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Lauffohr (Brugg), Switzerland

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).

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.

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.

Tasset D.,Institute for Radiological Protection and Nuclear Safety | Frischknecht A.,Swiss Federal Nuclear Safety Inspectorate ENSI | Lamarre G.,Oecd Nuclear Energy Agency | Gil-Montes B.,Consejo de Seguridad Nuclear
8th International Topical Meeting on Nuclear Plant Instrumentation, Control, and Human-Machine Interface Technologies 2012, NPIC and HMIT 2012: Enabling the Future of Nuclear Energy | Year: 2012

The crucial role that human and organizational factors (HOF) plays in the safety performance of high hazard industries, including nuclear has been proven time and again based on the lessons coming out of such high profile events and accidents such as Texas City, Deepwater Horizon, Challenger/Columbia shuttle accidents as well as the Chernobyl and other well known nuclear accidents. Further, nuclear industry accidents and events such as Fukushima Daiichi NPP, Sellafield MOx, Tokai Mura and Davis-Besse have increased awareness of the contribution to nuclear safety performance that is made by a licensee's leadership and the way in which it manages for safety. Within this context, the NEA/CSNI Working Group on Human and Organisational Factors (WGHOF) brings HOF experts together, representing regulators, technical safety organizations, research institutions and industry to discuss and develop common positions on some of the key challenges facing the safety of the nuclear industry in these specialized fields. Realizing that the strength of its influence and ability to advance the fields of knowledge of HOF (which includes safety culture) lies within its ability to be able to bring together the key international voices in the field of HOF, WGHOF has consistently reached out to other organizations such as the IAEA, EC-JRC, WANO in its work. The products of WGHOF from safety reports including best practice guides to technical opinion papers have had a significant impact on both the operational and regulatory approaches in the areas of human and organizational factors within the participating OECD-NEA member and associated member countries. Spanning the topical areas of HOF in new technology, safety culture, leadership and managing for safety, human reliability analysis and organizational performance and capabilities, to name a few, WGHOF has had a very positive influence on harmonizing the thinking and approaches in these technical areas internationally. Consequently, these international collaborative efforts have translated into some important safety improvements in the participating countries. Looking to the future, WGHOF recognizes that with the most recent Japanese accident at Fukushima Daiichi, the international nuclear safety community is once again looking to it to address some of the key human and organizational factors issues (for example, human performance under severe accident conditions over an extended time period, training and validation of training procedures for severe accident situations, and many others) coming out of the lessons learnt from this tragedy. WGHOF is well positioned and well structured to continue to meet these challenges and deliver key products in a timely fashion into the hands of the regulators, technical safety organizations and industry participants.

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.

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