Swiss Federal Nuclear Safety Inspectorate ENSI

Brugg, Switzerland

Swiss Federal Nuclear Safety Inspectorate ENSI

Brugg, Switzerland
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Anne C.,University of Bern | Naki A.,University of Bern | Susan I.-O.,ETH Zurich | Fritz S.,University of Bern | And 5 more authors.
Geomorphology | Year: 2017

Deckenschotter (‘Cover Gravels’) are proximal glaciofluvial gravels located in the northern Alpine Foreland mainly beyond the extent of the Last Glacial Maximum. They cover Tertiary Molasse or Mesozoic bedrock with an erosional unconformity. In Switzerland, Deckenschotter are referred to as Höhere (Higher) and Tiefere (Lower) Deckenschotter based on their topographical positions with a significant phase of incision that separates these two units. For this study, we performed sedimentological analyses to identify the provenance, transport mechanisms and depositional environment of these gravels. In addition, we established the chronology of the Höhere Deckenschotter gravels at Stadlerberg using cosmogenic 10Be depth-profile dating technique. The inherited 10Be concentration then allowed estimation of a catchment-wide palaeo-denudation rate. The results from clast fabric investigations indicate that braided rivers within a glaciofluvial environment transported these sediments to the study site mainly as bedload. In addition, the petrographic composition of the deposits shows that a large portion of the gravels was derived through erosional recycling of Miocene Molasse conglomerates. Some material was additionally sourced in the northern Central Alps. We then conclude that gravel accumulation in the Swiss Alpine Foreland was completed at 1.9 ± 0.2 Ma. This age, however, represents a minimum age and the oldest 10Be depth-profile age ever obtained for a geological unit. Furthermore, a palaeo-denudation rate of c. 0.3–0.4 mm/a was estimated for the catchment of Stadlerberg gravels. Finally, elevation differences between the bedrock underlying the Höhere Deckenschotter and the modern base level imply a long-term regional incision rate of c. 0.12 mm/a. © 2016 Elsevier B.V.

Hermann D.,Swiss Federal Nuclear Safety Inspectorate ENSI
Nuclear Engineering and Technology | Year: 2017

Precursor analysis is widely used in the nuclear industry to judge the significance of events relevant to safety. However, in case of events that may damage equipment through effects that are not ordinary functional dependencies, the analysis may not always fully appreciate the potential for further evolution of the event. For fires, which are one class of such events, this paper discusses modelling challenges that need to be overcome when performing a probabilistic precursor analysis. The events used to analyze are selected from the Organisation for Economic Cooperation and Development (OECD) Fire Incidents Records Exchange (FIRE) Database. © 2017

Schindler H.-J.,Materials Tec AG | Kalkhof D.,Swiss Federal Nuclear Safety Inspectorate ENSI
Journal of Testing and Evaluation | Year: 2015

An increased loading rate causes not only a shift of the ductile-to-brittle transition curve, but also a slight change of the shape of this curve. The latter tends to become steeper as the loading rate increases. This effect was observed even at loading rates that are considered to be quasi-static according to ASTM E1921 [ASTM E1921-13: Standard Test Method for Determination of Reference Temperature, T0, for Ferritic Steels in the Transition Range, Annual Book of ASTM Standards, ASTM International, West Conshohocken, PA, 2013. Actually, the coefficient 0.019 in the exponent of the MC turned out to be substantially higher at elevated loading rates. This means that a basic assumption of the evaluation procedure of ASTM E1921 is not met, which leads to an increased uncertainty of T0 or T0,x, respectively. This effect of is most pronounced in testing at elevated loading rates using the single-temperature option. An improved method to determine the reference temperature is proposed, where the exponent in the median transition curve in ASTM E1921 is considered to be an open parameter. The resulting reference temperatures, denoted as T100 and T100,x, respectively, are expected to be more accurate than standard T0, which is confirmed by comparison with experimental data. Furthermore, the validity requirements for T100 are less restrictive and more suitable than those in ASTM E1921, since they do not depend on the outcome of the tests. Based on the improved data, an improved estimation formula for the rate-induced shift of T0 is derived. Suggestions are made for improvement of ASTM E1921. Copyright © ASTM Int'l (all rights reserved).

Kuhlemann J.,Swiss Federal Nuclear Safety Inspectorate ENSI | Rahn M.,Swiss Federal Nuclear Safety Inspectorate ENSI
Swiss Journal of Geosciences | Year: 2013

Re-evaluation of the river history, palaeosurface levels and exhumation history in northern Switzerland for the last 10 million years reveals that distinct morphotectonic events about 4.2 and 2.8 million years ago (Ma) caused major reorganisation of river networks and morphosculpture. As a result of the earlier formation of the Swiss Jura, potential relief energy in the piggy-back North Alpine Foreland Basin (NAFB) of northern central Switzerland south of the Jura fold belt was built up after 11-10 Ma. It was suddenly released by river capture at about 4.2 Ma when the Aare-Danube was captured by a tributary of the Rhône-Doubs river system which rooted southeast of the Black forest. This event triggered rapid denudation of weakly consolidated Molasse sediments, in the order of about 1 km, as constrained by apatite fission track data from drillholes in the NAFB. Likely mechanisms of river capture are (a) headward erosion of Rhône-Doubs tributaries, (b) uplift and rapidly increasing erosion of the Swiss Alps after about 5.3 Ma, and (c) gravel aggradation at the eastern termination of the Jura fold belt in the course of eastward and northward tilt of the piggy-back NAFB. A morphotectonic event between 4.2 and 2.5 Ma, probably at about 2.8 Ma, caused a phase of planation, accompanied by local gravel aggradation and temporary storage of Alpine debris. Between 2.8 and 2.5 Ma, the Aare-Rhône river system is cannibalised by the modern Rhine River, the latter later connecting with the Alpine Rhine River. © 2013 Swiss Geological Society.

Podofillini L.,Paul Scherrer Institute | Reer B.,Swiss Federal Nuclear Safety Inspectorate ENSI
Reliability, Risk and Safety: Back to the Future | Year: 2010

The objective of the International Human Reliability Analysis (HRA) Empirical Study is to assess HRA methods, comparing their results with data from simulator observation. Throughout 2007 and 2008, the Study has addressed HRA predictions on 11 Human Failure Events (HFEs) in 4 scenarios: 2 variants of a Steam Generator Tube Rupture (SGTR) and 2 variants of a Loss of Feedwater (LOFW) scenario. This paper presents the results of the HRA predictions on the SGTR scenarios of one HRA analysis team and discusses how the predicted analysis compared to the observed outcomes from the simulator. The HRA method used is the quantification module of the Commission Errors Search and Assessment method (CESA-Q), developed within the HRA research project at the Paul Scherrer Institut (PSI). In general, CESA-Q performed satisfactorily: the analyses predicted reasonably well the factors that were observed to influence the performance of the operators. In some cases, a tendency towards optimism (i.e. predicted action difficulty lower than observed) was found, especially for operator actions with some execution difficulties (but note that the LOFW results, whose publication is forthcoming, do not appear to be optimistic). Insights on the method and directions for future improvements are identified as a result of the comparison. ©2010 Taylor & Francis Group.

Wang H.,Key Laboratory of Orogenic Belt and Crustal Evolution | Rahn M.,Swiss Federal Nuclear Safety Inspectorate ENSI | Zhou J.,Chinese Academy of Geological Sciences | Tao X.,Chengdu University of Technology
Tectonophysics | Year: 2013

Low temperature metamorphic indicators were used to investigate the tectonothermal evolution of the Triassic flysch in the Songpan-Garzê orogen, eastern margin of the Tibetan plateau. Iso-thermal zones mapped with illite crystallinity (Kübler index, KI) describe a complex pattern of the diagenetic, anchimetamorphic and epimetamorphic zones. From this pattern, a general increase in grade toward the Longmenshan fault belt is observed, and across the Longmenshan fault belt, greenschist facies and anchizonal rocks on its NW side are juxtaposed to diagenetic rocks in the Sichuan basin on its SE side. This juxtaposition is marked by KI jumps of 0.23°δ2θ in the SW portion of the Longmenshan fault through 0.39°δ2θ in the Middle, and reaching 0.71°δ2θ in the NE of the Longmenshan fault thus describing a clockwise rotation of the upper part of the Longmenshan fault after metamorphism. Across the Xianshuihe fault, the truncated KI zones within the Triassic flysch suggest a total offset of roughly 50-60. km due to post-metamorphic sinistral strike-slip. Peak metamorphic conditions are estimated at 365-431. °C with a pressure facies of low to intermediate type (3. kbar).Compression at the end of the Triassic was induced by the interaction of the South China, North China and North Tibetan blocks, which caused the closure of the Paleo-Tethys Ocean and led to the folding of the Triassic flysch within the Songpan-Garzê basin. Very low to low grade metamorphism was caused by crustal thickening due to an accretionary wedge setting, which led to an increase in the thickness of the Triassic flysch to >. 10. km, and resulted in a temperature increase in those rocks due to burial. Finally, the Indo-Asia collision caused the formation of the Longmenshan and the Xianshuihe strike-slip faults in the early Tertiary and disturbed the distribution of the metamorphic zones. © 2013 Elsevier B.V.

Szymczak S.,Friedrich - Alexander - University, Erlangen - Nuremberg | Hetzer T.,Friedrich - Alexander - University, Erlangen - Nuremberg | Brauning A.,Friedrich - Alexander - University, Erlangen - Nuremberg | Joachimski M.M.,Friedrich - Alexander - University, Erlangen - Nuremberg | And 2 more authors.
Quaternary Science Reviews | Year: 2014

We present a new multi-parameter dataset from Corsican black pine growing on the island of Corsica in the Western Mediterranean basin covering the period AD 1410-2008. Wood parameters measured include tree-ring width, latewood width, earlywood width, cell lumen area, cell width, cell wall thickness, modelled wood density, as well as stable carbon and oxygen isotopes. We evaluated the relationships between different parameters and determined the value of the dataset for climate reconstructions. Correlation analyses revealed that carbon isotope ratios are influenced by cell parameters determining cell size, whereas oxygen isotope ratios are influenced by cell parameters determining the amount of transportable water in the xylem. A summer (June to August) precipitation reconstruction dating back to AD 1185 was established based on tree-ring width. No long-term trends or pronounced periods with extreme high/low precipitation are recorded in our reconstruction, indicating relatively stable moisture conditions over the entire time period. By comparing the precipitation reconstruction with a summer temperature reconstruction derived from the carbon isotope chronologies, we identified summers with extreme climate conditions, i.e. warm-dry, warm-wet, cold-dry and cold-wet. Extreme climate conditions during summer months were found to influence cell parameter characteristics. Cold-wet summers promote the production of broad latewood composed of wide and thin-walled tracheids, while warm-wet summers promote the production of latewood with small thick-walled cells. The presented dataset emphasizes the potential of multi-parameter wood analysis from one tree species over long time scales. © 2014 Elsevier Ltd.

Viehrig H.-W.,Helmholtz Center Dresden | Houska M.,Helmholtz Center Dresden | Kalkhof D.,Swiss Federal Nuclear Safety Inspectorate ENSI | Schindler H.-J.,Materials Tec AG
International Journal of Pressure Vessels and Piping | Year: 2015

The multi-layer beltline welding seam of the Biblis C reactor pressure vessel was characterized by hardness, tensile, ISO-V impact and fracture toughness testing. The reference temperature, T0, was determined according to the test standard ASTM E1921 at different thickness positions of the multi-layer welding seam. Additionally, the influence of the specimen orientation on the ISO-V ductile-to-brittle transition temperature and T0 was investigated. In contrast to the T-S orientation (crack extension through the thickness) the crack front of the T-L oriented specimens (crack extension in welding direction) penetrates several welding beads. By means of fractographic and metallographic analyses of the fractured surface of fracture mechanics SE(B) specimens was shown that the distribution of the crack initiation sites is not necessarily correlated to the structure of the different welding beads along the crack front. Furthermore, it was found that the scatter of the fracture toughness values at cleavage failure, KJc, determined with T-S specimens is significantly higher than in case of the T-L specimens. T0 values measured at different thickness locations of the multi-layer welding seam vary in a range of about 40 K.The evaluated T0 values are used to determine the reference temperature RTTo for indexing the lower bound curve KIc(T) according to the Regulatory Guide ENSI-B01 for the ageing surveillance of nuclear power plants in Switzerland. It could be shown that the KIc values converted from the KJc values are enveloped by the lower bound curves. © 2015 Elsevier Ltd.

Schindler H.-J.,Materials Tec AG | Kalkhof D.,Swiss Federal Nuclear Safety Inspectorate ENSI | Viehrig H.-W.,Helmholtz Center Dresden
Engineering Fracture Mechanics | Year: 2014

The fracture behaviour of a component or specimen that contains a sharp notch is governed essentially by the same theoretical relations known from cracks. The blunt notch root only causes an increase of the resistance against crack initiation, which depends on the fracture mechanism. In the present paper, the relation between fracture toughness and notch toughness is investigated by simple analytical models. The derived formulas were compared with experimental results obtained from fracture toughness tests on RPV-steel 24 NiCrMo 3-7 at various temperatures. 1T-CT- and 0.4T-SEB-specimens that contained a sharp notch with a root radius of 0.06mm introduced by spark erosion (EDM) instead of the standard fatigue crack were used. The predictions were found to agree well with the experimental data. The effect of the notch radius on fracture toughness is most pronounced in the brittle to ductile transition regime, where fracture toughness can be characterized by the master curve and the corresponding reference temperature T0 according to ASTM E1921. Accordingly, the effect of the notch radius can be quantified by a shift of T0. Since the shape of the transition curve depends on the notch radius, the procedure of ASTM E1921 to determine T0 is not applicable. An alternative is suggested. As limiting cases, ductile tearing and brittle fracture are also considered. © 2014 Elsevier Ltd.

Kalkhof D.,Swiss Federal Nuclear Safety Inspectorate ENSI | Schindler H.-J.,Materials Tec AG
19th European Conference on Fracture: Fracture Mechanics for Durability, Reliability and Safety, ECF 2012 | Year: 2012

The reference temperature T0 according to ASTM E1921 can serve to determine a lower bound of fracture toughness of RPV-steel in the ductile-to-brittle transition range by a correlation between T0 and RTNDT. However, T0 is known to be affected by a bias related to specimen size, which leads to some uncertainties. Therefore, questions concerning transferability of T0 to large structures and adequate safety margins arise. These and related issues are explored in the present paper experimentally and theoretically. On a typical RPV-steel the effects of loading rate, specimen size and shape, crack depth and loading rate were investigated experimentally. It was found that the shape of the MC is sensitive to the loading rate, even in the range of quasi-static loading, but even more pronounced at higher loading rates. This effect leads to a dependence of T0 on the test temperature. Furthermore, T0 turned out to be size-dependent to some degree, which indicates that the requirements of ASTM E1921 are not restrictive enough to guarantee size-independence. Based on these findings a modified formula to determine RTNDT from T 0 is suggested.

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