Study On Short-term Early Warning Of Jellyfish Invasion Around Hongyanhe Nuclear Power Plant

In recent years,the occurrence of jellyfish blooms has occurred globally.Not only causing ecological disasters,it also has often led to the blockage of cold water intakes of coastal nuclear power plants,which might threaten the safe operation of nuclear power plants.Short-term early warning of jellyfish disasters in the vicinity of nuclear power plants becomes more and more urgent to be solved.Taking the Hongyanhe nuclear power plant as an example,this study established a short-term early warning system for jellyfish disaster based on the marine model FVCOM.This study was divided into three parts.Firstly,a high-resolution hydrodynamic model covering the entire Bohai Sea is built to accurately simulate the hydrodynamic field in the waters near the Hongyanhe nuclear power plant.Then jellyfish particles under different initial position,wind direction,wind speed,tide time and tidal range were tracked.Finally,the jellyfish invasion early warning system was established based on the statistical relationship between jellyfish invasion and initial position of jellyfish,wind speed,wind direction,tide time and tidal range.On the basis of the analysis of the influence of water intake and drainage on the flow field near the nuclear power plant,it is found that the area where the flow rate is affected by the water intake and drainage is within 5 km of the nuclear power plant,and the water intake has a prominent impact on the Euler transport within 1500 m.Therefore,1500 m is selected as the outermost edge of the warning circle.By analyzing the influencing factors of jellyfish invasion,it is found that the wind direction determines the geographical location of the region with large probability of jellyfish invasion;the greater the wind speed,the more obvious the influence of wind direction on the probability distribution of jellyfish invasion;the tide time determines the regional distribution of the probability of jellyfish invasion in the direction of the main axis of the tide;the larger the tidal range,the wider the distribution of areas with a high probability of jellyfish intrusion.An analysis of the unfavorable scenarios of jellyfish invasion reveals that the jellyfish invasion is most likely to occur within 24 hours of the beginning of the tide,the wind direction is between 225° and 315°,and the wind level is relatively high.It indicates that the unfavorable wind direction that affects the safe operation of the water intake is the westerly wind,which will enhance the transport to the shore when the wind is enhanced,and the larger tide will make the jellyfish more transportable.In July the jellyfish particles on the south side of the nuclear power plant are more likely to pose a threat to nuclear power plants under gale events,and in August the jellyfish particles on the north side of nuclear power plants are more likely to pose a threat to nuclear power plants under gale events,as a result of the major wind directions in gale events in July and August which are south and north respectively.On the basis of more than 6 million particle tracking cases,the water intake intrusion risk database of the Hongyanhe nuclear power plant was constructed.An early warning system was constructed using this database and the inverse distance weighting method,which can carry out short-term warning of jellyfish invasion risk under the real jellyfish source area,wind direction,wind speed,tidal range and tide time.Taking the jellyfish invasion incident of the Hongyanhe nuclear power plant in July 2014 as an example,the early warning system is applied.The comparison between the early warning map output by the early warning system and the early warning map obtained by the particle tracking experiment proves the authenticity and effectiveness of the early warning system.It is confirmed that the threat of jellyfish invasion in the southern sea area is large under that circumstance.