Pu In Soil Research Articles

A study of the bioavailability of90Sr,137Cs, and239+240Pu in soils at two locations of Spain affected by different radionuclide contamination events

It is well known that the bioavailability of artifical radionuclides such as 90 Sr, 137 Cs and 239+240 Pu in contaminated soils depends on the source term origin of the contamination. Altough the behaviour of the mentioned radionuclides in the soil is also influenced by the time passed from the contamination event and the characteristics of the contamination receiving soils. The objective of the present work is to analyse the different bioavailability and possible chemical-physical associations of 90 Sr, 137 Cs, and 239+240 Pu in soils located in different Spanish ecosystems (Almeria and Caceres provinces) by application of a sequential extraction procedure based on the NIST standard sequential extraction protocol. The resulting fractions obtained are: a) water soluble and exchangeable, b) associated to organic matter, and c) residual fraction. They will be studied jointly with the polluting sources (deposit of nuclear fallout-50s and 60s, Palomares accident in 1966 and the cesium release by Acerinox in 1998) in each ecosystem to interpret the observed behaviour of radionuclides.

Environmental study of fall-out 239+240Pu in soil samples in Iran

The result of a general survey on the concentration of fall-out 239+240Pu in soil collected from several regions in Iran are presented. The samples represent mixed soil averaged over the depth of 0–50 mm. According to the results obtained by alpha spectrometry on 96 soil samples from 32 locations, the 239+240Pu concentrations vary in the range 80–360 mBq kg −1. Under normal operating conditions and present counting setup, the minimum detectable activity (MDA) was approximately 8 mBq kg −1 for soil samples.

Bioavailability of 239+240Pu and 137Cs in aerosols and deposited dusts: a comparative study by fractional extraction

The bioavailability of (137)Cs and (239+240)Pu in soil, dust and aerosols has been determined by applying a fractional extraction procedure. In aerosols, 47-57% of (137)Cs was found to be easily exchangeable. This differs significantly from soil and deposited dust samples collected on a nearby street as well as on grassland where (137)Cs was quantitatively found in the acid-soluble fraction and the residue. A similar difference was observed for (239+240)Pu: 47% of (239+240)Pu in aerosols was associated with the organic fraction, while in soil and deposited dust from grassland 63-75% of (239+240)Pu was found in the acid-soluble fraction. In deposited street dust, 53% of (239+240)Pu was associated with the oxide fraction.

A comparative study of 239,240Pu in soil near the former Rocky Flats Nuclear Weapons Facility, Golden, CO

The Rocky Flats Nuclear Weapons Plant near Golden, CO released plutonium into the environment during almost 40 years of operation. Continuing concern over possible health impacts of these releases has been heightened by lack of public disclosure of the US Department of Energy (DOE) activities. A dose reconstruction study for the Rocky Flats facilities, begun in 1990, provided a unique opportunity for concerned citizens to design and implement field studies without participation of the DOE, its contractors, or other government agencies. The Citizens Environmental Sampling Committee was formed in late 1992 and conducted a field sampling program in 1994. Over 60 soil samples, including both surface and core samples, were collected from 28 locations where past human activities would have minimal influence on contaminant distributions in soil. Cesium-137 activity was used as a means to assess whether samples were collected in undisturbed locations. The distribution of plutonium (as 239,240Pu) in soil was consistent with past sampling conducted by DOE, the Colorado Department of Public Health and Environment, and others. Elevated levels of 239,240Pu were found immediately east of the Rocky Flats Plant, with concentrations falling rapidly with distance from the plant to levels consistent with background from fallout. Samples collected in areas south, west, and north of the plant were generally consistent with background from fallout. No biases in past sampling due to choice of sampling locations or sampling methodology were evident. The study shows that local citizens, when provided sufficient resources, can design and implement technical studies that directly address community concerns where trust in the regulated community and/or regulators is low.

Simultaneous analysis of 237Np and Pu isotopes in environmental samples by ICP-SF-MS coupled with automated sequential injection system

A simultaneous analytical method for 237Np, 239Pu and 240Pu has been developed using sector field inductively coupled plasma mass spectrometry (ICP-SF-MS) detection combined with an automated sequential injection (SI) separation system. The chemical purification of these actinides was carried out on an actinide-specific extraction chromatographic resin, TEVA-Spec, in an automated SI system. The similar chemical behaviors of Np and Pu on TEVA-Spec was confirmed by recovery test after treating with ascorbic acid in 5 M HNO3. TEVA-Spec maintained its re-usability, giving high and consistent chemical recovery, and showed good selectivity for Np and Pu and a low memory effect during the consecutive analysis of nine replicate samples. The high chemical recovery (>90%), reliable accuracy and repeatability of 237Np and Pu isotope purification using the SI system were proved using standard reference materials. Low detection limits of 2.5, 2.1 and 0.42 fg ml−1 were obtained for 237Np, 239Pu and 240Pu, respectively, which make it possible to analyze these nuclides in samples of soil and sediment as low as 1 g. With the exception of the preparation process required prior to loading a sample, all chemical purifications were carried out automatically by the programmed SI system, and were completed within 1 hour, which included measurement by ICP-SF-MS. This method was successfully applied to the analysis of the environmental levels of 237Np and Pu in soil, sediment and in biological samples.

Application of isotope-dilution laser ablation ICP-MS for direct determination of Pu concentrations in soils at pg g(-1) levels.

The methods available for determination of environmental contamination by plutonium at ultra-trace levels require labor-consuming sample preparation including matrix removal and plutonium extraction in both nuclear spectroscopy and mass spectrometry. In this work, laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was applied for direct analysis of Pu in soil and sediment samples. Application of a LINA-Spark-Atomizer system (a modified laser ablation system providing high ablation rates) coupled with a sector-field ICP-MS resulted in detection limits as low as 3x10(-13) g g(-1) for Pu isotopes in soil samples containing uranium at a concentration of a few microg g(-1). The isotope dilution (ID) technique was used for quantification, which compensated for matrix effects in LA-ICP-MS. Interferences by UH+ and PbO2+ ions and by the peak tail of 238U+ ions were reduced or separated by use of dry plasma conditions and a mass resolution of 4000, respectively. No other effects affecting measurement accuracy, except sample inhomogeneity, were revealed. Comparison of results obtained for three contaminated soil samples by use of alpha-spectrometry, ICP-MS with sample decomposition, and LA-ICP-IDMS showed, in general, satisfactory agreement of the different methods. The specific activity of (239+240)Pu (9.8 +/- 3.0 mBq g(-1)) calculated from LA-ICP-IDMS analysis of SRM NIST 4357 coincided well with the certified value of 10.4 +/- 0.2 mBq g(-1). However, the precision of LA-ICP-MS for determination of plutonium in inhomogeneous samples, i.e. if "hot" particles are present, is limited. As far as we are aware this paper reports the lowest detection limits and element concentrations yet measured in direct LA-ICP-MS analysis of environmental samples.

Radiological status of Rongelap Island in 1999

A radiological survey and whole body counting of 137Cs were carried out in Rongelap Island (main island) of Rongelap Atoll in July 1999. The maximum values of 137Cs contamination and of g-ray dose rate were 39 kBq/m2 and 0.033 mSv/h, respectively. The maximum a and b gross counting rates on the surface of ground were 1 cpm and 182 cpm in active area of 72 cm2, respectively. Activity of 239,240Pu for soil was 80 Bq/kg in the top 5 cm and aerial deposition was 3.4 kBq/m2 in Rongelap Island in 1999. The body burden of 137Cs was observed to be 27±11 Bq/kg for 6 workers. Assessment of external and internal annual doses (0.1 and 0.07 mSv/y) indicates that as of 1999 there is no large risk to the inhabitants of Rongelap Island from a radiological point of view. The radiological status of Rongelap Island, which was severely contaminated by the radiological fallouts of nuclear testings carried out in 1954, has improved year by year as shown by the decrease of 137Cs. The effective halftime of 137Cs, which is estimated to be 6.6 y is much shorter than the physical half-life of 137Cs. Radioactive contamination in Kaballe Island, (a part of the northern islands used for farming) which is located 25 km northeast of Rongelap Island, was still high in 1999. One site nearby a beach was highly contaminated with 137Cs, where the maximum activity of 137Cs was 3.4 MBq/m2, a-ray of 2 cpm, b-ray of 1205 cpm and g-ray of 0.73 mSv/h. Activity of 239,240Pu in soil (n = 1) was 294 Bq/kg (top 5 cm) and 16 kBq/m2.

Effect of industrial pollution on soil-to-plant transfer of plutonium in a Boreal forest

Plutonium in a forest ecosystem was studied at different distances from the copper and nickel smelter at Monchegorsk, Kola Peninsula, Russia. Soil and plant samples were collected 7 (site A), 16 (B), 21 (C) and 28 (D) km from the smelter and at a reference site situated in Finland, 152 km from Monchegorsk. The deposition of Cu in litter and in the organic layer decreased from 10 700 mg/m 2 at site A to 33 mg/m 2 at the reference site, the deposition of Ni from 14 300 to 29 mg/m 2. From the reference site to site A, the volume of the litter layer increased almost five-fold. Most of the 239,240Pu in soil was found in the organic layer and in the litter layer. When industrial pollution increased, the content of 239,240Pu in the litter layer increased (from approx. 0.5 at site D to 15 Bq/m 2 at site A) whereas, that in the organic layer decreased (from approx. 20 at site D to 5 Bq/m 2 at site A). Four different plant species typical for the subarctic environment were collected at each sampling site: Deschampsia flexuosa (forest hair grass); Empetrum nigrum (crowberry); Vaccinium myrtillus (blueberry); and Vaccinium vitis idaea (lingonberry). The concentration of 239,240Pu increased with pollution in Deschampsia flexuosa (from approx. 2 at site D to 7 mBq/kg at site A), Empetrum nigrum (from approx. 3 at site D to 14 mBq/kg at site A) and Vaccinium myrtillus (from approx. 1 at site D to 8 mBq/kg at site A). In Vaccinium vitis idaea, the Pu concentration did not have any clear trend of association with pollution. With the exception of Vaccinium vitis idaea, the aggregated transfer factors of plutonium (m 2/kg) for the plants studied increased almost ten-fold from site D to site A, the range being 3×10 −5–3×10 −4 m 2/kg for Deschampsia flexuosa, 7×10 −5–5×10 −4 m 2/kg for Empetrum nigrum and 3×10 −5–3×10 −4 m 2/kg for Vaccinium myrtillus. The most likely explanation for the higher transfer factors of plutonium near the smelter is contamination of the plants by litter rather than root uptake.

Fallout 137Cs, 90Sr and 239+240Pu in soils polluted by heavy metals: Vertical distribution, residence half-times, and external gamma-dose rates

The industrial pollution of an ecosystem, e.g., by heavy metals, might also affect the behavior of fallout radionuclides in the soils of these areas. To study such effects, we determined at various distances from the huge copper-nickel smelters at Monchegorsk on the Kola Peninsula (Russia) and at a reference site: (1) the vertical distribution of fallout 137Cs,90Sr and239+240Pu in the soil, (2) the corresponding residence half-times in different soil horizons, and (3) the resulting external gamma-dose rates at these sites in 1 m height due to 137Cs in the soil. The data show that the residence half-times and the partitioning of the fallout radionuclides among the various soil horizons depend significantly on the extent of the heavy metal pollution at the sites. The resulting external gamma-dose rate in 1 m height due to 137Cs in the soil is, however, rather similar at the various sites.

Dynamics of Radiation Situation on the Territory of Belarus and Migration of Radionuclides in Different Types of Soils after Chernobyl Catastrophe

A vertical migration of radionuclides Cs, Sr and Pu in soils (in upper 5 cm) of Belarus is given. Influence of genetic parameters of soil for vertical migration of radionuclides is introduced. The main factor of the velocity for radionuclides migration is super humidity. A forecast of vertical migration of radionuclides is made for the year 2016.

Association of fallout-derived [formula omitted] and [formula omitted] with natural organic substances in soils

Activity concentrations and associations of fallout-derived Cs, Sr and Pu in soils were investigated. The activity concentrations of 137 Cs, 90 Sr and 239,240 Pu in volcanic ash soil were much higher than those in granite soil. They decreased with increasing depth in the soil. The activity ratios of 239,240 Pu/ 137 Cs and 90 Sr/ 137 Cs tended to increase slightly with increasing soil depth. Alkali extraction experiments with 0.1 M NaOH solution showed that the percentage activities of the fallout radionuclides found in the organic acid fractions were in the order 239,240 Pu> 90 Sr> 137 Cs . The concentrations of 137 Cs and 239,240 Pu reacted with humic fractions were higher than those with fulvic fractions. In contrast to 137 Cs and 239,240 Pu, 90 Sr reacted more with fulvic fractions than with humic fractions. These results provide information about the effects of organic substances on the retention and migration of 137 Cs, 90 Sr and 239,240 Pu in soils under natural conditions.

Determination of137Cs,90Sr and fallout Pu in the volcanic soil of Korea

The cumulative depositions of137Cs,90Sr and fallout Pu in the volcanic ash soil of Korea were determined. The average accumulated depositions of137Cs,90Sr and fallout Pu in the volcanic soil were much higher than those in other forest sites of Korea. From depth profiles, it was found that137Cs,90Sr and239,240Pu in the volcanic soil are more mobile than those in other forest sites of Korea, and that the downward movement of90Sr is faster than137Cs and239,240Pu. A significant correlation was found between the concentration of137Cs and those of90Sr and239,240Pu. The activity ratios of238Pu/239,240Pu and241Pu/239,240Pu in soils are close to those observed in the cumulative deposit from the global fallout of nuclear weapon testings.

Dose assessment considerations for remedial action on plutonium‐contaminated soil

This article describes some of the dose assessment issues that should be considered when planning and executing a soil remedial activity. What is the proper dose scenario/ model? What are the appropriate cleanup criteria? How is the data gathered and analyzed (both before and after) cleanup? By describing the features and aspects of how these issues and others were considered or not considered in planning for the remedial action underway at Maralinga, Australia (former site of the Nuclear Weapons Testing Program of the United Kingdom) when compared with historical international experience of this type, the author attempts to illustrate that it is almost nonsensical to preselect a single soil value for Pu in soil (for national or international use), particulariy when expressed as a soil concentration (pCi/g or bq/g). This is especially so when the problem is Pu on the surface or near the surface of the soil. This is the situation common at nuclear test sites where “one point safe tests” were conducted. At these locations aspects of resuspension (i.e., area size, particle size, wind speed, etc.) become the dominant drivers for the development of cleanup criteria, sampling regimes, data gathering, and analysis regimes, etc. These particular elements and others are discussed and illustrated.

Comparative Distribution of 241Am and 239,240Pu in Soils around the Rocky Flats Environmental Technology Site

The distribution and behavior of 241 Am and 239,240 Pu in soils from the buffer zone of the Rocky Flats Environmental Technology Site have been investigated. Concentrations of both radionuclides decreased at similar rates with soil depth. More than 80% of the total inventory of both contaminants was found in the upper 9 cm of the soils with over 50% of the inventory residing in the top 3 cm. Comparison with earlier studies indicate that the plutonium depth profile has not changed significantly over the last 25 y. The inventories of 241 Am and 239,240 Pu decreased with distance from the 903 Pad (a former waste storage site) according to a power function, and the plume extended mainly toward the east. The lateral movement of the two contaminants away from the 903 Pad was not significantly different. The median activity ratio of 241 Am: 239,240 Pu ranged from 17 to 19% and was independent of sampling location and soil depth. This observation provided further evidence that the movement of both contaminants is indistinguishable in the study area. Because of the strong correlation between the two radionuclides, 241 Am concentrations can then be used to infer 239,240 Pu by counting the 241 Am via gamma spectroscopy.

Particle-associated Chernobyl fall-out in the local and intermediate zones

Fuel and condensed particle components of the Chernobyl fall-out are differentiated and the constitution of the fuel component is displayed on a map of the area to about 60 km from the reactor. The nuclear physics related properties of the fuel “hot particles” are discussed. The possibility of a long-term increase in the bioavailability of Sr and Pu in soils due to dissolution of these hot particles is commented upon.

Measurement of Trace Radionuclides in Soil by L X-Ray Spectrometry

L x-ray spectrometry is shown to be a promising cost efficient technique for assaying several radionuclides in soil simultaneously without prior chemical separation. Analysis is performed with a unique Si(Li)-NaI(Tl) spectrometer. The Si(Li) detector, with thin windows on both surfaces, is mounted on its edge to permit counting x rays from two samples simultaneously. With a thin soil sample on each of its sides this detector is sandwiched between two large NaI(Tl) scintillators. When the Si(Li) detector is operating in anticoincidence with the NaI(Tl) crystals the ? background in the x-ray spectrum is reduced by 50%. Thus, this spectrometer has four times the sensitivity of a conventional Si(Li) spectrometer. Initial measurements were made with a prototype spectrometer consisting of a 3 cm2 Si(Li) detector having a resolution of 350-400 eV and two 5?×4? naI(Tl) scintillators. A 30 cm2 Si(Li) detector array with two 12?×6? NaI(Tl) crystals is under development. Measurements of Pu in soil containing 241Am, from Rocky Flats, and Pu in soil containing 137Cs, from a waste-discharge site, are in good agreement with radiochemical measurements. Activity as low as 1 pCi/g of the natural U and Th in soil has been measured. With the array the minimum detectable Pu activity is expected to be 1 pCi/g which corresponds to a concentration of 10-7 - 10-5 ppm by weight.

A Detector System for In-Situ Spectrometric Analysis of 241Am and Pu in Soil

This system for quantitative analysis of Pu in soil via 241Am has four 2.5-mm high-purity Ge detectors of 33 cm2 total detecting surface area. These detectors are paralleled by gating circuitry to avoid the degradation of energy resolution associated with electronic output summing. In field tests the system was approximately three times as sensitive as a 70-cm3 Ge(Li) detector and approximately an order of magnitude more sensitive than the FIDLER system.