Inventories of 239+240Pu, 137Cs, and excess 210Pb in sediment cores from brackish Lake Obuchi, Rokkasho Village, Japan

The aim of this study was to measure the distribution and inventories of ^239+240Pu, ¹³⁷Cs, and excess ²¹⁰Pb (²¹⁰Pb_excess) in sediment core samples from brackish Lake Obuchi, which is in the vicinity of nuclear fuel facilities in Rokkasho Village, Japan. The inventory of the ^239+240Pu activity in the sediment samples from the estuary of a freshwater river, the central point of the lake, and the deepest point in the lake were 0.18, 0.29, and 0.24 kBq·m^–2, respectively. The inventories of ¹³⁷Cs and ²¹⁰Pb_excess in sediments were 0.83–1.2 kBq·m^–2 and 25–30 kBq·m^–2, respectively. The mean ^239+240Pu/¹³⁷Cs and ²¹⁰Pb_excess/¹³⁷Cs activity ratios were 0.23 and 28, respectively. The^239+240Pu/¹³⁷Cs activity ratios were approximately 13–24 times the ratio expected from global fallout. The inventories of ^239+240Pu and ²¹⁰Pb in sediments were higher than the inventory expected from atmospheric fallout, but the ¹³⁷Cs inventory was significantly lower than expected.This revised version was published online in November 2005 with corrections to the Cover Date.     

Studies of the vertical distribution of134Cs,137Cs,238Pu,239, 240Pu,241Pu,241Am and210Pb in ombrogenous mires at mid-latitudes

Six peat cores taken from three unmodified blanket and raised bogs in Ireland were sectioned and analyzed for a range of radionuclides including¹³⁴Cs,¹³⁷Cs,²³⁸Pu,²³⁹Pu,²⁴¹Am, and²¹⁰Pb.¹³⁴Cs and¹³⁷Cs were measured by high resolution gamma-spectrometry, while the transuranium nuclides were determined after chemical separation by alpha-spectrometry.²⁴¹Pu, present on the electroplated discs together with Pu(), was measured directly by low-level liquid scintillation counting. Core chronologies were established by measuring the unsupported²¹⁰Pb component using low energy photon spectrometry (LEPS). From the resulting profiles, relaxation depths and migration rates for the above mentioned radionuclides have been determined and differences in the values of these parameters interpreted.²³⁸Pu/^239,240Pu and²⁴¹Pu/^239,240Pu ratios have been examined carefully and are discussed in some detail. Finally, the contribution from Chernobyl to the total radiocaesium inventory in each core has been established using the¹³⁴Cs/¹³⁷Cs ratio observed in the initial fallout from Chernobyl.     

Simultaneous analysis of 137Cs, 90Sr, 238Pu and 239+240Pu in Brazilian seawater

Methodologies for simultaneous analysis of ¹³⁷Cs, ⁹⁰Sr, ²³⁸Pu and ^239+240Pu were developed and applied to seawater samples. ¹³⁷Cs levels in Brazilian coastal seawater ranged from 0.12 to 4.7 Bq·m^-3, for ⁹⁰Sr from 2.0 to 8.6 Bq·m^-3, for ^239+240Pu from 0.8 to 4.5 mBq·m^-3 and for ²³⁸Pu it was of 1.9 mBq·m^-3. The artificial radioactivity levels in Brazilian seawater are typical values due to fallout deposition.     

239Pu, 240Pu, 241Pu, 241Am, 137Cs,and 210Pb in seafloor sediments in the western North Pacific Ocean and the Sea of Japan: distributions,sources and budgets

Journal of Radioanalytical and Nuclear Chemistry - Vertical distributions of 239Pu, 240Pu, 241Pu, 241Am, 137Cs, and 210Pb concentrations, and 240Pu/239Pu ratios were determined in seafloor...     

239+240Pu and 137Cs in Sediments from Tokyo Bay: Distribution and Inventory

Four sediment cores were collected from Tokyo Bay and analyzed for their ^239+240Pu and ¹³⁷Cs concentrations. Shallow nearshore sediments from Tokyo Bay have ^239+240Pu inventories which average 214±14 MBq/km². They are five times greater than the supply expected from the atmospheric global fallout at the same latitude of 42 MBq/km². The measured mean ¹³⁷Cs inventory of 433±93 MBq/km² is approximately one fifth the value expected from global fallout. Furthermore, the ^239+240Pu/¹³⁷Cs activity ratios, with a mean ratio of 0.50±0.14, are significantly greater than the ratio expected from the global fallout of 0.021. Excess ^239+240Pu inventories can be considered to have been introduced into Tokyo Bay as weathering products by soil erosion, transported via rivers and winds, and to be much more efficiently scavenged from seawater by particles resuspended at the sediment-water interface.     

Radiochronology of sediments from the Mediterranean Sea using natural210Pb and fallout137Cs

The²¹⁰Pb and¹³⁷Cs profiles of sediment cores from two locations in southern Spain, three locations in southern Turkey and two locations in northern Cyprus were determined by direct -ray spectroscopy. Sedimentation rates were derived for all locations using the²¹⁰Pb data. The rates range from 1.39±0.12 cm · y^–1 (0.50±0.04 g · cm^–2 · y^–1) to 0.08±0.01 cm · y^–1 (0.039±0.003 g · cm^–2 · y^–1). Except for one core, the¹³⁷Cs profiles were also used to compute sedimentation rates. The results are in good agreement with those of²¹⁰Pb values. The results of the Constant Initial Concenration and Constant Rate of Supply dating models are in good agreement with each other. The flux of unsupported²¹⁰Pb varies between 0.11±0.03 to 0.74±0.01 pCi · cm^–2. The average depositional flux was found to be considerably lower for cores from the Eastern Mediterranean.     

239+240Pu and137Cs concentrations in salmon (Oncorhynchus keta) collected on the Pacific coast of Japan

Salmon (Oncorhynchus keta) samples were collected on the Pacific coast of Japan and analyzed for their^239+240Pu and¹³⁷Cs concentrations in six places, i.e., muscle, viscera, gill, gonad, skin and spine. The^239+240Pu concentrations in muscle ranged from 0.07 to 0.14 mBq/kg (wet) and had the lowest value among the six regions. The mean^239+240Pu concentrations in viscera, gonad and spine were more than 1 mBq/kg (wet_ while those in muscle and skin were one order of magnitude lower. The largest amounts of^239+240Pu were accumulated in gonad. The^239+240Pu/¹³⁷Cs activity ratios in all positions were lower than that of the global fallout ratio of 0.022, suggesting that¹³⁷Cs could be accumulated with greater ease than^239+240Pu in all positions and ratios of uptake differed remarkably from position to position. The total accumulations of^239+240Pu and¹³⁷Cs in salmon were 1.32 and 328 mBq/individual, respectively.     

Dating of Black Sea sediments from Romanian coast using natural 210Pb and fallout 137Cs

The sediment samples collected near the shore from Romania were used for the determination of levels of natural ²¹⁰Pb, ²²⁶Ra and fallout ¹³⁷Cs radionuclides. The sediment samples were dried and ground to a fine powder. Airtight sealed samples were counted by gamma-spectrometer with 110 cm³ well-type HPGe detector for one week each. By using the isotopic analysis results, sediment accumulation rate was determined. A sedimentation rate of 0.20±0.01 cm^.y^-1 was determined using ²¹⁰Pb method and 0.15±0.03 cm^.y^-1 using ¹³⁷Cs isotope. Fallout peak from Chernobyl reactor accident, as well as the peaks due to nuclear tests, act as time markers.     

239+240Pu and137Cs distributions in seawater from the Yamato Basin and the Tsushima Basin in the Japan Sea

Comparative studies between column and batch liquid emulsion membrane techniques based on HDEHP/HCl system were carried out to develop a system for isolation of²³⁴Th from natural uranium. For column investigations a spray column was constructed and used with two different modes. In the first mode the feed solution was circulated through the membrane while in the second mode the membrane phase was circulated through the feed solution. The results showed that, kinetically, the equilibrium for thorium separation using batch technique is faster than the continous column system. Quantitative permeation of thorium was achieved within one minute of mixing whereby the permeation of uranium reached equilibrium after 3 minutes with a permeation percentage less than 6%. A procedure was developed to separate²³⁴Th from natural uranium with high radiochemical purity of more than 98%.     

90Sr, 137Cs, 238Pu, 239+240Pu and 241Am levels in terrestrial and marine ecosystems around the Italian base in Antarctica

During the last 14 years the Radioecology Laboratory of Parma University and the General Chemistry Institute of Urbino University collaborated on a radioecological programme having the aim to observe the evolution of antropogenic radioactivity in Antarctica in the period 1987-2001. The artificial radionuclides considered were ⁹⁰Sr, ¹³⁷Cs, ^239+240Pu,²³⁸Pu and ²⁴¹Am. The contamination seems to be higher in the continental environment rather than in the marine one. Mosses, algae and lichens showed the highest values for all radionuclides analyzed. The results prove that the Antarctic continent is interested by radioactive pollution. As far as ¹³⁷Cs is concerned, a progressive decrease was observed.     

238Pu, 239+240Pu, 241Am, 90Sr and 137Cs in mountain soil samples from the Tatra National Park (Poland)

Activity concentrations and inventory for ²³⁸Pu, ^239+240Pu, ²⁴¹Am, ⁹⁰Sr, and ¹³⁷Cs in soil from Tatra Mountains of Poland are presented. Soil samples were collected using 10 cm diameter cores down to 10 cm and sliced into 3 slices. Details of the applied procedure are described with the quality assurance program. The maximum activity concentrations found for various samples were: 1782±13 Bq/kg, 17.4±0.9 Bq/kg, 3.4±0.3 Bq/kg and 84±7 Bq/kg for ¹³⁷Cs, ^239+240Pu, ²⁴¹Am and ⁹⁰Sr, respectively. The maximum cumulated deposition of ^239+240Pu is 201±8 Bq/m². The origin of radionuclides is discussed, based mostly on the observed isotopic ratio of Pu. Significant correlations were found between ^239+240Pu, ²⁴¹Am and ¹³⁷Cs. The effective vertical migration rate seems to be in the order of: ⁹⁰Sr≫Pu>Am>Cs.     

Vertical Profiles, Inventories, and Activity Ratios of 239+240Pu and 137Cs in Sediments from Sagami Bay, Western Northwest Pacific Margin

Marine sediment cores were taken from Sagami Bay of the western Northwest Pacific and analyzed for ^239+240Pu and ¹³⁷Cs activities. A significant correlation was observed between ^239+240Pu and ¹³⁷Cs activities in sediment cores, i.e., their vertical profiles. The measured activities which were used to obtain the inventories of ^239+240Pu and ¹³⁷Cs in the sediment column, showed large variations, ranging from 36 to 474 MBq/km² for ^239+240Pu and 49 to 652 MBq/km² for ¹³⁷Cs. ^239+240Pu inventories in the sediment from one region in the Bay, Sagami Nada were 5–10 times greater than those predicted from atmospheric global fallout 42 MBq/km² at the same latitude. On the other hand, ¹³⁷Cs inventories, with a mean value of 297±168 MBq/km², were much less than predicted, 2040 MBq/km². The activity ratios of ^239+240Pu/¹³⁷Cs obtained, with a mean of 0.65±0.17, were significantly greater than the ratio predicted from fallout, 0.021. Furthermore, there was a clear relationship between both ^239+240Pu and ¹³⁷Cs inventories and the water content, indicating that higher inventories may be attributed principally to concentration in, and scavenging by, fine-grained particles.     

Radionuclide ratios of90Sr/137Cs and239(240)Pu/137Cs in contaminated surface air after the Chernobyl accident in Asutria

Energy straggling in pulse height distributions of plastic scintillation counters of 4 and 10 cm in thickness was measured for 1 GeV/c pions and studied by Monte Carlo simulations. Calculated energy loss distributions are in good agreement with the experimental data and also with the prediction by the Landau straggling function.     

Determination of 238Pu, 239+240Pu and 241Am in air filters

The aim of this work is to present the method for sequential plutonium and americium activity determination in air filters using chromatographic radionuclide separation and alpha spectrometry measurement. The developed method may be employed for the purposes of workplace monitoring and as an indicator of the need of introducing the individual monitoring as well as a useful complementation of individual monitoring. Basic parameters describing the developed method such as values of chemical recoveries and minimum detectable activities for plutonium and americium isotopes have been determined. Applied counting efficiency was obtained using Monte Carlo calculation method.

     

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 and^239+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.     

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 and^239,240Pu in the volcanic soil are more mobile than those in other forest sites of Korea, and that the downward movement of⁹⁰Sr is faster than¹³⁷Cs and^239,240Pu. A significant correlation was found between the concentration of¹³⁷Cs and those of⁹⁰Sr and^239,240Pu. 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.     

Radioanalytical approach to determine 238Pu, 239+240Pu, 241Pu and 241Am in soils

The simultaneous determination of multiple actinide isotopes in samples where total quantity is limited can sometimes present a unique challenge for radioanalytical chemists. In this study, re-determination of ²³⁸Pu, ^239+240Pu, and ²⁴¹Am for soils collected and analyzed approximately three decades ago was the goal, along with direct determination of ²⁴¹Pu. The soils had been collected in the early 1970’s from a shallow land burial site for radioactive wastes called the Subsurface Disposal Area (SDA) at the Idaho National Lab (INL), analyzed for ²³⁸Pu, ^239+240Pu, and ²⁴¹Am, and any remaining soils after analysis had been archived and stored. We designed an approach to reanalyze the ²³⁸Pu, ^239+240Pu, and ²⁴¹Am and determine for the first time ²⁴¹Pu using a combination of traditional and new radioanalytical methodologies. The methods used are described, along with estimates of the limits of detection for gamma-and alpha-spectrometry, and liquid scintillation counting. Comparison of our results to the earlier work documents the ingrowth of ²⁴¹Am from ²⁴¹Pu, and demonstrates that the total amount of ²⁴¹Am activity in these soil samples is greater than would be expected due to ingrowth from ²⁴¹Pu decay.     

Total deposition velocities and scavenging ratios of 7Be and 210Pb at Rokkasho, Japan

The atmospheric concentrations and deposition fluxes of ⁷Be and ²¹⁰Pb were observed biweekly in Rokkasho, Japan on the Pacific Ocean coast at the northern end of Honshu Island, from March 2000 to March 2006, to clarify their regional features. Seasonal variation pattern of atmospheric ⁷Be concentrations had double peaks, and that of ²¹⁰Pb had a single peak. Deposition fluxes of ⁷Be and ²¹⁰Pb showed the same patterns. The total deposition pattern of ⁷Be was similar to that commonly seen on the Pacific Ocean side of northern Honshu Island, while the pattern of ²¹⁰Pb was similar to that commonly seen on the Japan Sea side. The lack of high spine mountains windward in Rokkasho may be the cause of this ambiguity in the winter monsoon season. Total deposition velocities and scavenging ratios of ²¹⁰Pb were similar to those of ⁷Be from spring to fall, and showed that both nuclides had a similar removal process from the atmosphere. However, the scavenging ratios of ²¹⁰Pb were slightly larger than those of ⁷Be in winter, indicating different behaviors for both nuclides in the scavenging process. The scavenging ratios of both nuclides inversely correlated with precipitation rate, and the ratios in winter were larger than in the other seasons.     

Vertical migration of plutonium-239 + -240, americium-241 and caesium-137 fallout in a forest soil under spruce.

The vertical activity distributions of fallout 238Pu, 239+240Pu, 241Am, 134Cs and 137Cs in a forest soil (Hapludult) were determined at several locations in a spruce stand separately according to their origin (global fallout or Chernobyl fallout). To determine the rate of migration of these radionuclides in each soil horizon, the observed depth profiles of the radionuclides were evaluated with a compartment model. In the top organic horizons (LOf1 and Of2), the migration rates for all radionuclides from both sources were above 0.5 cm per year. In the Oh horizon the migration rates observed for global fallout Pu, Am and Cs were similar (0.2-0.4 cm per year). Compared with Pu, however, the mobility of Am is slightly, but statistically significantly, enhanced. The highest rate in this layer was found for Chernobyl-derived radiocaesium (2 cm per year). In the layers of the mineral horizon (depth 0-2, 2-5 and 5-10 cm) the observed migration rates were very similar for global fallout Pu (0.08-0.7 cm per year) and Am (0.1-2 cm per year). In comparison, the migration rate of global fallout radiocaesium was about half in each layer. The highest rate was observed again for Chernobyl-derived radiocaesium (0.5-3 cm per year).