Research On The Optimization Of AP1000 ADS Stage 1,2,and 3

As the most advanced Generation-III PWR nuclear power plant in the world at present,AP1000 has long been highly concerned by the international and domestic nuclear power fields since its launch.Based on the design philosophy of passive safety,the AP1000 is pursuing top-level goals of simplified design,simplified system configuration,and significant reductions in safety-related systems,equipment and structures.AP1000 Engineering Safety Feature(ESF)facilities as a key element of defense-in-depth design,ESF is also an important embodiment of AP1000 passive design.The AP1000 Automatic Depressurization System(ADS)is an important part of the AP1000’s ESF that primarily performs the pressure relief function of a primary loop with loss of coolant accident(LOCA).As a relatively important system,ADS receives more attention in the background of AP1000 performance improvement research.To some extent,the ADS system shows the redundancy and complexity of the design.The relatively complicated piping arrangement increases the difficulty of on-site construction and operation,as well as maintenance.The step-by-step pressure relief introduces extra vent load into the system piping and equipment.The research objectives of this paper are determined by analyzing the AP1000 ADS system to be improved.This paper focuses on simplifing the system flow,optimizing layout and vent load.In the aspect of ADS system flow simplification,this paper analyzes the necessity,rationality and improvement space of the original three stages of valve opening.Starting from ADS typical condition of pressure relief function after the small break loss of coolant accident(SB-LOCA)in primary loop,the safety related design criteria to be followed by the ADS system,the most serious single fault assumption,the minimum flow area,system simplification program proposed are determined by the whole plant transient process study.In the aspect of ADS system layout optimization,this paper studies in depth the general layout requirements,special layout requirements and module design adaptability of the system,and optimizes the layout design.From simplification of pipeline and valve design,substantial reduction of overall quality and effective reduction of centroid height and so on,under the premise of simplified system,the original structural space and original system layout boundary conditions are fully utilized to explore and design new layout schemes.In the aspect of optimizing the discharge load of ADS system,this paper studies the main influencing factors such as the control valve characteristic curve,the piping resistance and the proportion of the regulating valve resistance,and makes full use of the RELAP 5 program to simulate the transient process of the primary loop of the NPP,quantitative study of the contribution of influencing factors,and synthesize the results of various factors to seek quantitative system parameters that are conducive to reducing emission load effectively.In this paper,ADS system is systematically researched,and successfully put forward the system simplification plan,layout optimization plan,equipment selection(regulating valve characteristic curve)scheme which is propitious to improve the overall performance of ADS,and support the system design plan.This study proves the accuracy of the research direction and the practical importance of the research results.