Results 1 - 10 of 1419
Results 1 - 10 of 1419. Search took: 0.017 seconds
|Sort by: date | relevance|
[en] This paper presents a nuclear criticality safety analysis of an operation to recover containers from a 30-year-old storage site. There are 145 containers containing waste from fuel elements with fissile material. The storage consists of 15 cement wells, 7 m deep and 0.4 m in diameter. Each well contains up to 10 60-liter containers stacked on top of each other. Waste containers contain mixtures of various fuel element sections and samples which have various shapes (rods, needles, bars, etc.), different physical or chemical forms (metal, oxide) and variable isotopic compositions. The analysis is based on an inventory of the quantities of fissile material and their composition, which are well known. Given the duration of storage and the possibility of dropping a container during handling, two methods of taking up containers are envisaged. The first one is handling the container as a whole (without opening the container), and the second is opening the container inside the well and recovering the waste directly into the container. For the recovery of the containers, nuclear critical safety of the operation is ensured by limiting the masses of handled fissile material. These masses must remain below the safe masses under normal condition (gripping of a container) or under an abnormal situation (falling of a container on the one below with grouping of the fissile material of the two containers). These safe masses are calculated at optimal moderation for homogeneous or heterogeneous media with reflection by concrete. Different criteria are used for normal and abnormal situations. The paper presents the method for determining a reference fissile medium that bounds all fissile material present in the two containers without being too penalizing. It takes into account the nature of the fissile material (oxide or metallic, homogeneous or heterogeneous), 235U enrichment and the moderating material. The paper also presents calculations of critical and safe mass limits of fissile material for all the reference fissile media. For each grouping of two containers, the paper presents the calculations of an equivalent mass of fissile material in both containers and then verifies that it is below the safe mass limit. Thanks to this method, it is possible to handle a majority of containers (90%) as a whole (without opening) thus saving time and reducing worker exposure for the operation all the while ensuring nuclear criticality safety control.
[en] Due to the operation of TRIGA reactor, post-irradiation examination laboratory, radioactive waste treatment plant on Institute for Nuclear Research (INR) site it is mandatory to assess the radiological impact of these activities. Institute for Nuclear Research has implemented an Environmental Monitoring Program in compliance to the Romanian Regulatory Body requirements. The Environmental Monitoring Program includes on-site and off-site sampling locations for soil, vegetation, surface water, underground water. The location types used in the Monitoring Program can be divided into four distinct categories: indicator locations, background locations, control locations and supplementary locations. The current paper presents the gross beta measurement results in environmental samples (soil and vegetation) monitored during the period 2014-2018. The gross beta activity concentration monitoring in environmental samples in the surroundings of a nuclear facility is necessary to be performed according with the regulatory requirements, to prove that nuclear activities haven’t a negative impact on the environment and population. (author).
[en] The decision for the energy turnaround was one of the most important decisions of the last decades. Research for the safe and environmentally compatible dismantling of nuclear facilities is an important contribution to their success. This task will take us years to accomplish and presupposes the preservation of existing technical and scientific competence as well as the securing of the next generation of specialists. We want to support German companies in securing and expanding their leading position in international competition. Here too, technological innovations can help improve the quality of life for every individual. Research for the dismantling of nuclear facilities should improve the protection of man and the environment.
[de]Die Entscheidung für die Energiewende war eine der wichtigsten Weichenstellungen der letzten Jahrzehnte. Die Forschung für einen sicheren und umweltverträglichen Rückbau nuklearer Anlagen ist ein wichtiger Beitrag für deren Erfolg. Diese Aufgabe wird uns noch Jahre beanspruchen und setzt den Erhalt vorhandener technisch-wissenschaftlicher Kompetenz sowie die Sicherung des Fachkräftenachwuchses voraus. Deutsche Unternehmen wollen wir unterstützen, ihre führende Stellung im internationalen Wettbewerb zu sichern und auszubauen. Auch hier gilt: Technologische Innovationen können dazu beitragen, die Lebensqualität für jeden Einzelnen zu verbessern. Durch die Forschung für den Rückbau kerntechnischer Anlagen soll sich der Schutz von Mensch und Umwelt verbessern.
[en] A historical Magnox fuel element debris storage facility presents one of the highest radiological hazards on the Sellafield Site. Preparations to retrieve the solid radiological inventory into waste packages and put these into modern storage facilities are reaching fruition, with retrievals due to commence later this year. The vast majority of the Magnox fuel fissile waste in the facility presents no credible criticality risk. A very small mass fraction of the waste, Enriched Fissile Tippings (EFT), presents a theoretical criticality risk during the operations to retrieve and safe-store the waste. At the onset of work on the criticality safety case the understanding of the EFT inventory was inadequate and it appeared that the criticality risk could be near to a level regarded as intolerable in UK custom and practice. The criticality safety case has required a detailed investigation of the records concerning the EFT. This has been a challenging task requiring expert identification, interpretation and reconciliation of records from multiple archives and document stores. As this work has progressed, our understanding of the uncertainties in the data and our level of confidence in the data has improved, to the extent that it is now considered adequate to underpin the criticality safety case. Various theoretical accumulations and arrangements of the EFT have been modelled and used to map a 'criticality safety envelope'. The developed EFT inventory (with uncertainties) has then been compared against the safety envelope and it has been demonstrated that the likelihood of sufficient EFT accumulating in an arrangement that could cause criticality is very low. The criticality risk is now demonstrated to be tolerably low within the context of the overwhelming need to reduce the high radiological risk as soon as reasonably practicable. Furthermore, the susceptibility of criticality to uncertainties and unknown factors is considered so low that there would be no benefit from having a Criticality Emergency Plan (CEP) and hence no requirement for a Criticality Warning System. The paper will discuss the investigation of the EFT inventory, the development of the criticality safety case and the consideration of the need for a CEP. (author)
[en] Introduction: Derived from the importance of implementing dosimetric safety procedures in radiodiagnosis to patients, as well as complying with the international agreements signed by Mexico, the Ismael Cosío Villegas National Institute of Respiratory Diseases (INER) initiated a pilot project to implement the history Dosimetry (booklet) of patients who attend X-ray radiodiagnosis and nuclear medicine services, which is why the challenges and opportunities related to said project are shown at present. Objective: To analyze the difficulties and opportunities to implement the dosimetric history in the INER. Material and Methods: An analysis was carried out on the electronic system and procedure for requesting studies; regarding the reasons for repeating studies; diagnostic image quality; the cost-benefit to the patient; the level of safety culture, as well as the competencies of the technical and medical staff regarding the issue of radiological safety of patients; Likewise, an institutional dosimetric history format was designed. Result: The identification of a poor level of culture of radiological safety of the patient was carried out; failures in the processes of care, communication and education of medical personnel in training and technicians; Regarding the importance of intercommunication between the various software used in the patient care process, the implementation of a quality management system in radiodiagnosis; teamwork to analyze matters related to justification, optimization, differences in operating doses and guidance levels, diagnostic image quality, and standardization of technical acquisition procedures; to end with the implementation of a pilot dosimetric history format. Conclusion: It is necessary to work as a team and increase the culture of radiological safety of patients, as well as establish standardized operating procedures, as well as the determination of institutional dose guidance levels.
[en] A method of noninvasive recovery of gas-discharge detectors degraded due to operation in intense radiation fields is described. The plasma-chemical reactions are the basis of the presented techniques; these reactions take place during the detector training in a gas discharge of special recovering gas mixtures. The results of recovery of operating parameters for proportional chambers and counters are presented.
[en] BIOPROTA is an international collaborative forum that seeks to address the key uncertainties in long term assessments of radionuclide and other contaminant releases into the environment arising from solid radioactive waste disposal. (see www.bioprota.org). Two workshops have been organized through the BIOPROTA forum to consider the non-radiological post-disposal impacts of radioactive waste disposal. In these workshops, it was noted that, ideally, the assessment of radionuclides and hazardous materials should be such that consistent assumptions and criteria are used in risk evaluation and that in cases where this is not possible, a clear understanding of the reasons why needs to be provided. Accordingly, a detailed review was organized through BIOPROTA to provide information to support development of a consensus on how to address this issue. The study suggests that there is a continuing need for some common measure of hazard that supports identification of risk management priorities for mixed hazardous waste. Without it, effective optimization of management of these mixed hazardous wastes will be restricted. (authors)
[en] The use of analogues to help understand and to build confidence in radioactive waste management approaches and safety cases was reviewed by the NEA Forum on Stakeholder Confidence. Analogues can only contribute to safety cases as a line of evidence. They cannot be relied upon as the sole line of evidence. As the degree of similarity with possible repository situations diminishes, examples become analogies or anecdotes, and their arguments are more useful in terms of supporting generic and conceptual feasibility of geological disposal. Analogies and anecdotes could help the public to grasp time scale and understand the basic rationale and principles of geological disposal. This is more important in early stages of public information and involvement. When the project becomes more real, however, the public may find a national analogue more persuasive and comprehensible, since it is geographically and culturally closer to its own experience and likely to be very concrete, especially in the case of anthropogenic analogues. The application of contemporary analogues as input to the design and choice of materials with a view to suggest safe and reversible operation deserves attention. (author)
[en] This paper treats the subject of the accident analysis for the operational phase of a deep geological repository (DGR) for radioactive waste. It describes the further development of the procedures used in the accident analysis. The procedures of the scenario development for the post-closure phase of DGRs are used as example for this further development. Nine international projects regarding scenario development were analyzed to create an advanced and more systematic method for the accident analysis. (authors)
[en] Flattening filter free (FFF) beams have reached widespread use for clinical treatment deliveries. The usual methods for FFF beam characterisation for their quality assurance (QA) require the use of associated conventional flattened beams (cFF). Methods for QA of FFF without the need to use associated cFF beams are presented and evaluated against current methods for both FFF and cFF beams. Inflection point normalisation is evaluated against conventional methods for the determination of field size and penumbra for field sizes from 3 cm × 3 cm to 40 cm × 40cm at depths from dmax to 20 cm in water for matched and unmatched FFF beams and for cFF beams. A method for measuring symmetry in the cross plane direction is suggested and evaluated as FFF beams are insensitive to symmetry changes in this direction. Methods for characterising beam energy are evaluated and the impact of beam energy on profile shape compared to that of cFF beams. In-plane symmetry can be measured, as can cFF beams, using observed changes in profile, whereas cross-plane symmetry can be measured by acquiring profiles at collimator angles 0 and 180. Beam energy and ‘unflatness’ can be measured as with cFF beams from observed shifts in profile with changing beam energy. Normalising the inflection points of FFF beams to 55% results in an equivalent penumbra and field size measurement within 0.5 mm of conventional methods with the exception of 40 cm × 40 cm fields at a depth of 20 cm. New proposed methods are presented that make it possible to independently carry out set up and QA measurements on beam energy, flatness, symmetry and field size of an FFF beam without the need to reference to an equivalent flattened beam of the same energy. The methods proposed can also be used to carry out this QA for flattened beams, resulting in universal definitions and methods for MV beams. This is presented for beams produced by an Elekta linear accelerator, but is anticipated to also apply to other manufacturers’ beams. (paper)