Reliable determination of 237Np in environmental solid samples using 242Pu as a potential tracer

This paper reports an analytical method for rapid determination of neptunium (²³⁷Np) in environmental solid samples exploiting automated sequential injection (SI)-based anion exchange separation. Pivotal issues on analytical method performance were investigated including sorption behavior of ²³⁷Np onto various AG 1-type anion exchangers; suitability of ²⁴²Pu as a tracer for ²³⁷Np determination in environmental solid samples; and long-term chemical stability of tetravalent Np. Experimental results revealed that the degree of resin cross-linking has a significant influence on the separation efficiency in terms of chemical yields of ²³⁷Np and removal of interfering nuclides. Although ca. 30% of sorbed Np onto AG 1-×4 was stripped out during HCl rinsing step for the removal of Th, chemical yield ratios of ²³⁷Np to ²⁴²Pu were proven steady with an average value of 0.67 ± 0.04 (n = 15) under selected experimental conditions. Disulfite-8 M HNO₃ was selected as a redox pair for valence adjustment to Np(IV) and the tetravalent Np in the sample solution was demonstrated to be stabilized for up to 5 days under 3 °C. The analytical results for reference materials showed a good agreement with the expected values, thereby demonstrating the usefulness of ²⁴²Pu as a non-isotopic tracer for ²³⁷Np chemical yield monitoring. The on-column separation procedure fosters rapid analysis as required in emergency situations since each individual sample can be handled within 2.5 h, and leads to a significant decrease in labor intensity compared to conventional batch-wise protocols.     

Simultaneous radiochemical determination of237Np and239Np with235Np as a tracer,and application to environmental samples

Neptunium is sorbed, together with plutonium, uranium and iron on Bio Rad AG 1×4 anion exchange resin from 9 mol/1 HCl, eluted with 7 mol/l HNO₃ and 1.2 mol/l HCl, purified on a second, identical column and electrodeposited on stainless steel discs.²³⁷Np is determined by -spectrometry,²³⁹Np by -spectrometry with a Ge detector, or via its 14.3 keV LX-rays in a Si(Li) measurement. The neptunium yield is determined from the count rate of the 13.6 keV LX rays of the tracer²³⁵Np in a later Si(Li) measurement. The average chemical yield is 78±11%. The detection limit for²³⁷Np is 1 mBq. The procedure allows the sequential determination of neptunium, together with plutonium, strontium, uranium and iron from one sample. The method was applied to air and total deposition samples from Munich-Neuherberg and to sediment samples from the Irish sea.     

Determination of237Np and241Pu in environmental samples: In soil and sediment

This paper describes the analytical methods for the determination of²³⁷Np, Pu isotopes, and²⁴¹Am, with particular emphasis on²³⁷Np by alpha-ray spectrometry and²⁴¹Pu by liquid scintillation technique. Results are also presented for the sediment cores collected from Mikata Five Lakes in Fukui Prefecture, Japan.     

Determination of239,240Pu and241Am in environmental samples

An accurate and reliable method has been developed and routinely carried out for the sequential determination of^239,240Pu and²⁴¹Am in environmental samples. After suitable pretreatment.^239,240Pu and²⁴¹Am are separated from other elements by means of the anion exchange resin method. Americium-241 is purified by coprecipitation with calcium oxalate and then ion exchanged in mixed media of the mineral acid-methanol. In the analysis,²⁴²Pu (or²³⁶Pu) and²⁴⁴Cm are used as chemical yield monitors. The recoveries of the yield monitors in the analyses of some kinds of environmental samples were 7080% for plutonium and 7686% for curium. The concentration of^239,240Pu in the coastal sea water were 7.022 Bq/l and that of²⁴¹Am was 1.26.3 Bq/l. The mean concentrations of^239,240Pu in the edible parts of the marine products ranged from 0.22 to 7.4 mBq/kg · fresh and those of²⁴¹Am ranged from 0.11 to 2.6 mBq/kg · fresh.     

Photoluminescence of crystallophosphors for the determination of 237Np and 239Pu

The photoluminescence of crystallophosphors, activated by neptunium and plutonium has been studied in connection with the necessity of discovering and elaborating on new analytical methods for actinides determination. Crystallophosphors on the base of fluorides, molybdates and tungstates have been prepared by introducing neptunium and plutonium solutions into the powder matrix, further drying and blend calcination. Luminescence spectra at room temperature have been found to have some broad bands in the near i.r. region independently of the method of crystallophosphor preparation, the oxidation state of introduced elements and the conditions of u.v. irradiation. The effect of matrix nature, flux content and concentration of quenching elements in analyzed solution on crystallophosphors luminescence has been studied. The methods of neptunium and plutonium     

Measurement of 237Np in environmental water samples by accelerator mass spectrometry

Accelerator mass spectrometry (AMS) was used to measure 237Np in environmental water samples extracted from Irish Sea sediments. The samples were of limited volume (approximately 700 ml) and of low activity (0.06-0.79 mBq l-1; 2.30-30.3 pg l-1). AMS proved to have the required sensitivity for measuring these samples, and was in principle capable of measuring much smaller amounts, as low as 0.4 microBq (3.9 x 10(7) atoms). However, the background level in the procedural blanks showed that there was a systematic low level 237Np contamination of each sample, arising from the 239Np yield monitor used in the separations procedure, which effectively increased the detection limit of these analyses.     

Inter-laboratory exercise with an aim to compare methods for 90Sr and 239,240Pu determination in environmental soil samples

In order to deliver reliable results for a multitude of different scenarios, e.g. emergency preparedness, environmental monitoring, nuclear decommissioning and waste management, there is a constant process of method development in the field of radioanalytical chemistry. This work presents the results of a method comparison exercise aimed at quantifying ⁹⁰Sr and ^239,240Pu in environmental soil samples, with the intention of evaluating the performance and applicability of different methods. From the methods examined in this work, recommendations are given in order to find a radioanalytical measurement procedure, for ⁹⁰Sr and ^239,240Pu analysis, which is fit-for-purpose for a particular scenario.

     

Measurement of thermal neutron capture cross sections of 237Np and 242Pu using prompt gamma neutron activation

Several samples of ²³⁷Np and ²⁴²Pu were irradiated in the guided cold neutron beam of the prompt gamma activation analysis facility at the Budapest Research Reactor. The thermal neutron capture cross sections of ²³⁷ Np and ²⁴²Pu were evaluated from the obtained prompt and delayed gamma ray data. The thermal neutron capture cross sections for ²³⁷Np(n,γ)²³⁸Np was found to be $ \sigma_{0} ({}^{237}{\text{Np}}) = 170.4 \pm 7.4\,{\text{b}} $ and for ²⁴²Pu(n,γ)²⁴³Pu to be $ \sigma_{0} ({}^{242}{\text{Pu}}) = 19.6 \pm 3.9\,{\text{b}} $ .     

242Pu为稀释剂电感耦合等离子质谱定量分析237Np的可行性理论研究

研究了以242Pu为稀释剂时,电感耦合等离子质谱(ICP-MS)定量分析237 Np的理论可行性。研究结果表明:237 Np和242Pu灵敏度的差异主要是由两者电离度的差异和质量歧视效应引起的。在等离子体温度为7 000～10 000K和样品提升率为50～1 000μL/mL时,经过质量岐视校正后,237 Np和242Pu灵敏度的差异只在于两者电离度的差异,且两者相对差异<1%。以242Pu为稀释剂ICP-MS定量分析237 Np的方法在理论上是可行的。     

Determination of237Np in environmental samples using inductively coupled plasma mass spectrometry

Ammonium uranates (AU) obtained by the addition of aqueous NH₄ OH to a solution of UO₂ (NO₃)₂ or the equilibrium reaction of UO₃ · 2H₂ O with the vapour over concentrated NH₄ OH have been studied by X-ray diffraction (XRD) analysis, diffuse reflectance Fourier transform infrared spectrometry (DR-FTIR) and chemical analysis. Ammonia can be present as either NH₃ or NH ₄ ⁺ . For precipitates obtained at a pH of 3.7, ammonia in the form of NH₃ is predominant. For ammonium uranate obtained by reaction over concentrated NH₄OH, most of the ammonia is bonded as NH ₄ ⁺ . The reaction mechanism and structures of the products are also discussed.     

Determination of 237Np and Pu isotopes in large soil samples by inductively coupled plasma mass spectrometry

A new method for the determination of (237)Np and Pu isotopes in large soil samples has been developed that provides enhanced uranium removal to facilitate assay by inductively coupled plasma mass spectrometry (ICP-MS). This method allows rapid preconcentration and separation of plutonium and neptunium in large soil samples for the measurement of (237)Np and Pu isotopes by ICP-MS. (238)U can interfere with (239)Pu measurement by ICP-MS as (238)UH(+) mass overlap and (237)Np via (238)U peak tailing. The method provides enhanced removal of uranium by separating Pu and Np initially on TEVA Resin, then transferring Pu to DGA resin for additional purification. The decontamination factor for removal of uranium from plutonium for this method is greater than 1×10(6). Alpha spectrometry can also be applied so that the shorter-lived (238)Pu isotope can be measured successfully. (239) Pu, (242)Pu and (237)Np were measured by ICP-MS, while (236)Pu and (238)Pu were measured by alpha spectrometry.     

Erratum to: Inter-laboratory exercise with an aim to compare methods for 90Sr and 239,240Pu determination in environmental soil samples

Journal of Radioanalytical and Nuclear Chemistry - In the original article, the LOD assigned to method Sr-B in Table&nbsp;1 was published incorrectly as 24&nbsp;Bq/kg, the correct LOD for...     

Isolation and alpha-particle spectrometric determination of238Pu and239,240Pu in sediments

A simple method is described for the isolation and determination of plutonium isotopes in sediments. The method involves leaching of sample with nitric acid and subsequent separation of plutonium on an anion-exchange column. Major matrix elements and several potential radiochemical interferences are removed during 8M HNO₃ sample loading on the column. Thorium is removed by thorough washing with 10M HCl. Plutonium (IV) is eluted with 4M HCl. Source for alpha-particle spectrometry is prepared by LaF₃ coprecipitation technique at which stage a complete separation from uranium(VI) is also achieved. The entire analytical procedure is completed in about two days.     

Determination of Pu in environmental soil using238Pu as a yield tracer

A procedure for determining Pu in environmental soil using²³⁸Pu as a yield tracer is described. The method involves radiochemical separation and electrodeposition onto a stainless steel disc followed by alpha-spectrometric measurement with a solid-state detector. In order to eliminate error in calculation caused by²³⁸Pu contained in original samples, a new calculating method is introduced in this paper. By using this method, the activity of²³⁸Pu contained in original samples can be substracted from the total activity of samples, to which the²³⁸Pu tracer is added. This procedure has been applied satisfactorily to the determination of Pu in a soil reference sample, which was supplied by the Institute of Metrological Science of China.     

Distribution and behaviour of99Tc,237Np,239,240Pu,and241Am in the coastal and estuarine sediments of the Irish Sea

Intertidal coastal and estuarine sediments from 24 sites in the Irish Sea have been analyzed for⁹⁹Tc,²³⁷Np,²³⁸Pu,^239,240Pu and²⁴¹Am. The²³⁷Np activity and²³⁹Pu/²⁴⁰Pu ratio were measured simultaneously by ICP-MS, and⁹⁹Tc was determined by HR-ICP-MS which is ten times more sensitive than Q-ICP-MS.The activities of⁹⁹Tc,²³⁷Np,^239,240Pu and²⁴¹Am were distributed over a wide range of 1.5–70.5, 0.01–13.3, 2.3–1589, 2.6–1894 Bq/kg, respectively. Activities of these radionuclides decreased exponentially with distance from the Sellafield source. The²⁴¹Am/^239,240Pu and²³⁷Np/^239,240Pu ratios were almost constant with distance from the Sellafield. This result suggests that the distribution and behavior of Np and Pu are controlled by complicated factors such as the influence of transport, the variation with time of Np/Pu ratio in the Sellafield discharges and sedimentary mixing processes in the Irish Sea.     

Rapid determination of 237Np and Pu isotopes in water by inductively-coupled plasma mass spectrometry and alpha spectrometry

A new method that allows rapid preconcentration and separation of plutonium and neptunium in water samples was developed for the measurement of ²³⁷Np and Pu isotopes by inductively-coupled plasma mass spectrometry (ICP-MS) and alpha spectrometry. ²³⁸U can interfere with ²³⁹Pu measurement by ICP-MS as ²³⁸UH⁺ mass overlap and ²³⁷Np via peak tailing. The method provide enhanced removal of uranium by separating Pu and Np initially on TEVA Resin, then moving Pu to DGA resin for additional removal of uranium. The decontamination factor for uranium from Pu is almost 100,000 and the decontamination factor for U from Np is greater than 10,000. This method uses stacked extraction chromatography cartridges and vacuum box technology to facilitate rapid separations. Preconcentration is performed using a streamlined calcium phosphate precipitation method. Purified solutions are split between ICP-MS and alpha spectrometry so that long and short-lived Pu isotopes can be measured successfully. The method allows for simultaneous extraction of 20 samples (including QC samples) in 4?C6 h, and can also be used for emergency response. ²³⁹Pu, ²⁴²Pu and ²³⁷Np were measured by ICP-MS, while ²³⁶Pu, ²³⁸Pu, and ²³⁹Pu were measured by alpha spectrometry.     

Sorption characteristics of237Np,238Pu and241Am in sedimentary materials

Adsorption experiments were performed to measure distribution coefficients of²³⁷Np(V),²³⁸Pu(IV) and²⁴¹Am(III) for sedimentary sequential chemical extraction of the adsorbed radionuclides was carried out with water, CaCl₂, KCl, NH₂OH−HCl, K-oxalate and H₂O₂ solutions, to elucidate their dominant sorption mechanisms. The distribution coefficient of²³⁷Np was two orders of magnitude smaller than that of²³⁸Pu and²⁴¹Am. Most of²³⁷Np adsorbed was extracted with CaCl₂ solution and its sorption was controlled by a reversible ion exchange reaction. The adsorbed²³⁸Pu was mainly extracted with NH₂OH−HCl+K-oxalate solution and its sorption was possibly controlled by irreversible reactions.     

Rapid determination of 237Np in soil samples by multi-collector inductively-coupled plasma mass spectrometry and gamma spectrometry

A radiochemical procedure is developed for the determination of ²³⁷Np in soil with multi-collector inductively-coupled plasma mass spectrometry (MC-ICP-MS) and gamma-spectrometry. ²³⁹Np (milked from ²⁴³Am) was used as an isotopic tracer for chemical yield determination. The neptunium in the soil is separated by thenoyl-trifluoracetone extraction from 1 M HNO₃ solution after reducing Np to Np(IV) with ferrous sulfamate, and then purified with Dowex 1 × 2 anion exchange resin. ²³⁹Np in the resulting solution is measured with gamma-spectrometry for chemical yield determination while the ²³⁷Np is measured with MC-ICP-MS. Measurement results for soil samples are presented together with those for two reference samples. By comparing the determined value with the reference value of the ²³⁷Np activity concentration, the feasibility of the procedure was validated.     

Determination of traces of 237Np in environmental samples by ICP-MS after separation using TOA extraction chromatography

A simple, rapid, cost-efficient, and robust method for separation of 237Np with an extraction chromatographic column (TOA: tri-n-octylamine on Teflon powder) is outlined in detail and further improved for direct ICP-MS analysis. The column efficiently retained 237Np in 2 mol L(-1) HNO3 medium and all of the 237Np was easily eluted with 0.02 mol L(-1) oxalic acid in 0.16 mol L(-1) HNO3 at 95 degrees C. The separated solutions were free from most matrix elements and were aspirated into the ICP-MS directly. The decontamination factor for 238U is more than 10(4). The instrumental detection limit for 237Np was 0.46 pg mL(-1), which corresponds to 1.2 x 10(-5) Bq mL(-1). The method is more rapid than traditional radiometric techniques. It is also considered to be more suitable for environmental monitoring than existing methods based on TOA.