Swiss Federal Nuclear Safety Inspectorate

Lauffohr (Brugg), Switzerland

Swiss Federal Nuclear Safety Inspectorate

Lauffohr (Brugg), Switzerland
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PubMed | Federal office of Public Health of Fribourg, Muhleberg Nuclear Power Plant, Swiss National Accident Insurance Fund, University of Lausanne and 3 more.
Type: Journal Article | Journal: Radiation protection dosimetry | Year: 2016

Individual monitoring for both external and internal exposures is well regulated in Switzerland. The article gives an overview on the occupational exposure to external radiation of workers based on the data collected in the Swiss national dose registry (NDR) in 2013. The NDR records the monthly doses of radiation workers since the introduction of ICRP 60 recommendations and is manifested in the Swiss ordinance since 1994. Annual dose limits for effective dose are typically exceeded once a year in Switzerland, mostly in medicine. The NDR is a useful optimisation tool to identify and characterise areas with the highest exposures. While exceeded dose limits were often related to accidental acute exposure in the past, they are now more related to continuous exposure during normal work, especially in medicine.

Testa G.,Swiss Federal Nuclear Safety Inspectorate | Isaak H.,Swiss Federal Nuclear Safety Inspectorate | Von Arx C.,Swiss Federal Nuclear Safety Inspectorate
Proceedings of the 15th International Conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes, HARMO 2013 | Year: 2013

Atmospheric dispersion and dose calculations play an essential role in the assessment of a nuclear emergency situation, especially if they are used to decide upon appropriate off-site emergency response measures. From the point of view of a national regulatory body, a system providing such calculations has to satisfy highest requirements on quality of results as well as on reliability and availability. It is clear, however, that any numerical calculation suffers from uncertainties as well as modelling constraints, which put limits on the informative value of the results (e.g. radiological dose prognosis). In 2010, the Swiss Federal Nuclear Safety Inspectorate ENSI launched a project to replace the current atmospheric dispersion calculation system ADPIC by 2015. The goal is to provide high-quality dispersion calculations on an Intel-based, highperformance computing platform. In collaboration with the developers of JRODOS and LASAT, ENSI is currently implementing a new atmospheric dispersion system for a range of up to 250 km from the site, based on the requirements of the Swiss concept for emergency preparedness in case of radiological accidents in nuclear power plants. Additionally, the system design shall be chosen based on known limitations of input data and optimised regarding general simulation parameters, in order to permit fast and reliable dose prognoses.

Schindler H.-J.,Materials Tec AG | Kalkhof D.,Swiss Federal Nuclear Safety Inspectorate
13th International Conference on Fracture 2013, ICF 2013 | Year: 2013

The inherent scatter of fracture toughness of ferritic steels in the brittle-to-ductile transition regime require statistical methods to be applied for testing and evaluation. However, for engineering purposes lower bounds of KIc such as the ASME-reference curve are often preferred since they allow deterministic worst-case predictions to be made. So the question is how to derive lower bounds of a quantity that is governed by weakest-link-statistics. Actually, neither the MC-approach nor the empirical ASME-reference curve deliver well-founded lower bounds for components of relatively small thicknesses. A theoretical model is suggested to fill this gap. The key element of the approach is the hypothesis that the weakest-link-effect is saturated at a certain thickness. The corresponding upper limit of size-dependence turned out to be close to the minimum thickness required for plane-strain conditions at the crack-front. The derived mathematical relations enables KIc to be calculated from KJc as measured on a smaller specimen. In reverse, from a lower-bound KIc as provided by the ASME-code a thickness-dependent lower bound of KJc can be obtained. The proposed model is shown to yield predictions that are consistent with experimental data as well as with the ASME-lower bound. Copyright © (2013) by International Conference on Fracture.

Hofer D.,University of Bern | Raible C.C.,University of Bern | Dehnert A.,Swiss Federal Nuclear Safety Inspectorate | Kuhlemann J.,Swiss Federal Nuclear Safety Inspectorate
Climate of the Past | Year: 2012

Using a highly resolved atmospheric general circulation model, the impact of different glacial boundary conditions on precipitation and atmospheric dynamics in the North Atlantic region is investigated. Six 30-yr time slice experiments of the Last Glacial Maximum at 21 thousand years before the present (ka BP) and of a less pronounced glacial state - the Middle Weichselian (65 ka BP) - are compared to analyse the sensitivity to changes in the ice sheet distribution, in the radiative forcing and in the prescribed time-varying sea surface temperature and sea ice, which are taken from a lower-resolved, but fully coupled atmosphere-ocean general circulation model. The strongest differences are found for simulations with different heights of the Laurentide ice sheet. A high surface elevation of the Laurentide ice sheet leads to a southward displacement of the jet stream and the storm track in the North Atlantic region. These changes in the atmospheric dynamics generate a band of increased precipitation in the mid-latitudes across the Atlantic to southern Europe in winter, while the precipitation pattern in summer is only marginally affected. The impact of the radiative forcing differences between the two glacial periods and of the prescribed time-varying sea surface temperatures and sea ice are of second order importance compared to the one of the Laurentide ice sheet. They affect the atmospheric dynamics and precipitation in a similar but less pronounced manner compared with the topographic changes. © 2012 Author(s).

Hofer D.,University of Bern | Raible C.C.,University of Bern | Merz N.,University of Bern | Dehnert A.,Swiss Federal Nuclear Safety Inspectorate | Kuhlemann J.,Swiss Federal Nuclear Safety Inspectorate
Geophysical Research Letters | Year: 2012

Winter circulation types under preindustrial and glacial conditions are investigated and used to quantify their impact on precipitation. The analysis is based on daily mean sea level pressure fields of a highly resolved atmospheric general circulation model and focuses on the North Atlantic and European region. We find that glacial circulation types are dominated by patterns with an east-west pressure gradient, which clearly differs from the predominantly zonal patterns for the recent past. This is also evident in the frequency of occurrence of circulation types when projecting preindustrial circulation types onto the glacial simulations. The elevation of the Laurentide ice sheet is identified as a major cause for these differences. In areas of strong precipitation signals in glacial times, the changes in the frequencies of occurrence of the circulation types explain up to 60% of the total difference between preindustrial and glacial simulations. © 2012. American Geophysical Union. All Rights Reserved.

Ramezanian A.,Swiss Federal Nuclear Safety Inspectorate | Hausherr R.,Swiss Federal Nuclear Safety Inspectorate
11th International Probabilistic Safety Assessment and Management Conference and the Annual European Safety and Reliability Conference 2012, PSAM11 ESREL 2012 | Year: 2012

Operator actions (OA) can play an important role in probabilistic safety assessments (PSA) of nuclear power plants (NPP). The more OA are considered in a PSA, the more dependencies between such OA should be accounted for. In SELF models a commonly accepted approach to model such dependencies is to represent a series of OA in minimal cut sets by one joint human error probability (joint HEPs). Two major disadvantages are linked to the use of joint HEPs. First, importance measures for OA do not yield correct results because contributions of OAs to joint HEPs are not taken into account. Second, success of OA cannot be treated properly when calculating a core damage frequency (CDF). Therefore, a new scheme to model OA dependencies within the fault trees is presented. It uses conditional HEPs depending on preceding or following OA. Still there is no need to evaluate every possible combination of OA. A placeholder for a non-evaluated conditional HEP may be complemented by an evaluated one if top cut sets indicate that a certain combination needs further evaluation. The definition of conditional HEPs together with the associated independent HEP as a system, enables the calculation of realistic importance measures for OA. However, exact treatment of success probabilities for OA on event tree node level is only possible by use of larger event trees.

Sentis M.L.,Swiss Federal Nuclear Safety Inspectorate
Nuclear Technology | Year: 2014

FORGE (Fate of Repository Gases) is an international research project supported by funding under the European Commission FP7 Euratom program and lasting four years from 2009 to 2013. The project is dedicated to understanding gas generation and migration as part of the quantitative assessment of a geological repository for radioactive waste. Within the FORGE project, Work Package 1 is dedicated to numerical modeling of a two-phase flow system (hydrogen gas due to corrosion and groundwater) in a geological repository for radioactive waste. Several benchmark exercises were proposed that cover the modeling of a deep geological repository from the disposal cell scale to the repository scale with different codes. During the definition of the exercises, special emphasis was given to the roles of the excavation-disturbed zone and of the interfaces between materials, which could act as a conduit for preferentialflow. Some changes were made in the TOUGH2 code to enable the implementation of the prescribed conditions, models, and parameters of the benchmark. The results of the calculations performed with different codes show that TOUGH2 gives comparable results under the numerically challenging conditions defined in the exercise. Some differences were observed resulting from the use of different codes and also from some simplifications in the parameters and models adopted by the participating teams. In this paper, the cell-scale benchmark exercise and the results obtained by the Swiss Federal Nuclear Safety Inspectorate (ENSI) with TOUGH2 will be described, together with some difficulties encountered during the simulation, e.g., convergence problems. The results of other teams participating in the benchmark are in good agreement with the ENSI results.

Von Hagke C.,Helmholtz Center Potsdam | Von Hagke C.,California Institute of Technology | Cederbom C.E.,Swedish Geotechnical Institute | Oncken O.,Helmholtz Center Potsdam | And 3 more authors.
Tectonics | Year: 2012

The evolution of the Central Alpine deformation front (Subalpine Molasse) and its undeformed foreland is recently debated because of their role for deciphering the late orogenic evolution of the Alps. Its latest exhumation history is poorly understood due to the lack of late Miocene to Pliocene sediments. We constrain the late Miocene to Pliocene history of this transitional zone with apatite fission track and (U-Th)/He data. We used laser ablation inductively coupled mass spectrometry for apatite fission track dating and compare this method with previously published and unpublished external detector method fission track data. Two investigated sections across tectonic slices show that the Subalpine Molasse was tectonically active after the onset of folding of the Jura Mountains. This is much younger than hitherto assumed. Thrusting occurred at 10, 8, 6-5Ma and potentially thereafter. This is contemporaneous with reported exhumation of the External Crystalline Massifs in the central Alps. The Jura Mountains and the Subalpine Molasse used the same detachments as the External Crystalline Massifs and are therefore kinematically coupled. Estimates on the amount of shortening and thrust displacement corroborate this idea. We argue that the tectonic signal is related to active shortening during the late stage of orogenesis. © 2012. American Geophysical Union. All Rights Reserved.

Bucher B.,Swiss Federal Nuclear Safety Inspectorate
Radiation Protection Dosimetry | Year: 2014

During an international intercomparison exercise of airborne gamma spectrometry held in Switzerland 2007 teams from Germany, France and Switzerland were proving their capabilities. One of the tasks was the composite mapping of an area around Basel. Each team was mainly covering the part of its own country at its own flying procedures. They delivered the evaluated data in a data format agreed in advance. The quantities to be delivered were also defined in advance. Nevertheless, during the process to put the data together a few questions raised: Which dose rate was meant? Had the dose rate to be delivered with or without cosmic contribution? Activity per dry or wet mass? Which coordinate system was used? Finally, the data could be put together in one map. For working procedures in case of an emergency, quantities of interest and exchange data format have to be defined in advance. But the procedures have also to be proved regularly. © The Author 2014. Published by Oxford University Press. All rights reserved.

Powell K.J.,University of Canterbury | Brown P.L.,Research Avenue | Byrne R.H.,University of South Florida | Gajda T.,University of Szeged | And 4 more authors.
Pure and Applied Chemistry | Year: 2011

The numerical modeling of CdII speciation amongst the environmental inorganic ligands Cl-, OH-, CO3 2-, SO4 2-, and PO4 3- requires reliable values for the relevant stability (formation) constants. This paper compiles and provides a critical review of these constants and related thermodynamic data. It recommends values of log10 βp,q,r° valid at Im = 0 mol kg-1 and 25 °C (298.15 K), along with the equations and empirical reaction ion interaction coefficients, Δε, required to calculate log10 βp,q,r values at higher ionic strengths using the Brønsted-Guggenheim-Scatchard specific ion interaction theory (SIT). Values for the corresponding reaction enthalpies, ΔrH, are reported where available. Unfortunately, with the exception of the CdII-chlorido system and (at low ionic strengths) the CdII-sulfato system, the equilibrium reactions for the title systems are relatively poorly characterized. © 2011 IUPAC.

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