Scaling factors for activated corrosion products in low-level-wastes from power reactors

Long-lived isotopes of corrosion products are very important for the disposal of low-level radioactive wastes. These nuclides serve for risk calculations of accidents. Their determination needs the radiochemical separation from high active main nuclides. Supervision of waste vessels is done by direct non-destructive -spectrometry of the key nuclide⁶⁰Co for corrosion products. The activity ratios of the long-lived nuclides to the key nuclides are called scaling factors. We have determined such factors radiochemically in evaporation residues of power water and cooling water. They are used for activity calculations of long-lived nuclides in the waste vessels. In case of⁵⁹Ni the obtained scaling factor was compared with a literature value and values calculated on the basis of nuclear data. Our value was in a good agreement with the calculated one. Due to the fact, that we have used low-level measurement techniques, we could perform the necessary chemical separations in a laboratory not exceeding the 10-fold free-level limit.     

Determination of U, Pu, Am and Cm in water coolant of nuclear power plants using membranes impregnated with hydrated manganese dioxide

Methods have been developed for the rapid determination of the total activity of α-emitting radionuclides in water coolant. The samples with a volume of 0.05–2.5 dm³ are filtered at a flow rate of 2–2.5 dm³/h through a system of membranes. The first membrane is a mechanical filter for the separation of suspensions, the second one is impregnated with manganese dioxide which is intended for the deposition of actinoids in an ionic state. The detection limit for a 2.5 l sample measured with a low-background alpha-radiometer is equal to 0.037 Bq. The measurement error does not exceed 30% at a confidence level of 0.95 over a determined concentration range from 0.037 to 3.7·10⁵ Bq/l.     

Producing radioisotopes in power reactors

The demand of radioisotopes is rising due to wide-ranging applications in industry, agriculture, medicine and in research. Two sources of artificial radioisotopes are accelerators and reactors. The reactor offers large volume for irradiation, simultaneous irradiation of different samples and economy of production, whereas accelerators are generally used to produce those isotopes which can not be produced by reactor. Radioisotope production started on a significant scale in several countries with the commissioning of research reactors starting from the late 1950s. The period from 1950 to 1970 saw construction of a large number of research reactors with multiple facilities. After 1980, because of the decommissioning of many old ones, the number of operating reactors has been steadily decreasing. The research reactors used for radioisotope production could be broadly classified into swimming pool type and tank type reactors. CANDU power reactors currently produce many millions of curies per year of ⁶⁰Co for MDS Nordion’s use in industry and commerce. Studies related to production of other isotopes in power reactors have also been performed. Indeed, while a very few reactors have come online in the past decade, many more have been retired or may retire in coming years. After failure of MAPLE project, there has been unwillingness to built new reactors. Activism and politics has made it so difficult to build new reactors that we are left to use only the reactors we inherited from a nuclear era. Many design considerations and requirements for the production of isotopes in power reactors must be assessed, such as; operator and public safety, minimum impact on station efficiency and reactor operations, shielding requirements during reactor operation with target adjusters and removal of the target adjusters from core, transportation within the station, and finally the processing and shipment off-site. Use of power reactors for isotope production is reviewed.     

Sequential determination of Am, Cm, Pu, Np and U by extraction chromatography

Environmental contamination by artificial radionuclides and the evaluation of their sources require precise isotopic analysis and accurate determination of actinide elements above all plutonium and americium. These can be achieved by alpha spectrometry or by inductively coupled plasma mass spectrometry (ICP-MS) after chemical separation. In the present work, a simple, rapid method has been developed for the sequential separation of actinide elements from aqueous solutions and their determination by alpha spectrometry. Extraction chromatography was applied to the separation of ²⁴¹Am, ²⁴⁴Cm, ^{239 + 240,238}Pu, ²³⁷Np and ^238,235,234U using microporous polyethylene supporting tri-n-octylamine as the stationary phase and hydrochloric acid with and without reducing agents as the mobile phase. Actinide in 9 M HCl solution is introduced into the anion exchange column; Pu (IV), Np (IV) and U(VI) are retained on the column while Am (III) and Cm passed through. Pu is eluted first, reductively, after which, Np and then U are eluted. The method can be applied to all aqueous solutions which do not contain strong complexing or precipitation agents for the elements considered.     

A separation procedure for the analysis of90Sr,154Eu, and the actinides237Np,239Pu,241Am and244Cm

A procedure for the analysis of⁹⁰Sr,¹⁵⁴Eu,²³⁷Np,²³⁹Pu,²⁴¹Am and^242−244Cm was developed. Separation was done with the separating agent, di-2(ethyl hexyl)-phosphoric acid (HDEHP), and results in fractions containing the different elements to be analysed.⁹⁰Sr analysis was done by analysing its daughter nuclide⁹⁰Y, detected through the Cherenkov radiation emitted by this high energy β⁻-emitter.¹⁵⁴Eu was detected using γ-spectrometry with a lower Compton background as a result of the removal of other fission products.²⁴¹Am could also be detected with γ-spectrometry or together with^242−244Cm with α-spectrometry. The long-lived radionuclides²³⁷Np and²³⁹Pu were detected using inductively coupled plasma mass spectrometry (ICP-MS).     

Studies on the separation of Pu,Am and Cm with solid and liquid anion exchanges

Systematic studies are carried out on the distribution of Pu(IV), Am(III) and Cm(III) from nitric acid media using solid (Dowex) and liquid (TCMA) anion exchangers. The distribution of these elements from nitric acid-organic solvent mixtures is also investigated. In view of the given results, convenient procedures for interseparation of the mentioned elements are recommended.     

Simultaneous determination of238Pu,239+240Pu,241Pu,241Am,242Cm,244Cm,89Sr,and90Sr in vegetation samples,and application to Chernobyl-fallout contaminated grass

A radiochemical procedure is described for the simultaneous determination of²³⁸Pu,^239+240Pu,²⁴¹Pu,²⁴¹Am,²⁴²Cm,²⁴⁴Cm,⁸⁹Sr, and⁹⁰Sr in vegetation samples. The method was applied for the determination of these, radionuclides in grass, collected near Munich after the fallout from the reactor accident at Chernobyl, USSR. The specific activities observed were (in Bq kg^–1 dry weight):²³⁸Pu, 0.077;^239+240Pu, 0.15;²⁴¹Pu, 3.9;²⁴¹Am, 0.031;²⁴²Cm, 3.0;²⁴⁴Cm, 0.008;⁸⁹Sr, 2000;⁹⁰Sr, 99.     

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.

     

Determination of243Am in244Cm by gamma spectroscopy

Gamma spectroscopy with a high resolution Ge(Li) detector is used to determine²⁴³Am by its 74.7-keV gamma transition in solutions containing much higher specific activities of other actinides and fission products. As little as 100 ppm of²⁴³Am relative to²⁴⁴Cm can be determined. A relative standard deviation of 1.4% was obtained for routine samples. The method is well suited for analytical control of curium process steps because of its simplicity, speed, and reliability.     

Study of the interferences in the determination of Pu, Am and Cm in radioactive waste by extraction chromatography

This paper describes the experimental studies carried out to determine (238)Pu, (239/40)Pu, (241)Pu, (241)Am, (242)Cm and (244)Cm in samples from nuclear power plants (mainly spent ion exchange resins and evaporator concentrates) using an organophosphorus compound immobilized on an inert support. These materials are commercially available under the name TRU Resin (for Transuranium Specific) from Eichrom Industries, Darien, IL. An attempt is made to develop a rapid, accurate method of analysis, with minimum waste generation. Standard solutions of Pu and Am and one sample of spent ion exchange resin that contains fission, activation products, Pu, Am and Cm were analyzed to study the separation factors and interferences in the measurement of Pu, Am and Cm isotopes.     

Solubility equations for the ethylsulphates of trivalent Y,Pm, Pu,Am and Cm as determined by co-crystallization

Assuming that the correlation between the cocrystallization coefficients and solubilities of the co-crystallizing ethylsulphates in the [(Ln,M) (H₂O)₉] (C₂H₅SO₄)₃–H₂O system is valid when M is changed from lanthanides into the title elements, the solubilities of the ethylsulphates of trivalent Y, Pm, Pu, Am and Cm in water at 288–318 K have been determined from the matrix. The solubilities of Y, Pm, Pu, Am and Cm ethylsulphates and of all the lanthanide ethylsulphates are given in the form of smoothing equations of the lg molality=A+B/T type. From the B parameters of the solubility equations the enthalpies of solution have been estimated. The crystallization behaviour of yttrium in the ethylsulphate system is between that of holmium and that of erbium.     

Am,Cm recovery from genuine HLLW by extraction chromatography

Journal of Radioanalytical and Nuclear Chemistry - The extraction chromatography experiments for Am(III) and Cm(III) recovery from genuine HLLW were carried out in order to demonstrate modified 2...     

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.     

Fusion and chemical separation of Am,Pu and Sr from barite-concrete

Journal of Radioanalytical and Nuclear Chemistry - The goal of this study was to omit the hazardous hydrofluoric acid for silica removal before fusion of barite-concrete. Furthermore, the goal was...     

Improvements on radiochemical method for the determination of Am and Cm in typical waste streams from nuclear power plants

The determination of Am and Cm in typical waste streams from nuclear power plants using anion exchange chromatography has some drawbacks like the contamination by Pu and Po. This improved procedure solves these problems, and it has been applied with success to the analysis of Am and Cm in nuclear waste samples: ion exchange resins, ion exchange resins solidified with cement and evaporator concentrates.     

Improvement of Am and Cm determination in soil samples

The determination of Am and Cm in a radiochemical procedure for the sequential analysis of Pu, Am, and Cm in soils was improved and optimized. This method uses only solvent extraction and extraction chromatography for the separation and cleaning of Am and Cm from soils up to 50 g sample weight. After leaching with 8M nitric acid, Pu is extracted with TOPO/cyclohexane. Am and Cm are extracted out of the remaining leaching solution at pH 1 with TOPO/cyclohexane, too. After backextraction with 2M nitric acid, Am and Cm are separated from traces of matrix elements, especially Fe, on a TRU-column, afterwards on a TEVA-column from lanthanides (TRU-resin and TEVA-resin of Eichrom Europe, SARL, Paris, France). The clean Am/Cm-fraction is electroplated and measured by alpha-spectrometry. The detection limit of this optimized procedure is 0.03 Bq/kg soil at a 95% confidence level.     

Activities and transfers of Pu and Am in rice samples from Camargue, France

In Camargue, the use of Rhone water does not cause any significant increase in additional Pu and Am contamination to rice. Ultra-trace quantities of these radionuclides in rice grains are mainly due to root transfer. Estimated transfer factors for Am and Pu isotopes are higher than mean values proposed in international report, however, are consistent with the 95% confidence intervals that are recommended.     

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.