A New System Risk Definition and System Risk Analysis Approach Based on Improved Risk Field

Risk is an objective quantity applied to describe the degree of harm to a specific system of many activities and technologies. In order to manage risk successfully and ensure the normal operation of a system, an explicit system risk definition and a system risk analysis approach are essential. After analyzing the system risk change curve, a new definition of system risk is given, which is formulated as the risk energy change in a system. A Gaussian pulse energy function is introduced to calculate the changed risk energy, and a new unit $\text{H}$ is given to describe the system risk, where $\text{H}$ formulates each unit energy change in the system or subsystem caused by the risk pulse. Based on the Gaussian pulse energy function, an improved risk field is modeled and described from two perspectives: risk potential and risk field strength. The characteristics of the improved risk field are modeled and simulated, including the superposition law of the risk potential, superposition law of the risk field strength and risk force, the flux and divergence of the risk field, and the ring flux and rotation of the risk field. The risk potential superposition law and the risk field strength superposition law provide a new system risk analysis approach to explain the formation process of system coupling risk and the interaction laws of the risk factors in a system. Finally, a real-world case study is conducted by taking a railway dangerous goods transportation accident in 2001 as a background. The simulation results of risk pulse energy show that the system risk energy value of the risk-accident critical state is between 1.712e−04 $\text{H}$ and 1.922e−04 $\text{H}$ . When the fourth risk pulse appeared, the system risk change curve crossed the risk-accident critical state line, and the accident happened. The simulation results of the risk potential and risk field strength show that risk source 1 has the biggest risk potential value and risk field strength value, followed by risk sources 1, 3, and 4, which means that risk source 1 has the biggest contribution to the accident, and it has the biggest risk impact strength to other matters.