Consequence analysis in LPG installation using an integrated computer package

This article highlights the debate on social security regimes applicable to platform workers in Italy. As social security regimes differ according to the type of employment or self‐employment relationship, Italian case law dealing with platform workers’ employment status will be illustrated. Italian legislation, case law and collective bargaining on health and safety at work will then be presented, clarifying the coverage to which platform workers are entitled in the event of accidents at work and occupational diseases, with a focus on the COVID‐19 pandemic impact. In turn, the two main Italian minimum income schemes and the related scholarly debate will be outlined, as well as their impact on the ability of digital labour platforms to avoid their responsibilities as regards workers’ rights, including access to adequate social protection.

Comparison of heavy gas dispersion models for instantaneous releases

The consequences of a rod ejection accident are investigated in relation to the latest, high power density Westinghouse reactors. Limiting criteria are presented, based on experimental evidence, and if not exceeded these criteria will ensure that there will be no interference with core cooling capability, and radiation releases, if any, will be within the guidelines of 10CFR100. A basis is presented for the conservative selection of plant parameters to be used in the analysis, such that the analysis is applicable to a wide range of past, present, and future reactors. The calculational method employs a one-dimensional spatial kinetics computer code and a transient fuel heat transfer computer code to determine the hot spot fuel temperature versus time following a rod ejection. Using these computer codes, the most limiting hot channel factor (which does not cause the fuel damage limit criteria to be exceeded) has been determined as a function of the ejected rod worth. By this means, the limit criteria have been translated into ejected rod worths and hot channel factors which can be used effectively by the nuclear designer and safety analyst. The calculational method is shown to be conservative, compared to the results of a three-dimensional spatial kinetics analysis. (auth)

Hypothetical core disruptive accident experiments on simple fast test reactor models

The worldwide concern due to the increasing frequency of ecological disasters on our planet urged the scientific community to take action. One of the possible measures are analytical descriptions of pollution related phenomena, or simulations by effective and operational models with quantitative predictive power. The atmosphere is considered the principal vehicle by which pollutant materials are dispersed in the environment, that are either released from the productive and private sector or eventually in accidental events and thus may result in contamination of plants, animals and humans. Therefore, the evaluation of airborne material transport in the Atmospheric Boundary Layer (ABL) is one of the requirements for maintenance, protection and recovery of the ecological system. In order to analyse the consequences of pollutant discharge, atmospheric dispersion models are of need, which have to be tuned using specific meteorological parameters and conditions for the considered region. Moreover, they shall be subject to the local orography and shall supply with realistic information concerning environmental consequences and further help reduce impact from potential accidents such as fire events and others. Moreover, case studies by model simulations may be used to establish limits for the escape of pollutant material from specific sites into the atmosphere.

Approximately 2.6 x 10(4) TBq (700,000 Ci) of 131I were released to the air from reactor fuel processing plants on the Hanford Site in southcentral Washington State from December 1944 through December 1949. The Hanford Environmental Dose Reconstruction Project developed a suite of codes to estimate the doses that might have resulted from these releases. The Regional Atmospheric Transport Code for Hanford Emission Tracking (RATCHET) computer code is part of this suite. The RATCHET code implements a Lagrangian-trajectory, Gaussian-puff dispersion model that uses hourly meteorological and release rate data to estimate daily time-integrated air concentrations and surface contamination for use in dose estimates. In this model, iodine is treated as a mixture of three species (inorganic gases, organic gases, and particles). Model deposition parameters are functions of the mixture and meteorological conditions. A resistance model is used to calculate dry deposition velocities. Equilibrium between concentrations in the precipitation and the air near the ground is assumed in calculating wet deposition of gases, and irreversible washout of the particles is assumed. RATCHET explicitly treats the uncertainties in model parameters and meteorological conditions. Uncertainties in 131I release rates and partitioning among the nominal species are treated by varying model input. The results of 100 model runs for December 1944 through December 1949 indicate that monthly average air concentrations and deposition have uncertainties ranging from a factor of two near the center of the time-integrated plume to more than an order of magnitude near the edge. These results indicate that approximately 10% of the 131I released to the atmosphere decayed during transit in the study area, approximately 56% was deposited within the study area, and the remaining 34% was transported out of the study area while still in the air.

STATIC_TEMP: a useful computer code for calculating static formation temperatures in geothermal wells

Predictive models, which leverage the relationship between environmental variables and river health, serve as a valuable tool for predicting the river health at unmonitored sites. Such models should be generalizable to unseen data. However, predictions derived from machine learning (ML) models can exhibit large variability even with minor changes in the training dataset. The potentially unstable behaviors of a ML model decrease the model’s generalizability to unseen data, likely limiting its applicability as an assistant tool for decision making. Heterogeneous ensemble models are recognized to achieve greater generalizability compared to single models owing to their structural diversity. In this study, various machine learning (ML) models are employed to understand the relationship between environmental factors and benthic macroinvertebrate health. To obtain a model with better generalizability, the present study compares the generalizability of heterogeneous ensembles with those of homogeneous ensembles and single models by using the bias–variance decomposition. The models classified five grades (very good to very poor) of benthic macroinvertebrate index (BMI). The models incorporated diverse environmental factors, including water quality, hydrology, meteorological conditions, land cover, and stream properties, as input variables. The data were monitored at 2,915 sites in the four major river watersheds in South Korea during the 2016–2021 period. The results indicated better generalizability of the heterogeneous and homogeneous ensembles than single models. Moreover, heterogeneous ensembles tended to show higher generalizability than homogeneous ensembles, although the differences were marginal. Weighted soft voting was the most generalizable of the heterogeneous ensembles, with loss of 0.49. Weighted soft voting also delivered acceptable classification performance on the test set, with accuracy of 0.52. The identified contributions of the environmental factors to BMI predictions and the directions of their effects agreed with established knowledge, confirming the reliability of the predictions. These results demonstrate the usefulness of the heterogeneous ensemble models for increasing the generalizability of ML model predictions. Furthermore, despite the slightly lower generalizability than voting-based ensembles, homogeneous ensembles demonstrated comparable levels of generalizability to heterogeneous ensembles.

In the alpine region as well as in other European areas the ozone concentration appears to be increasing (Warmbt, 1977). During this century the ozone levels in the atmospheric boundary layer have been almost doubled (Volz and Kley, 1988). After Puxbaum et al. (1991) the ozone concentration in the Zillertal (a small valley in the Austrian Alps) has been increased by a factor of 3 since 1950. Beside this long term trend high ozone values of 100 ppb and more are increasingly observed during pollution episodes. These episodes are associated with high pressure systems, when the meteorological condition, in particular warm temperatures, clear skies and low wind speeds, encourage the photochemical formation of ozone. Calms and inversions causing reduced ventilation occur more frequently in mountain valleys than over flat terrain (Dreiseitl and Weber, 1991). Therefore the meteorological conditions in the Alps conduce the ozone production.

The small modular reactor (SMR) class core design concept of once-through SuperCritical light Water-cooled Reactor (SCWR) with fast neutron spectrum (Super FR) is being developed at Waseda University. The preceding studies revealed that SMR class Super FR core can be designed, whose performance is compatible to large Super FR core with respect to average power density and average coolant outlet temperature with small core pressure drop, which is favorable from the viewpoint of achieving natural circulation cooling after reactor shutdown. However, consequences of severe accident of such SMR class Super FR has never been considered. Two major issues need to be addressed. The first issue is the fundamental issue for a water-cooled reactor, which is the possibility of the whole core meltdown as the coolant boils off at low temperature under depressurized condition. Second issue is the fundamental issue for a fast spectrum core, which is to avoid re-criticality of molten core as the reactivity increases with core compaction. With the above described background, this study proposes In-Vessel Retention (IVR) of SMR class Super FR, which can avoid re-criticality even if the whole core relocates to the lower plenum of the Reactor Pressure Vessel (RPV). The debris coolability may be a subject for the future study. The core characteristics with a given set of design specifications and criteria are evaluated based on fully coupled neutronics and thermal-hydraulics core burnup calculations. The neutronics calculations are based on interpolation of macroscopic cross sections with neutron diffusion approximation (SRAC and COREBN codes with JENDL-4.0 nuclear data library). The thermal-hydraulics calculations are based on in-house code that adopts single channel model with Watts’ correlation for evaluating supercritical water heat transfer. The batch fuel shuffling pattern is considered to evaluate the equilibrium core characteristics. The debris criticality is evaluated based on Monte-Carlo based method (MVP) to consider the RPV lower plenum and debris configurations. The fuel debris are assumed to be homogeneous. Firstly, for a given discharge burnup, quantitative relationship between the core criticality and the debris criticality is evaluated. The results show that downsizing the core increases the debris criticality when relocated to the RPV lower plenum, because the Pu enrichment needs to be raised to attain the same discharge burnup with larger neutron leakage. The results also show that some measures are necessary to prevent re-criticality of the debris if the whole core is assumed to relocate to the lower plenum. Then, the new “debris dispersion IVR” concept is proposed. In this concept, heat resistant structure (tentatively ZrO2), which contains some neutron absorbing material (tentatively, B4C) is placed at the center of the lower plenum to disperse the debris and gain neutron leakage and absorption. Then, the trade-off relationships between the core discharge burnup and the size of the debris dispersion structure are evaluated with considerations of core design specifications such as average Pu enrichment, operation cycle length, and fuel shuffling patterns.

On line simulation system for industrial accidents

New explicit microplane model for concrete: Theoretical aspects and numerical implementation

In India, Odisha state experienced major natural hazards like floods and cyclones. Floods were experienced fifteen times during 2001–2018 and had two major catastrophic cyclones (super-cyclone 1999 and Phailin 2013). Flood is triggered due to meteorological, hydrological, and terrain conditions at any given place. Considering the terrain parameters namely elevation, slope, drainage density, soil and land use/land cover as the contributing factors for flood inundation, a new technique is developed to calculate flood hazard using analytical hierarchy process (AHP). Using multi-temporal satellite derived flood extent, spatial flood frequency map (SFFM) were generated based on the frequency of inundation. SFFM which represents the observed flood extent on ground at different magnitudes of flood and the terrain conditions on the ground are used synergistically for generating the hazard map. Part of Mahanadi River in Odisha which is highly flood-prone is taken for analysis in this study. More than 100 satellite data sets both microwave SAR and optical data acquired at different magnitudes of flood during 2001–2018 were analysed to prepare the SFFM maps. Pair wise comparison rating was given among flood producing factors and weightage of each factor was computed by using GIS based AHP and multi-criteria evaluation techniques. The individual derived weights (in percentage) of the contributing factors obtained were 50.874 for SFFM, 22.775 for elevation, 10.966 for drainage density, 7.225 for slope, 5.914 for land use and 2.936 for soil. Further, the layers were used in weighted overlay tool and respective weights in percentage were given for generating the flood hazard map in GIS environment. The flood hazard was classified into five hazard classes i.e. very high, high, moderate, low, and very low and corresponding hazard area was estimated to be 7467 ha, 12,871 ha, 28,700 ha, 35,518 ha and 292 ha respectively. These statistics and hazard map will help the concerned local authorities for formulating strategic policies for land use planning and minimize the effect of flood on agricultural land and human lives.

Idealized structural unit method (ISUM) is now well recognized as one of the most efficient methods to analyze nonlinear behavior of large-sized structures under extreme or even accidental actions. This paper presents some techniques of ISUM modeling and surveys the literature on the ultimate limit state assessment of ship structures using ISUM. Theoretical formulations of ISUM elements for the progressive hull girder collapse analysis of ships that were implemented into ALPS/HULL computer code are outlined. Some benchmark studies are made by a comparison with physical test data and ALPS/HULL analyses on a frigate ship hull model under sagging moment tested by UK Royal Navy and on two double-skin tanker hull models under sagging or hogging moments tested by US Navy. Some ALPS/HULL application examples to progressive collapse analysis of a double-skin shuttle tanker hull under combined vertical and horizontal bending moments are then demonstrated. It is concluded that ISUM is very useful for the progressive hull girder collapse analysis of ships because it provides very accurate results while the computing time is very short.

This paper shows the benefits of synchronous multichannel PD measurements. Different methods of evaluation as 3PARD, 3PTRD and 3CFRD are presented in theory and by application examples. These advanced evaluation techniques require a fully synchronized multi-channel PD measuring system for advanced PD data evaluation. PD source separation and the separation of PD and interferences can simplify the PD analyses to get more reliable results when estimating the condition of the insulation of HV apparatus.