Probabilistic ecological risk assessment of cadmium in the Bohai Sea using native saltwater species

Predicted no-effect concentration （PNEC） is often used in ecological risk assessment to determine low-risk concentrations for chemicals. In the present study, the chronic data from native saltwater species were used to calculated PNEC values using four methods： log-normal distribution （ETX 2.0）, log-triangle distribution （US EPA＇s water quality criteria procedure）, burr III distribution （BurrliOZ） and traditional assessment fac-tor （AF）. The PNECs that were calculated using four methods ranged from 0.08 μg/L to 1.8 μg/L. Three of the SSD-derived PNECs range from 0.94 to 1.8 μg/L, about a factor of two apart. To demonstrate the use of SSD-based PNEC values and comprehensively estimate the regional ecological risk for cadmium in surface water of the Bohai Sea, in the Liaodong Bay, Bohai Bay, and Laizhou Bay, China, the dissolved cadmium con-centrations were measured and obtained 753 valid data covering 190 stations from July 2006 to November 2007. Based on three ecological risk assessment approaches, namely hazard quotient （HQ）, probabilistic risk quotient and joint probability curve （JPC）, the potential ecological risk of cadmium in surface water of the Liaodong Bay, Bohai Bay, and Laizahou Bay were estimated. Overall, the ecological risk of cadmium to aquatic ecosystem in the whole Bohai Sea was at acceptable ecological risk level, the order of ecological risk was Liaodong Bay〉Bohai Bay〉Laizhou Bay. However, more concerns should be paid to aquatic ecological risk in the Liaodong Bay which is the home of many steel, metallurgy and petrochemical industrial in China.

Pesticide residues in bayberry(Myrica rubra)and probabilistic risk assessment for consumers in Zhejiang,China

As pesticide residues in bayberry has raised serious concern from the public in China, a monitoring survey was carried out during 2013–2014 and 157 samples were analyzed in total. Twenty-three pesticides were detected among the 44 pesticides analyzed and at least one pesticide was detected in 63% of 99 samples. Whereas 45.6% of samples were found with two or more pesticide residues, and 23.6% of samples with four or more pesticide residues. Probabilistic risk assessments indicated that estimated daily intake（EDI） of cyhalothrin at the P97.5th percentile level is 1.11 times larger than the acceptable daily intake（ADI） for children, the estimated short-term intake（ESTI） at the P97.5th percentile level is 1.9 and 1.78 times larger than the acute reference dose（ARf D） for adult and children, respectively, indicating the potential risk concern from pyrethroids. EDI of the pesticides with anti-androgenic effects ranged from 0.15–2.46 of ADI, the probability of exposure exceeding the ADI was 7.1 and 31.1% for adults and children, respectively, the probability of exposure of pyrethroids exceeding the ADI was 3.8% for children. Exposures for other pesticides and groups were below 1.0. Because the co-occurrence of frequency of cyhalothrin and cypermethrin was 9.55%, the combinations of pesticides detected with anti-androgenic effects has not been found in the present monitoring, the results indicate that the pesticide residues in bayberry will not constitute serious public health risk, however, they are significant for the management of pesticide use on bayberry and dietary health risk in China.

Risk Assessment of Nitrogen Discharge from a Coastal Watershed

Probabilistic risk assessment （PRA） uses probability theory to quantify the probability of occurrence of an event. In this study, PRA was conducted for the discharge of excess nitrogen （N） from an agricultural （Jiulong River） watershed in Southeast China. Using fault tree analysis, a type of PRA, the probability of occurrence of excess N discharge into the river during a runoff event was evaluated both qualitatively and quantitatively. Land use maps, soil maps, fertilizer use records, and expert opinions were used to determine probabilities of individual events within the fault tree and to calculate the overall probability of excess N discharge during a runoff event. Qualitative analysis showed that the risk of excess N discharge was mainly related to crop and livestock practices in the watershed. Proper management of tillage, fertilizer, and manure was necessary to control N releases. Quantitative assessment results indicated that alternative practices including reduction of fertilization, installation of vegetative strip buffer around the pig farms, and installation of more riparian buffers along the Jiulong River could reduce the likelihood of N discharge through runoff.

Recent Research Advances in the Risk Assessment Method of an Underground Pressure Pipeline

This paper reviews the risk assessment method of an underground pressure pipeline, introduces the risk assessment method of expert grading, fuzzy integrative assessment, probabilistic risk assessment and extenics assessment in an underground pressure pipeline. Moreover, it puts forward the developing orientation of risk assessment.

Severe accident risks from external events

This paper reviews the early development of design requirements for seismic events in USA early developing nuclear electric generating fleet. Notable safety studies,including WASH-1400,Sandia Siting Study and the NUREG1150 probabilistic risk study,are briefly reviewed in terms of their relevance to extreme accidents arising from seismic and other severe accident initiators. Specific characteristic about the nature of severe accidents in nuclear power plant (NPP) are reviewed along with present day state-of-art analysis methodologies (methods for estimation of leakages and consequences of releases (MELCOR) and MELCOR accident consequence code system (MACCS)) that are used to evaluate severe accidents and to optimize mitigative and protective actions against such accidents. It is the aim of this paper to make nuclear operating nations aware of the risks that accompany a much needed energy resource and to identify some of the tools,techniques and landmark safety studies that serve to make the technology safer and to maintain vigilance and adequate safety culture for the responsible management of this valuable but unforgiving technology.

Maritime Oil Spill Risk Assessment for Hanhikivi Nuclear Power Plant

Fennovoima is planning to build a new nuclear power plant unit-Hanhikivi 1, on a greenfield site in Northern Finland. A nearby maritime oil spill accident is one of the external events analysed in the probabilistic risk assessment of the plant. In the worst case, the oil could cause a loss of the ultimate heat sink by blocking the sea water intake screens. By considering the maritime traffic, oil transport and oil spill accident data in the Baltic Sea area, the annual probabilities of nearby, significant oil spills are evaluated. Event tree analysis is used to evaluate the probability that significant amount of oil enters the plant intake tunnel. The spill behaviour is considered, including oil spreading, dissolution, dispersion and movement due to wind and currents. In addition, oil combat measures including the use ofoil booms and skimmers are evaluated.

The Role of Countermeasures in Mitigating the Radiological Consequences of Nuclear Power Plant Accidents

The countermeasures are the actions that should be taken, after the occurrence of a nuclear accident to protect the public against the associated risks. These actions may be represented by sheltering, evacuation, distribution of stable iodine tablets and/or relocation. This study represents a comprehensive probabilistic study to investigate the role of the adoption of the countermeasures in case of a hypothetical accident of type LOCA for nuclear power plant of PWR （1000 Mw）. The effective doses in different organs, short and long health effects, and the associated risks are calculated with and without countermeasures. In addition, the overall costs of the accident and the costs of countermeasures are estimated which represent our first trials to know how much the proposed accident cost. The results showed that, the area around the site requires early and late countermeasures action after the accident especially in the downwind sectors. For late countermeasures, the duration time of relocation ranged from about two to 10 years. The adoption of the countermeasures increases the costs of emergency plan by 40% but reduces the risk associated the accident.

Application of probabilistic risk assessment at a coking plant site contaminated by polycyclic aromatic hydrocarbons

Application of Probabilistic Risk Assessment （PRA） and Deterministic Risk Assessment （DRA） at a coking plant site was compared. By DRA, Hazard Quotient （HQ） following exposure to Naphthalene （Nap） and Incremental Life Cancer Risk （ILCR） following exposure to Benzo（a）pyrene （Bap） were 1.87 and 2.12 × 104. PRA revealed valuable information regarding the possible distribution of risk, and risk estimates of DRA located at the 99.59th and 99.76th percentiles in the risk outputs of PRA, which indicated that DRA overestimated the risk. Cleanup levels corresponding acceptable HQ level of 1 and ILCR level of 104 were also calculated for both DRA and PRA. Nap and Bap cleanup levels were 192.85 and 0.14mg.kg-1 by DRA, which would result in only 0.25% and 0.06% of the exposed population to have a risk higher than the acceptable risk, according to the outputs of PRA. The application of PRA on cleanup levels derivation would lift the cleanup levels 1.9 times for Nap and 2.4 times for Bap than which derived by DRA. For this coking plant site, the remediation scale and cost will be reduced in a large portion once the method of PRA is used. Sensitivity analysis was done by calculating the contribution to variance for each exposure parameter and it was found that contaminant concentration in the soil （Cs）, exposure duration （ED）, total hours spent outdoor per day （ETout）, soil ingestion rate （IRs）, the air breathing rate （IRa） and bodyweight （BW） were the most important parameters for risk and cleanup levels calculations.

Probabilistic ecological risk assessment for three chlorophenols in surface waters of China

Individual and combined assessment of risks of adverse effects to aquatic ecosystems of three chlorophenols（CPs）,including 2,4dichlorophenol（2,4-DCP）,2,4,6-trichlorophenol（2,4,6-TCP） and pentachlorophenol（PCP）,were conducted.A probabilistic approach based on the concentrations of CPs in surface waters of China was used to determine the likelihood of adverse effects.The potential risk of CPs in surface waters of China was determined to be of concern,especially PCP and mixtures of CPs.The risks of adverse effects were examined as the joint probabilities of exposure and response.The joint probability for PCP was 0.271 in the worst case and 0.111 in the median case,respectively.Based on the cumulative probability,5% of aquatic organisms included in the assessment would be affected 21.36% of the time in the worst case and 5.99% of the time in median case,respectively.For the mixtures of CPs,the joint probability were 0.171 in the worst case and 0.503 in median case,respectively and 5% of species would be affected 49.83% of the time for the worst case and 12.72% in the median case,respectively.Risks of effects of the individual CPs,2,4-DCP and 2,4,6-TCP were deemed to be acceptable with a overlapping probability of 0.1 with 5% of species being affected less than 4% of the time.

Engineering approach for human error probability quantification

A novel approach for engineering application to human error probability quantification is presented based on an overview of the existing human reliability analysis methods. The set of performance shaping factors is classified as two subsets of dominant factors and adjusting factors respectively. Firstly, the dominant factors are used to determine the probabilities of three behavior modes. The basic probability and its interval of human error for each behavior mode are given. Secondly, the basic probability and its interval are modified by the adjusting factors, and the total probability of human error is calculated by a total probability formula. Finally, a simple example is introduced, and the consistency and validity of the presented approach are illustrated.

Integration of Probabilistic and Multi-Hazard Risk Assessment Within Urban Development Planning and Emergency Preparedness and Response: Application to Manizales,Colombia

The details of a multi-hazard and probabilistic risk assessment, developed for urban planning and emergency response activities in Manizales, Colombia, are presented in this article. This risk assessment effort was developed under the framework of an integral disaster risk management project whose goal was to connect risk reduction activities by using open access and state-of-theart risk models. A probabilistic approach was used for the analysis of seismic, landslide, and volcanic hazards to obtain stochastic event sets suitable for probabilistic loss estimation and to generate risk results in different metrics after aggregating in a rigorous way the losses associated to the different hazards. Detailed and high resolution exposure databases were used for the building stock and infrastructure of the city together with a set of vulnerability functions for each of the perils considered. The urban and territorial ordering plan of the city was updated for socioeconomic development and land use using the hazard and risk inputs and determinants, which cover not only the current urban area but also those adjacent areas where the expansion of Manizales is expected to occur. The emergency response capabilities of the city were improved by taking into account risk scenarios and after updating anautomatic and real-time post-earthquake damage assessment.

Probabilistic Seismic Risk Assessment in Manizales,Colombia: Quantifying Losses for Insurance Purposes

A fully probabilistic seismic risk assessment was developed in Manizales, Colombia, considering assets of different types. The first type includes elements that are part of the water and sewage network, and the second type includes public and private buildings. This assessment required the development of a probabilistic seismic hazard analysis that accounts for the dynamic soil response,assembling high resolution exposure databases, and the development of damage models for different types of elements. The economic appraisal of the exposed assets was developed together with specialists of the water utilities company of Manizales and the city administration. The risk assessment was performed using several Comprehensive Approach to Probabilistic Risk Assessment modules as well as the R-System, obtaining results in terms of traditional metrics such as loss exceedance curve, average annual loss, and probable maximum loss. For the case of pipelines, repair rates were also estimated. The results for the water and sewage network were used in activities related to the expansion and maintenance strategies, as well as for the exploration of financial retention and transfer alternatives using insurance schemes based on technical,probabilistic, and prospective damage and loss estimations.In the case of the buildings, the results were used in the update of the technical premium values of the existing collective insurance scheme.

Handling epistemic uncertainties in PRA using evidential networks

In order to overcome the limitations of traditional methods in uncertainty analysis, a modified Bayesian network(BN), which is called evidence network(EN), was proposed with evidence theory to handle epistemic uncertainty in probabilistic risk assessment(PRA). Fault trees(FTs) and event trees(ETs) were transformed into an EN which is used as a uniform framework to represent accident scenarios. Epistemic uncertainties of basic events in PRA were presented in evidence theory form and propagated through the network. A case study of a highway tunnel risk analysis was discussed to demonstrate the proposed approach. Frequencies of end states are obtained and expressed by belief and plausibility measures. The proposed approach addresses the uncertainties in experts' knowledge and can be easily applied to uncertainty analysis of FTs/ETs that have dependent events.

Review and Prospects of the Global Earthquake Model Project ( GEM)

This paper reviewed the main target,functions,tool( Open Quake software) and research achievements of the Global Earthquake Model( GEM) Foundation,and made a simple prospect on the development and application of projects of GEM in the future. Learning from GEM and Open Quake is helpful to improve the seismic hazard model of China and enhance the scientificity of the seismic hazard assessment for metropolitans and major engineering facilities near major seismogenic structures.

Holistic Disaster Risk Evaluation for the Urban Risk Management Plan of Manizales,Colombia

Disaster risk depends on both the physical vulnerability and a wide range of social, economic, and environmental aspects of a society. For a better risk understanding, a holistic or integrated perspective was considered when risk was assessed for the city of Manizales, Colombia. This assessment accounts not only for the expected physical damage and loss, but also for the socioeconomic vulnerability factors that favor secondorder effects in a disaster. This comprehensive approach allows the identification of different aspects related to physical vulnerability, social fragility, and lack of resilience that can be improved, thus enhancing integrated disaster risk management actions. The outcomes of this comprehensive assessment are currently being used as input to update the disaster risk management plan of Manizales.

Atmospheric dispersion of chemical,biological,and radiological hazardous pollutants:Informing risk assessment for public safety

Modern society is confronted with emerging threats from chemical,biological,and radiological(CBR)hazardous substances,which are intensively utilized in the chemical,medical,and energy industries.The atmospheric dis-persion of released CBR hazardous pollutants can influence a large percentage of the population owing to their rapid process with extensive spatial coverage.It is important to comprehensively understand the behaviors of the released CBR pollutants in the atmosphere to fully evaluate the risks and protect public safety.In this study,we reviewed the advancements in the atmospheric transport of CBR pollutants,including the urban atmospheric boundary layer,unique concepts,and models for CBR pollutants.We underlined the development of innovative methodologies(e.g.,inverse estimation and data assimilation methods)for the atmospheric transport of acciden-tally released CBR pollutants to reduce uncertainties in emissions and accumulated errors during dispersion by combining numerical models with monitoring data.Finally,we introduced progress in quantitative risk assess-ment,including exposure assessment and dose-response relationships for CBR hazardous pollutants.A framework,source,assimilation,fundamentals,exposure,and risk(SAFER),has been proposed to integrate the key compo-nents in the risk assessment of airborne CBR hazardous pollutants.These methods and models can contribute to effective risk preparedness,prevention,evidence-based policymaking,and emergency response to airborne CBR pollutants.

Influence of DC Supply Systems on Unplanned Reactor Trips in Nuclear Power Plants

Operational experience has shown that some components in nuclear power plants are so important that their failures, which would be a single failure, may cause the entire plant to shutdown. Such shutdowns have often occurred in the past in commercial nuclear power plants. Nuclear power plant authorities try to avoid such unplanned plant shutdowns because of the large economic loss. Unfortunately, it is difficult to identify all the important components from the numerous components in each complex nuclear power plant system. FMEA and FTA methods, which are often applied to probabilistic risk assessments, are used in this paper to identify the key components that may cause unplanned reactor trips. As an example, the 48V DC power supply system in a typical Chinese nuclear power plant, which is a major cause of many unplanned reactor trips, was analyzed to show how to identify these key components and the causes for nuclear power plant trips.