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.     

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.     

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.     

Determination of 237Np by k0 RNAA

The determination of very low concentrations of ²³⁷Np is of key-interest for environmental monitoring. The application of the k ₀-method to neutron activation analysis was not possible so far, since the k ₀-parameters were lacking. The parameters required for the k ₀-method are: the effective resonance energy r, the resonance integral (1/E) to 2200 m^.s^-1 cross section ratio Q ₀, and the k ₀ values. In this work, the experimental values of these parameters were determined by using two nuclear reactors with very different flux characteristics.     

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 of237Np in urine by reversed-phase partition chromatography

A sensitive, rapid and selective method for the determination of²³⁷Np in urine is described. Neptunium(IV) is isolated by batch-extraction with a slurry of Microthene-710 (microporous polyethylene) supporting a cyclohexane solution of tri-n-octylphosphine oxide, the slurry is transferred into a column and neptunium eluted by oxidation to Np(V) with a mixture of HCl+Cl₂. After electroplating on a stainless steel disc, neptunium is counted with a solid-state alpha-detector. The final recovery is 83.2%; the decontamination factors are sufficiently high and the sensitivity limit is suitable for radiotoxicological purposes.     

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.     

Determination of237Np in spent fuel by use of inherent239Np as a chemical yield monitor

A method for analyzing the content of²³⁷Np in spent fuel has been developed using inherent²³⁹Np as a chemical yield monitor. After ion-exchange separations for the dissolved fuel solution, the²³⁷Np content in the neptunium fraction was determined from the activity of²³⁷Np or of²³³Pa, which is in radioactive equilibrium with²³⁷Np. The chemical yield in the separations was determined both from the content of²⁴³Am which is in radioactive equilibrium with²³⁹Np before the separations and from the²³⁹Np content in the neptunium fraction after the separations by alpha- and gamma-ray spectrometry.     

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 of 237 Np in marine sediment and seawater

Procedures for determination of neptunium in marine sediment and seawatersamples are described. Iron hydroxide Fe(OH)₂ –Fe(OH)₃ is used for preliminary pre-concentration of neptunium. Secondly,neptunium Np⁴⁺ and Pu³⁺ are separated by tri-isooctylamine-(TIOA)extraction in 8–10M HCl by redox with SO₃ ^2–-Fe³⁺ Neptunium Np⁴⁺ and uranium U⁶⁺ areseparated by back extraction the Np⁴⁺ with 2M HCl. Finally, theneptunium is purified from the uranium and thorium by anion exchange in 8MHNO₃ and 12M HCl. The stripping of 6M HCl + NH₂ OH HClfurther separates the neptunium Np³⁺ and uranium. Reduction bySO 3_2– –Fe³⁺ appeared to be an efficientway to obtain Np⁴⁺ The decontamination factors of the procedureare 4.0. 10⁴ for ²³² Th, 5.6 . 10⁴ for uraniumand 1.6 . 10⁴ for plutonium.     

Determination of cadmium in water samples by substoichiometric radiochemical method employing potassium ethyl xanthate

A radiochemical method has been developed for the determination of microgram amounts of cadmium based on the substoichiometric extraction of its 1:2 complex with potassium ethyl xanthate into 1:4 v/v mixture of pyridine and ethyl acetate from 2.5 M sodium formate. 10-90 micrograms of cadmium was determined with an average error of +/- 1.96%. The method developed was successfully applied to the determination of Cd contents in water samples.     

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.     

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.     

A new radiochemical procedure for uranium assay in environmental samples

A new and economical method for assay of environmental samples for uranium isotopes is proposed. Separation and radiochemical purification of uranium isotopes (²³⁴U,²³⁵U and²³⁸U) from other elements is achieved on a single anion exchange column by washing with various concentrations of hydrochloric acid. Iron, the principal interfering element is removed from the colum by washing with 4.5M hydrochloric acid with a combination of reducing agents under the conditions described. Weightless samples of uranium are prepared by either evaporation in a polished stainless steel dish or electroplated on a stainless steel planchet. This method is applicable for air particulates, soils, sediments, coal, water, vegetation, and biologicals. Text of the paper presented in the symposium on Practical Applications of Nuclear and Radiochemistry, at Las Vegas, Nevada, August 25–29, 1980. Submitted for publication in Advances in Chemistry Series.     

Determination of polynuclear aromatic hydrocarbons in water samples using large volume on-column injection capillary gas chromatography

An automated large volume on-column injection technique for capillary gas chromatography (GC) with solvent divert and heated retention gap technology has been utilized to determine polynuclear aromatic hydrocarbons (PAHs) in samples of industrial plant process water. Injecting large sample volumes on-column enabled the sample preparation procedure to be simplified and provided a fast, labor-saving technique for screening water samples. Diverting approximately 95% of the solvent away from the analytical column and the detector enabled chromatography to reflect classical capillary loading and detector conditions. Simplifications include significant reduction of sample and eluent volumes used during extraction and the elimination of Kuderna-Danish evaporative concentration. System performance, such as linearity and limit of detection, were evaluated for selected PAHs. Spiked water samples were prepared in the lower μ/L range to determine extraction efficiency. Results are compared with those obtained by a reputable contract laboratory following EPA Method 625.     

242Pu as tracer for simultaneous determination of 237Np and 239,240Pu in environmental samples

A procedure has been developed using ²⁴²Pu as tracer for simultaneous determination of ²³⁷Np and ^239,240Pu in environmental samples. The validity of the method has been demonstrated by ICPMS and a-spectroscopy for up to 10 gram soil and sediment, seawater up to 200 litres. The paper describes a suitable chemical procedure for Np and Pu including a quantitative pre-concentration of neptunium and plutonium, preparation of Np⁴⁺ and Pu⁴⁺, Np(NO₃)₆ ^2- and Pu(NO₃)₆ ^2-. The ratio of ²³⁷Np/²⁴²Pu (or ²³⁷Np/²³⁹Pu) before and after the procedure has been determined using 10 g soil (free from Np and Pu) R _before/R _after = 1.004±3.3% (S.D n = 20) and 1 litre seawater R _before/R _after = 1.019±1.9% (S.D., n = 12). Results from the intercomparison samples IAEA-135, IAEA-381 and from environmental samples are presented.     

Determination of Fe and Zn in biological samples by radiochemical neutron activation analysis

Radiochemical NAA methods have been developed for the simultaneous determination of Fe and Zn in biological samples. The method involves reactor irradiation, dissolution in 3M HCl and solvent extraction followed by counting on a scintillation gamma-ray spectrometer. Iron was separated with aqueous cupferron and extracted into chloroform while Zn was extracted with 2-thenoyl trifluoroacetone (TTA) into methyl isobutyl ketone (MIBK). Reaction conditions such as pH and the effect of solvents and various ions were studied using tracer activities. The methods have been employed for trace level determination of Fe and Zn in NBS, SRMs, Bowen's Kale, IAEA CRMs and other plant leaves.     

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.     

Distribution of global fallout237Np,Pu isotopes,and241Am in lake and sea sediments

In order to investigate the sedimentary behaviour of neptunium,²³⁷Np together with Pu isotopes and²⁴¹Am have been measured for the sediment cores collected from Lake Mikata (freshwater) and from Lake Kugushi (brakish water) both belonging to the Mikata Five Lakes, and from Nyu Bay (sea water). In all sediment core samples²³⁷Np was detected, and its concentrations were far below those of^239,240Pu and²⁴¹Am measured for the same samples. Inventories of²³⁷Np in Lake Mikata, Lake Kugushi and Nyu Bay were estimated to be 0.53, 0.29 and 0.34 MBq/km², respectively. The activity ratio of²³⁷Np/^239,240Pu calculted from the inventories in each sediment core was 0.29% for Lake Mikata, 0.15% for Lake Kugushi and 0.10% for Nyu Bay. These values except for the value for Lake Mikata are two or three times lower than the value of 0.3–0.4% observed for surface soils of 0–20 cm depth, suggesting that Np is more soluble compared with Pu.     

Determination of copper by a radiochemical displacement method

Determination of copper/II/ by radiochemical displacement of labelled cobalt from cobalt-o-hydroxybenzaldehyde isonicotinoyl hydrazone /Co-BIH/ complex has been studied. Borate buffer of pH 5 was found to be a suitable medium for quantitative displacement. 10–70 g of copper could be determined. The effect of various foreign metal ions on the determination has also been studied.