[en] Located about 30 km south of the ancient Carthage (present Tunis, Tunisia), the hot spring of Jebel Oust is a great model of the interactions between travertine – i.e., hydrothermal waters deposits - and human activities. The exploitation of this hot spring since Roman times has led to the transition from a natural gentle slope deposit model to one with anthropogenic controls on carbonate deposit. This results in a larger diversity of morphologies and facies of the travertine. The ancient sanctuary built just above the vent of the hot spring is dominated by ironrich hydrothermal deposits. A deep underground aqueduct, providing hot waters from the spring to well-preserved Roman baths located downstream, is mostly filled with puff-pastry travertine and some terrigenous sediments. Finally, the travertine preserved in the baths complex show several morphologies and facies due to the diversity of human structures. Hot pools are filled with alternate dark/bright laminated travertine, whereas the tepid ones are characterized by alternate dense/porous laminate deposits - marked by a biological influence - and pools used as tanks (colder waters) are filled with spongy fabric travertine showing higher isotopic values of δ 13C and δ 18O. Facies of water canalizations and pipes, with a well-known particular morphology, and some crystalline crusts travertine forming small cascades, which are correlated to the decay of the site during Late Antiquity, complete the whole deposits panel. These anthropogenic travertines truly reflect strong human forcing on the environment and the palaeohydrological dynamics of the hot spring. Moreover, their sedimentological and geochemical features are great sedimentary records of past human engineering and management of waters. (author)

[en] Fowler - Nordheim current in Si-poly (n⁺)-SiO₂ - Si(p) structures, with an oxide thickness varying between 3 and 12 nm, has been measured and numerically computed with the exact electric field in the oxide, the field dependence of the barrier shape with the image force, and the temperature effects. The fit of the experimental data leads to an accurate determination of the electron affinity difference and the barrier height at the emitting Si - poly (n⁺)-gate-electrode - oxide interface. The evolution of these two parameters with temperature is discussed in relation with the oxide thickness. [copyright] 2001 American Institute of Physics

[en] Many perennial species, such as trees, show large variations of fruit production between years (the so-called masting) which can have major consequences on forest dynamic and species interactions. Among other drivers of fruit production failure, years of reduced fruit production can be due to the increase of temperature and the resulting advance in vegetative and reproductive phenology and timing of extreme events, such as drought or late frost. Indeed, flowers may fail to complete their maturation due to a ‘veto’ effect, i.e. variation of climatic conditions, promoting pollen limitation, fruit abscission, or more generally inducing reproductive failure. This veto effect may alter reproductive cycle which in turn impacts forest ecosystem functioning. Our hypothesis is that interactions between shifts in phenology and “veto” effects have major consequences on reproductive tree cycle at species range scale, considering the increasing number of extreme climatic events associated to ongoing and predicted climate change. To investigate this hypothesis, we used a process-based model (CASTANEA) previously calibrated and validated on European beech, a major European temperate tree. The model simulates stocks and fluxes between forest and atmosphere, from physiological characteristics of tree species. We simulated fruit production across Europe with a scenario accounting for veto (frost or drought) and a scenario without veto in order to detect the species margins associated to reproduction failure for that species. The detailed comparison of the two scenarios allowed us to assess when and where the different “vetos” explain the reproductive failure and how they interact with phenology changes. This study highlight how extreme climatic events can disrupt phenology of reproduction and thus change species distribution. (author)

[en] River channels and hillslopes are shaped by the joint action of localized, vertical fluvial incision along the channel and of diffuse surface creep, landslides or rock falls on the adjacent slopes, the latter being often gathered under the generic term of hillslope processes. The interplay between river incision and hillslope processes is responsible for various landscape forms, from smooth, low-relief areas to sharp and deeply incised domains. In areas where river incision is the dominant erosive process, determining the gradual exposure of river gorge walls by cosmogenic radionuclide dating permits to estimate the long-term (several ka) local incision rate. However, strongly cohesive rocks like massive limestones or sandstones may be prone, from time to time, to abrupt and localized degradation by rock falls. On a gorge wall, besides resetting the exposure age signal on the area where a block has been detached, rock fall events also produce debris that transiently protect the bedrock from river incision and the bottom of the gorge wall from cosmic radiations. In some extreme cases, rock fall events can even lead to the formation of epigenetic gorges. Although gorge walls appear as good markers of river incision, the random occurrence of rock falls may therefore add complexity to the interpretation of exposure ages, to the point where the actual river incision imprint is barely discernable. In this presentation, we simulate the 1D evolution of topography and Cosmogenic Radionuclides Exposure (CRE) ages on a gorge wall progressively formed by river incision and randomly reshaped by rock falls, in order to evaluate the imprint of these events on the CRE signal. We then discuss the implications of these models on the sampling strategy and on the interpretation of previously dated river gorges in the Southern French Alps and Provence.

[en] Significant improvements have been observed in LWR nuclear fuel reliability over the past years. As a result, the number of fuel failures in PWRs and BWRs has recently dramatically decreased. Nevertheless, a few remaining challenges still exist. One of them is that the industry has recently started seeing a relatively new type of fuel failure, so-called 'weak leak failures', which could be characterized by a very small release of gaseous fission products and essentially almost zero release of iodines or any other soluble fission products in the reactor coolant. Correspondingly, the behavior of these weak leakers does not follow typical behavior of a conventional leaker characterized by a proportionality of the amount of released Xe¹³³ related to the failed rod power. Instead, for a weak leaker, the activity of Xe¹³³ is directly correlated to the size of the cladding defects of the leaker. The presence of undetected weak leaker in the core may lead to carryover of a leaker into the subsequent cycle. Even if the presence of weak leaker in the core is suspected, it typically requires more effort to identify the leaker which could result in extended duration of the outage and ultimately to economic losses to the utility operating the reactor. To effectively deal with this issue the industry has been facing, several changes have been recently realized, which are different from the methodology of dealing with conventional leaker. These changes include new assessment methods, the need for improved sipping techniques to better identify low release leakers, and correspondingly better equipment to be able to locate small clad defects associated with weak leaker, such as sensitive localization device of failed rods, sensitive eddy current coil for the failed rod, ultra high definition cameras for the failed rod examination and experienced fuel reliability engineers performing cause of failure and rood cause research and analyses. Ultimately, the destructive methods of analysis such as hot cell examinations are also beneficial when non-destructive testing methods fail to identify the weak leaks

[en] Background: For patients with localized non operable bronchial carcinoma, combination of radiotherapy and chemotherapy can achieve only a 15 to 20 % local control rate. For some selected cases, high dose rate brachytherapy (HDRB) could be added to external beam radiotherapy to increase local tumour control. The risk of such a combined treatment is of increased toxicity. A feasibility study was developed in our Department. Methods: The HDRB is given once a week (I¹⁹² source) during the last four weeks of a conventional radiotherapy giving 60 Gy in 6 Weeks (4 x 2.5 Gy/week). A dose escalation study was planned with 4 x 3 Gy HDRB, then 4 x 4 Gy and 4 x 5Gy. Five patients have been treated at a dose of 4 x 3 Gy and two at 4 x 4 Gy. The given dose was prescribed according to the target volume and the physical dose was specified at 1 cm. The treatment catheter was positioned by the pneumologist (P.B.), and the treatment volume defined according to the endoscopy and to pre-treatment CT scanner, with a 2 cm safety margin on each extremity of the macroscopic tumour. The catheter was checked by X rays before any HDR treatment. Results: Median age of the patients was 65 year, with an OMS status <2. The location of the tumour was an upper lobe in 4 cases and a lower lobe in 3 cases. The mean treated volume was 14 cm3. With a mean follow up time of 6 months one fistulae, one pneumothorax and one radiation induced pneumonitis have been observed. Four patients have died: two from distant metastases with local tumour control, one from a myocardial infarct and one from local recurrence. Conclusion: In this feasibility study, some toxicity of combined external beam irradiation and HDRB has been found. The role of such a combined approach has to be very carefully assessed in the future

[en] Based on three decades of fuel supply to 169 PWR and BWR plants on four continents, Framatome ANP has a very large database from operating experience feedback. The performance of Framatome PWR and BWR fuel is discussed for the period 1992-2001 with special emphasis on fuel failures, countermeasures and their effectiveness. While PWR fuel performance in most reactors has been good, the performance in some years did suffer from special circumstances that caused grid-to-rod fretting failures in few PWRs. After solving this problem, fuel of all types showed high reliability again. Especially the current PWR fuel products AFA 3G, HTP, Mark B and Mark BW showed a very good operating performance. Fuel reliability of Framatome ANP BWR fuel has been excellent over the last decade with average annual fuel rod failure rates under 1x10-5 since 1991. More than 40% of all BWR fuel failures in the 1992-2001 decade were caused by debris fretting. The debris problem has been remedied with the FUELGUARDTM lower tie plate, and by reactor operators' efforts to control the sources of debris. PCI, the main failure mechanism in former periods, affected only 10 rods. All of these rods had non-liner cladding. (author)

[en] Objective: High dose rate brachytherapy (HDRB) is an effective palliative treatment for bronchial carcinoma with an obstructive component. Patients with previous radiotherapy may be at risk of morbidity. We have studied the toxicity and efficacy of palliative HDRB for endobronchial tumors in areas both previously irradiated and unirradiated. Protocole: HDRB (I192 source) delivered a total dose of 24 Gy, given as 6 x 4 Gy over 36 days for patients with previous irradiation (group A), or 3 x 8 Gy over 15 days for patients without previous irradiation (group B). The dose was prescribed according to the target volume, and the physical dose was specified at 1 cm depth. The treatment catheter was positioned by the pulmonologist and the treatment volume defined according to the endoscopy, with a 2 cm margin proximal and distal to the macroscopic tumor. The catheter position was verified by radiographic films before any HDR treatment. Population: 20 patients were included in group A, and 10 in group B. With a mean follow-up time of 9 months, 5 patients out of 10 in group B developed lethal hemoptysis (toxicity grade V) and 3 patients several necrosis (toxicity grade III). No toxicity was found in group A. Results: 80 % symptomatic respiratory response Conclusion: HDBR is a safe and effective palliative treatment in patients without previous irradiation. For patients with previous irradiation, we document severe complications even with protracted treatment using low dose per fraction

[en] In the context of high coal injection and high productivity operation, the coke behaviour inside the blast furnace hearth is the main parameter to control. Different and complementary investigations as radioactive and helium tracer injections, liquids and coke samplings, have been carried out at Sollac Fos BF1 using the tuyere probe to determine the hearth permeability and its evolutions as a function of the main control parameters, and to understand the hearth activity. The results of all these experiments give a very consistent picture of a heterogenous hearth with three concentric areas of various permeabilities to gas and liquids. A two concentric zones model has been built, which is in good agreement with the experimental results. It enables to evaluate the impact of the central zone on the liquids flow at the periphery. (author)

[en] Brachytherapy plays an important role in the treatment of patients with cervical carcinoma. Technical modalities have evolved during the last years and have benefited from imaging modalities development, specially MRI. Imaging modalities contribute to a better knowledge of tumoral extension and critical organs. Ultrasound during brachytherapy has led to the almost complete eradication of uterine perforation. In the future, a more systematic use of systems allowing optimization may induce a better dose distribution in the tumor as well as in the critical organs. Recent data provided information in favor of a better analysis in the relative role of dose-rate, total dose and treated volume and their influence on the local control and complication incidence. Concomitant radio-chemotherapy represents a standard in the treatment of patients with tumoral size exceeding 4 cm. Some questions still remain: is concomitant chemotherapy of benefit during brachytherapy? Is there any place for complementary surgery, specially in patients with complete response after external irradiation with concomitant chemotherapy and brachytherapy? In order to answer the former question, a phase III randomized trial is going to start, with the Federation Nationale des Centres de Lutte Contre le Cancer as a promoter. (authors)