Geographical distribution of plutonium derived from the atomic bomb in the eastern area of Nagasaki

In order to know the distribution of plutonium derived from the Nagasaki atomic bomb, soil samples were measured to determine the ²⁴⁰Pu/²³⁹Pu isotope ratio of and concentrations of ^239+240Pu and ¹³⁷Cs. The ^239+240Pu concentrations in soils, except for Nishiyama area, were close to the average concentration of soil collected in Japan. In soils collected at the Nishiyama area and at the eastern area of Nagasaki Prefecture and at part of northern area in Kumamoto Prefecture, the ²⁴⁰Pu/²³⁹Pu ratios were lower than the global fallout values. This suggests that plutonium from the atomic bomb was deposited in the eastern area from the hypocenter reaching up to 100 km eastwards.     

Migration of239Pu in soluble and insoluble forms in soil

A field experiment study was performed at the rural site of South-East Lithuania. The main tasks of the study included an evaluation of the peculiarities of partition of²³⁹Pu in soluble (²³⁹Pu(NO₃)₄,²³⁹PuCl₃) and insoluble (²³⁹PuO₂) forms in soddy and forest soil horizons. The results of durable experiments (418 and 326 days) have shown that from 44.1% to 92.2% of²³⁹Pu of investigated chemical forms were accumulated in the top (0–5 cm) soil layer. Some share (5.7–39.2%) of plutonium from studied chemical forms was found in the 5–20 cm layers of studied soil samples (columns). Obtained distribution of plutonium in soil layers may be attributed to the consideration that the migration rate to the soil depth for plutonium is 0.1–1.0 cm·y⁻¹ but for some part of plutonium 10 times higher migration rate is characteristic as well. Plutonium transfer factor (TF) to the grassland plants was calculated, the values ranged from 10⁻² to 10⁻¹.     

Plutonium Activity Ratios in Plankton: New Evidence of Hold-Up Time in Irish Sea Sediments

The determination of activity ratios for radioisotopes of different half-lives can be used to estimate transit times from a point source to locations further away. For conservative elements, this time is approximately equivalent to the net hydrological transport. However, for non-conservative elements such as plutonium, the additional influence of biogeochemical processes decreases the net transport time. In this study, ²⁴¹Pu and ^239,240Pu concentrations in Irish Sea plankton samples, collected in May 1994, were determined and the ²⁴¹Pu/^239,240Pu ratios calculated. Plutonium-239,240 was measured using a standard method by ion exchange chromatography and alpha counting, and ²⁴¹Pu was determined by liquid scintillation counting using the disk-supported technique. The latter showed some methodological problems, which are briefly discussed. The ²⁴¹Pu/^239,240Pu ratios gave an estimate of the "transit time" from Sellafield to the different sampling points. In fact, this time represents the age of plutonium in plankton, i.e., the time lag between release from Sellafield and detection at the different sampling stations. The mean plutonium age was 17±2 years (n = 10) and 18.6±0.8 years (n = 13) in phytoplankton and zooplankton, respectively. The spatial distribution was reasonably homogeneous over the Irish Sea. The assimilation-elimination processes of plutonium in plankton are rather rapid. Therefore, it may be assumed that, in this time scale, the plutonium concentrations were in equilibrium with surrounding waters. Thus, it is concluded that plutonium was rather old because resuspension-sedimentation processes had occurred that delayed its transport within the Irish Sea. Therefore, the age of plutonium in plankton represented the hold-up time of plutonium in the sediments from the Irish Sea.     

Redox speciation of plutonium

Knowledge of the oxidation state distribution of plutonium in natural waters is necessary in modeling its behavior in environmental systems. The redox speciation of plutonium is complicated by such effects as hydrolysis, complexation, disproportionation, solubility, and redox interchange reactions. The insolubility of Pu(OH)₄ is often the limiting factor of the net solubility of plutonium in oxic natural waters where Pu(V)O ₂ ⁺ is the most stable oxidation state. Perturbations to the oxidation state speciation due to the complexation chemistry of the different oxidation states of plutonium and to the insolubility of plutonium(IV) in neutral aquatic systems are discussed. The merits and limitations of some chemical separation techniques used to study redox speciation of plutonium are presented, and recommendations made for obtaining reliable oxidation state distribution data.     

Separation of uranium and plutonium isotopes for measurement by multi collector inductively coupled plasma mass spectroscopy

Uranium (U) and plutonium (Pu) isotopes in coral soils, contaminated by nuclear weapons testing in the northern Marshall Islands, were isolated by ion-exchange chromatography and analyzed by mass spectrometry. The soil samples were spiked with ²³³U and ²⁴²Pu tracers, dissolved in minerals acids, and U and Pu isotopes isolated and purified on commercially available ion-exchange columns. The ion-exchange technique employed a TEVA^® column coupled to a UTEVA^® column. U and Pu isotope fractions were then further isolated using separate elution schemes, and the purified fractions containing U and Pu isotopes analyzed sequentially using multi-collector inductively coupled plasma mass spectrometer (MCICP-MS). High precision measurements of ²³⁴U/²³⁵U, ²³⁸U/²³⁵U, ²³⁶U/²³⁵U, and ²⁴⁰Pu/²³⁹Pu in soil samples were attained using the described methodology and instrumentation, and provide a basis for conducting more detailed assessments of the behavior and transfer of uranium and plutonium in the environment.     

Plutonium isotopes in the surface air in Japan: Effect of Chernobyl accident

Plutonium isotope concentrations in the surface air at Tsukuba, Japan are reported during the period from 1981 to the end of 1986. The^239,240Pu concentration in the surface air, which showed a marked seasonal variation with a spring maximum and fall minimum, decreased until the end of 1985 according to the stratospheric residence time of 1.15 years. In May 1986, elevated^239,240Pu concentrations with high²³⁸Pu/^239,240Pu activity ratios were observed. The serial trend of plutonium concentration in the surface air is similar to the concentrations of the Chernobyl-released radionuclides. These findings suggest that a significant part of the plutonium in the surface air in May 1986 was due to the Chernobyl fallout. The size distribution of plutonium bearing particles indicates that plutonium isotopes were mechanically released in the Chernobyl accident. The surface air concentration of plutonium from the Chernobyl accident was much lower than the concentrations of the volatile fission products, and increased the monthly mean^239,240Pu concentration by only 0.03 Bqm^–3.     

Migration of plutonium isotopes in forest soil profiles in Lublin region (Eastern Poland)

The distribution of Pu isotopes in three profiles of forest soil in Lublin region was determined. The retention half-time and migration velocity of^239,240Pu originated from global and Chernobyl fallouts was calculated. The average rate of migration of the global fallout plutonium was 0.4 cm/year and that of the Chernobyl one 0.7 cm/year. Good correlation between Pu concentration and organic matter contents was found only in the case of podzolic soil profile. In two profiles a good negative correlation between Pu activity and exchangeable pH of the soil layer was determined.     

On peculiarities of vertical distribution of 239,240Pu, 238Pu and 137Cs activity concentrations and their ratios in lake sediments and soils

Distributions of ^239,240Pu, ²³⁸Pu and ¹³⁷Cs activity concentrations in the cores of sediments in the shallow lake, flooded and upland forest soils taken in the vicinity of Vilnius city were analyzed. The radiochemical, α-spectrometric and mass spectrometric methods were used for the plutonium evaluation and γ-spectrometry was used for the radiocesium evaluation. The only peak of enhanced radionuclide activity concentrations was determined for the lake bottom sediments, whereas vertical profiles of the radionuclide activity concentrations in flooded and upland forest soil cores were distinguished by two peaks. The obtained values of the activity concentration ratio ²³⁸Pu/^239,240Pu and the isotopic ratio ²⁴⁰Pu/²³⁹Pu indicated that the global fallout was a source of plutonium in the investigated environment. Chernobyl-derived radiocesium was detected solely in the surface layers (2–11 cm) of the studied sample cores. The contribution of the Chernobyl deposits amounted to about 2.26, 6.11 and 20.9 % of the total radiocesium inventory in the bottom sediments, the upland soil and flooded soil, respectively.     

Determination of 239,240Pu, 238Pu isotopes in soil samples using molecular recognition technology product AnaLig?Pu-02 gel

Procedure for analysis of plutonium isotopes in soil samples was developed using a new molecular recognition technology product AnaLig^?Pu-02 gel. Extraction chromatography TEVA^? Resin was used for purification of plutonium phase to remove thorium impurities which interfere in Pu determination by alpha spectrometry. The performance of the method was successfully tested by analysis of a sand stimulant sample and a soil sample spiked with known activity of ²³⁹Pu. The results obtained for procedures were compared in terms of activities and recoveries.     

Age determination of plutonium using inductively coupled plasma mass spectrometry

The age of plutonium is defined as the time since the last separation of the plutonium isotopes from their daughter nuclides. In this paper, a method for age determination based on analysis of ²⁴¹Pu/²⁴¹Am and ²⁴⁰Pu/²³⁶Pu using ICP-SFMS is described. Separation of Pu and Am was performed using a solid phase extraction procedure including UTEVA, TEVA, TRU and Ln-resins. The procedure provided separation factors adequate for this purpose. Age determinations were performed on two plutonium reference solutions from the Institute for Reference Materials and Measurements, IRMM081 (²³⁹Pu) and IRMM083 (²⁴⁰Pu), on sediment from the Marshall Islands (reference material IAEA367) and on soil from the Trinity test site (Trinitite). The measured ages based on the ²⁴¹Am/²⁴¹Pu ratio corresponded well with the time since the last parent-daughter separations of all the materials. The ages derived from the ²³⁶U/²⁴⁰Pu ratio were in agreement for the IRMM materials, but for IAEA367 the determination of ²³⁶U was interfered by tailing from ²³⁸U, and for Trinitite the determined age was biased due to formation of ²³⁶U in the detonation of the “Gadget”.     

Origin and release date assessment of environmental plutonium by isotopic composition

The origin and release date of environmental plutonium have been assessed by the measurement of plutonium and americium isotopic composition. The applicability and sensitivity of different plutonium isotope ratios, ²⁴⁰Pu/²³⁹Pu and ²⁴¹Pu/²³⁹Pu measured by inductively coupled plasma sector field mass spectrometry and ²³⁸Pu/²³⁹Pu analysed by alpha spectrometry, have been evaluated for origin determination in several types of environmental samples. With use of mixing models the contribution of different sources (e.g. global fallout or Chernobyl) can be calculated. By the measurement of the ²⁴¹Am/²⁴¹Pu isotope ratio, the release date (i.e. formation of ²⁴¹Pu by irradiation) can be estimated in environmental samples, which is an important parameter to distinguish recent plutonium release from previous (e.g. Chernobyl) emissions.     

A gamma-spectrometric method for the determination of plutonium isotope ratios

A gamma-spectrometric method using an intrinsic high resolution germanium detector has been developed for the determination of isotope ratios of plutonium from samples in solution form. The method is based on the assay of low energy gamma-rays of²³⁸Pu,²³⁹Pu,²⁴⁰Pu and²⁴¹Pu and does not require the use of branching intensities or the knowledge of detection efficiencies for different gamma rays. Since low energy gamma-rays are used, the effect of²⁴¹Am has also been studied. It is found that results are not affected up to 0.5 wt% of²⁴¹Am in plutonium samples. An accuracy of 3% is achievable in the determination of²⁴⁰Pu/²³⁹Pu and²⁴¹Pu/²³⁹Pu atom ratios as demonstrated by carrying out measurements on isotopic standards of plutonium.     

Leaching of glass components and surrogate nuclides from glassy waste forms for radioactive incineration ash

Three kinds of soil, collected in various places (in northwestern and southeastern Poland and near Chernobyl) were used as a subject of sequential extraction and plutonium distribution study. The modified method of Tessier was applied to separate readily available, carbonate, organic, Fe/Mn oxide and residual fractions. Plutonium isotope activity in soil as well as in particular separated fractions was determined by means of alpha spectrometry. The method of plutonium separation and purification for alpha-spectrometric measurements was modified according to the chemical properties of the extracted fraction. It was found that the major part (about 90%) of ^239,240Pu is bound to organic and Fe/Mn oxide fractions (in uncultivated soil samples of northwestern Poland and Chernobyl). In soil samples coming from river valley (southeastern Poland) almost equal amounts of plutonium are distributed between the available, organic and residual fractions.     

Biochemical fractionation and cellular distribution of americium and plutonium in the biomass of freshwater macrophytes

Accumulation of americium (²⁴¹Am) and plutonium (^238,242Pu) and their distribution in cell compartments and biochemical components of the biomass of freshwater aquatic plants Elodea canadensis, Ceratophyllum demersum and Myrioplyllum spicatum and aquatic moss Fontinalis antipyretica have been investigated in laboratory experiments. Americium and plutonium taken up from water by Elodea canadensis apical shoots were mainly absorbed by structural components of plant cells (90% for ²⁴¹Am; 89% for ²³⁸Pu and 82–87% for ²⁴²Pu). About 10–18% of isotope activity was recorded in the cytosol fraction. The major concentration (76–92%) of americium was bound to cell wall cellulose-like polysaccharides of Elodea canadensis, Myriophyllum spicatum, Ceratophyllum demersum and Fontinalis antipyretica, 8–24% of americium activity was registered in the fraction of proteins and carbohydrates, and just a minor concentration (<1%) in the lipid fraction. The distribution of plutonium in the biomass fractions of Elodea was similar to that of americium. Hence, americium and plutonium had the highest affinity to cellulose-like polysaccharides of cell walls of freshwater submerged macrophytes.     

<Superscript>241</Superscript>Pu in the environment: insight into the understudied isotope of plutonium

Studies of plutonium in the environment have focused on the α-emitting isotopes ²³⁸Pu, ²³⁹Pu and ²⁴⁰Pu, often overlooking the β-emitting isotope ²⁴¹Pu  because of its relatively short half-life (14.4 years). Here, we summarize sources of  ²⁴¹Pu and discuss its distribution and behavior in the environment. In the short term, ²⁴¹Pu, the largest contributor to the total plutonium radioactivity whereas in the long term its decay products, ²⁴¹Am and ²³⁷Np, are the major contributors as some 46% of current total ²⁴¹Am is attributable to ²⁴¹Pu decay. In this context, understanding the fate and transport of ²⁴¹Pu is crucial to assessing long-term radiological dose.     

Determination of the plutonium concentration by isotope dilution mass spectrometry using239Pu as a spike

A method is described for the determination of plutonium concentration in the presence of a bulk of other impurities by isotope dilution mass spectrometry /IDMS/ using²³⁹Pu as a spike. The method involves the addition of²³⁹Pu spike / 90 atom%/ to samples with²³⁹Pu / 70 atom%/ and vice versa. After ensuring chemical exchange between the sample and the spike isotopes, plutonium is purified by conventional anion exchange procedure in 7M HNO₃ medium.²³⁹Pu/²⁴⁰Pu atom ratio in the purified spiked sample is determined with high precision /better than 0.1%/ using a thermal ionization mass spectrometer. Concentration of plutonium in the sample is calculated from the changes in²³⁹Pu/²⁴⁰Pu atom ratio in the spiked mixture. Results obtained on different plutonium samples using²³⁹Pu as a spike are compared with those obtained by the use of²⁴²Pu spike. Precision and accuracy comparable to those achieved by using²⁴²Pu are demonstrated. The method provides an alternative in the event of non-availability of enriched²⁴²Pu or²⁴⁴Pu required in IDMS of plutonium and at the same time, offers certain advantages over the use of²⁴²Pu or²⁴⁴Pu spike.     

241Pu in the biggest Polish rivers

In the paper the results of ²⁴¹Pu activity concentration determination in the biggest Polish rivers are presented. The analysis of more than 100 river water samples showed the Vistula and the Odra as well as three Pomeranian Rivers are important sources of ²⁴¹Pu in the southern Baltic Sea. There were differences in ²⁴¹Pu activities depending on season and sampling site and the plutonium contamination came mainly from the global atmospheric fallout as well as the Chernobyl accident, which is confirmed by plutonium activity ratios of ²⁴¹Pu/^239+240Pu and ²³⁸Pu/^239+240Pu.     

ICP-MS analysis of plutonium activities and <Superscript>240</Superscript>Pu/<Superscript>239</Superscript>Pu ratio in alpha spectrometry planchet deposits

Plutonium isotopes were measured by alpha-spectrometry and ICP-MS in sediment samples from two European lakes: Blelham Tarn in U.K. and Stechlin lake in Germany. The ICP-MS measurements were made after alpha-spectrometry counting of the planchets. The planchets were prepared by traditional electrodeposition method after radiochemical extraction, separation and purification of the Pu fraction. A short radiochemical separation using plutonium selective resin, between the two spectrometry measures, is presented. The results show that these two complementary methods are in good agreement, the plutonium activity concentrations are the same. Alpha-spectrometry allows the ²³⁸Pu determination and ICP-MS individual measurement of ²³⁹Pu and ²⁴⁰Pu. ²³⁸Pu/^239+240Pu and ²⁴⁰Pu/²³⁹Pu ratios are calculated to determine the plutonium contamination source. With the results of these two techniques, it could be demonstrate that the plutonium is of global fallout origin.     

Multi-isotopic determination of plutonium (239Pu, 240Pu, 241Pu and 242Pu) in marine sediments using sector-field inductively coupled plasma mass spectrometry

Among the transuranic elements present in the environment, plutonium isotopes are mainly attached to particles, and therefore they present a great interest for the study and modelling of particle transport in the marine environment. Except in the close vicinity of industrial sources, plutonium concentration in marine sediments is very low (from 10⁻⁴ ng kg⁻¹ for ²⁴¹Pu to 10 ng kg⁻¹ for ²³⁹Pu), and therefore the measurement of ²³⁸Pu, ²³⁹Pu, ²⁴⁰Pu, ²⁴¹Pu and ²⁴²Pu in sediments at such concentration level requires the use of very sensitive techniques. Moreover, sediment matrix contains huge amounts of mineral species, uranium and organic substances that must be removed before the determination of plutonium isotopes. Hence, an efficient sample preparation step is necessary prior to analysis. Within this work, a chemical procedure for the extraction, purification and pre-concentration of plutonium from marine sediments prior to sector-field inductively coupled plasma mass spectrometry (SF-ICP-MS) analysis has been optimized. The analytical method developed yields a pre-concentrated solution of plutonium from which ²³⁸U and ²⁴¹Am have been removed, and which is suitable for the direct and simultaneous measurement of ²³⁹Pu, ²⁴⁰Pu, ²⁴¹Pu and ²⁴²Pu by SF-ICP-MS.     

Study on the rate of plutonium vertical migration in various soil types of Lublin region (Eastern Poland)

Soil contamination level with ^239+240Pu of Lublin region was determined using the alpha spectrometric method. Results were compared with similar data from the study performed 15 year earlier. Decrease in total ^239+240Pu concentration and reducing quantity of Chernobyl fraction (up to almost negligible value of 1 %) has been observed in upper soil layer. Determination of ^239+240Pu concentration in soil profile layers allows calculating a vertical migration velocity of plutonium applying a compartment migration model. It was found that ^239+240Pu migration rate varies depending on soil type from 0.29 cm year^?1 in Podsols to 0.58 cm year^?1 in Fluvisols with mean value of 0.5 cm year^?1.