Application of Risk Analysis Results in Emergency Planning of a Nuclear Power Plant

NPP Goesgen developed a full-scope probabilistic risk assessment (PRA) model, allowing for an estimate of the risk of offsite consequences. The model considers all operational modes of the plant, power operation, low power operation and shutdown conditions and all risk-relevant initiating events that may lead to a plant accident. The model allows computing different risk metrics starting from core damage frequency, frequency of a large offsite release to detailed plant damage states, activity release categories as well as the risk of offsite consequences expressed in radiological health effects. The risk model is programmed in the software system RISKMAN™ in the format of a set of linked event trees with associated fault trees. Analysis tools for the estimation of accident progression and offsite consequences support the model. A plant-specific simulator for severe accidents is in use, which is based on the MELCOR code. Off-site consequences in terms of dose levels are calculated using the MACCS 2.0 code. The full power models are used to support emergency planning by providing information on the possible consequences of hypothetical accidents in dependence on weather conditions. In cooperation with the responsible governmental agencies, this allows to support evacuation actions in case of severe accidents. Simple cartographic aids are available for emergency planning accounting for a possible loss of offsite power during an emergency, preventing the use of computational tools. The paper presents the methodology and key insights of the risk assessment of offsite consequences for NPP Goesgen and demonstrates the use of the results in emergency planning

Floating stones off El Hierro, Canary Islands: xenoliths of pre-island sedimentary origin in the early products of the October 2011 eruption

The eruption that started off the south coast of El Hierro, Canary Islands, in October 2011 has emitted intriguing eruption products found floating in the sea. These specimens appeared as floating volcanic "bombs" that have in the meantime been termed "restingolites" (after the close-by village of La Restinga) and exhibit cores of white and porous pumice-like material. Currently the nature and origin of these "floating stones" is vigorously debated among researchers, with important implications for the interpretation of the hazard potential of the ongoing eruption. The "restingolites" have been proposed to be either (i) juvenile high-silica magma (e.g. rhyolite), (ii) remelted magmatic material (trachyte), (iii) altered volcanic rock, or (iv) reheated hyaloclastites or zeolite from the submarine slopes of El Hierro. Here, we provide evidence that supports yet a different conclusion. We have collected and analysed the structure and composition of samples and compared the results to previous work on similar rocks found in the archipelago. Based on their high silica content, the lack of igneous trace element signatures, and the presence of remnant quartz crystals, jasper fragments and carbonate relicts, we conclude that "restingolites" are in fact xenoliths from pre-island sedimentary rocks that were picked up and heated by the ascending magma causing them to partially melt and vesiculate. They hence represent messengers from depth that help us to understand the interaction between ascending magma and crustal lithologies in the Canary Islands as well as in similar Atlantic islands that rest on sediment/covered ocean crust (e.g. Cape Verdes, Azores). The occurrence of these "restingolites" does therefore not indicate the presence of an explosive high-silica magma that is involved in the ongoing eruption

Origin and ascent history of unusually crystal-rich alkaline basaltic magmas from the western Pannonian Basin

The last eruptions of the monogenetic Bakony-Balaton Highland Volcanic Field (western Pannonian Basin, Hungary) produced unusually crystal- and xenolith-rich alkaline basalts which are unique among the alkaline basalts of the Carpathian- Pannonian Region. Similar alkaline basalts are only rarely known in other volcanic fields of the world. These special basaltic magmas fed the eruptions of two closely located volcanic centres: the Bondoró-hegy and the Füzes-tó scoria cone. Their uncommon enrichment in diverse crystals produced unique rock textures and modified original magma compositions (13.1-14.2 wt.% MgO, 459-657 ppm Cr, 455-564 ppm Ni contents). Detailed mineral-scale textural and chemical analyses revealed that the Bondoró-hegy and Füzes-tó alkaline basaltic magmas have a complex ascent history, and that most of their minerals (~30 vol.% of the rocks) represent foreign crystals derived from different levels of the underlying lithosphere. The most abundant xenocrysts, olivine, orthopyroxene, clinopyroxene and spinel, were incorporated from different regions and rock types of the subcontinental lithospheric mantle. Megacrysts of clinopyroxene and spinel could have originated from pegmatitic veins / sills which probably represent magmas crystallized near the crust-mantle boundary. Green clinopyroxene xenocrysts could have been derived from lower crustal mafic granulites. Minerals that crystallized in situ from the alkaline basaltic melts (olivine with Cr-spinel inclusions, clinopyroxene, plagioclase, Fe-Ti oxides) are only represented by microphenocrysts and overgrowths on the foreign crystals. The vast amount of peridotitic (most common) and mafic granulitic materials indicates a highly effective interaction between the ascending magmas and wall rocks at lithospheric mantle and lower crustal levels. However, fragments from the middle and upper crust are absent from the studied basalts, suggesting a change in the style (and possibly rate) of magma ascent in the crust. These xenocryst- and xenolith-rich basalts yield divers tools for estimating magma ascent rate that is important for hazard forecasting in monogenetic volcanic fields. According to the estimated ascent rates, the Bondoró-hegy and Füzes-tó alkaline basaltic magmas could have reached the surface within hours to few days, similarly to the estimates for other eruptive centres in the Pannonian Basin which were fed by "normal" (crystal- and xenolith-poor) alkaline basalts

Corrigendum to "Floating stones off El Hierro, Canary Islands: xenoliths of pre-island sedimentary origin in the early products of the October 2011 eruption" published in Solid Earth, 3, 97–110, 2012

No abstract available

The comparison of macroseismic intensity scales

The number of different macroseismic scales that have been used to express earthquake shaking in the course of the last 200 years is not known; it may reach three figures. The number of important scales that have been widely adopted is much smaller, perhaps about eight, not counting minor variants. Where data sets exist that are expressed in different scales, it is often necessary to establish some sort of equivalence between them, although best practice would be to reassign intensity values rather than convert them. This is particularly true because difference between workers in assigning intensity is often greater than differences between the scales themselves, particularly in cases where one scale may not be very well defined. The extent to which a scale guides the user to arrive at a correct assessment of the intensity is a measure of the quality of the scale. There are a number of reasons why one should prefer one scale to another for routine use, and some of these tend in different directions. If a scale has many tests (diagnostics) for each degree, it is more likely that the scale can be applied in any case that comes to hand, but if the diagnostics are so numerous that they include ones that do not accurately indicate any one intensity level, then the use of the scale will tend to produce false values. The purpose of this paper is chiefly to discuss in a general way the principles involved in the analysis of intensity scales. Conversions from different scales to the European Macroseismic Scale are discussed

The magmatic plumbing system beneath El Hierro (Canary Islands): constraints from phenocrysts and naturally quenched basaltic glasses

A thermobarometric and petrologic study of basanites erupted from young volcanic cones along the submarine portions of the three El Hierro rift zones (NE-Rift, NW-Rift and S-Ridge) has been performed to reconstruct magma plumbing and storage beneath the island. Mineral-melt thermobarometry applied to naturally quenched glass and clinopyroxene rims yields pressures ranging from 350 to 1070 MPa with about 80% of the calculated pressures being in the range of 600–800 MPa. This corresponds to a depth range of 19–26 km, implying that the main level of final crystal fractionation is within the uppermost mantle. No systematic dependence between sample locality and fractionation pressures could be observed. Olivine and clinopyroxene crystals in the rocks are complexly zoned and have, on an inter-sample as well as on an intra-sample scale, highly variable core and rim compositions. This can best be explained by mixing of multiply saturated (olivine, magnetite, clinopyroxene, ilmenite), moderately evolved magmas with more mafic magmas being either only saturated with olivine + spinel or with olivine + spinel + clinopyroxene. The inter-sample differences indicate derivation from small, isolated magma chambers which have undergone distinct fractionation and mixing histories. This is in contrast to oceanic intraplate volcanoes situated on plumes with high melt supply rates, e.g. Kilauea Volcano (Hawaii), where magma is mainly transported through a central conduit system and stored in a shallow magma chamber prior to injection into the rift zones. The plumbing system beneath El Hierro rather resembles the magma storage systems beneath, e.g. Madeira or La Palma, indicating that small, intermittent magma chambers might be a common feature of oceanic islands fed by plumes with relatively low fluxes, which results in only limited and periodic magma supply

METEOR Fahrtbericht / Cruise Report M146, Henry Seamount Seepage Exploration (HESSE), Recife (Brazil) - Las Palmas de Gran Canaria (Spain), March 17 - April 16, 2018

The main objective of cruise M146 was the discovery and documentation of inferred fluid venting sites at Henry Seamount, an extinct 126 Ma old volcano located 40 km to the southeast of El Hierro island. Evidence of recent fluid discharge at this seamount was provided by rock and shell samples from a reconnaissance dredging campaign during METEOR cruise M66/1. Such discharge could reflect hydrothermal circulation of seawater through the old oceanic crust, a globally important process. This type of circulation requires basement outcrops through the impermeable sediment cover, which can be provided by seamounts and island flanks. To achieve the goals, we carried out a hydroacoustic survey of Henry Seamount using the ship's multibeam echosounder and PARASOUND system, and mapped an area of 31 km² in detail during seven AUV dives. About 600 km of reflection seismic profiles were shot across the seamount and its vicinity to reveal sub-bottom structures and basement outcrops. As a potential tracer for fluid discharge or recharge sites, the heat flow in the area was determined by more than 50 measurements along four profiles using a heat flow probe. During seven TV sled surveys we explored the seafloor on the top and flanks of Henry Seamount, and logged temperature, turbidity and geochemical potential of the bottom water. Five gravity cores and 13 grabs provided samples of sediment, shells and other biota, and revealed conspicuous basaltic ash and lapilli layers. Our data show that surprisingly large areas of the seamount are covered with Abyssogena clam shells, testifying widespread past fluid discharge, even though this is not reflected in the heat flow data. Oxydation-reduction potential (ORP) anomalies in the bottom water indicate that in some areas fluids are still discharging