Filtern
Erscheinungsjahr
Dokumenttyp
- Zeitschriftenartikel (19)
- Buchkapitel (3)
- Beitrag zu einem Tagungsband (3)
- Beitrag zu einem Sammelband (2)
- Sonstiges (2)
- Forschungsbericht (2)
- Vortrag (1)
- Posterpräsentation (1)
Schlagworte
- Archaeometry (5)
- Cultural heritage (5)
- Storage (3)
- Transport (3)
- Betoninstandsetzung (2)
- Flame retardance (2)
- Lagerung (2)
- Polyesters (2)
- Spent fuel (2)
- 3D X-ray spectroscopy (1)
Organisationseinheit der BAM
- 3 Gefahrgutumschließungen; Energiespeicher (5)
- 3.4 Sicherheit von Lagerbehältern (5)
- 6 Materialchemie (2)
- 3.3 Sicherheit von Transportbehältern (1)
- 5 Werkstofftechnik (1)
- 5.6 Glas (1)
- 6.1 Oberflächen- und Dünnschichtanalyse (1)
- 6.2 Material- und Oberflächentechnologien (1)
- 6.6 Physik und chemische Analytik der Polymere (1)
Eingeladener Vortrag
- nein (1)
Spent fuel storage periods well beyond those originally foreseen are a reality. This publication offers several ideas and approaches that may be considered to address the increasingly longer storage times. The aim is to raise awareness, encourage dialogue and provide ideas on how to manage spent fuel. Key messages include the following:
- Delays in reprocessing or disposal could result in spent fuel being stored for 100 years or longer. Safe, secure and effective storage of spent fuel manages fuel degradation while preserving future fuel cycle options.
- Ageing management programmes apply engineering, operations and maintenance actions to ensure safety is maintained during storage, future handling and transport.
- Site selection and facility and equipment design can significantly reduce the risks and costs of spent fuel storage over longer periods.
- Spent fuel storage configurations can be selected to accommodate uncertain storage periods, to facilitate ageing management and to provide flexibility needed to accommodate the uncertainty of future end points, such as reprocessing or disposal.
- By considering multiple licence renewals, regulatory frameworks can be designed to ensure safe storage until an acceptable end point is achieved.
- Safety can be assured by maintaining shielding, containment, decay heat removal and criticality control. Navigating the complexity of societal beliefs and values, as well as political systems, has proven to be a greater challenge for the management of spent fuel than maintaining its safety and security or addressing the technical and economic aspects.
- Sustainable spent fuel management requires policies and strategies to provide a clear, consistent and stable direction because they drive the need for spent fuel storage as well as the available options and timing for achieving an acceptable end point. Unless States address spent fuel reprocessing and disposal on a sufficient scale to accommodate their spent fuel discharges, then storage for longer and longer periods becomes the de facto end point — which is not considered to be consistent with the responsibility to protect human health and the environment.
An effective, periodic licence renewal process can ensure effective ageing management and strong institutional control. Hence, spent fuel can be safely and securely stored for as long as it may be necessary until transport for reprocessing or disposal. However, the risks and costs of storing the growing inventory of spent fuel will continue to increase; and in the absence of an end point, it will eventually become a significant societal burden.
Despite their enormous diversity, the bauplan of adult winged insects (pterygotes) is remarkably conservative since the Lower Devonian: a five-segmented head, a three-segmented thorax with three pairs of walking legs and an eleven-segmented abdomen without any non-sexual appendages 1 and 2. The only known exceptions are the abdominal appendages of adult male sepsid flies on the fourth segment; however, these are also used as copulatory organs and are supposedly maintained through sexual selection [3]. Here, we report a rod-like paired appendage from the third and fourth abdominal segments in adults of the Southeast-Asian Hemiptera taxon Bennini (Figure 1A,B; Supplemental information). These are fully musculated, innervated, and movable and bear highly organized sensory and secretory units. The appendages, termed LASSO (lateral abdominal sensory and secretory organs), are consistent in topology and structure in all species studied and not sexually dimorphic. The existence of these non-sexual abdominal appendages reveals the potential of the 300 million year old conserved bauplan of insects.
The molecular dynamics of two addition type polynorbornenes, exo-PNBSiand PTCNSi1, bearing microporosity has been investigated by broadbanddielectric spectroscopy, fast scanning calorimetry, and neutron scattering. Bothpolymers have the same side groups but different backbones. Due to theirfavorable transport properties, these polymers have potential applications inseparation membranes for gases. It is established in literature that molecularfluctuations are important for the diffusion of small molecules through poly-mers. For exo-PNBSi, two dielectric processes are observed, which are assignedto Maxwell/Wagner/Sillars (MWS) process due to blocking of charge carriersat internal voids or pore walls. For PTCNSi1, one MWS-polarization process isfound. This points to a bimodal pore-size distribution for exo-PNBSi. A glasstransition for exo-PNBSi and for PTCNSi1 could be evidenced for the first timeusing fast scanning calorimetry. For Tgand the corresponding apparent activa-tion energy, higher values were found for PTCNSi1 compared to exo-PNBSi.For both polymers, the neutron scattering data reveal one relaxation process.This process is mainly assigned to methyl group rotation probably overlayedby carbon–carbon torsional fluctuations.
Die Zielsetzung dieses Projektes war es, ein kombiniertes Schutzsystem aus Spritzverzinkung und abdichtendem Oberflächenschutzsystem für die Instandsetzung chloridbelasteter und korrosionsgeschädigter Stahlbetonbauteile zu entwickeln. Dabei soll die Spritzverzinkung der Betonoberfläche in den ersten Jahren nach der Instandsetzung einen kathodischen Korrosionsschutz der Bewehrung bewirken, bis der Beton infolge des Oberflächenschutzsystems soweit ausgetrocknet ist, dass auch ohne kathodischen Schutz praktisch keine Korrosion der Bewehrung mehr stattfinden kann.
Anhand von Untersuchungen zur Haftung zwischen Beton, Zinkschicht und verschiedenen Oberflächenschutzsystemen wurde der Aufbau des kombinierten Schutzsystems entwickelt. Es wurden verschiedene OS-11a-Systeme ein OS-13-System sowie zwei Systeme nach ZTV-ING, Teil 7 vor und nach künstlicher Bewitterung untersucht. Anhand der Ergebnisse wurde für das kombinierte System ein OS-11a-System ausgewählt und im weiteren hinsichtlich der Wirksamkeit des kathodischen Schutzes sowie hinsichtlich der Austrocknung des Betons untersucht.
Es zeigte sich sowohl an ausgelagerten Prüfköpfen sowie auf einer angelegten Versuchsfläche auf Freideck eines Parkhauses, dass ein wirksamer galvanischer kathodischer Korrosionsschutz der Bewehrung nur bei sehr hohen Chloridgehalten (4 M.-% bezogen auf den Zementgehalt) erreicht werden kann. Bei geringeren untersuchten Chloridgehalten kam es vermutlich infolge der Austrocknung der Zink/Beton-Kontaktzone nach relativ kurzer Zeit zu einer Inaktivierung des Zinks. Bei Chloridgehalten von 4 M.-% bildeten sich zwischen der Zinkschicht und dem ausgewählten OS-System gasgefüllte Blasen. Diese Problematik, sowie die Tatsache dass die Wirksamkeit des Prinzips W (Austrocknung des Betons) bei derart hohen Chloridgehalten bezweifelt werden muss, grenzt die Anwendbarkeit des Kombinationssystems mit der Zinkschicht als Opferanode deutlich ein.
An neun Jahre alten, ausgelagerten Prüfköpfen durchgeführte Untersuchungen zeigten jedoch, dass mittels Fremdstrombeaufschlagung zwischen Zinkschicht und Bewehrung ein wirksamer kathodischer Schutz auch bei geringeren Chloridgehalten erreicht werden kann. Der Einsatz des entwickelten Kombinationssystems mit Fremdstrombeaufschlagung erscheint somit durchaus durchführbar. Dabei sollte der Fremdstrom jedoch vorsichtig dosiert werden, um den Haftverbund zum Zink nicht zu sehr zu schwächen.
Das Ziel des Vorhabens wurde somit erreicht.
A combination of 3D micro X-ray fluorescence spectroscopy (3D micro-XRF) and micro-XRF was utilized for the investigation of a small collection of highly heterogeneous, partly degraded Dead Sea Scroll parchment samples from known excavation sites. The quantitative combination of the two techniques proves to be suitable for the identification of reliable marker elements which may be used for classification and provenance studies. With 3D micro-XRF, the three-dimensional nature, i.e. the depth-resolved elemental composition as well as density variations, of the samples was investigated and bromine could be identified as a suitable marker element. It is shown through a comparison of quantitative and semiquantitative values for the bromine content derived using both techniques that, for elements which are homogeneously distributed in the sample matrix, quantification with micro-XRF using a one-layer model is feasible. Thus, the possibility for routine provenance studies using portable micro-XRF instrumentation on a vast amount of samples, even on site, is obtained through this work.
The aim of the research project 'Typology of
Dutch Drawing' was to establish an interdisciplinary approach
for investigating heterogeneous drawing collections.
To define a type common to a group of drawings, we
determine elements that are common to them based on style
and the use of identical materials. To that end, we investigated
about 750 Dutch drawings from the sixteenth century at the
Dresden Kupferstich-Kabinett using art historical and
scientific methods. In this work, we present a detailed
analysis of 30 drawings ascribed to the Egmont Master.
The Erfurt Hebrew Giant Bible and the Experimental XRF Analysis of Ink and Plummet Composition
(2007)
In this work, the applicability of a new 3D micro X-ray fluorescence (3D Micro-XRF) laboratory spectrometer for the investigation of historical glass objects is demonstrated. The non-destructiveness of the technique and the possibility to measure three-dimensionally resolved fluorescence renders this technique into a suitable tool for the analysis of cultural heritage objects. Although absorption and resolution effects complicate qualitative analysis of the data, layered structures can be distinguished from homogeneous samples without the need for full quantification. Different manufacturing techniques were studied in this work with the help of hand-made reference samples. With the gained knowledge it could be shown for the investigated historical glass object, that black enamel as a stained glass contour colour was used in a cold painting. The object was not fired after the application of the black enamel, but instead the adhesion of the paint was solely provided through organic binding agents and the backing with metal foils. Thus, for the manufacturing of the object, a mixture of cold painting technique with a stained glass color was used. Quantitative measurements with a 3D Micro-XRF setup at the Berlin synchrotron BESSY II confirm the assumptions drawn on the basis of the qualitative investigation with the 3D Micro-XRF spectrometer with X-ray tube excitation.
Mit Veröffentlichung der europäischen Normenreihe EN 1504 in den Jahren 2004 bis 2008 mussten in Deutschland die bisherigen nationalen Regelungen für die Instandsetzung von standsicherheitsrelevanten Betonbauteilen angepasst werden. Im vorliegenden Entwurf der neuen Instandhaltungs-Richtlinie wurden die Hinweise zur Planung und Durchführung von Instandsetzungsmaßnahmen aus der Instandsetzungsrichtlinie des DAfStb von 2001 entsprechend überarbeitet und aufgrund neuer Erkenntnisse ergänzt. Außerdem wurde das Regelwerk um Gesichtspunkte der Instandhaltung erweitert, sodass die Aspekte Wartung, Inspektion und Verbesserung nun in Anlehnung an DIN 31051 berücksichtigt werden. Zudem wurden Regelungen aus der ZTV-ING sowie der ZTV-W übernommen. Im ersten Teil dieses Artikels geben wir einen Überblick über die Gliederung und wesentliche neue Inhalte wie die Ausweitung der Instandsetzungsprinzipien.
In einer Artikelserie stellen wir die neue Instandhaltungs-Richtlinie des Deutschen Ausschusses für Stahlbeton (DAfStb) vor. Im zweiten Teil geht es um Betonersatz- und Oberflächenschutzsysteme sowie Rissfüllstoffe. Es werden als Folge des EuGH-Urteils vom Oktober 2014 zukünftig keine Anforderungen an Bauprodukte mit dem Nachweis über allgemeine bauaufsichtliche Prüfzeugnisse gestellt. Stattdessen werden auf Basis der Anforderungen individueller Bauwerke notwendige Merkmale von Bauprodukten für die Instandsetzung definiert. Außerdem wird Teil 3 der neuen Instandhaltungs-Richtlinie "Ausführung der Instandsetzung und Überwachung" vorgestellt. Neu ist hier die Einführung von Überwachungsklassen, die sich aus der Art des instand zu setzenden Betonbauteils (standsicherheitsrelevant oder nicht) und der auszuführenden Arbeiten ergeben, zum Beispiel Instandsetzung oder Verstärkung. Am Ende dieses Artikels wird kurz der 4. Teil der neuen Instandhaltungs-Richtlinie erläutert.
Polycapillary halflenses are widely used to focus X-ray radiation onto a small spot. Additionally they can reduce the field of view of a semiconductor detector when placed in front of one. In 3D micro X-ray fluorescence spectroscopy (3D Micro-XRF) with synchrotron radiation, two polycapillary halflenses are used in a confocal geometry. Up until now, characterization measurements in the focal plane have only been performed in the case of the lens focusing parallel radiation. Assumptions have been made, that in the other case, when isotropic radiation from a spot source is transported to a detector, the acceptance distribution in the focal plane is also Gaussian. We performed measurements with an electron beam as well as a proton beam which confirm this assumption. In addition, a comparison between measurements in collecting and focusing mode show differences in spot size and transmission. These differences exemplify the fact that there is not one global spot size or transmission function of a polycapillary halflens. Illumination and divergence effects can alter both characteristic lens parameters.
Bei der Abschätzung der Beständigkeit von Kunststoffen gegenüber niedermolekularen Flüssigkeiten ist die Kohäsionsenergiedichte CED ein wichtiger Parameter auf molekularer Ebene. Die Vernetzungsdichte ν eines polymeren Festkörpers bildet hierbei einen bedeutsamen Kennwert, der darüber hinaus neben der Löslichkeit wichtige Eigenschaften wie thermische Stabilität und Steifigkeit des Materials charakterisiert. Für die experimentelle Bestimmung von CED und ν eignet sich die Untersuchung des Quellverhaltens in unterschiedlichen Lösungsmitteln. Es werden zwei Messmethoden miteinander verglichen und die Ergebnisse unter Berücksichtigung des molekularen Aufbaus von Proben aus Polyurethan (PU) und hochmolekularem – (HMWPE) und ultrahochmolekularem Polyethylen (UHMWPE) diskutiert. Zum Verständnis des Quellverhaltens dieser Polymerproben in niedermolekularen Lösungsmitteln werden neben den Messergebnissen Literaturdaten zu Grunde gelegt.
German approach and feedback on experience of transportability of SNF packages after interim storage
(2014)
In Germany, the concept of dry interim storage of spent fuel in dual purpose metal casks is implemented, currently for periods of up to 40 years. The casks being used have an approved package design in accordance with the international transport regulations. The license for dry storage is granted on the German Atomic Energy Act with respect to the recently revised 'Guidelines for dry interim storage of irradiated fuel assemblies and heat-generating radioactive waste in casks' by the German Waste management Commission. For transport on public routes between or after long term interim storage periods, it has to be ensured that the transport and storage casks fulfil the specifications of the transport approval or other sufficient properties, which satisfy the proofs for the compliance of the safety objectives at that time. In recent years, the validation period of transport approval certificates for manufactured, loaded and stored packages were discussed among authorities and applicants. A case dependent system of 3, 5 and 10 years was established. There are consequences for the safety cases in the Package Design Safety Report, including evaluation of long term behaviour of components and specific operating procedures of the package. The present research and knowledge concerning the long term behaviour of transport and storage cask components have to be consulted as well as experiences from interim cask storage operations. Challenges in the safety assessment are e.g. the behaviour of aged metal and elastomeric gaskets under IAEA test conditions to ensure that the results of drop tests can be transferred to the compliance of the safety objectives at the time of transport after the interim storage period. Assessment methods for the material compatibility, the behaviour of fuel assemblies and the aging behaviour of shielding parts are issues as well. This paper describes the state of the art technology in Germany, explains recent experience on transport preparation after interim storage and points out arising prospective challenges.
Determining a suitable and reliable end-of-lifetime criterion for O-ring seals is an important issue for long-term seal applications. Therefore, seal failure of ethylene propylene diene rubber (EPDM) and hydrogenated nitrile butadiene rubber (HNBR) O-rings aged in the compressed state at 125 °C and at 150 °C for up to 1.5 years was analyzed and investigated under static conditions, using both non-lubricated and lubricated seals. Changes of the material properties were analyzed with dynamic-mechanical analysis and permeability experiments. Indenter modulus measurements were used to investigate DLO effects. It became clear that O-rings can remain leak-tight under static conditions even when material properties have already degraded considerably, especially when adhesion effects are encountered. As a feasible and reliable end-of-lifetime criterion for O-ring seals under static conditions should include a safety margin for slight dimensional changes, a modified leakage test involving a small and rapid partial decompression of the seal was introduced that enabled determining a more realistic but still conservative end-of-lifetime criterion for an EPDM seal.
Spent nuclear fuel which is generated in the operation of nuclear reactors needs to be safely managed following its removal from the reactor core. On-site power reactor storage pools were designed on the assumption that after a short period of time spent nuclear fuel would be removed for reprocessing and disposal or further storage elsewhere. The amount of highly radioactive spent fuel that needs to be stored over longer periods of time is growing and additional storage capacity is required. One of the widely used options for additional storage capacity is the use of casks for dry storage of spent fuel. Among various existing dry storage concepts, several Member States are utilizing a concept of dual purpose casks (DPCs). This publication provides practical advice on the structure and contents of a DPC integrated safety case with reference to existing IAEA requirements relevant to the licensing and use of transport and storage casks for spent fuel.
Bulk metallic glasses (BMG) are amorphous metal alloys known for their unique physical and mechanical properties. In the present study, the formation of femtosecond (fs) laser-induced periodic surface structures (LIPSS) on the Zr-based BMGs Zr46Cu46Al8, Zr61Cu25Al12Ti2, Zr52.5Cu17.9Al10Ni14.6Ti5 (Vit105) and Zr57Cu15.4Al10Ni12.6Nb5 (Vit106) was investigated as a function of their different chemical composition. For this purpose, LIPSS were generated on the sample surfaces in an air environment by fs-laser irradiation (λ = 1025 nm, τ = 300 fs, frep = 100 kHz). The surface topography was characterized by scanning electron microscopy and atomic force microscopy. Moreover, the impact of LIPSS formation on the structure and chemical surface composition was analyzed before and after fs-laser irradiation by X-ray diffraction and X-ray photoelectron spectroscopy as well as by transmission electron microscopy in combination with energy dispersive X-ray spectroscopy. Despite the different chemical composition of the investigated BMGs, the fs-laser irradiation resulted in almost similar properties of the generated LIPSS patterns. In the case of Zr61Cu25Al12Ti2, Vit105 and Vit106, the surface analysis revealed the preservation of the amorphous state of the materials during fs-laser irradiation. The study demonstrated the presence of a native oxide layer on all pristine BMGs. In addition, fs-laser irradiation results in the formation of laser-induced oxide layers of larger thickness consisting of an amorphous ZrAlCu-oxide. The precise laser-structuring of BMG surfaces on the nanoscale provides a versatile alternative to thermoplastic forming of BMG surfaces and is of particular interest for the engineering of functional material surfaces.
It is important to evaluate the effect of thermal ageing on the sealing performance of metal gaskets under high temperature for long-term usage. Therefore, in order to gain representative data for this kind of metal-sealed lid System, BAM is currently performing laboratory tests of different gasket types with aluminum and silver jackets at three different temperatures under static conditions up to four years so far, using test flanges for gaskets with full scale cross section diameter but much smaller outer diameter. On the other hand, in order to investigate the applicability of the numerical methodology to evaluate the long-term behavior of the metal gaskets, such as a correlation between seal pressure force and holding time, CRIEPI is developing a modeling method including material tests (tensile and creep tests) at high temperature. In this paper, the applicability of the finite element method (ABAQUS) to predict the recovery displacement and residual seal pressure force of the gasket complex was verified by comparing the calculated values with BAM’s laboratory test results under the joint research agreement between BAM and CRIEPI.
German approach and experience feedback of transport ability of SNF packages after interim storage
(2013)
In Germany the concept of dry interim storage of spent fuel in dual purpose metal casks is implemented, currently for periods of up to 40 years.
The casks being used have an approved package design in accordance with the international transport regulations. The license for dry storage is granted on the German Atomic Energy Act with respect to the recently revised “Guidelines for dry interim storage of irradiated fuel assemblies and heat-generating radioactive waste in casks” by the German Waste management Commission (ESK).
For transport on public routes between or after long term interim storage periods, it has to be ensured that the transport and storage casks fulfil the specifications of the transport approval or other sufficient properties which satisfy the proofs for the compliance of the safety objectives at that time.
In recent years the validation period of transport approval certificates for manufactured, loaded and stored packages were discussed among authorities and applicants. A case dependant system of 3, 5 and 10 years was established. There are consequences for the safety cases in the Package Design Safety Report including evaluation of long term behavior of components and specific operating procedures of the package.
Present research and knowledge concerning the long term behavior of transport and storage cask components have to be consulted as well as experiences from interim cask storage operations. Challenges in the safety assessment are e.g. the behavior of aged metal and elastomeric gaskets under IAEA test conditions to ensure that the results of drop tests can be transferred to the compliance of the safety objectives at the time of transport after the interim storage period.
Abstract Hydrogenated nitrile butadiene rubber (HNBR) elastomer was thermo-oxidatively aged at different temperatures up to 150 °C. Fourier transform infrared spectroscopy (FTIR), compression stress relaxation (CSR) and international rubber hardness degree (IRHD) microhardness were used to characterise the chemo-mechanical changes of HNBR O-rings during thermo-oxidative ageing. FTIR shows the development of carbonyl, methyl and ester groups but the nitrile content was not affected by ageing. The effect of sample geometry during CSR was investigated. CSR data were converted through integrated kinetic laws. The conversion has proven its sensibility to detect heterogeneous ageing. This was confirmed by the IRHD measure-ments across the section of O-rings. The influence of compression during ageing was assessed through IRHD measurements across the section of compressed and uncom-pressed aged O-rings. The DLO effect was more pronounced in compressed O-rings. By applying the model of Wise et al., theoretical IRHD and oxidation profiles were determined on the basis of IRHD experimental data of compressed O-rings. Good agreements between the experimental and the theoretical IRHD profiles in the core region were obtained. However, near the edge, the theoretical IRHD values were overestimated.
Flame retardancy for thermoplastics is a challenging task where chemists and engineers work together to find solutions to improve the burning behavior without strongly influencing other key properties of the material. In this work, the halogen-free additives aluminum diethylphosphinate (AlPi-Et) and a mixture of aluminum phosphinate (AlPi) and resorcinol-bis(di-2,6-xylyl phosphate) (AlPi-H + RXP) are employed in neat and reinforced poly(butylene terephthalate) (PBT), and the morphology, mechanical performance, rheological behavior, and flammability of these materials are compared. Both additives show submicron dimensions but differ in terms of particle and agglomerate sizes und shapes. The overall mechanical performance of the PBT flame-retarded with AlPi-Et is lower than that with AlPi-H-RXP, due to the presence of larger agglomerates. Moreover, the flow behavior of the AlPi-Et/PBT materials is dramatically changed as the larger rod-like primary particles build a percolation threshold. In terms of flammability, both additives perform similar in the UL 94 test and under forced-flaming combustion. Nevertheless, AlPi-Et performs better than AlPi-H + RXP in the LOI test. The concentration required to achieve acceptable flame retardancy ranges above 15 wt %.
Flame retarded poly(butylene terephthalate) (PBT) is required for electronic applications and is mostly achieved by low molar mass additives so far. Three phosphorus-containing polyesters are suggested as halogen-free and polymeric flame retardants for PBT. Flame retardancy was achieved according to cone calorimeter experiments showing that the peak heat release rate and total heat evolved were reduced because of flame inhibition and condensed-phase activity. The presented polymers containing derivatives of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide form immiscible blend systems with PBT. Shear-rheology shows an increase in storage moduli at low frequencies. This is proposed as quantitative measure for the degree of phase interaction. The phase structure of the blends depends on the chemical structure of the phosphorus polyester and was quite different, depending also on the viscosity ratio between matrix and second phase. A lower viscosity ratio leads to two types of phases with spherical and additionally continuous droplets. Addition of the flame retardants showed no influence on the dielectric properties but on the mechanical behavior. The polymeric flame retardants significantly diminish the impact strength because of several reasons: (1) high brittleness of the phosphorus polyesters themselves, (2) thermodynamic immiscibility, and (3) weak phase adhesion. By adding a copolymer consisting of the two base polymers to the blend, an improvement of impact strength was obtained. The copolymer particularly acts as compatibilizer between the phases and therefore leads to a smaller phase size and to a stronger phase adhesion due to the formation of fibrils.
Quantum dots (QDs) are remarkable semiconductor nanoparticles, whose optical properties are strongly size-dependent. Therefore, the real-time monitoring of crystal growth pathway during synthesis gives an excellent opportunity to a smart design of the QDs luminescence. In this work, we present a new approach for monitoring the formation of QDs in aqueous solution up to 90 °C, through in situ luminescence analysis, using CdTe as a model system. This technique allows a detailed examination of the evolution of their light emission. In contrast to in situ absorbance analysis, the in situ luminescence measurements in reflection geometry are particularly advantageous once they are not hindered by the concentration increase of the colloidal suspension. The synthesized particles were additionally characterized using X-ray diffraction analysis, transition electron microscopy, UV-Vis absorption and infrared spectroscopy. The infrared spectra showed that 3-mercaptopropionic acid (MPA)-based thiols are covalently bound on the surface of QDs and microscopy revealed the formation of CdS. Setting a total of 3 h of reaction time, for instance, the QDs synthesized at 70, 80 and 90 °C exhibit emission maxima centered at 550, 600 and 655 nm. The in situ monitoring approach opens doors for a more precise achievement of the desired emission wavelength of QDs.
This publication summarizes the work carried out during an IAEA coordinated research project (CRP) on safe and reliabe management of spent nuclear fuel. This work contributes to the overall goal of demonstrating the performance of spent nuclear fuel and related storage systems components over long durations, and facilitates the transfer of this knowledge to Member States. The technical areas addressed by the CRP participants were related to potential degradation mechanisms in metal casks and concrete overpacks, such as stress corrosion cracking; long term integrity and performance of the fuel cladding; thermo-mechanical behaviour of the metal seals; and long term gamma and neutron shielding capability. The participants also considered past and ongoing demonstration programmes. For each technical topic addressed the main conclusions have been drawn, including information on the development of specific monitoring and inspection techniques as well as future opportunities for closing relevant data gaps. A major achievement is also the establishment of a worldwide network of experts working on current research projects to demonstrate the long term performance of spent fuel in dry storage systems.