PSA study of the effect of extreme snowfall on a floating nuclear power plant:case study in the Bohai Sea

This study presents a probabilistic safety analysis(PSA)method for the external event of extreme snowfall on a floating nuclear power plant(FNPP)deployed in the Bohai Sea.We utilized the Weibull and Gumbel extreme value distributions to fit the collected meteorological data and obtained a hazard curve for the event of an extreme snowfall where the FNPP is located,providing a basis for the frequency of extreme snowfall-initiating events.Our analysis indicates that extreme snowfall primarily affects the ventilation openings of the equipment,leading to the failure of devices such as the diesel generators.Additionally,extreme snowfall can result in a loss of off-site power(LOOP).Therefore,the developed extreme snowfall PSA model is mainly based on the LOOP event tree,considering responses such as snowfall removal by personnel.Our calculations indicate a core damage frequency(CDF)of 1.13×10^(-10) owing to extreme snowfall,which is relatively low.The results of the cut-set analysis indicate that valve failures in the core makeup tank(CMT),passive residual heat removal system(PRS),and in-containment refueling water storage tank(IRWST)significantly contribute to the CDF.

Investment risk evaluation of inland floating photovoltaic power plants in China using the HFLTS-TFN method

Inland floating photovoltaic power plants(IFPPPs)are the key to making full use of water advantages to develop solar resources in the future.Identifying the investment risk is an important prerequisite for promoting the projects on a large scale.This paper proposes a model to assess the investment risk of IFPPPs in China.First,this paper identifies the investment risk factors and establishes an evaluation indicator system from four aspects.Second,the indicator data are collected and described by adopting hesitant fuzzy linguistic term sets and triangular fuzzy numbers to ensure soundness and completeness.Third,a weighted method combining the best-worst method and the entropy method are utilized to determine the indicator weights under the consideration of the impact of subjective preferences and objective fairness.Fourth,the results show that the overall risk level of China’s IFPPPs is‘medium low’.Fifth,sensitivity analysis and comparative analysis are implemented to examine the stability of the evaluation results.Finally,this paper also provides some risk-response strategies for the development of China’s IFPPPs from economy,society,technology and environment.

Fault line selection in cooperation with multi-mode grounding control for the floating nuclear power plant grid

The Floating nuclear power plant grid is composed of power generation,in-station power supply and external power delivery.To ensure the safety of the nuclear island,the in-station system adopts a special power supply mode,while the external power supply needs to be adapted to different types of external systems.Because of frequent single phase-ground faults and various fault forms,the fault line selection protection should be accurate,sensitive and adaptive.This paper presents a fault line selection method in cooperation with multi-mode grounding control.Based on the maximum united energy entropy ratio(MUEER),the optimal wavelet basis function and decomposition scale are adaptively chosen,while the fault line is selected by wavelet transform modulus maxima(WTMM).For high-impedance faults(HIFs),to enlarge the fault feature,the system grounding mode can be switched by the multi-mode grounding control.Based on the characteristic of HIFs,the fault line can be selected by comparing phase differences of zero-sequence current mutation and fault phase voltage mutation before and after the fault.Simulation results using MATLAB/Simulink show the effectiveness of the proposed method in solving the protection problems.