Six-hierarchy model of accident analysis and its application in coal mine accidents

Accident analysis models play a significant role in accident investigation and analysis.Most traditional models,usually based on a chain of events,have serious limitations when used for complex systems,especially for coal mine accident.HFACS is a widely accepted accident cause model with complex structure and content.Based on HFACS and accident investigation need in China,a new systemic accident analysis method“Six-hierarchy model”is proposed.And the index database of accident causal factors at each hierarchy of coal mine accidents is established.This model provides clear guidance for the prevention of accidents from six levels,which helps to the targeted rectification after accidents and the improvement of safety management level.The source,ap-plication scope,advantages and disadvantages of HFACS and six-hierarchy model are compared.The“2.14”gas explosion accident in Sunjiawan coal mine is analyzed by using HFACS and six-hierarchy model and the safety management suggestions are put forward.The study shows that the Six-hierarchy model provides a clear guide for the prevention of accidents from six levels.And it benefits the targeted rectification after accidents and the continuous improvement of safety management.

A data mining approach to characterize road accident locations

Data mining has been proven as a reliable technique to analyze road accidents and provide productive results. Most of the road accident data analysis use data mining techniques, focusing on identifying factors that affect the severity of an accident. However, any damage resulting from road accidents is always unacceptable in terms of health, property damage and other economic factors. Sometimes, it is found that road accident occurrences are more frequent at certain specific locations. The analysis of these locations can help in identifying certain road accident features that make a road accident to occur frequently in these locations. Association rule mining is one of the popular data mining techniques that identify the correlation in various attributes of road accident. In this paper, we first applied k-means algorithm to group the accident locations into three categories, high-frequency, moderate-frequency and low-frequency accident locations. k-means algorithm takes accident frequency count as a parameter to cluster the locations. Then we used association rule mining to characterize these locations. The rules revealed different factors associated with road accidents at different locations with varying accident frequencies. Theassociation rules for high-frequency accident location disclosed that intersections on highways are more dangerous for every type of accidents. High-frequency accident locations mostly involved two-wheeler accidents at hilly regions. In moderate-frequency accident locations, colonies near local roads and intersection on highway roads are found dangerous for pedestrian hit accidents. Low-frequency accident locations are scattered throughout the district and the most of the accidents at these locations were not critical. Although the data set was limited to some selected attributes, our approach extracted some useful hidden information from the data which can be utilized to take some preventive efforts in these locations.

Analysis and Referential Significance of a Breakdown Accident of the Main Feed Water Pump in a 350 MW Supercritical CFB Boiler

Controversies still exist over the necessity of equipping with an emergency water supply system in the supercritical circulating fluidized bed/CFB unit.To resolve the dispute,research on the safety of the heating surfaces in the supercritical CFB boiler during the electricity failure accident under the assumption of not putting the emergency water supply system into use must be conducted.However,due to the low incidence rate of this accident,no relevant data have been reported yet.To provide useful data for the related research,a breakdown accident of the main feed water pump that happened in a 350 MW supercritical CFB boiler was introduced in this work.The analysis of the physical processes in both the furnace and water side of the boiler during this accident was performed.Then the discussion on the similarities and discrepancies between the two accidents was carried out.It was found out that with appropriate handling,the data collected in two periods of the breakdown accident of the main feed water pump can provide a reference for the verification of the prediction model of the electricity failure accident.Finally,a preliminary prediction model was established as the first step of the verification work.

Promoting Metro Operation Safety by Exploring Metro Operation Accident Network

Understanding the causation of accidents is essential to promote metro operation safety.In terms of 243 reported metro operation accident cases in China, a directed weighted network was constructed based on complex network theory, where nodes and directed edges denotes factors and event chains respectively. To reveal the key causal factors, the topological characteristics of metro operation accident network(MOAN) were analyzed from both global and local views. The results show that facility-type factors are more closely related to the occurrence of the accidents from the perspectives of average path length and cascading effects. Accident types like train delay and train suspension are the great risk recipients. Key causal factors with large out-degree, out-strength, betweenness centrality and cluster coefficient, such as communication and signal failure, vehicle failure and piling into the train should be noticed. The research framework proposed in the paper is not only applicable to China’s metro operation system, but also appropriate for other transportation system safety studies.

Experience gained in analyzing severe accidents for WWER RP using CC SOCRAT

The current Russian regulatory documents on the safety of nuclear power plant(NPP)specify the requirements regarding design basis accidents(DBAs)and beyond design basis accidents(BDBAs),including severe accidents(SAs)with core meltdown,in NPP design(NP-001-15,NP-082-07,and others).For a rigorous calculational justification of BDBAs and SAs,it is necessary to develop an integral CC that will be in line with the requirements of regulatory documents on verification and certification(RD-03-33-2008,RD-03-34-2000)and will allow for determining the amount of data required to provide information within the scope stipulated by the requirements for the structure of the safety analysis report(SAR)(NP-006-16).The system of codes for realistic analysis of severe accidents(SOCRAT)(formerly,thermohydraulics(RATEG)/coupled physical and chemical processes(SVECHA)/behavior of core materials relocated into the reactor lower plenum(HEFEST))was developed in Russia to analyze a wide range of SAs at NPP with water-cooled water-moderated power-generating reactor(WWER)at all stages of the accident.Enhancements to the code and broadening of its applicability are continually being pursued by the code developers(Nuclear Safety Institute of the Russian Academy of Sciences(IBRAE RAN))with OKB Gidropress JSC and other organizations.Currently,the SOCRAT/В1 code can be used as a base tool to obtain realistic estimates for all parameters important for computational justification of the reactor plant(RP)safety at the in-vessel stage of SAs with fuel melting.To perform analyses using CC SOCRAT/В1,the experience gained during execution of thermohydraulic codes is applied,which allows for minimizing the uncertainties in the results at the early stage of an accident scenario.This study presents the results of the work performed in 2010–2020 in OKB Gidropress JSC using the CC SOCRAT/В1.Approaches have been considered to develop calculational models and analyze SAs using CC SOCRAT.This process,which is clearly structured in OKB Gidropress JSC,provides a noticeable reduction in human involvement,and reduces the probability of erroneous results.This study represents the principal results of the work performed in 2010–2020 in OKB Gidropress JSC using the CC SOCRAT,as well as a list of the tasks planned for 2021–2023.CC SOCRAT/B1 is used as the base thermohydraulic SAs code.