| 1. |
- Ballesteros, Antonio, et al.
(författare)
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Reactor Pressure vessel surveillance
- 2014
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Ingår i: Nuclear Engineering International. - : GLobal trade media. - 0029-5507. ; 59:12, s. 19-20
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Tidskriftsartikel (refereegranskat)abstract
- This publication summarizes techniques suitable for surveillance program for the objective of long term operation (LTO) on European NPPs and provides recommendations on reactor pressure vessel (RPV) irradiation surveillance based on the work preformed in the work package 7 "Surveillance guidelines" of the LONGLIFE international project. The LONGLIFE project "treatment of long term irradiation embrittlement effects in RPV safety assessment" was 50% funded by the Euratom 7th framework programme of the European commision. The project coordinated by the Helmholtz-centrum Dresden Rossendorf successfully finalized in 2014.
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| 2. |
- Döscher, Ralf, et al.
(författare)
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The EC-Earth3 Earth system model for the Coupled Model Intercomparison Project 6
- 2022
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Ingår i: Geoscientific Model Development. - : Copernicus GmbH. - 1991-959X .- 1991-9603. ; 15:7, s. 2973-3020
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Tidskriftsartikel (refereegranskat)abstract
- The Earth system model EC-Earth3 for contributions to CMIP6 is documented here, with its flexible coupling framework, major model configurations, a methodology for ensuring the simulations are comparable across different high-performance computing (HPC) systems, and with the physical performance of base configurations over the historical period. The variety of possible configurations and sub-models reflects the broad interests in the EC-Earth community. EC-Earth3 key performance metrics demonstrate physical behavior and biases well within the frame known from recent CMIP models. With improved physical and dynamic features, new Earth system model (ESM) components, community tools, and largely improved physical performance compared to the CMIP5 version, EC-Earth3 represents a clear step forward for the only European community ESM. We demonstrate here that EC-Earth3 is suited for a range of tasks in CMIP6 and beyond.
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| 3. |
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| 4. |
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| 5. |
- Hieronymus, Jenny, 1981-
(författare)
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The global marine carbon system through time
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Carbon dioxide is an important greenhouse gas and in order to understand its effect on the climate we need to identify its sources and sinks. This thesis focuses on different aspects of the marine carbon system and the exchange of carbon between the ocean and the atmosphere.To understand the distribution of carbon between different reservoirs such as land, ocean and atmosphere, it is important to consider the origin of a carbon flux. If the carbon originates from rock, it comprises an external source. If, however, it originates from the atmosphere, such as a flux of organic carbon, it constitutes an internal exchange. We have re-calculated riverine fluxes that are commonly expressed in terms of ions, as fluxes of total carbon and alkalinity. Furthermore, we have separated the total carbon fluxes into their external and internal parts.External sources and sinks, as well as internal exchange can sometimes be more easily understood if the carbon in the ocean is separated into acidic and basic carbon (AC and BC). These two state variables have opposite effect on the partial pressure of carbon dioxide in the surface ocean. We have used these new variables to describe the effect of pyrite production during periods in the geological past when large parts of the oceans have been oxygen free, so called oceanic anoxic events. Sulfate reduction that occurs in oxygen free environments leads to an increase in alkalinity. We show that the net effect of photosynthesis, sulfate reduction and pyrite production leads to a reduction of acidic carbon and thereby a decreased surface pressure of CO2. Furthermore, we demonstrate the difference between a system with and without carbonate compensation that comprises a regulatory mechanism for the carbon system.During the anoxic events there is a shift in the composition of carbon isotopes in the system. A negative isotope shift is believed to be a result of increased supply of light carbon from volcanic activity or melting methane clathrates, while a positive shift is a result of increased burial of organic carbon. We have investigated the implications of different sources and sinks on the size of an isotope shift. This is done by comparing simple budget calculations with a more complete model. We show that carbonate compensation implies that more light carbon must be supplied to the system to obtain the same negative shift than for the simple budget calculations where sources and sinks of calcium carbonate are not considered.
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| 6. |
- Hieronymus, Jenny, 1981-, et al.
(författare)
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Unravelling the land source : an investigation of the processes contributing to the oceanic input of DIC and alkalinity
- 2013
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Ingår i: Tellus. Series B, Chemical and physical meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 65, s. 19683-
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Tidskriftsartikel (refereegranskat)abstract
- In models of the marine carbon system, it is important to correctly represent riverine and aerial inputs of dissolved inorganic carbon (DIC) and alkalinity. We have examined the different processes contributing to this exchange. In terms of DIC, we have divided the fluxes into their internal component, constituting the carbon ultimately derived from the atmosphere, and their external component originating from rocks. We find that the only process contributing to external DIC input is carbonate and fossil carbon weathering and that erosion of organic matter ultimately constitutes a DIC sink. A number of both riverine and aerial inputs affect the alkalinity. Beside carbonate and silicate weathering, we examine processes of pyrite weathering, aerial input of sulphuric acid, and riverine and aerial inputs of various nitrogen species. Using the observation that, in the ocean, the nitrate concentration follows that of phosphate, we assume a steady state in nitrate. This leads to the surprising result that the only processes affecting the alkalinity is riverine input of nitrate, constituting an alkalinity source and input of ammonia, constituting an alkalinity sink. Furthermore, we compare the flux sizes. As expected, carbonate and silicate weathering has the largest effect on alkalinity, though we note that burial of pyrite might be of importance during periods of large-scale anoxia.
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| 7. |
- May, Johannes, et al.
(författare)
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Extended mechanical testing of RPV surveillance materials using reconstitution technique for small sized specimen to assist Long Term Operation Extended mechanical testing of RPV surveillance materials using reconstitution technique for small sized specimen to assist Long Term Operation
- 2014
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Ingår i: Journal of ASTM International. - : ASTM International. - 1546-962X .- 1546-962X. ; STP:1576
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Tidskriftsartikel (refereegranskat)abstract
- For the Ringhals 3 and 4 PWR RPV, results from the irradiation surveillance program are available also for neutron fluences which cover long-term operation (LTO). These standard surveillance results are based on the RTNDT concept. The belt-line welds of both RPVs have an elevated nickel-content of 1.6 wt.-% and, as a consequence, irradiation response is higher than predicted by model equations. Therefore, the mechanical testing program has been expanded, exceeding the requirements of the standard testing program and covering both base and weld materials. To improve the understanding of the material behavior, extended Master Curve testing was performed on PCCV and subsize SE(B) specimens from irradiation surveillance capsules with the help of specimen reconstitution technique. Special care has been taken on the limited amount of weld material within the available broken Charpy halves before specimen reconstitution.Results have been compared to existing data on similar base and weld materials from the German research programs CARISMA and CARINA. Late-blooming effects or sudden saturation effects are not observed for base or weld materials under LTO conditions. The data for the four different weld materials of similar chemical composition indicate that not only the chemical composition, but also other influencing factors like e.g. the welding heat treatment may be important for the reference temperature of the unirradiated state as well as for the irradiation behavior. To investigate this effect more in detail, a future investigation program will be discussed including manufacturing of a surrogate weld material with the same chemical composition as in Ringhals 3 and 4 RPV. The influence of heat treatment condition can be investigated by applying different heat treatments and subsequently performing test reactor irradiation and mechanical testing. Specimen reconstitution will be required due to limited space inside the test reactor irradiation capsules.
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| 8. |
- Roudén, Jenny, et al.
(författare)
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Towards Safe Long-Term Operation of Reactor Pressure Vessels
- 2015
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Ingår i: ATW. Internationale Zeitschrift für Kernenergie. - : Nucmag.com. - 1431-5254. ; 60:5, s. 287-293
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Tidskriftsartikel (refereegranskat)abstract
- This publication summarizes the long term operation (LTO) conditions on European NPPs and provides recommendations on reactor pressure vessel (RPV) irradiation surveillance based on the work preformed in the work package 7 "Surveillance guidelines" of the LONGLIFE international project. The LONGLIFE project "treatment of long term irradiation embrittlement effects in RPV safety assessment" was 50% funded by the Euratom 7th framework programme of the European commision. The project coordinated by the Helmholtz-centrum Dresden Rossendorf successfully finalized in 2014.
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| 9. |
- Takano, Yohei, et al.
(författare)
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Simulations of ocean deoxygenation in the historical era : insights from forced and coupled models
- 2023
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Ingår i: Frontiers in Marine Science. - 2296-7745. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Ocean deoxygenation due to anthropogenic warming represents a major threat to marine ecosystems and fisheries. Challenges remain in simulating the modern observed changes in the dissolved oxygen (O2). Here, we present an analysis of upper ocean (0-700m) deoxygenation in recent decades from a suite of the Coupled Model Intercomparison Project phase 6 (CMIP6) ocean biogeochemical simulations. The physics and biogeochemical simulations include both ocean-only (the Ocean Model Intercomparison Project Phase 1 and 2, OMIP1 and OMIP2) and coupled Earth system (CMIP6 Historical) configurations. We examine simulated changes in the O2 inventory and ocean heat content (OHC) over the past 5 decades across models. The models simulate spatially divergent evolution of O2 trends over the past 5 decades. The trend (multi-model mean and spread) for upper ocean global O2 inventory for each of the MIP simulations over the past 5 decades is 0.03 ± 0.39×1014 [mol/decade] for OMIP1, −0.37 ± 0.15×1014 [mol/decade] for OMIP2, and −1.06 ± 0.68×1014 [mol/decade] for CMIP6 Historical, respectively. The trend in the upper ocean global O2 inventory for the latest observations based on the World Ocean Database 2018 is −0.98×1014 [mol/decade], in line with the CMIP6 Historical multi-model mean, though this recent observations-based trend estimate is weaker than previously reported trends. A comparison across ocean-only simulations from OMIP1 and OMIP2 suggests that differences in atmospheric forcing such as surface wind explain the simulated divergence across configurations in O2 inventory changes. Additionally, a comparison of coupled model simulations from the CMIP6 Historical configuration indicates that differences in background mean states due to differences in spin-up duration and equilibrium states result in substantial differences in the climate change response of O2. Finally, we discuss gaps and uncertainties in both ocean biogeochemical simulations and observations and explore possible future coordinated ocean biogeochemistry simulations to fill in gaps and unravel the mechanisms controlling the O2 changes.
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| 10. |
- Walin, G., et al.
(författare)
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Source-related variables for the description of the oceanic carbon system
- 2014
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Ingår i: Geochemistry Geophysics Geosystems. - 1525-2027. ; 15:9, s. 3675-3687
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Tidskriftsartikel (refereegranskat)abstract
- The oceanic carbon system is commonly described in terms of the two state variables total carbon, DIC, and alkalinity, Alk. Here we suggest the use of alternative source adapted state variables, Acidic Carbon, AC and Basic Carbon, BC, defined by and related to (DIC, Alk) with a simple linear transformation. (AC, BC) can be interpreted as representing respectively the supply to the system of carbon dioxide and dissolved carbonate, keeping in mind that supply of hydrogen ions acts to transform from basic carbon to acidic carbon. Accordingly these variables tell us how much carbon dioxide or dissolved carbonate we actually have in the water, despite the fact that the major part of the carbon resides in bicarbonate ions. We claim that using these source-related variables as a compliment to the traditional variables, offers a number of advantages in the formulation of continuity equations, as well as in the interpretation of observations and modeling results. The traditional definition of alkalinity is related to a measuring procedure rather than to the supply of material to the system. Here we demonstrate that alkalinity, though defined in the traditional way, may be interpreted in terms of sources and sinks acting on the system. In the case of ocean water this amounts to twice the supply of dissolved carbonate minus the net supply of free hydrogen ions. We argue that this interpretation is a useful complement to the traditional definition. Every process that affects the state of the carbon system may be quantified in terms of supply of carbon dioxide, F-a, carbonate ions, F-b, or hydrogen ions, E.
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