Search

Intrinsic 40 K radioactive backgrounds from impurities of natural K in liquid scintillation cocktails have previously been demonstrated to limit their use in ultra-sensitive applications. This work explores two methodologies in parallel for the reduction of 40 K backgrounds in the cocktails, and lays the groundwork for use in ultra-sensitive applications. In one method, alternative low-K liquid scintillation matrix constituents were identified and in the other, a simple purification method for single components and finished cocktails was developed. Both methods were verified via ICP-MS analysis. Liquid scintillation counting of selected purified cocktails demonstrated background reduction, improved stability, and enhanced performance. The best performing purified cocktail was also counted on a custom-built ultra-low background liquid scintillation counter, with results below the detector background. [ABSTRACT FROM AUTHOR]

Cancer continues to be a leading cause of global death despite decades of research on its prevention and cure. In the mid-twentieth century, anecdotal evidence began to accumulate that certain chemicals might be cancer-causing and this was followed up with animal model studies. These suspected substances were termed carcinogens and among those investigated were N-nitrosamines (or simply nitrosamines). Interest in nitrosamines is now more than a century old and research continues to explore their biology. Since the 1950's, steady progress has been made in perfecting chemistry techniques to label interesting compounds with 14C or tritium. However, there have been relatively few reports concerning the synthesis of nitrosamines with these radioisotopes, providing substances which could be valuable in advancing key nitrosamine biology research. Most of the previous literature examples of 14C or tritium labelled nitrosamines related to very specific compounds lacking wider interest and relevance. Also, the resulting products were usually of low specific activity. This paper outlines strategies to accomplish the labelling of more broadly relevant nitrosamines with 14C or tritium at high specific activity. Particularly, a library of 14C labelled nitrosamines with diverse structures was created. Exemplary experimental details are provided for the synthesis of [14C] N-nitrosodiethanolamine as well as the repurification of [ethyl-1-14C] N-nitroso-N-ethylurea. The storage and general stability of 14C nitrosamines is also discussed. Finally, as an example of a typical strategy to prepare a nitrosamine labelled with tritium, the synthesis of [3, 4-3H] N-nitrosopyrrolidine is described in detail. [ABSTRACT FROM AUTHOR]

Although methods for the chemical separation of samarium from a rock matrix are well established, chemical separation of samarium from non-natural isotopic impurities for the purpose of 146Sm half-life measurement requires modifications to these procedures, as well as additional checks for effective separation. This work describes the chemical purification procedures associated with the 146Sm source and the results from gamma spectroscopy. The purification procedure allowed for the quantitative determination of the number of 146Sm atoms using a modified isotope dilution technique. Alpha-decay counting of the sample will be applied in the future to determine the half-life of 146Sm. [ABSTRACT FROM AUTHOR]

This work presents the combination of two chemical separation methods to purify protactinium (Pa) oxide from its decay daughter chain. It combines precipitation and basic to neutral washing with ion exchange to reach radiochemical pure 231Pa. The method is suitable to purify 231Pa in milligram scales. Precipitation and washing of Pa hydroxide removes most of the daughter activity and the dose rate. Losses of Pa occurs predominantly in the precipitation stage and are dependent on the conditions used. The subsequent ion exchange procedure showed essentially no losses of Pa and is efficient to fully remove all decay products leaving less than 0.4% of the Th as an impurity in the purified Pa solution. Full radiochemical purity was obtained by repeating the separation procedure. The radiochemical pure Pa solution was characterised by an alpha ratio method by addition and mixing of a known Cm spike. The specific activity and concentration of 231Pa was determined with an uncertainty of 1% (coverage factor k = 1). [ABSTRACT FROM AUTHOR]

The liquid–liquid extraction, recovery of Np(VI) and Np(V) from the solution of Na2CO3 by methyltrioctylammonium carbonate in toluene was investigated. By the graphic slope analyses method, as well as by recording of absorption spectra for obtained solutions and method of calculated determination of solution properties taking into account water activity, composition was established for the carbonate complexes of Np(VI) and Np(V) being extracted, which, depending on extraction conditions, can be expressed by the following formulae's: (R4N)2[NpVIO2(CO3)2], (R4N)3[NpVO2(CO3)2], (R4N)6[NpVIO2(CO3)4], (R4N)2[NpVIO2(CO3)2]·2(R4N)2CO3, (R4N)5[NpVO2(CO3)3], (R4N)7[NpVO2(CO3)4], (R4N)3[NpVO2(CO3)2]·(1–2)(R4N)2CO3, where R4N is the quaternary ammonium cation. The results have been obtained in the experiments, has much interest both in the field of alkaline radioactive waste management and with respect to their usage for extraction of transuranium elements during reprocessing of alkaline radioactive waste, as well as for liquid–liquid extraction purification of uranium and plutonium from admixtures of fission products. These techniques are used within the framework of a new alternative method for reprocessing of spent nuclear fuel in carbonate media the CARBEX (CARBonate EXtraction) process. [ABSTRACT FROM AUTHOR]

A radiochemical method was developed for the accurate 55Fe determination in various radioactive waste, in particular samples contaminated with 241Pu. It consisted of three purification steps based on first ammonium hydroxide precipitation, and then anion exchange separation followed by TRU®-based extraction chromatography. It was characterized by an iron recovery yield of about 80% for all the studied samples and a 60Co decontamination factor of 106. In comparison to a standard protocol based on iron cupferrate extraction in chloroform, an improvement of a 30-fold factor was achieved towards plutonium. The developed TRU®-based procedure was validated by participating in interlaboratory exercises. [ABSTRACT FROM AUTHOR]

The stable isotope-labeled rosuvastatin was requested in order to fully understand the metabolic process of rosuvastatin. An effective synthesis approach was developed for [2H4] rosuvastatin calcium. After ten steps, [2H4] rosuvastatin calcium was prepared with excellent chemical purification and isotope enrichment which can be applied as an internal standard. Moreover, this synthesis method could be useful in synthesis of other statins. [ABSTRACT FROM AUTHOR]

Purification of berkelium-249 (249Bk) at Oak Ridge National Laboratory requires a multi-step process with Bk Finishing as the final step. The current multi-process takes 6-7 months, including ~ 3 months spent on Bk Finishing. Recent trials of using columns of either LN resin or MP-1 anion exchange resin adsorbing the tetravalent 249Bk4+ in 8M HNO3-0.5M NaBrO3, followed by eluting impurities (e.g. Ce4+, Cf3+) and stripping 249Bk resulted in a new dual column method of selectively separating 249Bk from other trans-curium elements and fission product impurities, which is proposed to replace the current Bk Finishing with higher Bk purification efficiency and shorter processing period. This paper displays the experimental results and describes the dual column method with relevant chemistry issues. [ABSTRACT FROM AUTHOR]

Production of no-carrier-added (NCA) Pd, which will decay to Rh, was experimented using the Nb(B, 3n)Pd reaction. The 36 MeV boron beam on natural niobium generated 1 MBq/µA.h yield of Pd along with minute contaminants. A chemical separation method based on the liquid-liquid-extraction (LLX) was developed for the separation of trace amount of Pd from the bulk Nb. Stable isotopes of Pd and Nb were used to simulate the reaction with the help of inductively coupled plasma-optical emission spectroscopy (ICP-OES). A high separation factor (~10) was achieved at the optimum separation condition. [ABSTRACT FROM AUTHOR]

Solvent extraction studies on the purification of uranium from zirconium rich sodium diuranate (SDU) feed was carried out using n-tri butyl phosphate (TBP) as extractant and n-decanol as phase modifier. The presence of Zr in SDU leached solution leads to the formation of third phase during liquid-liquid extraction of uranium which was successfully prevented by addition of n-decanol in 30% (v/v) TBP/ n-dodecane mixture. A seven stage counter current extraction of SDU feed solution followed by five stage stripping were carried out using optimum concentration of phase modifier 15% n-decanol-30% TBP in n-dodecane as solvent. Based on the findings a process flow-sheet has been developed for the purification of SDU to nuclear grade ammonium diuranate. [ABSTRACT FROM AUTHOR]

Idaho National Laboratory (INL) produces Xe, Xe, Xe, and Xe standards for the calibration and testing of the collection equipment and analytical techniques used to monitor radioactive xenon emissions. At INL, xenon is produced and collected as one of several spontaneous fission products from a Cf source in a stagnant volume of pressurized helium. Solids are separated from gases by sintered steel filtration. Further chromatographic purification of the fission gases separates the xenon fraction for selective collection. An explanation of gas system, separation, and purification is presented. Xe and Xe activity ratio adjustments are explained. [ABSTRACT FROM AUTHOR]

Detector sensitivity and purification challenges have limited published Si sediment dating studies. The cosmogenic isotope Si can fill the sediment geochronology gap between Pb (<150 years) and C (>1000 years). Targeting this age range can provide geochronological reconstructions of paleoindicators that identify recent human and climate-induced shifts in coastal areas. We are preparing detectors and kilogram-scale sample preparation techniques for such a study of Puget Sound sediments. This work considers the impact of background on counting time and Si age-dating reach. Design and performance of new low-background, gas-proportional beta counters to measure Si (via P) are discussed. [ABSTRACT FROM AUTHOR]

Recently a Np-237 target (26 mg) was analyzed for trace Pu isotopes (approximately 300 ppb). This work describes the chemistry required for a Np/Pu separation sufficient for Thermal Ionization Mass Spectrometry (TIMS), as well as the Pu purification from other potential contaminants. A point source was prepared from the purified Pu fraction and the atom ratios were measured via TIMS. The Pu isotopics provide a picture of the Np target's irradiation history, which will also be discussed. [ABSTRACT FROM AUTHOR]

Sr was produced via Y(n, p) Sr using yttria as target in Fast Breeder Test Reactor (FBTR), Kalpakkam, India. A radiochemical procedure has been developed for the separation of bulk yttrium using TBP by solvent extraction followed by purification of Sr source by ion exchange chromatography using the cation exchange resin Dowex 50WX8 (100-200 mesh) and nitric acid of variable molarity as eluant. The present study establishes the purification of Sr source from the other radionuclidic impurities like Y, Zn, Mn, Co, Rb, Ir, Ru, Sn, Ce, Tb, Eu etc. produced during the irradiation of yttria by using the complexing agent tri-sodium tri-meta phosphate (SMP) in nitric acid medium instead of nitric acid alone as an eluant. The purification was achieved by using 0.1 M SMP as complexing agent which was optimized based on the distribution ratio data and final elution of Sr fraction was obtained in nitric acid medium. This resulted into a faster purification of Sr source in a smaller volume of eluant. Purity of Sr source from the cross contamination of the complexing agent SMP was also ensured. [ABSTRACT FROM AUTHOR]

A methodology to purify a Ho solution has been developed by a combination of activity and mass concentration measurements in order to further determine the Ho half-life. The isobaric interference at m/ q ≃ 166 requires Ho purification from non-natural Er with a high purification degree due to the large amount of Ho as opposed to Er. The Ho/Er separation was achieved using high-performance liquid chromatography on a semi-preparative column followed by purification on gravitational chromatography. The efficiency of the separation was evaluated after precise determination of the Er isotopic composition. The purification methodology enabled to separate Ho from Er. [ABSTRACT FROM AUTHOR]

This paper describes a method for the separation and purification of Sr from PUREX-HLLW employing solvent extraction and precipitation techniques. 30 % TBP in n-dodecane was used for the removal of residual uranium, plutonium and neptunium from HLLW. Trivalent actinides and lanthanides were subsequently removed using N, N, N', N'-tetra(2-ethylhexyl) diglycolamide (TEHDGA, 0.20 M in 30 % isodecyl alcohol and n-dodecane). Sr was selectively extracted from actinides and lanthanides depleted HLLW using 0.3 M TEHDGA in 5 % isodecyl alcohol and dodecane. Loaded strontium was stripped using 0.01 M HNO and further purified by radiochemical precipitation technique after adding Fe and natural strontium as carriers. Based on the experimental results, a flow-sheet was formulated and mCi levels of Sr recovered. [ABSTRACT FROM AUTHOR]

A piece of scrap uranium metal bar buried in the dirt floor of an old, abandoned metal rolling mill was analyzed using multi-collector inductively coupled plasma mass spectroscopy (MC-ICP-MS). The mill rolled uranium rods in the 1940 and 1950s. Samples of the contaminated dirt in which the bar was buried were also analyzed. The isotopic composition of uranium in the bar and dirt samples were both the same as natural uranium, though a few samples of dirt also contained recycled uranium; likely a result of contamination with other material rolled at the mill. The time elapsed since the uranium metal bar was last purified can be determined by the in-growth of the isotope Th from the decay of U, assuming that only uranium isotopes were present in the bar after purification. The age of the metal bar was determined to be 61 years at the time of this analysis and corresponds to a purification date of July 1950 ± 1.5 years. [ABSTRACT FROM AUTHOR]

Uranium-233 ( t ~ 1.59E5 years) is an artificial, fissile isotope of uranium that has significant importance in nuclear forensics. The isotope provides a unique signature in determining the origin and provenance of uranium-bearing materials and is valuable as a mass spectrometric tracer. Alpha spectrometry was employed in the critical evaluation of a U standard reference material (SRM-995) as a dual tracer system based on the in-growth of Th ( t ~ 7.34E3 years) for ~35 years following radiochemical purification. Preliminary investigations focused on the isotopic analysis of standards and unmodified fractions of SRM-995; all samples were separated and purified using a multi-column anion-exchange scheme. The Th/U atom ratio for SRM-995 was found to be 1.598E−4 (±4.50 %) using recovery-corrected radiochemical methods. Using the Bateman equations and relevant half-lives, this ratio reflects a material that was purified ~36.8 years prior to this analysis. The calculated age is discussed in contrast with both the date of certification and the recorded date of last purification. [ABSTRACT FROM AUTHOR]

In this study we describe a method for uranium dating (i.e. determination of the date of the last chemical purification undergone by the material) by measurement of the Th/U ratio, applicable to sub-microgram quantities. The chosen protocol (AG1x8 resin in hydrochloric acid medium) has been tested on separation microcolumns (100 μl). This 'microchemistry' technique considerably limits the risks of contamination by reagents or the environment. Thorium extraction efficiencies were greater than 90 % and reproducible. The quantities of Th introduced by the chemical purification procedure were negligible. Using an ultra-sensitive inductively coupled plasma mass spectrometry measurement technique, detection limits of the order of femtograms (10 g) of Th were obtained. The complete procedure, chemical separation and isotope measurement, was successfully tested and validated on a few micrograms of uranium. [ABSTRACT FROM AUTHOR]

In support of nuclear safeguards and non-proliferation efforts, Oak Ridge National Laboratory is responsible for characterizing uranium ore concentrate (UOC) samples obtained from two ore mining and milling sites. A sorptive extraction method has been developed for analysis of non-volatile organic compounds that might be used to identify characteristics of the purification process by which uranium was separated from these ores. This method utilizes Gerstel Twister stir bars coated with polydimethylsiloxane to extract organic components from aqueous media. A slurry of UOC is extracted with the Twister stir bar in 20 % methanol/80 % water containing deuterated internal hydrocarbon standards. Following extraction of non-volatile organics, the Twister stir bar is analyzed directly in the inlet of a gas chromatograph fitted with a quadrupole mass spectrometric detector. Results have been consistent and have shown excellent recoveries of internal standards, with the average recovery being 97.5 %. Both qualitative and quantitative differences have been identified between the two sources of UOC utilizing this method. One source contained an increased concentration of amines which commonly are used in the recovery and purification of ores. Amines that were identified in this UOC source include dioctylamine, triisoctylamine, and Alamine 336, a common industrial complexant. Also, when comparing both sources, the same UOC source contained various decanol and C20 compounds. Based on the results from this study, non-volatile organic analysis of UOC using sorptive extraction with Twister stir bars and GC-MS is a tool that can be used to facilitate sourcing of unknown UOC. [ABSTRACT FROM AUTHOR]

Perchloric acid was found to be a suitable medium for the quantitative leaching of Sr(II) from homogeneous and calcined (Th,Sr)O particularly with respect to the contamination from Th(IV). Sr is a cause of major concern to the environment due to its long half life (28.6 years), significant abundance in large inventory of spent nuclear fuels (~350 thousand tons) awaiting geological disposal and its chemical similarity to Ca(II), an essential element for the living beings. Application of Sr as a parent radionuclide for Y (used in therapy radiopharmaceuticals) is possible provided it can be made available at desired high purity. In this context, the distribution coefficients of Sr(II), Th(IV), Zr(IV), Y(III), Eu(III) and Cs(I) were determined using Sr selective crown ether 4,4′(5′)-di -tert-butyl -dicyclohexano -18 -crown -6 by solid-liquid extraction in perchloric acid medium. Feasibility of employing extraction chromatography using Sr selective resin for the recovery and purification of Sr(II) from leached perchloric acid medium was explored. Perchloric acid medium is better than nitric acid medium for the uptake of Sr by Sr selective chromatographic resin under varying loading conditions of Sr(II). Similarly pH 2 solution appears better eluent of Sr(II) than distilled water. Present work offers a novel approach for setting up a Sr-Y generator. [ABSTRACT FROM AUTHOR]

Spent fuel discharged from Fast Breeder Test Reactor (FBTR) in Kalpakkam is being reprocessed by modified plutonium uranium reduction extraction (PUREX) process using 30% TBP (tributylphosphate) as extractant in the presence of heavy normal paraffin (HNP) as diluent. Partitioning of uranium (U) and plutonium (Pu) is carried out using oxalate precipitation method. Uranium oxide product obtained by this method contains appreciable amount of plutonium which has to be recovered. Recovery of plutonium from this uranium oxide product is carried out by reducing Pu to inextractable Pu(III) using hydroxyurea (HU) and then uranium is extracted into 30% TBP. A small amount of Pu which is extracted in the organic phase is stripped back to aqueous phase by scrubbing with scrubbing agent containing 0.1 M HU in 4 M nitric acid. Similarly U and Pu are co-extracted into 30% TBP and then Pu is removed by scrubbing with 0.1 M HU in 4 M nitric acid. Further decontamination from Pu is obtained in the stripping stages. By this method Pu contamination in the uranium oxide is brought from 7300 ppm to 0.4-3 ppm (wt/wt). This uranium product obtained can be handled on table top. [ABSTRACT FROM AUTHOR]

1-H-1-(3-[F]fluoro-2-hydroxypropyl)-2-nitroimidazole ([F]FMISO), is the most used hypoxia-imaging agent in oncology and we have recently reported a fully automated procedure for its synthesis using the Nuclear Interface FDG module and a single neutral alumina column for purification. Using 1-(2′-nitro-1′-imidazolyl)-2- O-tetra-hydropyranyl-3- O-toluenesulfonylpropanediol (NITTP) as the precursor, we have investigated the yield of [F]FMISO using different reaction times, temperatures, and the amount of precursor. The overall yield was 48.4 ± 1.2% ( n = 3), (without decay correction) obtained using 10 mg NITTP with the radio-fluorination carried out at 145 °C for 3 min followed by acid hydrolysis for 3 min at 125 °C in a total synthesis time of 32 ± 1 min. Increasing the precursor amount to 25 mg did not improve the overall yield under identical reaction conditions, with the decay uncorrected yield being 46.8 ± 1.6% ( n = 3), but rather made the production less economical. It was also observed that the yield increased linearly with the amount of NITTP used, from 2.5 to 10 mg and plateaued from 10 to 25 mg. Radio-fluorination efficiency at four different conditions was also compared. It was also observed by radio thin layer chromatography (radio-TLC) that the duration of radio-fluorination of NITTP, not the radio-fluorination temperature favoured the formation of labeled thermally degraded product, but the single neutral alumina column purification was sufficient enough to obtain [F]FMISO devoid of any radiochemical as well as cold impurities. [ABSTRACT FROM AUTHOR]

Potassium nickel hexacyanoferrate(II) matrix was prepared and characterized. Purification of neutron-activation Mo–molybdate(VI) solutes from some residual cross-contaminant radionuclides including Cs, Rb, Sb, Co and Cr was carried out onto small chromatographic columns of the matrix (each of 1.0 g). Gamma-ray spectrometric analysis data showed that the purification process was not affected by either Mo(VI) concentrations (0.13 and 0.02 M Mo) in the feeding solution of 3.5 M NaNO at pH 9.5 or flow rates (0.2 and 5.0 mL/min) at room temperature. Molybdenum(VI) average loss onto the column matrix did not exceed 7.7 × 10 mmol Mo. Except for Cr, the matrix has very high selectivity for Cs, Rb and Sb with ~50% Co elimination. The obtained data were briefly discussed. [ABSTRACT FROM AUTHOR]

In order to search for isotopic anomalies of U caused by the disintegration of 247Cm in meteorite samples, an analytical scheme for determining 235U/238U ratio for a small amount of uranium (less than 1 ng U) was established. The isotopic ratio of U was determined by double-focusing inductively coupled plasma mass spectrometry (DF-ICP-MS). With a great improvement of chemical procedure for purifying the uranium fraction separated from meteorite samples, a variation in 235U/238U ratios was resolved at an order of ±4‰ for 100 ppt or 200 pg U in solution. For applying the procedure in searching an evidence of 247Cm as an extinct radionuclide in the early solar system, a selective chemical dissolution of constituent minerals of meteorites using EDTA and HCl was introduced and a chemical purification scheme of uranium for ICP-MS was established. [ABSTRACT FROM AUTHOR]

Separation and purification of133Xe from acidic solution containing uranium,99Mo and131I has been developed. In the first step of this work, uranium pellets were dissolved under pressure (8-15 bar) in 8M nitric acid solution. Then133 Xe and other gases were conducted to activated charcoal cold trap. Final purification of133Xe from impurities such as NO x, radioiodine and krypton was performed by passing through a molecular sieve preparative chromatographic column using helium as mobile phase. The final recovery of133Xe from the separation-purification process was higher than 98%. Adsorption-desorption behavior of radioxenon on the charcoal and molecular sieves have also been studied and discussed. [ABSTRACT FROM AUTHOR]

Tritiated uracil and uridine have been prepared simultaneously from a mixture of their respective halogenated analogues (5-bromouracil and5-bromouridine) by halogen-tritium exchange in a one pot preparation, followed by purification. The tritiated products thus obtained have specific activities of 0.962 TBq/mmol and 1.036 TBq/mmol, respectively. [ABSTRACT FROM AUTHOR]

Iodination of meta-iodobenzylguanidine was carried out at optimum conditions. The labeling yield at these conditions was more than 95%. Further purification of the prepared compound increased the radiochemical purity to more than of 99.5%, this high purity was revealed in the quality of the images resulting from the use of the prepared compounds. [ABSTRACT FROM AUTHOR]