Enriched Targets Research Articles

Two Methods of Determination of Parities of Low-Lying States in 159Gd from Analysis of the γ-ray Intensities from Reaction 158Gd(nres, γ)159Gd

Energy levels and transitions in 159Gd were studied by means of radiative capture of resonance neutrons at 12 isolated resonances of 158Gd. The time-of-flight technique was used on an enriched target at the IBR-30 reactor at JINR Dubna. A total of 80 primary gamma-transitions were recorded and their absolute intensities were determined resulting in the observation of 1/2±, 3/2± levels up to 2.4 MeV. Parities of found levels were recalculated using two methods: the first method consists in analyzing of intensities averaging in 12 resonances and in the second method individual intensities are analyzed. The second method is described for the first time.

Fabrication of reactor target from enriched 50Cr for artificial neutrino source

The fabrication of the enriched 50Cr target for the artificial 51Cr neutrino source with activity > 3 MCi for the experiment BEST is presented. The processes of obtaining a target in the form of disks with a thickness of 4 mm and a diameter of 84 and 88 mm required to achieve the necessary activity using the reactor SM-3 are considered, including: enrichment of natural chromium in the form of oxyfluoride by gas centrifugation, electrolytic reduction and refining of metallic chromium, as well as the formation of chromium disks by spark plasma sintering.

Interplay of quasiparticle and vibrational excitations: First observation of isomeric states in 168Dy and 169Dy

The neutron-rich dysprosium isotopes 168Dy102 and 169Dy103 have been investigated using the EURICA γ-ray spectrometer, following production via in-flight fission of a high-intensity uranium beam in conjunction with isotope separation through the BigRIPS separator at RIBF in RIKEN Nishina Center. For 168Dy, a previously unreported isomer with a half-life of 0.57(7) μs has been identified at an excitation energy of 1378 keV, and its presence affirmed independently using γ-γ-γ coincidence data taken with Gammasphere via two-proton transfer from an enriched 170Er target performed at Argonne National Laboratory. This isomer is assigned Jπ=Kπ=(4−) based on the measured transition strengths, decay patterns, and the energy systematics for two-quasiparticle states in N=102 isotones. The underlying mechanism of two-quasiparticle excitations in the doubly midshell region is discussed in comparison with the deformed QRPA and multi-quasiparticle calculations. In 169Dy, the B(E2) value for the transition de-exciting the previously unreported Kπ=(1/2−) isomeric state at 166 keV to the Kπ=(5/2−) ground state is approximately two orders of magnitude larger than the E2 strength for the corresponding isomeric-decay transition in the N=103 isotone 173Yb, suggesting the presence of a significant γ-vibrational admixture with a dominant neutron one-quasiparticle component in the isomeric state.

Cross sections and production yields of 117mSn and other radionuclides generated in natural and enriched antimony with protons up to 145 MeV

Abstract Cross sections of a prospective medical radionuclide 117mSn along with 113Sn, 120m,122Sb, 111,114mIn and 118,119m,119g,121m,121g,123mTe generated in natural and enriched antimony targets by protons in a wide energy range up to 145 MeV were determined. A stacked-foil technique followed by gas chemical separation and γ-ray spectrometry were used. The obtained data were compared with experimental values reported in literature and with theoretical computations by ALICE, TALYS and Cascade-Evaporation-Fission codes. Production yields of 117mSn and the main impurity 113Sn were estimated for different irradiation modes.

Characteristics of free air carbon dioxide enrichment of a northern temperate mature forest

In 2017, the Birmingham Institute of Forest Research (BIFoR) began to conduct Free Air Carbon Dioxide Enrichment (FACE) within a mature broadleaf deciduous forest situated in the United Kingdom. BIFoR FACE employs large‐scale infrastructure, in the form of lattice towers, forming ‘arrays’ which encircle a forest plot of ~30 m diameter. BIFoR FACE consists of three treatment arrays to elevate local CO2 concentrations (e[CO2]) by +150 µmol/mol. In practice, acceptable operational enrichment (ambient [CO2] + e[CO2]) is ±20% of the set point 1‐min average target. There are a further three arrays that replicate the infrastructure and deliver ambient air as paired controls for the treatment arrays. For the first growing season with e[CO2] (April to November 2017), [CO2] measurements in treatment and control arrays show that the target concentration was successfully delivered, that is: +147 ± 21 µmol/mol (mean ± SD) or 98 ± 14% of set point enrichment target. e[CO2] treatment was accomplished for 97.7% of the scheduled operation time, with the remaining time lost due to engineering faults (0.6% of the time), CO2 supply issues (0.6%) or adverse weather conditions (1.1%). CO2 demand in the facility was driven predominantly by wind speed and the formation of the deciduous canopy. Deviations greater than 10% from the ambient baseline CO2 occurred <1% of the time in control arrays. Incidences of cross‐contamination >80 µmol/mol (i.e. >53% of the treatment increment) into control arrays accounted for <0.1% of the enrichment period. The median [CO2] values in reconstructed three‐dimensional [CO2] fields show enrichment somewhat lower than the target but still well above ambient. The data presented here provide confidence in the facility setup and can be used to guide future next‐generation forest FACE facilities built into tall and complex forest stands.

Systematic analysis of long non-coding RNA and mRNA expression changes in ApoE-deficient mice during atherosclerosis

Atherosclerosis plays an important role in the pathology of coronary heart disease, cerebrovascular disease, and systemic vascular disease. Long non-coding RNAs (lncRNAs) are involved in most biological processes and are deregulated in many human diseases. However, the expression alteration and precise role of lncRNAs during atherosclerosis are unknown. We report here the systematic profiling of lncRNAs and mRNAs in an ApoE-deficient (ApoE−/−) mouse model of atherosclerosis. Clariom D solutions for the mouse Affymetrix Gene Chip were employed to analyze the RNAs from control and ApoE−/− mice. The functions of the differentially expressed mRNAs and lncRNAs and the relationships of their expression with atherosclerosis were analyzed by gene ontology, co-expression network, pathway enrichment, and lncRNA target pathway network analyses. Quantitative real-time PCR (QRT-PCR) was used to determine the expression of mRNAs and lncRNAs. A total of 2212 differentially expressed lncRNAs were identified in ApoE−/− mice, including 1186 up-regulated and 1026 down-regulated lncRNAs (|FC| ≥ 1.1, p < 0.05). A total of 1190 differentially expressed mRNAs were found in the ApoE−/− mice with 384 up-regulated and 806 down-regulated (|FC| ≥ 1.1, p < 0.05). Bioinformatics analyses demonstrated extensive co-expression of lncRNAs and mRNAs and concomitant deregulation of multiple signaling pathways associated with the initiation and progression of atherosclerosis. The identified differentially expressed mRNAs and lncRNAs as well as the related signaling pathways may provide systematic information for understanding the pathogenesis and identifying biomarkers for the diagnosis, treatment, and prognosis of atherosclerosis.

Determinants of the effect of extracorporeal carbon dioxide removal in the SUPERNOVA trial: implications for trial design.

To describe the variability and determinants of the effect of extracorporeal CO2 removal (ECCO2R) on tidal volume (Vt), driving pressure (ΔP), and mechanical power (PowerRS) and to determine whether highly responsive patients can be identified for the purpose of predictive enrichment in ECCO2R trial design. Using data from the SUPERNOVA trial (95 patients with early moderate acute respiratory distress syndrome), the independent effects of alveolar dead space fraction (ADF), respiratory system compliance (Crs), hypoxemia (PaO2/FiO2), and device performance (higher vs lower CO2 extraction) on the magnitude of reduction in Vt, ΔP, and PowerRS permitted by ECCO2R were assessed by linear regression. Predicted and observed changes in ΔP were compared by Bland-Altman analysis. Hypothetical trials of ECCO2R, incorporating predictive enrichment and different target CO2 removal rates, were simulated in the SUPERNOVA study population. Changes in Vt permitted by ECCO2R were independently associated with ADF and device performance but not PaO2/FiO2. Changes in ΔP and PowerRS were independently associated with ADF, Crs, and device performance but not PaO2/FiO2. The change in ΔP predicted from ADF and Crs was moderately correlated with observed change in ΔP (R2 0.32, p < 0.001); limits of agreement between observed and predicted changes in ΔP were ± 3.9cmH2O. In simulated trials, restricting enrollment to patients with a larger predicted decrease in ΔP enhanced the average reduction in ΔP, increased predicted mortality benefit, and reduced sample size and screening size requirements. The increase in statistical power obtained by restricting enrollment based on predicted ΔP response varied according to device performance as specified by the target CO2 removal rate. The lung-protective benefits of ECCO2R increase with higher alveolar dead space fraction, lower respiratory system compliance, and higher device performance. ADF and Crs, rather than severity of hypoxemia, should be the primary factors determining whether to enroll patients in clinical trials of ECCO2R.

Supported ionic liquid phases for the separation of samarium and europium in nitrate media: Towards purification of medical samarium-153

Samarium-153 is a medical radionuclide that serves in nuclear medicine for bone pain palliation or imaging of the skeleton, and is produced in a nuclear research reactor by irradiation of an enriched samarium-152 target with a high flux of thermal neutrons. However, long-lived europium-154 impurities are formed concurrently, which restricts the use of the samarium-153 radiopharmaceutical. Previous research already showed the possibility to separate samarium and europium efficiently by solvent extraction with the undiluted ionic liquid [A336][NO3]. Current research efforts investigated the feasibility to convert the separation method to an extraction chromatography application, taking advantage of solid phase extraction techniques. TEVA particles, where the ionic liquid is immobilized onto a solid support, served as the stationary phase in the column. Eu3+ was reduced to Eu2+ in a concentrated nitrate salt solution prior to the separation step. After loading onto the extraction chromatography column, Eu2+ was not retained by the TEVA particles upon elution with a concentrated nitrate salt solution, whereas Sm3+ was extracted to the ionic liquid layer. Sm3+ could be efficiently removed from the column by elution with water, hence yielding a simple, yet efficient separation method.

Systematic Analysis of Intestinal MicroRNAs Expression in HCC: Identification of Suitable Reference Genes in Fecal Samples.

Hepatocellular carcinoma (HCC) is an extremely fatal malignancy. Intestinal microRNAs, which can be detected in fecal samples in humans may be involved in the pathological process of HCC. Therefore, screening for functional intestinal microRNAs in fecal samples and investigating their potential roles in the molecular progression of HCC are necessary. Quantitative real-time PCR (qRT-PCR) has been widely used in microRNA expression studies. However, few genes have been reported as reference genes for intestinal microRNAs in fecal samples. In order to obtain a more accurately analyzed intestinal microRNAs expression, we first searched for reliable reference genes for intestinal microRNAs expression normalization during qRT-PCR, using three software packages (GeNorm, NormFinder, and Bestkeeper). Next we screened and predicted the target genes of the differentially intestinal microRNAs of control and HCC mice through quantitative RT-PCR or miRtarBase. Finally, we also analyzed the mRNA targets for enrichment of Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways using the DAVID Bioinformatic Resources database. This study has successfully screened relatively suitable reference genes and we have discovered that the differential intestinal microRNAs play significant roles in the development of HCC. The top reference genes identified in this study could provide a theoretical foundation for the reasonable selection of a suitable reference gene. Furthermore, the detection of intestinal microRNAs expression may serve as a promising therapeutic target for the diagnosis and treatment of HCC.

Evidence of octupole-phonons at high spin in 207Pb

A lifetime measurement of the 19/2− state in 207Pb has been performed using the Recoil Distance Doppler-Shift (RDDS) method. The nuclei of interest were produced in multi-nucleon transfer reactions induced by a 208Pb beam impinging on a 100Mo enriched target. The beam-like nuclei were detected and identified in terms of their atomic mass number in the VAMOS++ spectrometer while the prompt γ rays were detected by the AGATA tracking array. The measured large reduced transition probability B(E3,19/2−→13/2+)=40(8) W.u. is the first indication of the octupole phonon at high spin in 207Pb. An analysis in terms of a particle-octupole-vibration coupling model indicates that the measured B(E3) value in 207Pb is compatible with the contributions from single-phonon and single particle E3 as well as E3 strength arising from the double-octupole-phonon 6+ state, all adding coherently. A crucial aspect of the coupling model, namely the strong mixing between single-hole and the phonon-hole states, is confirmed in a realistic shell-model calculation.

The methodology of characterization of neutron leakage field from PET production cyclotron for experimental purposes

During the production of 18F isotope for radiopharmaceuticals in 18O(p,n)18F reactions, the leakage neutrons are mostly considered as a waste product. The utilization of a cyclotron based neutron source might be an interesting application because its average energy is relatively high and emissivity is quite strong. Thus its use might be useful in many fields of neutron based research. This paper aims to define the methodology and its following use for the characterization of the secondary neutron field leaking from 18O enriched H2O target in IBA Cyclone 18/9. Experimental characterization is based on the employment of independent methods, namely the proton recoil method using a stilbene scintillation detector and neutron activation analysis with selected IRDFF materials. Neutron field characteristics were also tested by calculation in the standard MCNP6 code model and using FENDL-3, TENDL-2017 nuclear data libraries for (p,n) reactions. The calculation models have been found as discrepant in some quantities more or less, thus it is recommended to use experimental characterization as a sole method.

Production and characterization of no-carrier-added 161Tb as an alternative to the clinically-applied 177Lu for radionuclide therapy

Background161Tb is an interesting radionuclide for cancer treatment, showing similar decay characteristics and chemical behavior to clinically-employed 177Lu. The therapeutic effect of 161Tb, however, may be enhanced due to the co-emission of a larger number of conversion and Auger electrons as compared to 177Lu. The aim of this study was to produce 161Tb from enriched 160Gd targets in quantity and quality sufficient for first application in patients.MethodsNo-carrier-added 161Tb was produced by neutron irradiation of enriched 160Gd targets at nuclear research reactors. The 161Tb purification method was developed with the use of cation exchange (Sykam resin) and extraction chromatography (LN3 resin), respectively. The resultant product (161TbCl3) was characterized and the 161Tb purity compared with commercial 177LuCl3. The purity of the final product (161TbCl3) was analyzed by means of γ-ray spectrometry (radionuclidic purity) and radio TLC (radiochemical purity). The radiolabeling yield of 161Tb-DOTA was assessed over a two-week period post processing in order to observe the quality change of the obtained 161Tb towards future clinical application. To understand how the possible drug products (peptides radiolabeled with 161Tb) vary with time, stability of the clinically-applied somatostatin analogue DOTATOC, radiolabeled with 161Tb, was investigated over a 24-h period. The radiolytic stability experiments were compared to those performed with 177Lu-DOTATOC in order to investigate the possible influence of conversion and Auger electrons of 161Tb on peptide disintegration.ResultsIrradiations of enriched 160Gd targets yielded 6–20 GBq 161Tb. The final product was obtained at an activity concentration of 11–21 MBq/μL with ≥99% radionuclidic and radiochemical purity. The DOTA chelator was radiolabeled with 161Tb or 177Lu at the molar activity deemed useful for clinical application, even at the two-week time point after end of chemical separation. DOTATOC, radiolabeled with either 161Tb or 177Lu, was stable over 24 h in the presence of a stabilizer.ConclusionsIn this study, it was shown that 161Tb can be produced in high activities using different irradiation facilities. The developed method for 161Tb separation from the target material yielded 161TbCl3 in quality suitable for high-specific radiolabeling, relevant for future clinical application.

Quinetides: diverse posttranslational modified peptides of ribonuclease-like storage protein from Panax quinquefolius as markers for differentiating ginseng species

BackgroundPeptides have diverse and important physiological roles in plants and are ideal markers for species identification. It is unclear whether there are specific peptides in Panax quinquefolius L. (PQ). The aims of this study were to identify Quinetides, a series of diverse posttranslational modified native peptides of the ribonuclease-like storage protein (ginseng major protein), from PQ to explore novel peptide markers and develop a new method to distinguish PQ from Panax ginseng. MethodsWe used different fragmentation modes in the LTQ Orbitrap analysis to identify the enriched Quinetide targets of PQ, and we discovered Quinetide markers of PQ and P. ginseng using ultrahigh-performance liquid chromatography–quadrupole time-of-flight mass spectrometry analysis. These “peptide markers” were validated by simultaneously monitoring Rf and F11 as standard ginsenosides. ResultsWe discovered 100 Quinetides of PQ with various post-translational modifications (PTMs), including a series of glycopeptides, all of which originated from the protein ginseng major protein. We effectively distinguished PQ from P. ginseng using new “peptide markers.” Four unique peptides (Quinetides TP6 and TP7 as markers of PQ and Quinetides TP8 and TP9 as markers of P. ginseng) and their associated glycosylation products were discovered in PQ and P. ginseng. ConclusionWe provide specific information on PQ peptides and propose the clinical application of peptide markers to distinguish PQ from P. ginseng.

Photonuclear production, chemistry, and in vitro evaluation of the theranostic radionuclide 47Sc

BackgroundIn molecular imaging and nuclear medicine, theranostic agents that integrate radionuclide pairs are successfully being used for individualized care, which has led to rapidly growing interest in their continued development. These compounds, which are radiolabeled with one radionuclide for imaging and a chemically identical or similar radionuclide for therapy, may improve patient-specific treatment and outcomes by matching the properties of different radionuclides with a targeting vector for a particular tumor type. One proposed theranostic radionuclide is scandium-47 (47Sc, T1/2 = 3.35 days), which can be used for targeted radiotherapy and may be paired with the positron emitting radionuclides, 43Sc (T1/2 = 3.89 h) and 44Sc (T1/2 = 3.97 h) for imaging. The aim of this study was to investigate the photonuclear production of 47Sc via the 48Ti(γ,p)47Sc reaction using an electron linear accelerator (eLINAC), separation and purification of 47Sc, the radiolabeling of somatostatin receptor-targeting peptide DOTATOC with 47Sc, and in vitro receptor-mediated binding of [47Sc]Sc-DOTATOC in AR42J somatostatin receptor subtype two (SSTR2) expressing rat pancreatic tumor cells.ResultsThe rate of 47Sc production in a stack of natural titanium foils (n = 39) was 8 × 107 Bq/mA·h (n = 3). Irradiated target foils were dissolved in 2.0 M H2SO4 under reflux. After dissolution, trivalent 47Sc ions were separated from natural Ti using AG MP-50 cation exchange resin. The recovered 47Sc was then purified using CHELEX 100 ion exchange resin. The average decay-corrected two-step 47Sc recovery (n = 9) was (77 ± 7)%. A radiolabeling yield of > 99.9% of [47Sc]Sc-DOTATOC (0.384 mg in 0.3 mL) was achieved using 1.7 MBq of 47Sc. Blocking studies using Octreotide illustrated receptor-mediated uptake of [47Sc]Sc-DOTATOC in AR42J cells.Conclusions47Sc can be produced via the 48Ti(γ,p)47Sc reaction and separated from natural Ti targets with a yield and radiochemical purity suitable for radiolabeling of peptides for in vitro studies. The data in this work supports the potential use of eLINACs for studies of photonuclear production of medical radionuclides and the future development of high-intensity eLINAC facilities capable of producing relevant quantities of carrier-free radionuclides currently inaccessible via routine production pathways or limited due to costly enriched targets.

Simultaneous determination of three sulfanilamide artificial sweeteners in foodstuffs by capillary electrophoresis coupled with contactless conductivity detection based on porous aromatic frameworks enhanced solid phase extraction

In this paper, a simple and easy method of solid phase extraction (SPE) followed by capillary electrophoresis (CE) with capacitively coupled contactless conductivity detection (C4D) is evaluated as a novel approach for the simultaneous determination of acesulfame-K (ACE), sodium saccharin (SAC), and sodium cyclamate (CYC) in foodstuffs without derivatization. To reduce the complex matrix interference resulting from the constituents of samples and enriched targets, porous aromatic frameworks (PAFs) enhanced SPE, a suitable sample pretreatment procedure, was introduced. Several factors affecting extraction efficiency and electrophoretic separation were investigated. Additionally, the interaction mechanisms between the host (PAF-6) and guests (ACE, SAC, and CYC) were studied. Under the optimum conditions, three sulfanilamide artificial sweeteners were baseline separated within 8 min, exhibiting a linear calibration over two orders of magnitude (R2 &gt; 0.995). The limits of detection (LOD) and quantification (LOQ) were considered better than those usually obtained by CE with ultraviolet and C4D detection. The proposed SPE–CE–C4D method has been successfully applied to analyse beverage samples and candied fruits with recoveries in the range of 78.89%–92.00%.

Recoiled and Sputtered Radioactive Impurities in 11 MeV Proton-based F-18 Production

One of the quality control measures in F-18 radionuclide production concerns the impurities which might be present in the proton-irradiated enriched H218O target. In this investigation, proton irradiations of enriched water targets were theoretically simulated by the Stopping and Range of Ions in Matter (SRIM) 2013 codes, followed by experimental measurements. First, the SRIM-calculated data were employed to understand the origins of the recoiled and sputtered species. Using a portable Gamma Ray Spectroscopy System, recoiled and sputtered radioactive impurities were measured in the enriched water target following F-18 production using 11 MeV proton beams. The experimental results indicate that Havar window-originated Co-56 radionuclide and silver body-originated Ag-110m radioisotope were identified in the post-irradiated enriched H218O target. In addition, after passing the 18F solution through a column containing Quaternary Methyl Acetate (QMA) resin, none of the radionuclidic impurities were any longer observed to any great extent in the sample.

Arabidopsis EMSY-like (EML) histone readers are necessary for post-fertilization seed development, but prevent fertilization-independent seed formation

Seed development is a complex regulatory process that includes a transition from gametophytic to sporophytic program. The synchronized development of different seed compartments (seed coat, endosperm and embryo) depends on a balance in parental genome contributions. In the most severe cases, the disruption of the balance leads to seed abortion. This represents one of the main obstacles for the engineering of asexual reproduction through seeds (apomixis), and for generating new interspecies hybrids. The repression of auxin synthesis by the Polycomb Repressive Complex 2 (PRC2) is a major mechanism contributing to sensing genome balance. However, current efforts focusing on decreasing PRC2 or elevating auxin levels have not yet resulted in the production of apomictic seed. Here, we show that EMSY-Like Tudor/Agenet H3K36me3 histone readers EML1 and EML3 are necessary for early stages of seed development to proceed at a normal rate in Arabidopsis. We further demonstrate that both EML1 and EML3 are required to prevent the initiation of seed development in the absence of fertilization. Based on the whole genome expression analysis, we identify auxin transport and signaling genes as the most enriched downstream targets of EML1 and EML3. We hypothesize that EML1 and EML3 function to repress and soften paternal gene expression by fine-tuning auxin responses. Discovery of this pathway may contribute to the engineering of apomixis and interspecies hybrids.

SP1 regulates KLF4 via SP1 binding motif governed by DNA methylation during odontoblastic differentiation of human dental pulp cells.

DNA methylation is a critical epigenetic modulation in regulating gene expression in cell differentiation process, however, its detailed molecular mechanism during odontoblastic differentiation remains elusive. We aimed to study the global effect of DNA methylation on odontoblastic differentiation and how DNA methylation affects the transactivation of transcription factor (TF) on its target gene. DNA methyltransferase (DNMTs) inhibition assay and following odontoblastic differentiation assay were performed to evaluate the effect of DNA methylation inhibition on odontoblastic differentiation. Promoter DNA methylation microarray and motif enrichment assay were performed to predict the most DNA-methylation-affected TF motifs during odontoblastic differentiation. The enriched target sites and motifs were further analyzed by methylation-specific polymerase chain reaction (MS-PCR) and sequencing. The functional target sites were validated in vitro with Luciferase assay. The regulatory effect of DNA methylation on the enriched target sites in primary human dental pulp cells and motifs were confirmed by in vitro methylation assay. Inhibition of DNMTs in preodontoblast cells increased the expression level of Klf4 as well as marker genes of odontoblastic differentiation including Dmp1 and Dspp, and enhanced the efficiency of odontoblastic differentiation. SP1/KLF4 binding motifs were found to be highly enriched in the promoter regions and showed demethylation during odontoblastic differentiation. Mutation of SP1 binding site at -75 within KLF4's promoter region significantly decreased the luciferase activity. The in vitro methylation of KLF4's promoter decreased the transactivation of SP1 on KLF4. We confirmed that SP1 regulates KLF4 through binding site lying in a CpG island in KLF4's promoter region which demethylated during odontoblastic differentiation thus enhancing the efficiency of SP1's binding and transcriptional regulation on KLF4.

Measurement of neutron capture cross section of 187W for production of 188W

Tungsten-188 (t1/2 = 69.4 d) is routinely produced by double neutron capture using highly enriched 186W target, 186W(n,γ)187W(n,γ)188W reaction, at the ORNL 85 MWt High Flux Isotope Reactor. While the thermal neutron cross section for the first reaction, 186W(n,γ)187W, is well known, the single reported 64 b cross-section for the second reaction, 187W(n,γ)188W, cannot be validated by experimental results that yield lower than expected activities of 188W. In this study, we report a new value for the thermal neutron capture cross section of 187W. After confirming the neutron capture cross section of 186W (σ0 = 37.8 ± 1.8 b for thermal and I0 = 476 ± 25 b for resonance integrals with σ0/I0 = 12.6 ± 0.4) in two short irradiations, longer irradiations (1–10 d) were performed to obtain a value of 6.5 ± 0.8 b for the σ0 of 187W, which is lower than the adopted value by a factor of 10. Due to the short half-life of 187W (t1/2 = 23.7 d), the σ0 for 187W was obtained empirically by comparing the 188W experimental yields with the theoretical yields generated by code IsoChain and varying the 187W cross section while keeping all other parameters constant.

Analysis of radioactive waste generated during the cyclotron production of 99mTc

Past and prospective shortages of medical radioisotopes have driven recent developments in the direct production of 99mTc via the 100Mo(p,2n)99mTc reaction. The cyclotron-based production method has been shown to successfully produce 99mTc, however trace impurities present in the enriched molybdenum target can also lead to the unintended creation of other radioisotopes which constitute waste. The isotopic composition of the waste has to be investigated in order to determine how it can be handled, transported and safely stored. In this article, we report which waste radioisotopes are created alongside 99mTc during target irradiation. Results are based on the gamma spectroscopy of waste produced. Significant complexities in the emission spectra made automated identification of radioisotopes inaccurate; complexities were resolved using a manual radioisotope identification procedure. The impact of target composition, integrated beam current and duration of target irradiation on the waste produced was studied. Results indicate that an average of 0.059 ± 0.003 GBq of waste is generated per 1 GBq of 99mTc produced. Two-thirds of the total waste activity produced was attributed to 99Mo (T1/2 = 66 h) alone, while a total of fifty radioisotopes were found in the waste. Long-lived isotopes (T1/2 > 2 months) constituted only 1% of the total waste activity at end of beam (EOB). In conclusion, it was determined that the waste generated during cyclotron-based 99mTc production was acceptably low for routine clinical production.