Evaluating the mobility of polymer-stabilised zero-valent iron nanoparticles and their potential to co-transport contaminants in intact soil cores.

The use of zero-valent iron nanoparticles (nZVI) has been advocated for the remediation of both soils and groundwater. A key parameter affecting nZVI remediation efficacy is the mobility of the particles as this influences the reaction zone where remediation can occur. However, by engineering nZVI particles with increased stability and mobility we may also inadvertently facilitate nZVI-mediated contaminant transport away from the zone of treatment. Previous nZVI mobility studies have often been limited to model systems as the presence of background Fe makes detection and tracking of nZVI in real systems difficult. We overcame this problem by synthesising Fe-59 radiolabelled nZVI. This enabled us to detect and quantify the leaching of nZVI-derived Fe-59 in intact soil cores, including a soil contaminated by Chromated-Copper-Arsenate. Mobility of a commercially available nZVI was also tested. The results showed limited mobility of both nanomaterials; <1% of the injected mass was eluted from the columns and most of the radiolabelled nZVI remained in the surface soil layers (the primary treatment zone in this contaminated soil). Nevertheless, the observed breakthrough of contaminants and nZVI occurred simultaneously, indicating that although the quantity transported was low in this case, nZVI does have the potential to co-transport contaminants. These results show that direct injection of nZVI into the surface layers of contaminated soils may be a viable remediation option for soils such as this one, in which the mobility of nZVI below the injection/remediation zone was very limited. This Fe-59 experimental approach can be further extended to test nZVI transport in a wider range of contaminated soil types and textures and using different application methods and rates. The resulting database could then be used to develop and validate modelling of nZVI-facilitated contaminant transport on an individual soil basis suitable for site specific risk assessment prior to nZVI remediation.

Decay Data Evaluation Project: Evaluation of (52)Fe nuclear decay data.

Within the Decay Data Evaluation Project (DDEP) and the IAEA Coordinated Research Project no. F41029, the evaluation of the nuclear decay data of (52)Fe, a radionuclide of interest in nuclear medicine, was performed. The main nuclear decay data evaluated are: the half-life, decay energy, energies and probabilities of the electron capture and ß(+) transitions, internal conversion coefficients and gamma-ray energies and emission intensities. This new evaluation, made using the DDEP methodology and tools, was included in the DDEP database NUCLEIDE.

Development of a protocol to measure iron-55 in solid matrices in the environment.

The development of metrology of iron-55 in low-level radioactivity in environmental solid matrices was realised for conducting radioecological studies. A protocol was developed based on the adaptation of existing methods for the purification of iron-55 with selective chromatographic resin, which was then measured with liquid scintillation. The loss attached treatment chemical steps were quantified with elemental iron by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). The tests were used to define the iron retention capacity of selective chromatographic resin, a key element in chemical treatment, and test sample size needed to reach the detection limit of 30 Bq kg(-1) dry. The solid samples were analysed with the developed protocol. The activities obtained from iron-55 were below the detection limit of 30 Bq kg(-1) dry.

Sequential separation of Fe and Sr from liquid samples by using Sr resin and rapid determination of 55Fe and (89,9°)Sr.

The obtained results showed that the Sr resin can be used for the chromatographic separation of Fe (III) and Sr (II) ions by using a mixture of HCl and HNO3. It was shown that the binding strength of Fe (III) decreases with increasing concentration of HNO3 while the binding strength of Sr (II) increases. It was found that the optimal bonding strength is achieved in 6 mol/L HCl:3 mol/L HNO3 and varying concentrations of acid in the mixture allow their selective separation. On basis of these results, a method for the separation of (55)Fe and (89,90)Sr from liquid samples which consists of binding of Fe and Sr on Sr resin and separation from a number of elements by 6 mol/L HCl:3 mol/L HNO3 and their mutual separation by eluting of Sr with 4 mol/L HCl is established. The method enables efficient simultaneous separation (with high recovery) of (89,90)Sr and (55)Fe and in combination with Cerenkov counting rapid determination of (89,90)Sr.

Uncertainties in 63Ni and 55Fe determinations using liquid scintillation counting methods.

The implementation of (63)Ni and (55)Fe determination methods in an environmental laboratory implies their validation. In this process, the uncertainties related to these methods should be analysed. In this work, the expression of the uncertainty of the results obtained using separation methods followed by liquid scintillation counting is presented. This analysis includes the consideration of uncertainties coming from the different alternatives which these methods use as well as those which are specific to the individual laboratory and the competency of its operators in applying the standard ORISE (Oak Ridge Institute for Science and Education) methods.

Measurement of 56Fe activity produced in inelastic scattering of neutrons created by cosmic muons in an iron shield.

We report on the study of the intensities of several gamma lines emitted after the inelastic scattering of neutrons in (56)Fe. Neutrons were produced via nuclear processes induced by cosmic muons in the 20tons massive iron cube placed at the Earth's surface and used as a passive shield for the HPGe detector. Relative intensities of detected gamma lines are compared with the results collected in the same iron shield by the use of the (252)Cf neutrons. Assessment against the published data from neutron scattering experiments at energies up to 14MeV is also provided. It allowed us to infer the qualitative information about the average energy of muon-created neutrons in the iron shield.

Rapid screening and analysis of alpha- and gamma-emitting radionuclides in liquids using a single sample preparation procedure.

A multifaceted radiochemical testing procedure has been developed to analyze a large number of liquid samples and measure a wide range of radionuclides in a short period of time. This method involves a single, unique and fast sample preparation procedure and allows sequential/concurrent determination of analytes with accuracy and precision. The same prepared sample can be selectively analyzed by gross alpha counting, gamma-ray spectroscopy, and alpha spectroscopy. This method is especially attractive in radiological emergency events where analytical data will be needed urgently as a basis for protective action. Given the simplicity and rapidity of the method, it may be suitable for field portable laboratories, which could save time and the cost associated with the transit of samples to a fixed laboratory. A 100 mL aliquot of sample was spiked with ¹³³Ba and 59Fe tracers and subjected to a chemical separation procedure using a combined BaSO4 and Fe(OH)3 co-precipitation scheme. Then, the gross alpha-particle activity of the prepared sample was measured with a low-background gas-proportional counter, followed by the analysis of its photon-emitters using a gamma-ray spectroscopy system with high-purity intrinsic Ge detectors. Gamma-ray determination of ¹³³Ba and 59Fe tracers was used to assess the chemical recoveries of BaSO4 and Fe(OH)3 fractions, respectively. Selectivity of the radionuclides for co-precipitation with either BaSO4 or Fe(OH)3 components was also investigated. Alpha mass-efficiency curves were derived using ²³°Th and ²4¹Am standards as alpha-calibration sources. Various mixtures of radionuclides, including 54Mn, 57Co, 6°Co, 85Sr, 88Y, ¹°9Cd, ¹¹³Sn, ¹³7Cs, ¹³9Ce, ²°³Hg, ²°9Po, ²²6Ra, ²²8Ra, ²³°Th, ²4¹Am, and natural uranium were used in this study. Most were quantitatively assayed with high chemical recoveries. Alpha-isotope identification and assessment of the prepared sample was achieved by alpha spectroscopy using passivated implanted planar silicon (PIPS) detectors. It has been shown that fission products could potentially be captured and analyzed by this method.

In vitro studies of ferric carboxymaltose on placental permeability using the dual perfusion model of human placenta.

An in vitro perfusion model of human placenta was used to study the transplacental passage of iron applied in the form of the drug compound ferric carboxymaltose (FCM) which had been radio-labelled with 59Fe. In four placental perfusion experiments, two simulated circuits for the maternal and fetal sides of the placenta were set up with two experimental phases each lasting 3 h. FCM was added to the maternal circuit at the beginning of each phase to a final iron concentration of 11 mM, which is at least 10 times higher than the maximal predicted level in blood after an administration of 200 mg iron as FCM. The effects of adding transferrin at a physiological concentration of 1.67 mg/ ml were also tested. The concentration profiles of 59Fe showed a 10% decrease within the first 30 min of perfusion on the maternal side. Thereafter the radioactivity levels remained unchanged. The addition of transferrin had no effect on the tissue uptake of 59Fe-FCM. No transferred iron radioactivity could be detected in the fetal circuit. Despite a loss of approximately 10% of the radio-labelled iron observed on the maternal side, only 0.5-2% of the radioactivity was detected in the placental tissue after perfusion. No free iron could be detected at the end of perfusion on the maternal side using ultrafiltration or acid precipitation methods. In addition, the production of transferrin receptor remained unchanged, with similar concentrations in placental tissue before and after perfusion. No effects of FCM on placental viability were observed in terms of energy metabolism (glucose consumption and lactate production), hormone release or placental permeability (assessed by the transfer rates of creatinine and antipyrine). However, two additional observations were made: firstly, a significant reduction in the rate of cell death compared to control conditions was observed in the presence of FCM; secondly, the integrity of the fetal capillary system was improved on the fetal side of the perfusion system. It is concluded that the iron compound FCM does not cross the placenta and may increase the integrity of placental tissue (at least under in vitro conditions), but this latter observation needs further investigation.

Fe-55 activity measurements at the NMISA revisited.

Twenty years ago South Africa's Radioactivity Standards Laboratory (now operated by the NMISA) was the first to measure the activity of (55)Fe by combining the triple-to-double coincidence ratio (TDCR) liquid scintillation method with theoretical efficiency formulae. The extracted activity was however found to be consistently low by about 6%. Due to improvements in both the counting system and analysis technique, it was decided to re-examine the method as applied at the NMISA. The latest results are presented and discussed, particularly with regard to a quantitative study into which vial type is better suited to obtaining accurate (55)Fe activity measurements.

Development of scaling factors for the activated concrete of the KRR-2.

The biological shielding concrete of KRR-2 was activated by a thermal neutron reaction during the operation of the reactor, thus a variety of radionuclides were generated in the concrete. In order to verify the radioactivity for the final disposal of waste and to achieve a more efficient cutting of the concrete, the radioactivity inventories and distributions of the activated concrete were evaluated. The activity of gamma-emitting radionuclides was measured by using an HPGe detector. The beta-emitting radionuclides were measured by an oxidation/combustion method for (3)H and (14)C and a combined method of an extraction chromatography and a liquid scintillation for (55)Fe and (63)Ni. The dominant radioactive nuclides in the activated concrete were (3)H, (14)C, (55)Fe and (60)Co, and the maximum gamma activity was 105Bq/g at the surface around the thermal column. The specific activities of all the nuclides were found to decrease almost linearly on a logarithmic scale along the depth from the inner surface of the concrete. Equations for scaling factors were obtained by a linear regression of logarithms from the radioactivity data of (3)H/(60)Co, (14)C/(60)Co and (55)Fe/(60)Co nuclide pairs of the activated concrete. The scaling factors can be utilized for the estimation of beta radioactivity without the time consuming separation processes of the nuclides.

Iron dissociates from the NaFeEDTA complex prior to or during intestinal absorption in rats.

Sodium iron ethylenediaminetetraacetate (NaFeEDTA) has superior iron bioavailability especially in foods containing iron absorption inhibitors. However, mechanisms involved in the absorption and subsequent partitioning of iron complexed with EDTA are poorly understood. Our objectives were to compare retention and tissue distribution of iron administered to rats either as FeSO4 or NaFeEDTA, either orally (OR) or subcutaneously (SC). Weanling rats were fed semipurified diets supplemented with either FeSO4 or NaFeEDTA for 7 days. They were then given a meal containing 59Fe-labeled FeSO4 or NaFeEDTA, or they were injected SC with these two forms of radiolabeled Fe. 59Fe retention was measured by whole body counting. Urine was collected and counted at 24 h intervals throughout the counting period. Tissue samples were analyzed for nonheme iron and 59Fe activity. Absorption of iron from FeSO4 or NaFeEDTA was similar (57.7 and 53.4%, respectively). Seventy-seven percent of the injected Na59FeEDTA was excreted in the urine within 24 h, whereas only 0.5, 0.8, and 1.4% of the injected 59FeSO4, oral 59FeSO4, and oral Na59FeEDTA, respectively, was excreted in the urine. The nonheme iron content was lower in the liver and spleen, by 56.8 and 28.4%, respectively, among rats consuming the NaFeEDTA diet as compared to rats fed FeSO4. We conclude that iron is dissociated from EDTA prior to or during intestinal absorption and that some fraction of the dissociated EDTA is absorbed separately from the iron.

Half-life measurement of 55Fe.

The half-life of 55Fe was determined experimentally and compared with literature values. A solid 55Fe source was prepared by electrodeposition and repeatedly measured in an X-ray detector at a constant, low solid angle. In total, more than six hundred measurements were performed over a period of ten months, corresponding to one third of the half-life. The experimental method and the corresponding uncertainty budget are presented. The result of 1005.2+/-1.4 days is slightly higher than the current recommended values.

The LSC efficiency for low-Z electron-capture nuclides.

In this paper, we apply the CIEMAT/NIST method to the three low-Z electron-capture nuclides 54Mn, 55Fe and 65Zn by using the KLM and KL1L2L3M atomic rearrangement models, respectively. The counting efficiencies are computed with the new code EMILIA, which comprises an improved model for the interaction of low-energy X-rays with the scintillation cocktail. The calculated counting efficiencies are compared with experimental results.

Statistics of the LS-detector in the case of low counting efficiency.

In the case of high-quenched 3H and 63Ni sources a distinct incompatibility of theoretical and experimental detection efficiency in the triple liquid scintillation (LS) detector was observed (Appl. Radiat. Isot. 52 (2000) 643). The authors concluded, that the Poisson distribution does not properly describe the detection process, when less than one photoelectron is expected in one of the photomultipliers. Application of other distributions of photoelectrons, e.g. binomial, does not solve the observable problem of incompatibility. Measurements of a set of 55Fe sources have been performed with phototubes defocusing and grey filters for decreasing the counting efficiency of the TDCR detector. Differences between counting results of the 55Fe source and the light emitting diode (LED), simulating the scintillation source, excited by a pulse generator have been observed. Various distributions (Poisson, binomial and Polya) were used for the determination of the theoretical counting efficiency in both cases. The Poisson law gave a good result in the case of the LED but the Polya law had to be applied in the case of 55Fe. The results were independent of the scintillator volume. It seems that the validity of the Polya law in the case of LS-sources is related to the scintillator itself. Measurements of the 3H solution confirmed that conclusion.

LSC measurements of the half-life of 40K.

Liquid scintillation counting techniques combined with the CIEMAT/NIST method have been applied to measure the specific activity of natural potassium salts. Samples have been prepared with three different scintillators. The individual atomic composition as well as the density of the cocktails have been taken into account for the efficiency calculation. With the specific activity the half-life is calculated to be T1/2 = 1.248(3) x 10(9) a. The result is in reasonable agreement with other measurement results provided the same isotopic concentration of 40K is used.

Ionization quenching in LSC.

Ionization quench function Q(E) introduces an important correction in the CIEMAT/NIST tracing method. In this paper we present a detailed analysis of the equations used to compute the counting efficiency of 55Fe. The counting efficiency of this radionuclide is very sensitive to the shape and values of Q(E) for this method. We demonstrate that the Birks equation and stopping power are not adequate to obtain low discrepancies between the experimental and computed efficiencies. An empirical procedure to compute accurate Q(E) functions is also given.

[Radioactivity for 137Cs, 125I, 131I, 59Fe, y 57Co windows from foods included in the basic alimentary basket and in the water, consumed in the state of Carabobo, Venezuela]. / Radioactividad en las ventanas de 137Cs, 125I, 131I, 59Fe, y 57Co de alimentos incluidos en la cesta básica y en el agua, consumidos en el estado Carabobo, Venezuela.

One of the input ways of radionucleids into the organism is through food intake. The aim of the present study is to measure the radioactivity levels in food and water samples within energy windows corresponding to 137Cs, 125I, 131I, 59Fe, and 57Co. Samples were taken from local and imported food belonging to the venezuelan basic alimentary basket and included: beef meat, hen egg, chicken bone, tomato, black bean, rice, powder milk from local dealers or imported from Italy and New Zeeland, potable water from the Valencia city aqueduct and bottled water from local sources or imported from Portugal. Radioactivity was measured with a well type Nal (TI) scintillation counter. Analyzed foods and water presented levels lower than the minimal detectable activity for 137Cs, 131I, 59Fe, 57Co, but it was detected in the Valencia city aqueduct water and in bottled water imported from Portugal, levels greater than the minimal detectable activity for the 125I energy window. These results strongly suggest the need of repeated multienergy windows monitoring of radioactivity of basic alimentary basket foods and potable water.

Radioassays and experimental evaluation of dose calibrator settings for 18F.

The positron emitter 18F continues to be one of the most important imaging radionuclides in diagnostic nuclear medicine. Assays of radiopharmaceuticals containing this nuclide are often performed in the clinic using commercial reentrant ionization chambers, or "dose calibrators". Meaningful quantitative clinical studies require accurate knowledge of the injected activity which requires proper calibration of these instruments. Radioassays were performed at the National Institute of Standards and Technology (NIST) on a solution of 18F produced at the National Institutes of Health (NIH) using 4pibeta liquid scintillation (fS) counting with 3H-standard efficiency tracing. Cocktails containing water fractions of approximately 0.9 and 9% (both as saline) were used. The massic activity values were measured to be 2.52+/-0.06 and 2.50+/-0.03 MBq g(-1), respectively, for the 0.9 and 9% water cocktails as of the reference time. The uncertainties on the activity measurements are expanded (k = 2) uncertainties. The largest uncertainty component was found to be the repeatability on a single LS source, with the cocktails containing 0.9% water fraction exhibiting a larger variability by nearly a factor of two. Reproducibility between LS cocktails with the same water fraction was also found to be a large uncertainty component, but with a value less than half that due to measurement repeatability. Radionuclidic impurities consisted of 48V and 46Sc, at levels of 0.11+/-0.08% (expanded uncertainties) and approximately 2 x 10(-3)% (upper limit) relative to the activity of the 18F, as of the reference time. Dose calibrator dial settings for measuring solutions of 18F were experimentally determined for Capintec CRC-12 and CRC-35R dose calibrators in three measurement geometries: a 5-ml standard NIST ampoule (two ampoules measured), a 12-ml plastic syringe containing 9 ml of solution and a 10-ml Mallinckrodt molded dose vial filled with 5 ml of solution. The experimental dial settings (and the corresponding expanded uncertainties) for these geometries were found to be 477+/-7, 474+/-6, 482+/-6 and 463+/-7 for the two ampoules, the syringe and the dose vial, respectively, in the CRC-12. The dial settings determined for the CRC-35R were 472+/-7, 470+/-7, 464+/-6 and 456+/-6 for the two ampoules, the syringe, and the dose vial, respectively. The uncertainties in the dial settings are expanded uncertainties. Comparisons between the empirically determined dial settings and the manufacturer's recommended setting of "439" indicate that use of the manufacturer's setting overestimates the activity by between 3 and 6%, depending upon the geometry used.