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[en] This work takes place in the context of the long-term behavior of nuclear glasses under repository conditions. The main objective is to identify, understand and compare the effects of some chemical elements present in the glass composition and/or in the repository media (Zn, Mg, Ni, Co, Fe, Ca, Gd, Ce, K, Cs, Cr and Ag) on the processes involved in glass alteration by water. The cumulative or competitive nature of the effects of these chemical elements was determined. To reach this goal, a 6 oxides simple glass (ISG) has been altered for more than 500 days in a solution containing one or more of the chemical elements of interest. The results indicate that Zn, Mg, Ni, Co and Fe elements increase glass alteration forming secondary phases with the same structure and stoichiometry (tri-octahedral smectites). To form, these silicates consume chemical elements (Si, Al) from the environment and induce a pH decrease until a limiting value of pH. Beyond this pH the precipitation of secondary phases is inhibited and these chemical elements can be integrated into the gel, replacing Ca whose solubility increases at lower pH. As long as they form secondary phases, the effects of these elements are cumulative. Rare earths Gd and Ce also increase glass alteration forming secondary phases but their effects are lower as they contain less silicon. These elements are not integrated in the gel. Chromium increases glass alteration by precipitating with Ca and leading to a less protective gel, depleted in Ca. Silver precipitates as AgCl and has no effect on the alteration of the glass. The chemical elements K, Cs and Ca limit glass alteration by integrating into the gel and slowing down the transport phenomena therein. This integration is competitive: the order of integration (quantity and effectiveness glass alteration limitation) is the following Ca≥≥Cs≥K. Thus, the increase of glass alteration may be proportional to the quantity of elements promoting the precipitation of secondary phases, but the pH decrease limits the process. The effects of the elements that reduce glass alteration by incorporating into the gel are quantitatively limited by the gel composition and its ability to incorporate them, and qualitatively by the nature of the elements. (author)
[fr]Cette these s'inscrit dans l'etude du comportement a long terme des verres nucleaires en conditions de stockage. Son objectif est de determiner, de comprendre et de comparer les effets de certains elements chimiques presents dans la composition du verre et/ou dans le milieu de stockage (Zn, Mg, Ni, Co, Fe, Ca, Gd, Ce, K, Cs, Cr et Ag) sur les differents processus mis en jeux lors de l'alteration aqueuse des verres nucleaires. Dans ce cadre, une attention particuliere a ete portee sur le caractere cumulatif ou competitif des effets de ces elements. Pour cela, un verre simple a 6 oxydes (ISG) a ete altere pendant plus de 500 jours dans une solution contenant un ou plusieurs des elements chimiques d'interet. Les elements Zn, Mg, Ni, Co et Fe augmentent l'alteration du verre en formant des phases secondaires de meme structure (smectites trioctaedriques) et de meme stoechiometrie (a l'element pres). Leur precipitation consomme des elements chimiques du milieu (Si, Al) et induit une diminution de pH. Ce processus se maintient jusqu'a l'atteinte d'un pH limite propre a chaque phase secondaire, au-dessous duquel leur precipitation est inhibee. Par la suite, ces elements peuvent s'integrer dans le gel d'alteration en remplacement du Ca rendu plus soluble par la baisse du pH. Tant qu'ils forment des phases secondaires, les effets de ces elements sont cumulatifs. Les terres rares Gd et Ce induisent une augmentation de l'alteration du verre en formant des phases secondaires, mais leurs effets sont plus faibles car les phases formees sont moins silicatees. Ces elements ne s'integrent pas dans le gel. Le Cr precipite avec le Ca pour former une phase qui appauvrit le gel en Ca, entraine une diminution du pH et augmente l'alteration du verre. Les elements K, Cs et Ca limitent l'alteration du verre en s'integrant dans le gel et en ralentissant les phenomenes de transport en son sein. Cette integration est competitive: l'ordre d'integration (quantite et efficacite sur la limitation de l'alteration) est le suivant Ca ≥≥ Cs ≥ K. L'element Ag precipitant sous forme d'AgCl, n'a pas d'effet sur l'alteration du verre: cette phase ne modifie ni le milieu, ni le developpement de la pellicule d'alteration. Ainsi, l'augmentation de l'alteration pourrait etre proportionnelle a la quantite d'elements favorisant la precipitation de phases secondaires, mais la diminution de pH qui l'accompagne limite ce processus. Les effets des elements qui diminuent l'alteration du verre en s'incorporant dans le gel, sont limites en quantite par la composition du gel et sa capacite a les recevoir, et en qualite par la nature meme des elements
[en] The LPNHE is a joint research unit (UMR 7585) of the National Institute of Nuclear Physics and Particle Physics (IN2P3), Institute of the National Centre for Scientific Research (CNRS), UPMC and Paris Diderot Paris 7. It hosts several research teams and technical services (computers, electronics, mechanical), and two support services (administration, logistics). The laboratory is engaged in several major experimental programs pursued in the framework of international collaborations with very large research facilities around the world, centers of particle accelerators and observatories. The research programs cover current issues in particle physics, astro-particle and cosmology. This report presents the activities of the laboratory during the years 2010-2012: 1 - Forewords; 2 - Highlights; 3 - Research: Masses and FUNDAMENTAL INTERACTIONS; Matter-antimatter asymmetry; Dark matter and dark energy; Cosmic radiation nature and origin; Publications, communications; 2 - Teaching, training, internships and PhDs; 3 - Competences and technical realisations (electronics and instrumentation, computers, mechanics departments, expertise and valorisation, conference participation, responsibilities); 4 - Laboratory operation (organisation, partnerships, financial and human resources, permanent training, communication and library, health and safety, radiation protection, general services, staff); 5 - Scientific life and communication (seminars, meetings..)
[en] An empirical relationship describing the bulk etch rate is formulated. The equation involves two free fitting parameters, which reproduce the bulk etch rate for CR-39 by alpha particles at different normalities of the etching solution. The values of the fitting parameters were obtained from the experimental data. This relationship is used to predict the bulk etch rate at different normalities. - Highlights: • Digital image processing is used to study bulk etch rate in CR-9 track detectors. • The track and bulk etch rate were determined from the change of track length and track diameter with time. • An equation with two fit parameters describing relation of bulk etch rate and etching solution concentration is introduced.
[en] This study focuses on investigating a new model of combined backscatter and transmission method for nuclear densitometer. In this method for density measurement, a true combination of transmission and backscatter methods was studied and related equations were developed. The MCNP4C code was used for simulation of this combined detector model (CDM) and by applying theoretical calculations, density equation was corrected for the proposed nuclear densitometer. In the new method presented here, the buildup effect was estimated by an online system that was improved in our laboratory and was replaced by a new conceptual calculation. Hence, for the purpose of buildup reduction, there was no need for the shield around the detector, as it was monitored and reduced online. Furthermore, this study showed that the RSQ function could be improved by the CDM. The measurement technique proposed in this study has a better linearity trend than the transmission technique. Thus, the ability of CDM to improve the accuracy of the nuclear densitometer was shown. - Highlights: • Combination of backscatter and transmission methods in nuclear densitometer. • On-line buildup monitoring and on-line buildup reduction. • The error of combined detectors model is less than transmission model. • R-squared value improved in comparison to the transmission technique. • In combination method no shielding needs around the detectors.
[en] Several terbium isotopes are suited for diagnosis or therapy in nuclear medicine. Tb-155 is of interest for SPECT imaging and/or Auger therapy. High radionuclide purity is mandatory for many applications in medicine. The quantification of the activity of the produced contaminants is therefore as important as that of the radionuclide of interest. The experiments performed at the ARRONAX cyclotron (Nantes, France), using the deuteron beam delivered up to 34 MeV, provide an additional measurement of the excitation function of the Gd-nat(d,x)Tb-155 reaction and of the produced terbium and gadolinium contaminants. In this study, we investigate the achievable yield for each radionuclide produced in natural gadolinium as a function of the deuteron energy. Other reactions are discussed in order to define the production route that could provide Tb-155 with a high yield and a high radionuclide purity. This article aims to improve data for the Gd-nat(d,x) reaction and to optimize the irradiation conditions required to produce Tb-155. - Highlights: • The medical interest of terbium-155. • Deuteron induced reactions on natural gadolinium up to 34 MeV. • Excitation functions measured with the stacked-foil technique. • Comparison with the TALYS code version 1.6. • Tb-155 achievable yield and radionuclide purity.
[en] A criticality analysis was benchmarked to sub-criticality measurements of the hexagonal fuel storage racks at the United States Geological Survey TRIGA MARK I reactor in Denver. These racks, which hold up to 19 fuel elements each, are arranged at 0.61 m (2 feet) spacings around the outer edge of the reactor. A 3-dimensional model was created of the racks using MCNP5, and the model was verified experimentally by comparison to measured subcritical multiplication data collected in an approach to critical loading of two of the racks. The validated model was then used to show that in the extreme condition where the entire circumference of the pool was lined with racks loaded with used fuel the storage array is subcritical with a k value of about 0.71; well below the regulatory limit of 0.8. A model was also constructed of the rectangular 2×10 fuel storage array used in many other TRIGA reactors to validate the technique against the original TRIGA licensing sub-critical analysis performed in 1966. The fuel used in this study was standard 20% enriched (LEU) aluminum or stainless steel clad TRIGA fuel. - Highlights: • Benchmarking subcritical neutron flux experiment performed on USGS TRIGA reactor in Denver. • A MCNP5 Monte Carlo model was constructed and validated against the experimental results. • Model is used to validate the safety of the fuel storage rack configuration used at the USGS TRIGA reactor and other facilities.
[en] A well-defined neutron spectrum is essential for many types of experimental topics and is also important for both calibration and testing of spectrometric and dosimetric detectors. Provided it is well described, such a spectrum can also be employed as a reference neutron field that is suitable for validating selected cross sections. The present paper aims to compare calculations and measurements of such a well-defined spectra in geometrically similar cores of the LR-0 reactor with fuel containing slightly different enrichments (2%, 3.3% and 3.6%). The common feature to all cores is a centrally located dry channel which can be used for the insertion of studied materials. The calculation of neutron and gamma spectra was realized with the MCNP6 code using ENDF/B-VII.0, JEFF-3.1, JENDL-3.3, ROSFOND-2010 and CENDL-3.1 nuclear data libraries. Only minor differences in neutron and gamma spectra were found in the comparison of the presented reactor cores with different fuel enrichments. One exception is the gamma spectrum in the higher energy region (above 8 MeV), where more pronounced variations could be observed. - Highlights: • Neutron spectra in special cores of similar geometry and various enrichment. • Comparison of the experimental data with calculation. • Discrepancies between calculational and experimental neutron spectra.
[en] A simple and highly efficient (shorter reaction time and almost no rework) method for production of iodine based radioactive silver seed cores for brachytherapy is described. The method allows almost quantitative deposition of iodine-131 on dozens of silver substrates at once, with even distribution of activity per core and insignificant amounts of liquid and solid radioactive wastes, allowing the fabrication of cheaper radioactive iodine seeds for brachytherapy. - Highlights: • Quantitative deposition of iodine-125 on silver cores for brachytherapy • Simple and efficient production process of radioactive silver cores. • Reproducible process with homogeneous distribution of activity. • Large scale batch production of iodine radioactive cores.
[en] The present paper describes the prototype of a calibration standard system for radon concentrations to be used in establishing the traceability of radon concentration measurements in dwellings. Radon gas was generated with a radium-226 solid source in a certified volume as a closed system. The activity of the radon that was released in the closed system was determined from the difference between the absolute activity of the standard radium solid source and the residual radon decay products ("2"1"4Bi or "2"1"4Pb). A high-purity germanium (HPGe) detector, which was calibrated using gamma reference standard sources, was used to measure the activity of a radium solid source and radon decay products ("2"1"4Bi or "2"1"4Pb). The emanation factor of the "2"2"6Ra source was controlled online with the HPGe detector. Radon activity was achieved at ~1500±45 Bq from the radium source at 3.95±0.2 kBq under equilibrium conditions. After this activity, the radon gas was transferred into the closed system producing radon activity concentrations of 31.1±0.3 kBq/m"3. Systematic errors were found of less than 4% with a random error around 0.5%. The random error is generally associated with the estimation of the count rate of the measured radon progenies ("2"1"4Po and "2"1"4Po for alpha measurements or "2"1"4Pb and "2"1"4Bi for gamma measurements), but systematic errors are associated with the errors introduced by the instrumentation and measurement technique. The system that was developed has a high degree of accuracy and can be recommended as a national or regional prototype standard of radon activity concentration to calibrate different working radon measurement devices. - Highlights: • Prototype of radon concentration standard system for calibration is presented. • The system uses a certified solid "2"2"6Ra source and HPGe detector in closed system. • Developed radon concentration standard system offers high accuracy and reliability.
[en] A fully automated system was developed to produce rubidium-81 ("8"1Rb), based on the "n"a"tKr (p, n) "8"1Rb reaction. The energy incident on the target was 26 MeV. Only 6 MeV was stopped inside the gas and the remainder was stopped by a specially designed flange. The target body was characterized by its conical shape and its inner walls were chemically plated with 100±10 µm of nickel (Ni). Ni is advantageous as a fairly good conductor of heat whose surface can resist solutions. Additionally, the Ni plated target allowed potassium chloride to dissolve "8"1Rb, with no further effect on the target body. The system produced "8"1Rb with a production yield of approximately 4.5 mCi/µA h, which is close to the calculated expected yield of 5.3 mCi/µA h. The system is able to deliver reliable and reproducible radioactivity for patients and can be operated up to 1500 µA h before preventive maintenance is due. Key steps in designing the "8"1Rb target for selected energy ranges are reported here.