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Sanchez-Doblado F.,Hospital Universitario Virgen Macarena | Sanchez-Doblado F.,University of Seville | Domingo C.,Autonomous University of Barcelona | Gomez F.,University of Santiago de Compostela | And 28 more authors.
Physics in Medicine and Biology | Year: 2012

Neutron peripheral contamination in patients undergoing high-energy photon radiotherapy is considered as a risk factor for secondary cancer induction. Organ-specific neutron-equivalent dose estimation is therefore essential for a reasonable assessment of these associated risks. This work aimed to develop a method to estimate neutron-equivalent doses in multiple organs of radiotherapy patients. The method involved the convolution, at 16 reference points in an anthropomorphic phantom, of the normalized Monte Carlo neutron fluence energy spectra with the kerma and energy-dependent radiation weighting factor. This was then scaled with the total neutron fluence measured with passive detectors, at the same reference points, in order to obtain the equivalent doses in organs. The latter were correlated with the readings of a neutron digital detector located inside the treatment room during phantom irradiation. This digital detector, designed and developed by our group, integrates the thermal neutron fluence. The correlation model, applied to the digital detector readings during patient irradiation, enables the online estimation of neutron-equivalent doses in organs. The model takes into account the specific irradiation site, the field parameters (energy, field size, angle incidence, etc) and the installation (linac and bunker geometry). This method, which is suitable for routine clinical use, will help to systematically generate the dosimetric data essential for the improvement of current risk-estimation models. © 2012 Institute of Physics and Engineering in Medicine. Source

Ibanez-Llano C.,Comillas Pontifical University | Rauzy A.,Dassault Systemes | Melendez E.,Consejo de Seguridad Nuclear CSN | Nieto F.,Comillas Pontifical University
Reliability Engineering and System Safety | Year: 2010

Over the last two decades binary decision diagrams have been applied successfully to improve Boolean reliability models. Conversely to the classical approach based on the computation of the MCS, the BDD approach involves no approximation in the quantification of the model and is able to handle correctly negative logic. However, when models are sufficiently large and complex, as for example the ones coming from the PSA studies of the nuclear industry, it begins to be unfeasible to compute the BDD within a reasonable amount of time and computer memory. Therefore, simplification or reduction of the full model has to be considered in some way to adapt the application of the BDD technology to the assessment of such models in practice. This paper proposes a reduction process based on using information provided by the set of the most relevant minimal cutsets of the model in order to perform the reduction directly on it. This allows controlling the degree of reduction and therefore the impact of such simplification on the final quantification results. This reduction is integrated in an incremental procedure that is compatible with the dynamic generation of the event trees and therefore adaptable to the recent dynamic developments and extensions of the PSA studies. The proposed method has been applied to a real case study, and the results obtained confirm that the reduction enables the BDD computation while maintaining accuracy. © 2010 Elsevier Ltd. All rights reserved. Source

Ibanez-Llano C.,Comillas Pontifical University | Rauzy A.,Dassault Systemes | Melendez E.,Consejo de Seguridad Nuclear CSN | Nieto F.,Comillas Pontifical University
Reliability Engineering and System Safety | Year: 2010

Binary decision diagrams are a well-known alternative to the minimal cutsets approach to assess the reliability Boolean models. They have been applied successfully to improve the fault trees models assessment. However, its application to solve large models, and in particular the event trees coming from the PSA studies of the nuclear industry, remains to date out of reach of an exact evaluation. For many real PSA models it may be not possible to compute the BDD within reasonable amount of time and memory without considering the truncation or simplification of the model. This paper presents a new approach to estimate the exact probabilistic quantification results (probability/frequency) based on combining the calculation of the MCS and the truncation limits, with the BDD approach, in order to have a better control on the reduction of the model and to properly account for the success branches. The added value of this methodology is that it is possible to ensure a real confidence interval of the exact value and therefore an explicit knowledge of the error bound. Moreover, it can be used to measure the acceptability of the results obtained with traditional techniques. The new method was applied to a real life PSA study and the results obtained confirm the applicability of the methodology and open a new viewpoint for further developments. © 2010 Elsevier Ltd. All rights reserved. Source

Garcia-Talavera M.,Consejo de Seguridad Nuclear CSN | Garcia-Perez A.,Spanish University for Distance Education (UNED) | Rey C.,Consejo de Seguridad Nuclear CSN | Ramos L.,Consejo de Seguridad Nuclear CSN
Journal of Radiological Protection | Year: 2013

Identifying radon-prone areas is key to policies on the control of this environmental carcinogen. In the current paper, we present the methodology followed to delineate radon-prone areas in Spain. It combines information from indoor radon measurements with γ-radiation and geological maps. The advantage of the proposed approach is that it lessens the requirement for a high density of measurements by making use of commonly available information. It can be applied for an initial definition of radon-prone areas in countries committed to introducing a national radon policy or to improving existing radon maps in low population regions. © 2013 IOP Publishing Ltd. Source

Wirth E.,Institute Atmospharische Radioaktivitat | Baciu A.C.,National Commission for Nuclear Activities Control | Gerich B.,Institute Atmospharische Radioaktivitat | Blaettler M.,National Emergency Operations Center | And 10 more authors.
Health Physics | Year: 2011

A two-step concept is proposed in order to derive a consistent set of intervention levels for early (sheltering, evacuation) and late (relocation/resettlement, returning) protective actions that have to be considered in radiation emergency planning. In the first step, the dose ratios of the projected effective doses have to be calculated for four defined time periods, which correspond with the integration times for sheltering and relocation. In the second step, it is necessary to adopt an intervention level for one protective action or a more general reference level for a certain time period as, for example, the reference level recommended by the International Commission on Radiological Protection (ICRP) Publication 103 in 2007. The adopted intervention level or reference level and the relationships between the projected effective doses are used to derive a consistent set of intervention levels for early and late protective actions. To illustrate the two-step concept, four sets of intervention levels are exemplarily derived for two accidental releases from nuclear power plants. Copyright © 2011 Health Physics Society. Source

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