Behaviour of239,240Pu and241Am in the Baltic Sea; Measurements and interpretation in 1980–1984

Concentrations of^239,240Pu and²⁴¹Am in filtered seawater, particulate fraction and sediment were measured. Methods for determination of these nuclides were critically chequed and a new rapid method for²⁴¹Am in sediment was developed. Due to seasonal variation a significant decrease of plutonium and americium concentrations in surface water takes place in summer. Americium is more efficiently associated with particulate matter than plutonium. From May 1980 to September 1984 soluble plutonium in the water was reduced to about half. The residence half-time of^239,240Pu in the water of Baltic Sea is of the order of 5 years. About similar concentrations of^239,240Pu and²⁴¹Am were found in particulates in water as in the surface layer of the sediment. The average K_d-values for plutonium and americium were 10⁵ and 10⁵–10⁶ ml/g, respectively.     

Radiochemical determination of the yields of transuranium nuclides produced from natural uranium irradiated in a reactor

Transuranium nuclides were produced by irradiating a pellet of natural uranium sulfide in the Japan Material Testing Reactor (JMTR). After irradiation, a successive separation of uranium, plutonium, americium and curium was carried out. The fractional concentrations of the nuclides²³⁸Pu,²³⁹Pu,²⁴⁰Pu,²⁴¹Am,²⁴³Am,²⁴²Cm and²⁴⁴Cm were determined by α-ray spectrometry, and those of²⁴¹Pu and^242mAm were estimated from the build-up of α-emitting daughters,²⁴¹Am and²⁴²Cm, respectively. As the yield of²⁴²Pu was too slight to be detected by α-counting, the neutron activation analysis of the plutonium fraction based on the²⁴²Pu(n, γ)²⁴³Pu reaction was carried out by γ-ray spectrometry, and it was shown that a few pg of²⁴²Pu could be determined. A burn-up of²³⁵U was also estimated by neutron activation analysis. The experimental results are compared with the calculated ones.     

Recovery of americium from analytical solid waste containing large amounts of uranium,plutonium and silver

Trace metallic impurity analysis by spectroscopic techniques is one of the important steps of chemical quality control of nuclear fuel materials. Depending on the burn-up and the storage time of the fuel, there is an accumulation of ²⁴¹Am in plutonium based fuel materials due to β decay of ²⁴¹Pu. In this paper, attempts were made to develop a method for separation of ²⁴¹Am from 1.2 kg of analytical solid waste containing 70% U, 23% Pu, 5% Ag and 1–2% C as major constituents along with other minor constituents generated during trace metal assay of plutonium based fuel samples by d. c. arc carrier distillation atomic emission spectrometry. A combination of ion exchange, solvent extraction and precipitation methods were carried out to separate ~45 mg of ²⁴¹Am as Am(NO₃)₃ from 15 L of the analytical waste solution. Dowex 1×4 ion exchange chromatographic method was used for separation of Pu whereas 30% TBP–kerosene was utilized for separation of U. Am was separated from other impurities by fluoride precipitation followed by conversion to nitrate. The recovery of Pu from ion exchange chromatographic separation step was ~93% while the cumulative recovery of Am after separation process was found to be ~90%.     

Comparison of alpha-spectrometry and alpha/gamma ratio method for the determination of americium in plutonium bearing fuel materials

Determination of americium is one of the requirements of chemical quality assurance of plutonium bearing fuel materials. Alpha-spectrometry is generally used for the determination of ²⁴¹Am in Pu bearing fuels since the efficiency of semiconductor detector used for alpha-spectrometry is independent of the alpha-particle energy in the 4 to 8 MeV range. However, this method has limitations for Pu samples containing extremely small or very large amounts of ²⁴¹Am. Thus an alternative methodology based on alpha/gamma (α/γ) activity ratio was developed and tested using different samples. The method is based on the determination of total γ-activity (of 60 keV peak) of an aliquot of the solution and the total α-activity present in the aliquot. The method is fast as it does not involve chemical separation of Pu and Am as required in the alpha-spectrometric method. Data obtained on synthetic and real life samples demonstrates the usefulness of the developed alpha/gamma ratio method for the determination of ²⁴¹Am in Pu bearing fuel samples.     

Plutonium and americium concentrations and vertical profiles in some Italian mosses used as bioindicators

We have examined the uptake of actinide elements Am and, Pu by different species of lichen and moss collected in two locations (Urbino, Central Italy; Alps region, North-east Italy). Plutonium and americium were separated and determined by extraction chromatography, electrodeposition and alpha-spectrometry. This paper summarizes our results with a special emphasis on the vertical profiles of these actinides in two different species of mosses. Several 1–2 cm depth sections were obtained and dated by²¹⁰Pb method. A typical peak for^239,240Pu and²⁴¹Am was found in the very old moss species (“Sphagnum Compactum”) at a depth corresponding to the period 1960–1970 which was the period characterized by the maximum nuclear weapon tests. In a younger moss species (“Neckeria Crispa”) no peak was observed and the regression curves showed that Am is more mobile than^239,240Pu and²³⁸Pu.     

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.     

Concentration and vertical distribution of plutonium and americium in Italian mosses and lichens

The plutonium and americium concentration and vertical distribution in some Italian mosses and lichens have been determined. The^239,240Pu,²³⁸Pu and²⁴¹Am concentration ranges in tree trunk lichens 0.83–1.87, 0.052–0.154 and 0.180–0.770 Bq/kg, respectively. The corresponding values in tree mosses are higher and more scattered ranging from 0.321 to 4.96, from 0.029 to 0.171 and from 0.200 to 1.93 Bq/kg. The mean²³⁸Pu/^239,240Pu and²⁴¹Am/^239,240Pu ratios are 0.088±0.037 and 0.38±0.13 in lichens and 0.091±0.072 and 0.54±0.16 in tree mosses. The Pu and Am concentrations are relatively low in terrestrial mosses. The^239,240Pu,²³⁸Pu and²⁴¹Am vertical distributions in a terrestrial moss core (Neckera Crispa) collected near Urbino (central Italy) show an exponential decrease with the height. On the contrary the²⁴¹Am vertical distribution in another terrestrial moss core (Sphagnum Compactum) collected in the Alps (northern Italy) shows an interesting peak at 16 cm which corresponds to the deposition of fallout from the nuclear weapon tests in 1960's. The²⁴¹Am movement upward and downward in the moss core is also studied. The results show once again that both mosses and lichens are very effective accumulators of Pu and Am and that they can be used as good biological indicators of the radionuclide airbome pollution from nuclear facilities and nuclear weapon tests. They can play a very impotant role in cycling naturally or artificially enhanced radionuclides in the atmosphere over long time scales.     

Separation of neptunium, plutonium, americium and curium from uranium with di-(2-ethylhexyl)-phosphoric acid (HDEHP) for radiometric and ICP-MS analysis

The possibility of using di-(2-ethylhexyl)-phosphoric acid (HDEHP) in solvent extraction for the separation of neptunium, plutonium, americium and curium from large amounts of uranium was studied. Neptunium, plutonium, americium and curium (as well as uranium) were extracted from HNO₃, whereafter americium and curium were back-extracted with 5M HNO₃. Thereafter was neptunium back-extracted in 1M HNO₃ containing hydroxylamine hydronitrate. Finally, plutonium was back-extracted in 3M HCl containing Ti(III). The method separates²³⁸Pu from²⁴¹Am for α-spectroscopy. For ICP-MS analysis, the interferences from²³⁸U are eliminated: tailing from²³⁸U, for analysis of²³⁷Np, and the interference of²³⁸UH⁺ for analysis of²³⁹Pu. The method has been used for the analysis of actinides in samples from a spent nuclear fuel leaching and radionuclide transport experiment.     

Refinement of Pu parent–daughter isotopic and concentration analysis for forensic (dating) purposes

Plutonium (Pu) metal samples from an interlaboratory exchange exercise and simulated swipe samples were dated using plutonium–uranium (Pu–U) and plutonium–americium (Pu–Am). Metal data were evaluated for consistency and the swipe data against its source material. Metal ages based on ²³⁹Pu versus ²³⁵U and ²⁴⁰Pu versus ²³⁶U agreed to within a few percent, while the ²³⁸Pu–²³⁴U and ²⁴¹Pu–²⁴¹Am measurements had larger uncertainties. Swipe ages compared favorably with the material’s known history. Neptunium (²³⁷Np) analyses were examined in the context of the ²⁴¹Pu–²⁴¹Am–²³⁷Np system to estimate whether Np can provide insights on material from which Am, Np, and U were removed.     

Determination of plutonium,americium and curium in airborne effluents of nuclear power plants

A radiochemical method has been developed for the determination of²³⁸Pu,^{239, 240}Pu,²⁴¹Am,²⁴²Cm and²⁴⁴Cm in airborne effluents of nuclear power plants. The method involves conversion of transuranium elements to acid-soluble forms, dissolution, purification, electrodeposition and alpha spectrometric determination. Final recovery ranged from 69.0 to 75.4% for plutonium and from 26.8 to 68.3% for americium and curium.     

Enzymatic degradation of large vegetation samples for the simultaneous determination of129I,actinides and strontium

A radiochemical procedure is given for the simultaneous determination of low levels of¹²⁹I, actinides (Pu, Am, Cm) and⁹⁰Sr in vegetation samples. It is shown that grass samples up to 5 kg fresh weight can be wet ashed conveniently by hydrogen peroxide under alkaline conditions, subsequent to an initial enzymatic disintegration. After purification of the iodine fraction,¹²⁹I is determined by neutron activation analysis. Using alpha spectrometry,²³⁸Pu and^239,240Pu are determined in the plutonium fraction, and²⁴¹Am,²⁴²Cm, and²⁴⁴Cm in the americium/curium fraction. The⁹⁰Sr is determined after separation by beta counting its decay product⁹⁰Y.     

Determination of plutonium and americium in moss and lichen samples

A simple, sensitive and selective method is described for the simultaneous determination of plutonium and americium in lichen and moss samples which can be used as the atmospheric radioactivity bioindicators. Plutonium is separated from a HCl leaching solution by a Microthene-TNOA column; americium is separated by a KL-HDEHP column and purified by PMBP-TOPO extraction. A special attention has been paid to the decontamination of plutonium and americium from²¹⁰Po. Ten lichen and 12 moss samples from tree trunks have been analyzed: starting from 2 g sample, the average yields and the detection limits were 70.2±12.5% and 28 mBq/kg for plutonium and 70.0±15.1% and 34 mBq/kg for americium. The concentrations (mBq/kg) ranged from 28 to 4960 for^239,240Pu, from 28 to 171 for²³⁸Pu and from 34 to 1930 for²⁴¹Am, respectively.     

Reverse isotope dilution alpha spectrometry using plutionium-239 spike for determining plutonium concentration in high burn-up fuel samples without purification from americium-241 and a bulk of other impurities

A reverse isotope dilution alpha spectrometric /R-IDAS/ method using²³⁹Pu as a spike is described for the determination of plutonium concentration in high burn-up fuel samples wth²³⁸Pu/(²³⁹Pu+²⁴⁰Pu) alpha activity ratio >0.5, without resorting to any purification from²⁴¹Am and a bulk of other impurities. It involves the addition of a pre-clibrated spike solution to a known aliquot of the plutonium sample solution followed by source preparation using TEG as a spreading agent. The results obtained on a number of plutonium samples containing 20–80% of²⁴¹Am /alpha activity wise/ using this method are compared with those achieved by R-IDAS using purification with TTA, with respect to precision and accuracy. Precision and accuracy of 0.5% are demonstrated. This method eliminates the need of any separation and purification of plutonium from²⁴¹Am and a bulk of other impurities like uranium.     

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”.     

Sequential separation and determination of plutonium, americium-241 and strontium-90 in soils and sediments

A sensitive and reliable metbod for the sequential separation and determination of plutonium,²⁴¹Am and⁹⁰Sr in soil samples was developed. Plutonium was separated by a Microthene-TNOA column. Then⁹⁰Y (for⁹⁰Sr determination) was separated from americium by a HDEHP column after elimination of large amounts of interfering stable or radioactive nuclides (iron,²¹⁰Bi and²¹⁰Po etc.) by an oxalate precipitation and a Microthene-TNOA column. Finally americium was purified by another HDEHP column and a PMBP-TOPO extraction. A special attention was paid to the decontamination of Pu and Am from²¹⁰Po and of⁹⁰Y from²¹⁰Bi; the relevant decontamination factors resulted greater than 10⁵, 10⁶ and 10⁴ respectively. The detection limits were 1.2 mBq/kg for Pu and 1.7 mBq/kg for²⁴¹Am and 0.32 Bq/kg for⁹⁰Sr. The procedure was checked by analyzing three certified samples supplied by IAEA. Some Italian soil samples were also analyzed giving average yields of 84.9±7.2% for Pu, 57.8±3.2%for Am and 96.7±1.6% for Y; the^239+240Pu,²³⁸Pu,²⁴¹Am and⁹⁰Sr contents (Bq/kg) ranged from 0.347 to 1.53, from 0.013 to 0.048, from 0.126 to 0.556 and from 2.89 to 11.6 respectively and the average ratios were 0.037±0.017 for²³⁸Pu/^239+240Pu, 0.357±0.040 for²⁴¹Am/^239+240Pu and 7.0±1.2 for⁹⁰Sr/^239+240Pu.     

Rapid determination of 239,240Pu, 238Pu, 241Am and 90Sr in radioactive waste using combined SPE sorbents AnaLig? Pu02, AnaLig? Sr01 and TRU? Resin

A rapid separation method has been developed which allows measurement of plutonium, americium and strontium isotopes in the radioactive sludge from Nuclear power plant A1 Jaslovske Bohunice (NPP A1) with high chemical recoveries and effective removal of matrix interferences. This method uses different commercial products stacked AnaLig^? Pu02, AnaLig^? Sr01 and TRU^? Resin cartridges from IBC Advanced Technologies and Eichrom Technologies. The method allows the rapid separation of plutonium, strontium and americium using a single multi-stage column in the vacuum box (cartridge technology) with rapid flow rates to minimize sample separation time. The ^239,240Pu, ²³⁸Pu and ²⁴¹Am were determined by alpha spectroscopy, ⁹⁰Sr was counted on TRICARB 2900 TR by Cerenkov counting of its progeny ⁹⁰Y.     

Low level Pu and Am estimation in liquid waste from nuclear reactor

Estimation of very low amount up to pico-gram of Am and Pu in the liquid waste of U–Pu fuel cycle of the irradiated U fuel from the nuclear reactor has been carried out using combined method of α- and γ-ray spectrometric techniques. ²⁴¹Am was estimated by γ-ray spectrometry from a plancheted source. In spite of the same α energy of 5.49 MeV for ²⁴¹Am and ²³⁸Pu, the amount ²³⁸Pu was estimated by α spectrometry from the same plancheted source after subtracting amount of the ²⁴¹Am obtained from γ-ray spectrometry. The amount of Am and Pu obtained by this technique is found to be superior compared to other techniques even in the presence of Th, U and fission products.     

Plutonium process control using an on-line gamma monitor for uranium,plutonium, and Americium

An On-Line Gamma Monitor profiles the concentration of uranium, plutonium, and americium in waste and product streams of the anion exchange process used to purify plutonium at Los Alamos. The Monitor employs passive gamma Spectrometry to measure the 59.5-KeV and 129-KeV gamma rays of²⁴¹Am and²³⁹Pu, respectively. Because the uranium impurity in typical process streams has no gamma ray suitable for passive measurement, a novel radiotracer technique is used. Uranium-237, always present in plutonium processed at Los Alamos as a minor alpha-decay daughter of²⁴¹Pu, has a 6.8-day half-life and 208-KeV gamma energy, which make it an ideal radiotracer for macro amounts of uranium in the process. The On-Line Gamma Monitor is used routinely to provide Los Alamos operators with continuous, real-time process control information.     

Alpha spectrum evaluation method for the simultaneous determination of plutonium,americium and curium

A method based on the geometric progression decrease of the counts in the far tail of the alpha spectrum is described for the simultaneous determination of plutonium, americium and curium by alpha spectrometry. For evaluating the precision and accuracy, synthetic mixtures were prepared from solutions of enriched isotopes and sources were prepared by direct evaporation method using tetraethylene glycol /TEG/ as a spreading agent and electropolished stainless steel discs as the backing material. Precision and accuracy of about 1% is demonstrated in the determination of²⁴⁴Cm/²³⁹Pu,²⁴¹Am/²³⁹Pu,²⁴⁴Cm/²³³U,²⁴¹Am/²³³U and²³⁹Pu/²³³U alpha activity ratios using a 450 mm² silicon surface barrier detector.     

Effect of industrial pollution on the distribution of Pu and Am in soil and on soil-to-plant transfer of Pu and Am in a pine forest in SW Finland

The effect of industrial pollution on the behavior of plutonium and americium was evaluated in a pine forest in the vicinity of a Cu-Ni smelter in SW Finland. Soil and vegetation were sampled at distances of 0.5, 2, 4 and 8 km from the smelter. The vertical distribution of plutonium and americium was studied in litter, organic layer and mineral layers. The amount of Pu and Am in the litter layer increased and that in the organic layer decreased towards the smelter. Concentrations of plutonium and americium in different vegetation species decreased in the order mushrooms > lichens (Cladina spp., Cetraria islandica) > Empetrum nigrum > Vaccinium vitis-idaea.