Study On Key Technologies Of Nuclear Emergency Evacuation And System Development

Nuclear accident emergency is the last defense line of nuclear safety.The nuclear accident emergency response is to control and mitigate the consequences of a nuclear or radiological accident.Nuclear accident emergency evacuation is an effective emergency protection measure,which can avoid or reduce the radiation exposure.In the event of a serious accident that may lead to the release of a large amount of radioactive substances,the emergency response organization shall carry out the emergency evacuation,and immediately transfer the personnel unrelated to emergency work and the surrounding residents within the emergency evacuation area to the designated resettlement area.However,nuclear accidents are highly uncertain and will show dynamic and phased changes.The evacuation process is affected by massive multi-source heterogeneous information such as environment,meteorology,resources,traffic and radiation environment,making it difficult for decision-makers to comprehensively analyze a large amount of complex information to make rapid and effective decisions.This work focuses on the two key links of emergency evacuation,personnel assembling and vehicle transport,and deeply study the key technologies including the allocation of emergency evacuation assembling point,evacuation path planning,and emergency database.Under the framework of the virtual nuclear power plant in the digital society environment Virtual4DS,the prototype system of decision support for nuclear accidents emergency response evacuation is designed and developed.The specific research contents are as follows:(1)A method of personnel allocation for nuclear emergency evacuation assembling points based on collective minimum risk is proposed.This method solves the problem that the risk of exposure cannot be quantified and reduced in the past when people are gathered by administrative regions,and realize the reasonable allocation of personnel in the nuclear accident emergency evacuation assembly point.In this method,firstly,the radiation risk value of each assembling point was calculated by combining the wind rosette and radiation dose field.Then,the Voronoi diagram method with radiation exposure risk as the weight was developed to divide the assembling point area,and the most appropriate assembling point for evacuation was assigned to the personnel in the affected area.According to the location of the area,the affected people were assigned to the assembling point with the minimum risk value.(2)An optimal nuclear accident evacuation path planning method based on the minimum collective dose is proposed.This method solves the problem that the evacuation plan cannot be obtained to minimize the collective dose in the evacuation process when the shortest route is the target of the previous path planning.In this method,firstly,considering the travel time and dose rate,the algorithm with dose value as weight is developed to find the optimal path.Then,based on the equilibrium model and considering the road resistance,a multi-path evacuation scheme with the collective cumulative dose minimization as the target was established.In the event of a nuclear accident,evacuation vehicles would be arranged reasonably on multiple evacuation routes to minimum the collective dose received by all persons during evacuation.(3)Based on the above key technologies,the prototype system of decision support for nuclear accidents emergency response evacuation is designed and developed.Aiming at the characteristics of multi-source heterogeneity of nuclear accident emergency data,the non-relational databases Redis and MongoDB are coupled on the basis of open source distributed relational database Greenplum to optimize the management of nuclear accident emergency information.This method solves the contradiction between data transactional and efficient access,and improves the efficiency of early information invocation in nuclear accidents.Structurally,hierarchical module design is adopted to complete the design and development of four functional modules of the system:assembly point personnel allocation module,path planning module,data management module and situation display module according to the business requirements of emergency evacuation of nuclear accidents.In this work,the developed methods and system are verified by simulating nuclear accident cases.The simulation results show that the allocation method to assembling point based on the collective minimum risk effectively reduce the exposed risk value of personnel by 14.25%.The path planning method based on the minimum collective dose developed can reduce the collective dose of personnel in evacuation by 6.38%.The verification shows that the key technology of nuclear emergency evacuation developed in this work and the prototype system of evacuation decision support can provide fast and effective technical support for nuclear accident emergency evacuation decision.