Probabilistic Risk Assessment Methods Research Articles

A response-based internal pressure risk assessment method for PCCV with steel fiber reinforcement

The probabilistic risk assessment (PRA) is a hot topic for highlighting the reliability and safety of infrastructures, especially for nuclear power plants (NPPs). The current internal pressure risk assessment method for prestressed concrete containment vessel (PCCV) generally adopts the internal pressure to characterize its fragility (namely internal-pressure-based fragility), even though the failure of PCCV is factually more tightly associated with PCCV’s realistic responses. This study proposes a novel response-based probabilistic risk assessment method for PCCV under internal pressure. The method adopts the response of the containment to characterize the fragility of components. Additionally, the steel fiber is introduced to form steel fiber reinforced concrete (SFRC) PCCV and the fragility and risk of the SFRC PCCV are quantitatively studied. The results indicate that a real and larger dispersion for the internal pressure risk of the PCCV would be induced by adopting the proposed internal pressure risk assessment method. The strategy of the addition of steel fiber to the conventional PCCV can decrease the internal pressure risk by about 72.1 % on average.

Dynamics simulation model for risk probability assessment based on cognitive modeling in manned deep dive mission scenario

The manned submersible, as the main vehicle of transportation for human navigation in deep sea, has closed and narrow cabin, and with longer operating time, harder operating environment. However, once a manned deep submergence accident occurs, it is highly likely to lead to disastrous consequences. Therefore, it is urgent to develop a dynamic probabilistic risk assessment method which can quantitatively assess the cognitive behavior performance and human error of oceanauts. In this paper, a cognitive behavior simulation method for oceanaut based on knowledge and experience was proposed, which integrated richer performance shaping factors (PIF) into the IDAC model, and a cognitive environment simulation program of the IDAC model was developed through the system dynamics method, so as to analyze the dynamic human error probability of the oceanaut. In addition, the effectiveness and feasibility of the proposed model were evaluated based on real case data of manned deep submergence tasks, and the cognitive characteristics of PIFs were interpreted and classified. The research results are helpful for research institutions of manned deep submersible to accurately identify key risk points, improve the operational efficiency of the human-machine system in the cabin, and reduce the risks of the overall operating system.

Risk-based path planning for preventing collisions and groundings of maritime autonomous surface ships

In this paper, we propose and demonstrate a method for risk-based path planning, generating risk-acceptable trajectories for an autonomous surface ship. This objective is achieved in two steps. The first step uses a dynamic probabilistic risk assessment method called K-shortest-paths Probabilistic Risk Assessment (KPRA), alongside risk models and dynamic system simulation, whose output is a list of paths ranked with respect to risk. Multiple risk influencing factors and accident types may be considered in this step. In this work, collision and powered grounding accidents, and their risk-influencing factors and indicators, are considered. The second step is to perform risk evaluation on the ranked scenarios, comparing them to predefined risk acceptance criteria and defining which scenarios have acceptable risk. Evaluating multiple paths allows operators to choose how strict the autonomous ship’s decision-making should be regarding risk, avoiding the problem of minimization algorithms being too conservative in terms of risk. One of the risk-acceptable paths is then chosen as a local plan to be acted by the autonomous ship. This paper has two main scientific contributions. First, an online Bayesian belief network risk model for navigation accident probability is designed and integrated to improve KPRA. Second, we propose a modified guidance, navigation, and control framework for autonomous ships, to include risk-based planning. We implement the modified framework into a real autonomous surface vehicle (ASV) named Grethe and demonstrate the method’s capabilities in field trials, where the ASV uses the method to generate local plans that avoid possible collision and grounding accidents.

Analysis of modern approaches to assessing reliability in construction

Introduction. The study considers modern strategies for ensuring the reliability of building structures in Russian and foreign regulations, including probabilistic, risk-informed and semi-probabilistic criteria of reliability assessment, at all stages of the life cycle of the structure. The advantages and disadvantages of prescriptive and parametric approaches are analyzed and ways of their further improvement are suggested.Aim. To clarify the terminology of parametric regulation in construction, to analyze the existing differences in its interpretation, and to develop an innovative strategy for further development of Russian regulation based on a comparative analysis of domestic and foreign approaches to reliability assessment.Materials and methods. The methodology involved studying the structure of Russian and foreign regulatory documents in the field of reliability and performing their comparative analysis. The study considered the main approaches to technical regulation in the construction industry.Results. The analysis outlined the criteria underlying the fastest introduction of innovations and ensuring the safety of technical solutions. The study demonstrated the difference between the meaning of the term “parametric regulation” in Russian strategy and its foreign interpretation. The regulation standards of the Russian Federation are based mainly on a semi-probabilistic approach and specification of partial reliability factors, i.e. individual parameters of strength and loads, while in the foreign standards, notably in ISO 2394:2016 and Eurocodes, the emphasis is shifted to qualitative and probabilistic criteria for assessing reliability. However, all social, economic and performance criteria should be observed only after all requirements for the reliability and safety of people have been met. Thus, both Russian and foreign approaches to regulation demonstrate no fundamental contradictions. The approaches are gradually moving towards convergence while maintaining continuity in the development of the regulatory framework.Conclusions. The principles of ensuring the reliability of the designed buildings and structures in Russian, international and foreign regulation standards are quite close and are based on the limit state method with a reasonable combination of mandatory and recommended parameters. The main criterion consists in ensuring the safety of human life. Under contemporary conditions, traditional semi-probabilistic approaches to regulation should be accompanied by mechanisms for rapid introduction of innovations and new technologies in construction. In terms of reliability, these mechanisms involve additional probabilistic reliability criteria and risk assessment methods. The reliability criteria will contribute in choosing the optimal design and technological solutions for the construction of unique buildings and structures, higher criticality structures, as well as in assessing existing structures during their life cycle.

Dynamic probabilistic risk assessment of emergency response for intelligent coal mining face system, case study: Gas overrun scenario

Intelligent coal mining has become an inevitable development trend of the coal industry in the era of artificial intelligence. Emergency response level is particularly important for preventing accidents and reducing accident losses in intelligent coal mine (ICM) operations, which urgently needs an accurate risk assessment method to assess the risk of ICM emergency response. Combining the ICM system structure and emergency response process (ERP) of human-system interaction based on the information, decision, and action in crew context (IDAC) model, this study proposes a dynamic probabilistic risk assessment (PRA) method based on dynamic Bayesian network (DBN), mainly including the event sequence diagram (ESD) from the cognitive perspective, human-system concurrent task analysis (CoTA) from success perspective and fault tree analysis (FTA) model from failure perspective, dependency model of performance influencing factor (PIF) from organizational impact perspective, and the “ESD-FTA-PIFs” coupled BN model. To address the uncertainty of risk factors (e.g., human factors and system equipment) and achieve quantitative analysis, the coupled BN model is mapped to the DBN model to perform dynamic PRA combining with existing databases, fuzzy set theory, Dempster-Shafer (D-S) evidence theory, and time-variant model. Finally, the practicality and advantages of the proposed methodology are demonstrated by a real case study in the gas overrun scenario. The results show that the DBN model can perform dynamic inference analysis to achieve the risk prediction of event and system state compared with the static BN model. The comprehensive integrated DBN model of “ESD-FTA-PIFs” not only enables bidirectional risk analysis of emergency response event, but also enables the systematic traceability of risk factors. The proposed methodology can be a useful tool to assess the dynamic risk of ICM emergency response and decision-making, and it can provide scientific guidance for risk assessment during emergency response of other safety-critical industries.

Modified Method for Surface Probabilistic Risk Assessment of Aero Engine Compressor Disks Considering Shot Peening

Aero engine compressor disks are typically life-limited parts and it is necessary to secure them through the implementation of an engineering plan and a manufacturing plan. Specifically, the engineering plan recommends the quantification of the safety of life-limited parts on the basis of probabilistic risk assessment (PRA). However, the direct correlation between plans is limited, and the effect of manufacturing parameters on the safety of life-limited parts remains to be investigated. Shot peening, as a typical method of surface manufacturing, can significantly improve the safety of life-limited parts. Therefore, a modified mathematical surface PRA method considering shot peening parameters is developed in this paper to further bridge the design and manufacturing processes. Additionally, a general database is established using the response surface method to overcome the simulation complexity. On the basis of this method and the general database, an innovative direct and efficient determination of key shot peening parameters through failure risk in the design stage is proposed. The results indicate that failure risk decreased by 3.26%, 11.31%, and 9.71%, respectively, with increasing number, diameter, and velocity of shots, with the effect of diameter being the greatest. In addition, the method improves the efficiency of determining the key parameters by 75.80%, thus satisfying the requirements of abundant and efficient iterations during the design stage.

Accumulation Characteristics and Probabilistic Risk Assessment of Cd in Agricultural Soils Across China

To understand cadmium (Cd) pollution status and associated health risks in agricultural soils of China, a database including Cd concentrations of 160446 soil samples from 240 cities (counties) in 31 provinces was constructed based on domestic and foreign literature. The contamination factor and geochemical accumulation index were applied to explore the pollution level of Cd, and then health risks for different population groups were evaluated with the probabilistic risk assessment method based on Monte Carlo simulation. The results indicated that soil Cd concentrations in China ranged from 0.012 to 23.33 mg·kg-1, with the geometric mean of 0.473 mg·kg-1, which was 1.58 times the risk screening value of heavy metals in the soil of agricultural land (GB 15186-2018) (6.5<pH ≤ 7.5). From the perspective of different regions, the highest concentrations of soil Cd were found in central China, followed by southwest, south, northwest, northeast, east, and north China. From the perspective of time, there was no significant difference in soil Cd in different time periods (P>0.05). Cd pollution in agricultural soils was mainly distributed in Yunnan, Hunan, Guangxi, and Gansu provinces in China, which may have been related to the mining and smelting activities. The non-carcinogenic risks for all the population groups could be negligible, whereas there were potential carcinogenic risks for adults and seniors, with 5.81% and 4.49% of carcinogenic risk values exceeding the threshold of 1E-06 set by USEPA for adults and seniors, respectively. The results of this study provided valuable information for the pollution prevention and risk control of soil Cd pollution. To improve the accuracy of health risk assessment results, the exposure ingestion route of agricultural products and bioavailability of soil Cd should be considered in the probabilistic ecological risk assessment.

Seismic risk of typical ageing petrochemical steel structure in harsh atmospheric conditions

This paper addresses the evaluation of the effects of corrosion on the performance of ageing steel industrial infrastructures. A novel probabilistic risk assessment method is presented with respect to a case study of a real petrochemical structure located in an atmospheric environment with high severity of corrosion. The results of damage assessment derived from refined fragility analyses revealed that long-term corrosion mass reduction can increase the probability of damage to the structure by an average of 40%. Furthermore, the risk analysis demonstrated that the annual failure rate of the corroded structure is at most 2.80 times that of the uncorroded counterpart. The vulnerability analysis showed that the difference in annual repair costs between corroded and uncorroded cases gradually increased as the severity of ground motion raised. Moreover, the results of comprehensive and refined nonlinear analyses indicated that the corroded structure after 50 and 100 years can increase the likelihood of causing corrosion repair costs in the first year by about 40 and 60 times, respectively. The evaluation of the ratio of construction to maintenance and retrofitting was also carried out; it was based on innovative retrofitting measures with the use of Carbon Fibre Reinforced Polymers for steel structures. The findings illustrated in the present numerical study can help owners and insurance companies to predict more reliably maintenance and repair costs, thus they can provide an efficient roadmap for industrial asset management.

Ascertaining priority control pollution sources and target pollutants in toxic metal risk management of a medium-sized industrial city

Re-suspended surface dust (RSD) often poses higher environmental risks due to its specific physical characteristics. To ascertain the priority pollution sources and pollutants for the risk control of toxic metals (TMs) in RSD of medium-sized industrial cities, this study took Baotou City, a representative medium-sized industrial city in North China, as an example to systematically study TMs pollution in RSD. The levels of Cr (242.6 mg kg−1), Pb (65.7 mg kg−1), Co (54.0 mg kg−1), Ba (1032.4 mg kg−1), Cu (31.8 mg kg−1), Zn (81.7 mg kg−1), and Mn (593.8 mg kg−1) in Baotou RSD exceeded their soil background values. Co and Cr exhibited significant enrichment in 94.0 % and 49.4 % of samples, respectively. The comprehensive pollution of TMs in Baotou RSD was very high, mainly caused by Co and Cr. The main sources of TMs in the study area were industrial emissions, construction, and traffic activities, accounting for 32.5, 25.9, and 41.6 % of the total TMs respectively. The overall ecological risk in the study area was low, but 21.5 % of samples exhibited moderate or higher risk. The carcinogenic risks of TMs in the RSD to local residents and their non-carcinogenic risks to children cannot be ignored. Industrial and construction sources were priority pollution sources for eco-health risks, with Cr and Co being the target TMs. The south, north and west of the study area were the priority control areas for TMs pollution. The probabilistic risk assessment method combining of Monte Carlo simulation and source analysis can effectively identify the priority pollution sources and pollutants. These findings provide scientific basis for TMs pollution control in Baotou and constitute a reference for environmental management and protection of residents' health in other similar medium-sized industrial cities.

Modelling potential human exposure to the nitrification inhibitor dicyandiamide through the environment-food pathway

Dicyandiamide (DCD) is a nitrification inhibitor that effectively reduces nitrogen losses from fertiliser applied to pastures and has the potential to reduce greenhouse gas emissions. Detection of DCD in dairy products in New Zealand led to safety concerns of food products from animals grazing pastures treated with DCD at high application rates (10 kg/ha). This study explores potential risks associated with DCD's application to agricultural grasslands wherein DCD is applied with fertiliser-N at recommended rates. Probabilistic risk assessment method was employed to calculate human Estimated Daily Intake (EDI) of DCD from milk following two application methods (co-application of DCD with granular N-fertiliser and liquid N-fertiliser). The exposure assessment model consists of five separate modules covering application/soil conditions, field conditions, animal feeding, milk production and human exposure/risk to characterise risk in humans. The predicted mean DCD concentration in milk was 0.005 mg DCD/kg milk for the granular method and 0.05 mg DCD/kg milk for the liquid method, respectively. Furthermore, EDI of DCD for both the granular and liquid methods (1 × 10−5 mg and 1 × 10−4 mg DCD/kg body weight/ day, respectively) were well below the European Food Safety Authority set Tolerable Daily Intake limit of 1 mg DCD/kg body weight/ day. Back-calculation revealed that under the conditions of co-application of DCD with granular and liquid nitrogen fertilisers at maximum permissible rates, for EDI to exceed TDI of 1 mg DCD/kg body weight/ day, DCD application rate would need to exceed DCD fertiliser limit (2.25–4.5% by mass of urea nitrogen) set in Commission Regulation (EC) No 1107/2008, and the bio-transfer factor would need to be over 100%. From the sensitivity analysis, for both application types it was found that phytoaccumulation factors, milk intake and the bio-transfer factors are critical factors influencing the EDI. From the present study, the Margin Of Safety values for both application types exceed 1; indicating DCD does not present a significant risk to human health.

Estimation of Probabilistic Environmental Risk of Heavy Metal(loid)s in Resuspended Megacity Street Dust with Monte Carlo Simulation

To improve the ecological environment quality of industrial cities and protect the health of residents, we determined the priority control factors of heavy metal(loid)s (HMs) pollution and risk in the resuspended street dust (RSD) of Shijiazhuang, an emblematic heavy-industrial city in North China, according to the probabilistic risk assessment method. The results showed that the HMs studied in Shijiazhuang RSD exhibited different pollution levels, that is, Hg showed moderate-to-severe pollution and above; Zn showed moderate-and-above pollution; Co, Cu and Pb showed non-pollution to moderate pollution; while As, Cr, Mn and Ni showed no pollution. The overall contamination of HMs in the RSD presented moderate-to-above contamination levels in &gt;94% of samples. Mercury exhibited considerable-to-very-high ecological risk. The synthetic ecological risks of the HMs were considerable-to-above. The comprehensive pollution and synthetic ecological risk of HMs in Shijiazhuang RSD were mainly caused by Hg. The carcinogenic risk of HMs in RSD to local inhabitants and their non-carcinogenic risk to children should not be ignored. Coal-related industrial sources are a priority source to control. Hg and As are priority HMs to control. We suggest that local governments should strengthen the management of coal-related industrial sources and As and Hg emissions.

Proposal of quantification method of dynamic system reliability model of digital RPS using Markov state-transition model

ABSTRACT In safety systems of the latest nuclear power plants such as the Advanced Boiling Water Reactor (ABWR) and the latest Pressurized Water Reactor (PWR), digital circuits are used for start-up signals of a reactor protection system (RPS) and emergency core cooling systems (ECCS). And several studies have been conducted to develop the method to build a system reliability model of RPS to be combined with probabilistic risk assessment (PRA) so far. However, these studies have not been sufficiently progressed in terms of the quantitative evaluation and coupling with the conventional PRA method. Despite of the efforts of Task group of Digital system reliability failure mode taxonomy (DIGREL, later becoming Working Group on Digital Instrumentation and Control [WGDIC]) of Organization for Economic Co-operation and Development (OECD)/Nuclear Energy Agency (NEA) in this field, the situation has not changed sufficiently. From these backgrounds, this paper presents a rational quantitative evaluation method of the dynamic system reliability model of the digital RPS which can represent time-dependency and is consistent with the conventional PRA method.

Risco determinístico e probabilístico no consumo de morangos com resíduos de agrotóxicos

ABSTRACT: Repeated presence of strawberries amongst produce with pesticide residues results in questionings related to the risks involved by its consumption. Deterministic and probabilistic risk assessment methods might be used depending on the available data. In the present study, both methods were used to estimate risks of pesticide intake by strawberry consumption. Strawberry samples along two years were analyzed via the multiresidue method. Results of active ingredients (a.i.) concentrations were organized and used for calculations for intake estimates. On the deterministic method, intake was calculated based on the data of a.i. concentration and consumption data coming from an online questionnaire and body weight between 5 and 70 kg. On the probabilistic method, the concentrations of a.i. and body weight of 60 kg were evaluated in two scenarios: a) consumption data from an online questionnaire or b) consumption data retrieved from Family Budget Survey of the Brazilian Institute of Geography and Statistics. In the 62 strawberry samples, 38 a.i. were quantified and in 25 samples the residue analyses were considered satisfactory and 37 had an unsatisfactory outcome. In the deterministic approach, 23% of the a.i. had a calculated intake higher than the acceptable daily intake (ADI) and risk concentrated in body weights between 5 and 30 kg. The risk is low when considering a body weight of 60 kg. All a.i. tested in the first scenario of the probabilistic method pointed towards some possibility of intake being higher than the ADI. In the second scenario, only the a.i. procymidone exceeded the ADI.

Quantitative Risk Assessment for Salmonella in Lettuce (Lactuca sativa) Consumed in Benin, West Africa

The present study aims at quantitatively assessing the risk associated with Salmonella in lettuce (Lactuca sativa) consumed in Benin (West Africa). To that end, a survey was conducted involving 550 respondents to determine the conditions under which the product is handled along the supply chain and its consumption pattern. The prevalence and concentration of Salmonella in lettuce were collected from the literature. The consumption data and the data on Salmonella concentrations in lettuce were combined to estimate the exposure to Salmonella using a probabilistic risk assessment method. The @Risk software package (Palisade USA) was used to run Monte Carlo simulations with 10,000 iterations. Three dose-response models were used to assess the risk of salmonellosis. Different scenarios were tested to identify factors that could influence the risk of salmonellosis. The results showed that lettuce is exposed to temperature abuse under inappropriate hygienic conditions. In 90% of the cases, the exposure to Salmonella was between 3 and 7 log CFU/serving. The risk of salmonellosis per serving varied from 7.7% to 95% depending on the dose-response used with the scenario taking into account the current handling conditions of the lettuce. In contrast, when considering the scenario where the cold chain is respected along the supply chain, the risk of salmonellosis varied from 0% to 3.3% depending on the dose response used. The study highlights the importance of the cold chain, good agricultural practices and good hygienic practices to reduce exposure to Salmonella through the consumption of lettuce and thus the risk of salmonellosis.

Ambient water quality criteria derived using probabilistic risk assessment.

National recommendations for numeric human health ambient water quality criteria (AWQC) for toxic substances are derived by the US Environmental Protection Agency (USEPA) using a deterministic approach that combines point estimates for exposure, toxicity, and acceptable risk. In accordance with the Clean Water Act, states, territories, and authorized tribes must either adopt these recommendations or modify and replace them with criteria using an alternative, scientifically defensible method. Recent reports have criticized the deterministic approach, stating that it suffers from compounded conservatism by selecting upper percentiles or maximum values for multiple inputs and that it cannot directly determine what portion of the population a given criterion protects. As an alternative, probabilistic risk assessment (PRA) has been promoted as a more transparent and robust method for deriving AWQC. Probabilistic risk assessment offers several advantages over the deterministic approach. For example, PRA uses entire data distributions rather than upper-percentile point estimates to specify exposures, thereby reducing compounded conservatism. Additionally, because it links acceptable risk targets with specific segments of the exposed population, PRA-based AWQC demonstrably protects multiple subsets of the population. To date, no study has quantitatively compared deterministic and PRA approaches and resulting AWQC using national inputs consistent with USEPA guidance. This study introduces a PRA method for deriving AWQC and presents case studies to compare probabilistically derived AWQC with USEPA's 2015 recommendations. The methods and results of this work will help federal and state regulators, water quality managers, and stakeholders better understand available approaches to deriving AWQC and provide context to assumption- and method-specific differences between criteria. Integr Environ Assess Manag 2023;19:501-512.© 2022 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Automatic Generation of Event Trees and Fault Trees: A Model-Based Approach

In the past few decades, the increasing complexity of modern engineering systems has been driven by the integration of a large number of components whose operations may involve many disciplines (e.g., thermal hydraulics, plant operations, cybersecurity). Most computational tools used by industry and regulators for system safety and reliability assessments are still based on the traditional fault tree (FT) and event tree (ET) approach, which may not be able to capture complex interactions among system constituents. The use of simulation tools has widely increased in the past few decades to improve the fidelity of the reliability and safety analyses. However, the direct use of simulation tools as part of dynamic probabilistic risk assessment (DPRA) methods is not getting traction since (1) modeling the whole system under consideration with DPRA methods may be computationally expensive and unnecessary, and (2) the manual integration of DPRA models into existing state-of-practice probabilistic risk assessment models (i.e., based on FTs and ETs) can be time consuming and prone to errors. In this paper we propose a procedure to overcome this limitation by presenting several algorithms designed to automatically construct subsystem ETs and FTs from DPRA methods for integration into an existing ET/FT system model.

Distribution Characteristics and Risk Assessment of Heavy Metal Pollution in Farmland Soils and Crops in Luancheng, Shijiazhuang City

In order to explore the distribution characteristics of heavy metal contamination of farmland soil surrounding Luancheng town, Shijiazhuang City, Henan province, the concentrations of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn in the surface soil and crops were determined and assessed. The principal components were also analyzed for source apportionment. The heavy metal concentrations in crops were further detected, and the non-carcinogenic health risks in the study area were evaluated using the probabilistic risk assessment method, as to provide a theoretical basis for the treatment, prevention, and control of heavy metal pollution in farmland soil in Luancheng. According to the results, ω(Cd), ω(Cr), ω(Cu), ω(Pb), and ω(Zn) in the soils were 0.06-1.08, 22.14-473.47, 12.83-150.74, 10.75-577.72, and 62.23-652.78 mg·kg-1, which exceeded the standard with over-standard rates reaching 1.83%, 1.22%, 0.61%, 0.61%, and 1.22%, respectively. Further, Cd and Pb were transported into crops, in which Cd concentrations exceeded the standard in some corn samples, and Cd and Pb concentrations exceeded the standard in some wheat samples. The total non-carcinogenic health risks (TTHQ) to the human body caused by the consumption of heavy metals in corn grown in the study area were all less than 1, with no obvious negative effects, and TTHQ was higher than 1 in wheat, increasing the likelihood of negative impacts on the human body. With the influence of the distribution of pollution-related enterprises in the industrial zone, heavy metal concentrations were higher in the south, west, and middle directions of the study area. Among them, the study area soil was slightly contaminated by Cd (Level 1). Cd and Hg had a slight potential ecological risk (Level 2), whereas other heavy metals had low potential ecological risk (Level 1). In general, most of the surface cultivated soil was not obviously polluted by heavy metals in the study area. According to the PMF results and survey, we speculated that soil heavy metals mainly came from soil parent material (52.05%), artificial pollution sources (historical sewage irrigation and industrial manufacture) (32.98%), and atmospheric deposition (14.97%). To summarize, the study area should be divided into a priority protection category and safe utilization category. The input of pollution sources should be strictly controlled for the priority protection category, and alternative planting, rotating, and fallow should be implemented for the safe utilization category to reduce the risk of standard-exceeding agricultural products.

A real-time probabilistic risk assessment method for the petrochemical industry based on data monitoring

Safety is of high societal concern in the petrochemical industry. With advancing digitalization, the techniques of probabilistic risk assessment (PRA), which provide a system-level perspective for industrial risk analysis, have become increasingly dynamic. This paper provides a further advancement in this direction by proposing a risk updating method based on the dynamic Bayesian network (DBN) to incorporate data monitoring into PRA in real-time. We update the probabilistic risk for basic events in Bayesian networks based on their prior probability and the probability of their online monitoring signals exceeding the alarm threshold. The key idea behind this approach is that if the signal of a basic event exceeds the alarm threshold, the corresponding risk should increase. Otherwise, the basic event should have a low risk. The contribution in this paper is twofold. First, residual methods are developed to estimate signal probabilities exceeding abnormal thresholds. Second, a DBN model is proposed to integrate prior risk with data monitoring for risk analysis. The proposed DBN model does not require additional expert knowledge and historical accident data to define the conditional relationship between data monitoring and prior risk. The proposed approach is validated using the RT 580 experimental setup and managed pressure drilling operations.

Introduction: Severe Uncertainty in Science, Medicine, and Technology

Introduction: Severe Uncertainty in Science, Medicine, and Technology

Stochastic Flood Risk Assessment under Climate Change Scenarios for Toronto, Canada Using CAPRA

Amongst all natural disasters, floods have the greatest economic and social impacts worldwide, and their frequency is expected to increase due to climate change. Therefore, improved flood risk assessment is important for implementing flood mitigation measures in urban areas. The increasing need for quantifying the impacts of flooding have resulted in the development of methods for flood risk assessment. The aim of this study was to quantify flood risk under climate change scenarios in the Rockcliffe area within the Humber River watershed in Toronto, Canada, by using the Comprehensive Approach to Probabilistic Risk Assessment (CAPRA) method. CAPRA is a platform for stochastic disaster risk assessment that allows for the characterization of uncertainty in the underlying numerical models. The risk was obtained by integrating the (i) flood hazard, which considered future rainfall based on the Representative Concentration Pathways (RCPs 2.6, 4.5, 6.0, and 8.5) for three time periods (short-term: 2020–2049, medium-term: 2040–2069, and long-term: 2070–2099); (ii) exposed assets within a flood-prone region; (iii) vulnerability functions, which quantified the damage to an asset at different hazard levels. The results revealed that rainfall intensities are likely to increase during the 21st century in the study area, leading to an increase in flood hazards, higher economic costs, and social impacts for the majority of the scenarios. The highest impacts were found for the climate scenario RCP 8.5 for the long-term period and the lowest for RCP 4.5 for the short-term period. The results from this modeling approach can be used for planning purposes in a floodplain management study. The modeling approach identifies critical areas that need to be protected to mitigate future flood risks. Higher resolution climate change and field data are needed to obtain detailed results required for a final design that will mitigate these risks.