium specific activity of Japanese particulate samples was 3.2 kBq kg− 1 ± 1.8 kBq kg− 1, and the mean was 25.7 kBq kg− 1(σ = 72 kBq kg− 1). The U.S. and Canadian mean and median radio‑cesium activity levels were < 0.03 kBq kg− 1. U.S. and Canadian samples had detectable 134Cs and 137Cs in one dust sample out of 32 collected, and four soils out of 74. The maximum US/Canada radio-cesium particulate matter activity was 0.30 ± 0.10 kBq kg− 1. The mean in Japan was skewed upward due to nine of the 180 (5%) samples with activities > 250 kBq kg− 1. This skewness was present in both the 2011 and 2016 sample sets.

300 individual radioactively-hot particles were identified in samples from Japan; composed of 1% or more of the elements cesium, americium, radium, polonium, thorium, tellurium, or strontium. Some particles reached specific activities in the MBq μg− 1 level and higher. No cesium-containing hot particles were found in the U.S. sample set. Only naturally-occurring radionuclides were found in particles from the U.S. background samples. Some of the hot particles detected in this study could cause significant radiation exposures to individuals if inhaled. Exposure models ignoring these isolated hot particles would potentially understate human radiation dose. ”

source to purchase whole study

Poison in the air — The New International, Opinion

” Three of the six reactors at Japan’s Fukushima-Daiichi complex were wrecked in March 2011 by an earthquake and tsunami. The destruction of emergency electric generators caused a ‘station blackout’ which halted cooling water intake and circulation. Super-heated, out-of-control uranium fuel in reactors 1, 2, and 3 then boiled off cooling water, and some 300 tons of fuel ‘melted’ and burned through the reactors’ core vessels, gouging so deep into underground sections of the structure that to this day operators aren’t sure where it is. Several explosions in reactor buildings and uncovered fuel rods caused the spewing of huge quantities of radioactive materials to the atmosphere, and the worst radioactive contamination of the Pacific Ocean ever recorded. Fukushima amounts to Whole-Earth poisoning.

Now, researchers say, radioactive isotopes that were spread across Japan (and beyond) by the meltdowns will continue to contaminate the food supply for a very long time.

According to a new study that focused on ‘radiocaesium’ – as the British call cesium-134 and cesium-137 – ‘food in japan will be contaminated by low-level radioactivity for decades’. The official university announcement of this study neglected to specify that Fukushima’s cesium will persist in the food chain for thirty decades. It takes 10 radioactive half-lives for cesium-137 to decay to barium, and its half-life is about 30 years, so C-137 stays in the environment for roughly 300 years.

The study’s authors, Professor Jim Smith, of the University of Portsmouth, southwest of London, and Dr. Keiko Tagami, from the Japanese National Institute of Radiological Sciences, report that cesium-caused ‘radiation doses in the average diet in the Fukushima region are very low and do not present a significant health risk now or in the future’.

This phraseology deliberately conveys a sense of security – but a false one. Asserting that low doses of radiation pose no ‘significant’ health risk sounds reassuring, but an equally factual framing of precisely the same finding is that small amounts of cesium in food pose a slightly increased risk of causing cancer.

This fact was acknowledged by Prof Smith in the June 14 University of Portsmouth media advisory that announced his food contamination study, which was published in Science of the Total Environment. Because of above-ground atom bomb testing, Prof. Smith said, “Radioactive elements such as caesium-137, strontium-90 and carbon-14 contaminated the global environment, potentially causing hundreds of thousands of unseen cancer deaths”.

No less an authority than the late John Gofman, MD, Ph D, a co-discoverer of plutonium and Professor Emeritus of molecular and cell biology at the University of California, spent 50 years warning about the threat posed by low doses of radiation. In May 1999, Gofman wrote, “By any reasonable standard of biomedical proof, there is no safe dose, which means that just one decaying radioactive atom can produce permanent mutation in a cell’s genetic molecules. My own work showed this in 1990 for X rays, gamma rays, and beta particles.”

The Fukushima-borne cesium in Japan’s food supply, and in the food-web of the entire Pacific Ocean, emits both beta and gamma radiation. Unfortunately, it will bio-accumulate and bio-concentrate for 300 years, potentially causing, as Dr Gofman if not Dr Smith might say, hundreds of thousands of unseen cancer deaths. ”

originally published in CounterPunch


Fukushima moms don lab coats to measure radiation in food, sand and soil — The Japan Times

At a laboratory an hour’s drive from the crippled Fukushima No. 1 nuclear plant, a woman wearing a white mask over her mouth presses bright red strawberries into a pot, ready to be measured for radiation contamination.

Six years after a massive earthquake off the Tohoku coast triggered tsunami that knocked out the plant’s cooling system, causing three reactor-core meltdowns, local mothers with no scientific background staff a laboratory that keeps track of radiation levels in food, water and soil.

As some women divide the samples between different bowls and handmade paper containers, others are logging onto computers to keep an eye on data — findings that will be published for the public to access.

The women on duty, wearing pastel-colored overalls, are paid a small salary to come in for a few hours each day, leaving them free to care for their children after school.

“In universities, data (are) handled by students, who have taken exams qualifying them to measure radiation. Here, it’s done by mothers working part time. It’s a crazy situation,” laughed Kaori Suzuki, director of Tarachine, the nonprofit organization that houses the mothers’ radiation lab.

“If (university professors) saw this I think they would be completely shocked by what they see.”

Tarachine was set up 60 km down the coast from the Fukushima plant, in the city of Iwaki. After the magnitude-9 quake struck on March 11, 2011, triggering mountainous tsunami, authorities declared a no-go zone around the plant.

Iwaki lay outside its 30 km radius, with lower radiation levels compared to the rest of Fukushima Prefecture.

But with public announcements advising locals to stay indoors in the aftermath of the worst nuclear calamity since Chernobyl, the “invisible enemy” of radiation has continued to worry the mothers working at the lab.

“As ordinary citizens we had no knowledge about radiation. All we knew was that it is frightening,” said Suzuki.

“We can’t see, smell or feel radiation levels. Given this invisibility, it was extremely difficult for us. How do we fight it? The only way is to measure it.”

To supplement readings by the central government and Tokyo Electric Power Company Holdings Inc., which manages the nuclear plant, Tarachine publishes its own findings every month.

With donations from the public that helped them buy equipment designed to measure food contamination, the mothers measure radioactive isotopes cesium-134 and-137, and collect data on gamma radiation, strontium-90 and tritium, all of which were released during the Fukushima disaster.

Strontium-90 gravitates toward the bones when absorbed by breathing it, drinking it in water, or eating it in food. It can remain for years, potentially causing bone cancer or leukemia.

Tritium goes directly into the soft tissues and organs of the human body. Although it is less harmful to humans who are exposed to small amounts every day, it could still be a hazard for children, scientists say.

The mothers say other parents trust the lab’s radioactivity readings in local food more than those from the government.

“This issue is part of everyday life for these mothers, so they have the capability to spot certain trends and various problems rather than just accumulating expert knowledge,” said Suzuki.

To handle potentially dangerous materials, the mothers have had to study for exams related to radiation and organic chemistry.

“At the beginning I was just completely clueless. It gave me so much of a headache, it was a completely different world to me,” said Fumiko Funemoto, a mother of two who measures strontium-90 at the lab.

“But you start to get the hang of it as you’re in this environment every day.”

As the lab only accepts items for testing from outside the exclusion zone, most results show comparatively low radiation levels.

But Suzuki said it was an important process and especially reassuring for the parents of young children. The women also measure radiation levels in sand from the beach, which has been out of bounds to their children.

“If the base is zero becquerels, and there is, say, 15 or 16 becquerels of cesium, that’s still higher than zero. That means there is slightly more risk,” Suzuki said.

“There are also times when you’re like, ‘Oh, I thought levels were going to be high there — but it’s actually OK.’ The importance lies in knowing what’s accurate, whether it’s high or low. Unless you know the levels, you can’t implement the appropriate measures.”

Since official screenings began following the meltdowns, 174 children in Fukushima Prefecture have been diagnosed with — or are suspected of having — thyroid cancer, according to figures from the prefecture.

Despite the International Atomic Energy Agency (IAEA) reporting in 2015 that an increase in thyroid cancer is unlikely, the mothers insist there is value in their work.

The first pictures from inside the nuclear plant were released by Tepco in January, announcing it may have found melted nuclear fuel below the damaged reactor 2 — one of three affected by the 2011 disaster.

“In general, the issue of nuclear power is not really talked about much these days,” Funemoto said. “It was talked about after the (meltdowns) for about a year or so, but today, conversations mentioning words like ‘radiation’ don’t happen anymore.”

However, she said “the reality is different.”

“The radiation isn’t going to go away. That’s why I’m doing this. So many places are still damaged. This idea that it’s safe and that we shouldn’t be anxious doesn’t really add up,” she said.

Ai Kimura, another mother, agreed. “My parents think I’m a bit paranoid. They keep saying, ‘It’s OK isn’t it?’ ” she said.

“But what if there’s a chance that in 10 or 20 years’ time, my own child gets thyroid cancer? And I could have done my bit to minimize the risks. My children are mine and I want to do whatever I can to protect them.” ”

by Mari Shibata, The Japan Times


The Fukushima nuclear meltdown continues unabated — Helen Caldicott, Independent Australia

Helen Caldicott sums up the situation here:

” Recent reporting of a huge radiation measurement at Unit 2 in the Fukushima Daichi reactor complex does not signify that there is a peak in radiation in the reactor building.

All that it indicates is that, for the first time, the Japanese have been able to measure the intense radiation given off by the molten fuel, as each previous attempt has led to failure because the radiation is so intense the robotic parts were functionally destroyed.

The radiation measurement was 530 sieverts, or 53,000 rems (Roentgen Equivalent for Man). The dose at which half an exposed population would die is 250 to 500 rems, so this is a massive measurement. It is quite likely had the robot been able to penetrate deeper into the inner cavern containing the molten corium, the measurement would have been much greater.

These facts illustrate why it will be almost impossible to “decommission” units 1, 2 and 3 as no human could ever be exposed to such extreme radiation. This fact means that Fukushima Daichi will remain a diabolical blot upon Japan and the world for the rest of time, sitting as it does on active earthquake zones.

What the photos taken by the robot did reveal was that some of the structural supports of Unit 2 have been damaged. It is also true that all four buildings were structurally damaged by the original earthquake some five years ago and by the subsequent hydrogen explosions so, should there be an earthquake greater than seven on the Richter scale, it is very possible that one or more of these structures could collapse, leading to a massive release of radiation as the building fell on the molten core beneath. But units 1, 2 and 3 also contain cooling pools with very radioactive fuel rods — numbering 392 in Unit 1, 615 in Unit 2, and 566 in Unit 3; if an earthquake were to breach a pool, the gamma rays would be so intense that the site would have to be permanently evacuated. The fuel from Unit 4 and its cooling pool has been removed.

But there is more to fear.

The reactor complex was built adjacent to a mountain range and millions of gallons of water emanate from the mountains daily beneath the reactor complex, causing some of the earth below the reactor buildings to partially liquefy. As the water flows beneath the damaged reactors, it immerses the three molten cores and becomes extremely radioactive as it continues its journey into the adjacent Pacific Ocean.

Every day since the accident began, 300 to 400 tons of water has poured into the Pacific where numerous isotopes – including cesium 137, 134, strontium 90, tritium, plutonium, americium and up to 100 more – enter the ocean and bio-concentrate by orders of magnitude at each step of the food chain — algae, crustaceans, little fish, big fish then us.

Fish swim thousands of miles and tuna, salmon and other species found on the American west coast now contain some of these radioactive elements, which are tasteless, odourless and invisible. Entering the human body by ingestion they concentrate in various organs, irradiating adjacent cells for many years. The cancer cycle is initiated by a single mutation in a single regulatory gene in a single cell and the incubation time for cancer is any time from 2 to 90 years. And no cancer defines its origin.

We could be catching radioactive fish in Australia or the fish that are imported could contain radioactive isotopes, but unless they are consistently tested we will never know.

As well as the mountain water reaching the Pacific Ocean, since the accident, TEPCO has daily pumped over 300 tons of sea water into the damaged reactors to keep them cool. It becomes intensely radioactive and is pumped out again and stored in over 1,200 huge storage tanks scattered over the Daichi site. These tanks could not withstand a large earthquake and could rupture releasing their contents into the ocean.

But even if that does not happen, TEPCO is rapidly running out of storage space and is trying to convince the local fishermen that it would be okay to empty the tanks into the sea. The Bremsstrahlung radiation like x-rays given off by these tanks is quite high – measuring 10 milirems – presenting a danger to the workers. There are over 4,000 workers on site each day, many recruited by the Yakuza (the Japanese Mafia) and include men who are homeless, drug addicts and those who are mentally unstable.

There’s another problem. Because the molten cores are continuously generating hydrogen, which is explosive, TEPCO has been pumping nitrogen into the reactors to dilute the hydrogen dangers.

Vast areas of Japan are now contaminated, including some areas of Tokyo, which are so radioactive that roadside soil measuring 7,000 becquerels (bc) per kilo would qualify to be buried in a radioactive waste facility in the U.S..

As previously explained, these radioactive elements concentrate in the food chain. The Fukushima Prefecture has always been a food bowl for Japan and, although much of the rice, vegetables and fruit now grown here is radioactive, there is a big push to sell this food both in the Japanese market and overseas. Taiwan has banned the sale of Japanese food, but Australia and the U.S. have not.

Prime Minister Abe recently passed a law that any reporter who told the truth about the situation could be [jail]ed for ten years. In addition, doctors who tell their patients their disease could be radiation related will not be paid, so there is an immense cover-up in Japan as well as the global media.

The Prefectural Oversite Committee for Fukushima Health is only looking at thyroid cancer among the population and by June 2016, 172 people who were under the age of 18 at the time of the accident have developed, or have suspected, thyroid cancer; the normal incidence in this population is 1 to 2 per million.

However, other cancers and leukemia that are caused by radiation are not being routinely documented, nor are congenital malformations, which were, and are, still rife among the exposed Chernobyl population.

Bottom line, these reactors will never be cleaned up nor decommissioned because such a task is not humanly possible. Hence, they will continue to pour water into the Pacific for the rest of time and threaten Japan and the northern hemisphere with massive releases of radiation should there be another large earthquake. ”

by Helen Caldicott


Fukushima radiation detected in Tillamook Bay, Gold Beach — K5

” For the first time, seaborne radiation from Japan’s Fukushima nuclear disaster has been detected on the West Coast of the United States.

Cesium-134, the so-called fingerprint of Fukushima, was measured in seawater samples taken from Tillamook Bay and Gold Beach in Oregon, researchers from the Woods Hole Oceanographic Institution are reporting.

Because of its short half-life, cesium-134 can only have come from Fukushima.

Also for the first time, cesium-134 has been detected in a Canadian salmon, the Fukushima InFORM project, led by University of Victoria chemical oceanographer Jay Cullen, is reporting.

In both cases, levels are extremely low, the researchers said, and don’t pose a danger to humans or the environment.

Massive amounts of contaminated water were released from the crippled nuclear plant following a 9.0 magnitude earthquake and tsunami in March 2011. More radiation was released to the air, then fell to the sea.

Woods Hole chemical oceanographer Ken Buesseler runs a crowd-funded, citizen science seawater sampling project that has tracked the radiation plume as it slowly makes its way across the Pacific Ocean.

The Oregon samples, marking the first time cesium-134 has been detected on U.S. shores, were taken in January and February of 2016 and later analyzed. They each measured 0.3 becquerels per cubic meter of cesium-134.

Buesseler’s team previously had found the isotope in a sample of seawater taken from a dock on Vancouver Island, B.C., marking its landfall in North America.

Meanwhile, in Canada, Cullen leads the InFORM project to assess radiological risks to that country’s oceans following the nuclear disaster. It is a partnership of a dozen academic, government and non-profit organizations, including Woods Hole.

Last month, the group reported that a single sockeye salmon, sampled from Okanagan Lake in the summer of 2015, had tested positive for cesium-134.

The level was more than 1,000 times lower than the action level set by Health Canada, and is no significant risk to consumers, Cullen said.

Buesseler’s most recent samples off the West Coast also are showing higher-than background levels of cesium-137, another Fukushima isotope that already is present in the world’s oceans because of nuclear testing in the 1950s and 1960s.

Those results will become more important in tracking the radiation plume, Buesseler said, because the short half-life of cesium-134 makes it harder to detect as time goes on.

Cesium-134 has a half-life of two years, meaning it’s down to a fraction of what it was five years ago, he said. Cesium-137 has a 30-year half-life.

A recent InFORM analysis of Buesseler’s data concluded that concentrations of cesium-137 have increased considerably in the central northeast Pacific, although they still are at levels that pose no concern.

“It appears that the plume has spread throughout this vast area from Alaska to California,” the scientists wrote.

They estimated that the plume is moving toward the coast at roughly twice the speed of a garden snail. Radiation levels have not yet peaked.

“As the contamination plume progresses towards our coast we expect levels closer to shore to increase over the coming year,” Cullen said.

Even that peak won’t be a health concern, Buesseler said. But the models will help scientists model ocean currents in the future.

That could prove important if there is another disaster or accident at the Fukushima plant, which houses more than a thousand huge steel tanks of contaminated water and where hundreds of tons of molten fuel remain inside the reactors.

In a worst-case scenario, the fuel would melt through steel-reinforced concrete containment vessels into the ground, uncontrollably spreading radiation into the surrounding soil and groundwater and eventually into the sea.

“That’s the type of thing where people are still concerned, as am I, about what could happen,” Buesseler said.

Scientists now know it would take four to five years for any further contamination from the plant to reach the West Coast. ”

by Tracy Loew