1,720,960 research outputs found
The International Intercomparison and Harmonisation Project on Demonstrating the Safety of Gological Disposal (GEOSAF)
Full text linkIl documento presenta una presentazione del progetto GEOSAF sullo smaltimento geologico dei rifiuti radioattivi, sviluppato in ambito IAEA. Sono riportate inoltre alcune considerazioni di base e i documenti, sebbene ancora a livello di bozza, predisposti durante il progetto
Considerazioni geologico-territoriali e ambientali nella scelta di un'area per l'ubicazione di un deposito di rifiuti radioattivi a bassa attività
Full text linkSono analizzati, in via preliminare, i principali aspetti geologici, territoriali, ambientali e antropici che possono influire direttamente e indirettamente sulla scelta di un sito per l'ubicazione di un deposito di rifiuti radioattivi a bassa attività. Lo studio è stato articolato in due sezioni, che analizzano rispettivamente l'impatto umano e dell'ambiente sull'opera e l'impatto della realizzazione e dell'esercizio del deposito sull'ambiente circostante
Un approccio metodologico strutturato nella caratterizzazione geologico-ambientale di un sito per l'ubicazione di un deposito superficiale di rifiuti radioattivi di seconda categoria
Full text linkNel rinnovato quadro di sviluppo nucleare promosso nei nostro paese, la realizzazione di un deposito di rifiuti radioattivi rappresenta una reale necessità. La conoscenza del sistema-ambiente su cui insisterà l'opera dovrà essere l'oggetto di studi approfonditi In particolare le attività di caratterizzazione geologico-ambientale dovranno rivelarsi esaustive e dettagliate. E' quindi opportuno definire un approccio metodologico alla caratterizzazione che risulti chiaro e pragmatico, ma che permetta anche di desumere un quadro completo e particolareggiato degli aspetti geologico-ambientale. Per tale ragione, riferendosi ad un approccio di tipo top down e al paradigma della rappresentazione ad oggetti, viene proposta una metodologia di caratterizzazione di uno o più siti ritenuti idonei per l'ubicazione di un deposito di rifiuti radioattivi di II categoria
Utilizzo del codice AMBER per la simulazione del rilascio nel sottosuolo de 14C, 137Cs e 234U da un deposito superficiale di rifiuti radioattivi
Full text linkIl documento descrive il processo di valutazione dei rilasci di radionuclidi nel sottosuolo mediante l'utilizzo del codice AMBER, nell'ipotesi di fallimento delle barriere ingegneristiche di un deposito superficiale di rifiuti radioattivi. La simulazione riguarda il calcolo del valore di dose all'obiettivo sensibile nel caso di rilascio di acqua contaminata da 14C, 137Cs, 234U. Viste le ipotesi semplificative adottate, i risultati vanno considerati solo come output di un caso studio e non come riferimento per la performance assessment, che necessita obbligatoriamente di ulteriori considerazioni tecniche, prime tra tutte una più accurata descrizione dei vari comparti del deposito e dei relativi fenomeni di trasporto nel modello stesso
Physical and geochemical aspects on strontium transport for safety assessment studies
No full textIn nuclear safety studies, the transport of radionuclides in environmental matrices (e.g. soil, groundwater, surface water, etc.) is one of the key issue to consider. Safety assessment aims to foresee and manage the environmental and radiological impact of possible radionuclide releases into the environment. In particular, the prediction of radionuclide dynamic due to its interaction with the subsoil and to the impact of meteorological conditions must be investigated. Several techniques can be used to perform these analysis, such as experimental data and/or simulation tools. In this work, the impact of different ground covers (e.g. grass, pasture, wheat) on the mobility of strontium in space and time was investigated focusing on its behaviour in the unsaturated zone. The results highlight the impact of different ground covers on the absorption of strontium by plant roots. They can be useful to evidence the factors affecting the transfer of radionuclides from environmental matrices to the food chain and to support Safety Assessment studies about nuclear plant activities during its life cycle
Transport dynamic of strontium in groundwater: Safety Assessment study
Full text linkOne of the activities of the Safety Assessment is the evaluation of the impact of a nuclear facility on the environment. The radionuclide transport into groundwater is subjected to different phenomena (e.g. groundwater dynamic, surface stream dynamic, the interaction between surface water and groundwater, radionuclide interaction with environmental matrix, etc.) that influence the risk of contamination of water. The investigation of the source term is fundamental to understand its impact on radionuclide transport. In this paper, in situ surveys and modelling were coupled to investigate the dynamic of strontium in an Italian nuclear site. On-site measurements have identified low quantities of strontium in monitoring wells, and through the modelling, the possible migration pathway of this radionuclide was identified. For a primary safety evaluation purpose, a parametric detailed analysis was carried out to identify which hydrogeological parameters and which artificial structure present in the area could influence the dynamic of strontium in the investigated site. In particular, the effect of the Cavour artificial channel on the strontium migration and dilution was demonstrated. The coupling of monitoring activities, periodically performed in the area, and the modelling activities, focused on the detailed relationships between the Cavour artificial channel and the underground water flow, contributes to better evaluate the possible radiological risk for population and environment and to support future safety studies
Groundwater system characterisation in support of safety assessment for radioactive waste disposal
No full textRadioactive waste disposal is a strategic activity in the nuclear field to safeguard the population and the environment from radiological risks. In the radioactive waste disposal field, safety assessment aims to foresee and manage the environmental and radiological impact of possible radionuclide releases. One of the main radionuclide transport pathways in the environment is through groundwater. This paper deals with an assessment process applied to a characterisation of a groundwater system and its relations with surface water, in order to foresee critical scenarios of possible radionuclide migration in environmental matrices (e.g., groundwater, surface water, soil, etc.). The study examines in depth the groundwater system of a nuclear site in Ital
Non-destructive radiological characterization applied to fusion waste management
No full textFuture nuclear fusion reactors will produce radioactive waste containing both activation products and Tritium. Since Tritium can potentially be removed from the reactor components, activation products in the materials directly exposed to neutrons are the main source of the radioactive inventory. Activated structures have to be replaced during the operation of future fusion power plants. Moreover, decommissioning will generate activated metals and concrete, requiring treatment and conditioning which, in turn, will generate secondary waste. Significant portions of the waste from maintenance and decommissioning are expected to not meet clearance or low level waste requirements, therefore some underground disposal might be required. To partially address such an issue, strategies are already considered for reducing the amounts of activated waste by adopting recycling, interim storage, and clearance. These imply detailed qualitative and quantitative knowledge of radionuclides occurring in the materials involved, making it pivotal to implement appropriate measurement techniques. Radionuclides with significant impact in the long-term management of activation waste include nuclides hard to measure, given their little-to-none emission of gamma radiation. Those decaying by electron capture are traditionally detected by destructive characterization techniques, either mass spectroscopy or Liquid Scintillation Counting. Given the potential amount of fusion waste produced, non-destructive characterization techniques are preferred since they may require less time and efforts. Here the performance of solid state detectors, for the spectrometry of the X ray counterpart of the Auger electrons and for traditional γ spectrometry, is investigated in terms of the measurement time necessary to collect a statistically significant quantification limit, as a function of the radionuclides activity concentration. An approximated deterministic model is suggested and applied to the case of the future ITER fusion reactor, providing evidence that most of the activation products can be quantified within minutes, and a few hours are needed to quantify the occurrence of the hard to measure radionuclides by means of X spectrometry
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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