Measurement of the 233^{233}U neutron capture cross section at the n_TOF facility at CERN

The Thorium-Uranium (Th-U) fuel cycle has been envisaged as an alternative to the Uranium-Plutonium (U-Pu) fuel cycle for electricity generation using nuclear power reactors. Indeed, thorium can be used as a nuclear fuel, and several studies and R&D programs seem to provide evidence on the sustainability of the Th-U fuel cycle, due to (i) the natural abundance of Thorium, (ii) the improved proliferation resistance offered by the Th-U fuel cycle relative to the U-Pu fuel cycle, (iii) the better neutronics performance of the Th-U fuel cycle throughout the whole neutron energy range compared to the U-Pu fuel cycle, (iv) the lower radiotoxicity of the generated spent fuel in reactors with Th-U fuel cycle and, consequently (v) better economics and public acceptance of the reactors operated using the Th-U fuel cycle compared to those using the U-Pu fuel cycle (prior to the Generation IV nuclear reactors). In a nuclear reactor operated using the Th-U fuel cycle, $^{233}$U is a key nuclide governing the neutronics performance of the system and consequently its economics, nuclear safety and proliferation resistance properties and characteristics. Therefore, the accurate knowledge of the neutron capture and neutron induced fission cross-sections in $^{233}$U are of paramount importance for the assessment of the sustainability of the Th-U fuel cycle and for the design of nuclear reactors using such fuel cycle. In this work, the neutron capture and neutron induced fission cross sections of $^{233}$U have been measured simultaneously at the neutron Time-Of-Flight facility (n_TOF) at European Organization for Nuclear Research (CERN) in the energy range from 1 eV to 1 keV using the 4$pi$BaF2 Total Absorption Calorimeter (TAC) as a detection device. The n_TOF facility is a premier neutron spectrometer worldwide, driven by a 20 GeV pulsed proton beam, operated with a low duty cycle and featuring high instantaneously neutron fluxes, excellent neutron energy resolution, low backgrounds and a Data Acquisition System supported by fast electronics. The measurement of the$^{233}$U capture cross section is a very challenging task requiring the discrimination of the neutron capture component from the neutron induced fission component. The neutron induced fission is the main competing reaction, whose cross-section is several times higher than the one for neutron capture. The total absorption technique has been employed together with the Calorimetric Shape Decomposition (CSD) method for discriminate between competing nuclear reactions for the first time in this work

Analysis of stable isotopic patterns on contemporary dyed wool and historical samples - a contribution to ascertain the provenance of Arraiolos' Rugs raw materials

A espectrometria de massa de razão isotópica precedida de análise elementar (EA-IRMS) tem sido utilizada para detetar padrões de razão isotópica como forma de determinar a origem de materiais em diversas áreas científicas. Neste trabalho, a análise de 13C e 15N por EA-IRMS foi utilizada para estudar matérias-primas utilizadas na confeção de Tapetes de Arraiolos (lãs, corantes). Para perceber a influência dos cromóforos na razão isotópica da lã, tingiu-se lã contemporânea com corantes naturais historicamente descritos e analisou-se por EA-IRMS. Adicionalmente, com o objetivo de determinar a sua proveniência, foram analisadas amostras de Tapetes de Arraiolos históricos. Também foram efetuadas medições colorimétricas em lã contemporânea tingida. Os resultados da análise elementar demonstraram a integridade da lã nas amostras históricas (C:Natom ≈ 3,4). De forma geral, os valores de 13C e 15N de lã contemporânea tingida não apresentaram diferenças significativas entre amostras (P > 0,05) o que refuta a hipótese de que a razão isotópica da lã é influenciada pela razão isotópica dos cromóforos em análise em volume. Para além dos resultados anteriores, os valores de 13C e 15N para amostras de lã contemporânea e históricas indiciam que a alimentação das ovelhas foi exclusivamente constituída por plantas C3 não fertilizadas. Apenas um tapete (Tapete L), cujos valores de 15N são compatíveis com plantas fertilizadas com fertilizantes orgânicos, não é concordante com os restantes. Em particular, os valores de 13C e 15N das amostras históricas apresentaram diferenças significativas entre tapetes (P < 0,05) o que pode evidenciar alterações meteorológicas ao longo dos anos. Diferenças entre amostras do mesmo tapete apenas foram detetadas em um dos três tapetes (Tapete L) o que pode estar relacionado com alterações à dieta e práticas de pastoreio relacionadas com condições de seca. Para finalizar, ficou provado que a utilização de EA-IRMS para estudo de lã tingida é possível sem que existam interferências dos cromóforos o que certamente será útil na determinação e certificação dos materiais dos Tapetes de Arraiolos. Não obstante, devido ao elevado número de variáveis envolvidas, análises complementares de EA-IRMS e análise de cromóforos isolados são fundamentais; - ABSTRACT: Elemental analyzer coupled with isotope ratio mass spectrometry (EA-IRMS) has been used to find isotope ratio patterns as a way of ascertaining the provenance of materials in several fields of science. In this work, EA-IRMS analysis of 13C and 15N was used to study Arraiolos’ Rugs raw materials (wool and dyes). To understand the influence of the chromophores in the isotope ratio of wool, contemporary wool was dyed using historically described traditional dyes and analyzed by EA-IRMS. Additionally, aiming towards provenance establishment, historical Arraiolos’ Rugs samples were analyzed. Colorimetric measurements of contemporary dyed wool were also made. EA results revealed wool integrity (C:Natom ≈ 3,4) in historical samples. In general, 13C and 15N of contemporary dyed wool showed no significant difference between samples (P > 0,05) which rebutted the hypothesis that chromophore isotope ratio influences wool isotope ratios and may be detected in bulk analysis. Furthermore, 13C and 15N of both contemporary and historical wool samples were indicative of sheep diets comprised exclusively of C3 unfertilized plants. Exception made for one rug (Rug L) in which 15N values were compatible with organically fertilized plants. In particular, 13C and 15N IRMS results of historical samples showed significant inter-rugs differences (P < 0,05) which could evidence meteorological changes over the years. Intra-rug differences were detected in only one of the three rugs (Rug L) which may be linked to changes in sheep diet and pastures practices due to drought conditions. Finally, it was proved that is possible to use EA-IRMS to study dyed wool without chromophore interference which will certainly help in Arraiolos’ Rugs materials definition and certification. Notwithstanding, due to the high number of variables at stake, complementary EA-IRMS analysis, as well as compound-specific analysis of chromophores, are essential

Workshop on He-3 alternatives for safeguards applications

On 13-17 October 2014, the Joint Research Centre (JRC) hosted the second of two workshops on helium-3 (He-3) alternative materials and technologies for safeguards applications, under the U.S. Department of Energy/National Nuclear Security Administration (DOE/NNSA)-Euratom Action Sheet 47, at the JRC Ispra Site. The recent Ispra workshop served as a direct follow-up to the Los Alamos workshop. Participants provided updates on several of the technologies discussed in 2013. In particular, workshop participants evaluated the applicability of the He-3 alternative technologies to a pre-established list of use cases and identify any capability gaps. In addition, the workshop included discussions of implementation strategies for advancing the prototype technologies to commercially deployable systems. The workshop included a demonstration of some of these technologies. Moreover, a field trial has been held on the margins of this workshop to provide a head-to-head comparison of various He-3 alternative prototypes for nuclear fuel verification.JRC.E.8-Nuclear securit

Highly Specific Blood-Brain Barrier Transmigrating Single-Domain Antibodies Selected by an In Vivo Phage Display Screening

A major bottleneck in the successful development of central nervous system (CNS) drugs is the discovery and design of molecules that can cross the blood-brain barrier (BBB). Nano-delivery strategies are a promising approach that take advantage of natural portals of entry into the brain such as monoclonal antibodies (mAbs) targeting endogenous BBB receptors. However, the main selected mAbs rely on targeting broadly expressed receptors, such as the transferrin and insulin receptors, and in selection processes that do not fully mimic the native receptor conformation, leading to mistargeting and a low fraction of the administered dose effectively reaching the brain. Thus, there is an urgent need to identify new BBB receptors and explore novel antibody selection approaches that can allow a more selective delivery into the brain. Considering that in vitro models fail to completely mimic brain structure complexity, we explored an in vivo cell immunization approach to construct a rabbit derived single-domain antibody (sdAb) library towards BBB endothelial cell receptors. The sdAb antibody library was used in an in vivo phage display screening as a functional selection of novel BBB targeting antibodies. Following three rounds of selections, next generation sequencing analysis, in vitro brain endothelial barrier (BEB) model screenings and in vivo biodistribution studies, five potential sdAbs were identified, three of which reaching &gt;0.6% ID/g in the brain. To validate the brain drug delivery proof-of-concept, the most promising sdAb, namely RG3, was conjugated at the surface of liposomes encapsulated with a model drug, the pan-histone deacetylase inhibitor panobinostat (PAN). The translocation efficiency and activity of the conjugate liposome was determined in a dual functional in vitro BEB-glioblastoma model. The RG3 conjugated PAN liposomes enabled an efficient BEB translocation and presented a potent antitumoral activity against LN229 glioblastoma cells without influencing BEB integrity. In conclusion, our in vivo screening approach allowed the selection of highly specific nano-antibody scaffolds with promising properties for brain targeting and drug delivery

Measurements of neutron cross sections for advanced nuclear energy systems at n_TOF (CERN)

The n_TOF facility operates at CERN with the aim of addressing the request of high accuracy nuclear data for advanced nuclear energy systems as well as for nuclear astrophysics. Thanks to the features of the neutron beam, important results have been obtained on neutron induced fission and capture cross sections of U, Pu and minor actinides. Recently the construction of another beam line has started; the new line will be complementary to the first one, allowing to further extend the experimental program foreseen for next measurement campaigns

Neutron cross-sections for advanced nuclear systems: the n_TOF project at CERN

The study of neutron-induced reactions is of high relevance in a wide variety of fields, ranging from stellar nucleosynthesis and fundamental nuclear physics to applications of nuclear technology. In nuclear energy, high accuracy neutron data are needed for the development of Generation IV fast reactors and accelerator driven systems, these last aimed specifically at nuclear waste incineration, as well as for research on innovative fuel cycles. In this context, a high luminosity Neutron Time Of Flight facility, n_TOF, is operating at CERN since more than a decade, with the aim of providing new, high accuracy and high resolution neutron cross-sections. Thanks to the features of the neutron beam, a rich experimental program relevant to nuclear technology has been carried out so far. The program will be further expanded in the near future, thanks in particular to a new high-flux experimental area, now under construction

Neutron capture cross section measurement of 238U at the CERN n_TOF facility in the energy region from 1 eV to 700 keV

The aim of this work is to provide a precise and accurate measurement of the 238U(n,γ) reaction cross section in the energy region from 1 eV to 700 keV. This reaction is of fundamental importance for the design calculations of nuclear reactors, governing the behavior of the reactor core. In particular, fast reactors, which are experiencing a growing interest for their ability to burn radioactive waste, operate in the high energy region of the neutron spectrum. In this energy region most recent evaluations disagree due to inconsistencies in the existing measurements of up to 15%. In addition, the assessment of nuclear data uncertainty performed for innovative reactor systems shows that the uncertainty in the radiative capture cross section of 238U should be further reduced to 1–3% in the energy region from 20 eV to 25 keV. To this purpose, addressed by the Nuclear Energy Agency as a priority nuclear data need, complementary experiments, one at the GELINA and two at the n_TOF facility, were proposed and carried out within the 7th Framework Project ANDES of the European Commission. The results of one of these 238U(n,γ) measurements performed at the n_TOF CERN facility are presented in this work. The γ-ray cascade following the radiative neutron capture has been detected exploiting a setup of two C6D6 liquid scintillators. Resonance parameters obtained from this work are on average in excellent agreement with the ones reported in evaluated libraries. In the unresolved resonance region, this work yields a cross section in agreement with evaluated libraries up to 80 keV, while for higher energies our results are significantly higher

Experimental neutron capture data of 58Ni from the CERN n_TOF facility

The neutron capture cross section of 58Ni was measured at the neutron time of flight facility n_TOF at CERN, from 27 meV to 400 keV neutron energy. Special care has been taken to identify all the possible sources of background, with the so-called neutron background obtained for the first time using high-precision GEANT4 simulations. The energy range up to 122 keV was treated as the resolved resonance region, where 51 resonances were identified and analyzed by a multilevel R-matrix code SAMMY. Above 122 keV the code SESH was used in analyzing the unresolved resonance region of the capture yield. Maxwellian averaged cross sections were calculated in the temperature range of kT = 5 – 100 keV, and their astrophysical implications were investigated