HUGE PLUTONIUM LEAKAGE LAND & SEA - Japan Fukushima Nuclear Reactor Meltdown
Cesium top threat to seafood
The damaged Fukushima No. 1 nuclear power plant is contaminating seawater with heavy amounts of iodine-131 and other radioactive materials.
Here are questions and answers regarding the latest threat from the ongoing radiation leaks.
Where is the leak into the ocean coming from?
Tokyo Electric Power Co. said it hasn't tracked down how radioactive materials leaked into the sea. Tepco officials speculated Saturday that it was somehow flowing directly from the plant, because no radioactivity spikes were observed on site. There was also no rain that could have caused atmospheric concentrations of iodine and other radioactive substances to fall to the sea.
Are the leaks substantial?
The Nuclear and Industrial Safety Agency said Monday it detected radioactive iodine-131 about 30 meters from reactors No. 5 and 6, or about 1,150 times the government safety limit. This followed revelations Sunday that iodine-131 measured about 300 meters away from reactor No. 1 hit 1,850 times the limit, suggesting the leak is spreading.
How long will the leaks continue to effect the environment?
That depends on the half-life of the materials, which is the time it takes the radioactivity of a specific substance to decrease by half. Iodine-131's half-life is about eight days but the half-life of cesium-137 is about 30 years.
The massive iodine-131 leak will not only be diluted by the sea, but also by the time it takes to reach fish and other marine products, pundits say. This is because both materials are water-soluble.
But this all depends on how fast Tepco can determine the cause of the leak and stop the radioactive water from discharging. So far the utility appear to be clueless.
Is the level of the leaks safe?
NISA said people within 20 km of the nuclear plant have already evacuated, hence the seawater contamination does not pose any immediate threat to their health. Nuclear Safety Commission of Japan Chairman Haruki Madarame also said Saturday that radioactive particles "are diluted and spread out" in seawater, adding there is no harm in eating fish from the coast because the levels of contamination would be negligible.
So far the agencies' claims appear to be true.
According to a survey conducted 30 km off the Fukushima plant by the Education, Culture, Sports, Science and Technology Ministry, the level of iodine-131 has seen a substantial drop.
Where is the radioactive water likely to flow?
The Okhotsk current and Kuroshio current meet off the Pacific coast. Seawater off Fukushima Prefecture is pushed southbound by the Okhotsk current toward Chiba Prefecture. There it will meet the northward Kuroshio (Black) current, and the two will push whatever radioactive water they contain away from Honshu into the Pacific.
Which marine products are vulnerable?
A survey by Tokyo-based Marine Ecology Research Institute shows that cesium-137 tends to accumulate in larger fish near the top of the food chain.
While the radioactivity of iodine-131 will be halved every 8 days, that will not be the case for cesium-137 — which is raising concerns.
Have there been any signs of fish contamination similar to that of the vegetables around the area?
At this point, no. For example, Chiba Prefecture on Friday studied anchovies, mackerel, spear squid and flounder caught off its shores. None was found to have contamination over state standards.
Is the situation under control?
As of now it appears things are not out of hand, but circumstances may change considering the tons of water that have been sprayed on the reactors to cool them down, as well as the leaks that may be coming from the reactor cores, or the spent-fuel pools above them, and the dangerous radioactive materials involved.
"The radioactive particles will be diluted, and iodine-131 has a half-life of 8 days," Kanazawa University professor Seiya Nagao told The Japan Times, hinting it is not a major concern.
But the expert on environmental monitoring and radionuclides warned that cesium has a much longer half-life and often accumulates in fish meat. While iodine-131 concentrates in the thyroid gland and increases the risk of thyroid cancer, cesium-137, once ingested, is accumulated by muscle tissues in the human body.
Experts say this may increase the risk of cancer.
"Its hard to tell if everything is under control at this point."By JUN HONGO
Radioactive contamination of the sea from Fukushima is likely to be only a local problem, but could lead to an exclusion zone if there is a major release of long-term pollutants, scientists say.So far, the biggest contaminant identified by Japanese officials has been radioactive iodine 131.
Samples of water taken close to the plant have been as high as 1,850 times the legal limit of iodine, but levels have fallen back, Japanese officials said on Tuesday.
Radioactive iodine can enter the marine food chain, especially through seaweed, which absorbs this element readily.
"There is the potential, when you're talking about certain types of seafood, that you can have reconcentration," said Ed Lyman of the Union of Concerned Scientists (UCS), a respected US NGO that focuses on nuclear safety.
"So, even dilute levels of contamination can be enhanced in certain marine life, you know, just like mercury concentrates in large fish like tuna. Also, plants like seaweed are known to concentrate certain isotopes, and so are certain types of shellfish."
Radioactive elements are hazardous in food because when ingested their radiation can damage DNA in cells, with the potential to cause cancer.
However, the contamination from iodine 131 is short-lived because the element has a half life -- the pace at which it loses half of its radioactivity -- of only eight days.
"This means that after a few months, it will be harmless, basically," said Simon Boxall, a lecturer at Britain's National Oceanography Centre at the University of Southampton, southern England, who praised early measures to stop fishing around the plant after the March 11 disaster.
"What worries me more is if caesium and plutonium get into the system," he said, referring to two radioactive heavy metals whose half-lives are around 30 years and potentially thousands of years respectively.
"That's more concerning, because that can build up in the sediments" of the sea bed at Fukushima, said Boxall.
At high levels, this could lead to the imposition of an exclusion zone of catches of fish and seafood, a measure that could last "years and years," he said.
"It's hard to know (how long) until they start taking measurements and determine how extensive the pollution is.
"You would basically not fish in an exclusion zone, period. And beyond the exclusion zone there would be an additional zone where you would come from time to time and see if there's any radioactivity."
Fukushima's plant operator, the Tokyo Electric Power Co. (TEPCO), reported on Saturday that levels of caesium were almost 80 times the legal maximum. On Monday it also said that plutonium, at very low and harmless levels, had been found at five locations in soil at the plant.
Given the scale of the Pacific -- the world's vastest body of water -- radioactivity in the sea at Fukushima will be flushed out beyond the local area by tides and currents and dilute to very low levels, Boxall said.
"It will get into the (ocean) food chain but only in that vicinity," he said. "Should people in Hawaii and California be concerned? The answer is no."
The Pacific, thanks to its size, is one of the cleanest seas in the world for radioactive contamination, according to the Woods Hole Oceanographic Institution in Massachusetts.
In 1990, radiation in the surface North Pacific was four becquerels of caesium 137 per cubic metre, while in the South Pacific it was 1.6 Bq/m3, it says. Most of it came from atmospheric nuclear tests before these blasts were stopped.
The most polluted seas were the Baltic, hit by fallout from the 1986 Chernobyl disaster, with 125 Bq/m3; the Irish Sea, with 55 Bq/m3 due to radioactive releases from Britain's Sellafield plant; and the Black Sea, also contaminated by Chernobyl, with 52 Bq/m3.
By comparison, the US Environmental Protection Agency (EPA) sets a maximum of 3,700 Bq/m3 of caesium in drinking water.
Fears of Fukushima nuclear contamination grow as tap water banned in Japan
The North Pacific Ocean Another Dead Zone?The International Atomic Energy Agency IAEA has indicated that cesium-137 which falls into a half life of an extended 30 years is the most relevant isotope of concern at the moment, (whereas Plutonium Mox Mixture from the cracked leaking Unit 3 will knock off an entire population) and that the possibility of distribution by sea will travel over a long distance within months to several years before the circulated isotope that was discharged into the seawater makes a landfall on other shores off of the Pacific further implicating the contamination risk for an already troubled Fishing Industry.
Radioactive Materials Found in Japanese Seawater Sampling:
Japanese authorities today reported data on radiation samples collected 30 kilometres off shore of the Fukushima Daiichi nuclear power plant on 24 March, and the levels of iodine-131 and cesium-137 showed slight variations from data collected at the same locations on 23 March A vessel from the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) collected water samples at eight points 30 kilometres from the coastline and found measurable concentrations of iodine-131 and cesium-137. The iodine concentrations measured were about at Japanese regulatory limits, and the cesium levels were well below those limits.
The IAEA's Marine Environmental Laboratory in Monaco has received the data and offered this preliminary analysis:
Dilution, both into deeper layers and by dispersion along the prevailing ocean currents will lead to a rapid decrease of the initial surface contamination.
For the short term, iodine-131 will be the relevant radionuclide as far as doses are concerned, but for the long term, cesium-137 will be the more important radionuclide in the marine environment. It will be possible to follow this nuclide over long distances for several years.
It can be expected that radionuclides will take months or years to reach other shores of the Pacific. The main transport of contamination takes place by atmospheric transport over long distances.
Discharge to seawater:
Results revealed on 22 March from a sample taken by TEPCO circa 100 meters south of the discharge channel of units 1-4 showed elevated levels of Cs-137, Caesium-134 (Cs-134) and I-131. A sample of seawater taken on 22 March 330 meters south of the discharge channel (30 kilometers off the coast line) had elevated levels of I-131 and Cs-137. Also north of the plant elevated levels of these ions were found (as well as Cs-134, Tellurium-129 (Te-129) and Tellurium-129m (Te-129m)), although the levels were lower. Samples taken one and/or two days later contained circa 80 Bq/L of iodine-31 26 Bq/L and caesium-137, most likely caused by atmospheric deposition. Furthermore, sea water containing measurable levels of iodine-131 and cesium-137 were collected by Japan Agency for Marine-Earth Science and Technology (JAMSTEC) on 22-23 March at several points 30 kilometres from the coastline Iodine concentrations were "at or above Japanese regulatory limits" while caesium was "well below those limits" according to an IAEA report on 24 March.
Effects on drinking water:
The safe level for iodine-131 and caesium137 in drinking water in Japan are 100 Bq/kg and 200 Bq/kg respectively. The Japanese science ministry said on 20 March that radioactive substances were detected in tap water in Tokyo, as well as Tochigi, Gunma, Chiba, Saitama prefectures. On March 23, Tokyo drinking water exceeded the safe level for infants, prompting the government to distribute bottled water to families with infants Measured levels were caused by iodine-131 (I-131) and were 103, 137 and 174 Bq/l. On 24 March, iodine-131 was detected in 12 of 47 prefectures, of which the level in Tochizi was the highest at 110 Bq/kg. Caesium-137 was detected in 6 prefectures but always below 10 Bq/kg. On March 25, tap water was reported to have reduced to 79 Bq/kg] and to be safe for infants in Tokyo and Chiba but still exceeded limits in Hitachi and Tokaimura. IAEA reported on 24 March that drinking water in Tokyo, Fukushima and Ibaraki had been above regulatory limits between 16 and 21 March.