Sunday, June 5, 2011

#Fukushima I Nuke Accident: Plutonium Found Outside the Plant

Actually, the sample was taken on April 21 but only now the researcher is disclosing it.

So, the US NRC's report in late March that the bits of spent fuel rods were found 1 mile (1.6 kilometer) from the plant was right.

From NHK World (6/5/2011):

Minute amounts of plutonium have been detected for the first time in soil outside the Fukushima Daiichi nuclear plant.

Shinzo Kimura of Hokkaido University collected the roadside samples in Okumamachi, some 1.7 kilometers west of the front gate of the power station. They were taken during filming by NHK on April 21st, one day before the area was designated as an exclusion zone.

Professor Masayoshi Yamamoto and researchers at a Kanazawa University laboratory analyzed the samples and found minute amounts of 3 kinds of plutonium.

The samples of plutonium-239 and 240 make up a total of 0.078 becquerels per kilogram.

This is close to the amount produced by past atomic bomb tests.

But the 3 substances are most likely to have come from the plant blasts, as their density ratio is different from those detected in the past.

Professor Yamamoto said the quantities are so minute that people's health will not be harmed.

But he recommended that the contamination near the plant should be fully investigated, saying that a study may shed light on how radioactive materials spread in the air.

Sunday, June 05, 2011 23:21 +0900 (JST)

This time, I found no egregious mistranslation from NHK World.


Anonymous said...

Robbie001 sez:

The Environmental Transport of
Radium and Plutonium:
(see chapter three)

As a result of an early belief that transuranic elements would be essentially immobile in the soil, Prior to 1970, wastes contaminated with such materials were not subject to any special regulations other than very weak ones pertaining to low-level radioactive waste. As a result, they were commonly disposed of along with low-level waste and chemical waste in a variety of ways, including burial in pits and trenches and, in the case of liquid wastes, direct dumping on the ground and injection into wells.

The contamination of soil and water with transuranic elements can pose a significant long-term risk in some cases. As summarized by Fioravanti and Makhijani Transuranic radionuclides pose special risks. First, the half-lives of some of the most important ones are very long. For example, plutonium-239 has a half-life of over 24,000 years and neptunium-237 has a half-life of over two million years. Despite this, the radioactivity per unit of weight (the “specific activity”) for these radionuclides is high enough for tiny quantities of the material to be dangerous. For instance, plutonium-239 is about 100,000 times more radioactive than natural uranium (which consists of a mixture of uranium-238, uranium-235 and a trace of uranium-234). One-millionth of an ounce (about 30 micrograms) of plutonium-239 deposited in small particles in the lung is very likely to induce cancer. Further, alpha radiation is far more damaging per unit of energy deposited in the body relative to gamma and beta radiation. The high concentrations of long-lived radionuclides in TRU waste require this waste to be disposed of in a geologic repository under Environmental Protection Agency rules similar to those for high-level waste (codified in 40 CFR 191).

Already plutonium from the DOE nuclear weapons production and testing program can be found in the surface waters and groundwater at a number of sites. In fact, plutonium contamination has been specifically identified at nine of the Superfund National Priorities List sites.
Like many contaminants, plutonium dissolved in groundwater or surface water can adsorb onto soil through ion exchange.

"Finally, as is typical of heavy metals, the amount of plutonium that is taken up into plants is several orders of magnitude less than the amount present in the soil. As such, transfer to vegetation is not likely to play a significant role in the transport of plutonium. Despite this, however, there are other biota effects that can impact the migration of plutonium. The roots of plants as well as microbes and funguses can introduce agents that enhance the formation of complexes which inhibit the adsorption of plutonium onto soil and thus enhance its mobility. In addition, some types of bacteria can have multiple impacts on the adsorption of plutonium. For example, in experiments with the bacteria Bacillus subtilis, it was found that between 80 and 90 percent of the plutonium was adsorbed by the bacteria at the end of the first day. In addition, it was observed that the plutonium was converted from the +6 oxidation state to the +5 state “within 2 hours” and that roughly four-fifths of the sorbed plutonium was in the +4 oxidation state after 48 hours. The enhanced mobility of plutonium in the presence of bacteria has been attributed to the production of “extracellular metabolic products, organic acids, such as citric acid, and sequestering agents, such as siderophores.”159 The impact of bacteria in the environment is complicated by the fact that, in some instances, the reduction of plutonium to lower redox states may inhibit its mobility, and by the possibility that living bacteria may act as colloids themselves upon which the plutonium may adsorb, thus increasing its mobility. A detailed examination is beyond the scope of this report."

Anonymous said...

Robbie001 sez:

"Sorption of actinides, particularly Pu, onto submicron-sized colloids increases their mobility, but these Pu-colloids are difficult to detect in the far-field. We describe actinides on colloids in the groundwater from the Mayak Production Association, Urals, Russia, where at the source the Pu-activity is ~1000 Bq/l. Pu-activities are still 0.16 Bq/l at 3 km distance, where 70-90 mol% of the Pu is sorbed onto colloids, confirming that colloids are responsible for the long distance transport of Pu. Nano-SIMS elemental maps reveal that amorphous Fe-oxide colloids adsorb Pu(IV)-hydroxides or -carbonates along with U-carbonates."

The first and second environmental releases of man-made 239 + 240Pu came from nuclear explosions at Alamagordo and Nagasaki in 1945. The release at Nagasaki was more serious than at Alamagordo, because it happened in an area with a high population density. Unfissioned 239 + 240Pu and various fission products (e.g. 90Sr and 137Cs) have been interacting here with various environmental materials (soils, sediments, and plants) under wet and temperate conditions for more than 45 years. To assess the environmental mobility of 239 + 240Pu, the distributions of radionuclides from this release were investigated at Nishiyama (3 km east of the hypocenter) where heavy black rain containing unfissioned plutonium and fission products fell 30 minutes after the nuclear explosion. The vertical distributions of 90Sr, 137Cs and 239 + 240Pu were determined in unsaturated soil cores up to 450 cm deep. Most radionuclides were found in the soil column 30 cm from the ground surface (95% of 90Sr, 99% of 137Cs and 97% of 239 + 240Pu). However, 90Sr and 239 + 240Pu were detected in the groundwater as well below a depth of 200 cm. No 137Cs was found below 40 cm from the ground surface or in groundwater. These observations reveal that about 3% of the total 239 + 240Pu has been migrating in the soil at a faster rate than the remaining 239 + 240Pu. Sharp peak of 137Cs and 239 + 240Pu, indicating heavy deposition from the Nagasaki local fallout of 1945, were found in sediment cores collected from the Nishiyama reservoir. On the other hand, since 90Sr is mobile in fresh water sediments, there was no 1945 90Sr peak in the sediment cores. 239 + 240Pu peaks were unexpectedly discovered in pre-1945 sediment core sections. Although 90Sr was found in these sections, no 137Cs was found. By contrast to the distribution in sediment cores, 137Cs in tree rings had spread by diffusion from the bark to the center of the tree without holding a fallout deposition record. Most of the 239 + 240Pu was distributed in the tree rings following a similar deposition record to that found in sediment cores. Furthermore, a very small amount of 239 + 240Pu (about 1%) was found unexpectedly in pre-1945 tree rings. The only reasonable explanation for these unexpected discoveries is the existence of mobile 239 + 240Pu in the environment.

Anonymous said...

Robbie001 sez:

"Over the past 50 years, explosions of nuclear weapons and releases from the nuclear industry have introduced anthropogenic plutonium into the environment. In the Arctic environment, the main source of plutonium is from atmospheric weapons testing, but studies of plutonium in the Kara Sea have shown that other releases have given rise to enhanced local concentrations. Since different plutonium sources are characterised by distinctive plutonium-isotope ratios, evidence of a localised influence can be supported by clear perturbations in the plutonium-isotope ratio fingerprints. To assess long-term consequences when radionuclides are released into the environment, information on the source term speciation, transport and transformation processes and biological uptake is needed. Among artificial radionuclides released to the environment, the transuranium elements are a major concern, due to very long half-lives and their accumulation in bone as well as high radiotoxicity. Plutonium has been produced in greater quantity than other transuranic elements, however, environmental assessments are complicated by the complex environmental behaviour.

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