秦山核电站海域有害盐在带温核级材料表面沉积实验设计

Experimental design for harmful sea salt deposition on the surface of nuclear-grade materials at Qinshan Nuclear Power Station

含Cl有害盐在服役构件表面的沉积量,是影响服役构件腐蚀进程的重要因素。秦山核电站临海而建,面临含Cl有害盐沉积引起的腐蚀问题。该文通过实地环境调研,并根据调研结果开展实验室盐雾沉积实验设计,结果表明:以ASTM D1141-98(2021版)标准中的人工海水Cl元素含量为基准,将秦山核电站海域海水各化合物含量乘以4.075 26进行放大,可得到符合ASTM标准设计的盐雾沉积用有害盐模拟溶液成分。之后,该文进一步开展90℃带温核级材料表面有害盐沉积实验,探究临海服役环境下,有害盐在秦山核电站乏燃料贮罐材料(带温核级材料)表面的沉积规律,为开展实际服役环境下的核电站材料服役寿命评估、服役性能评价提供一种实验室设计思路与借鉴。

[Objective]The deposition of Cl-containing harmful salts on the surface of service materials critically influences their corrosion process.The Qinshan Nuclear Power Station,located near the sea,has encountered corrosion issues due to the deposition of these harmful salts.Although researchers have conducted numerous in-depth studies on the corrosion behavior and mechanisms of materials in nuclear power plants,only limited literature addresses the deposition patterns of harmful salts on the surfaces of nuclear-grade materials.[Methods]A field environmental investigation was conducted to understand nuclear material corrosion in salty environments,and then a harmful salt solution for salt spray deposition experiments was formulated based on the investigation results following the ASTM standard.To investigate the deposition patterns of harmful salts on the surface of spent fuel storage canister materials,this solution was used for salt spray deposition on nuclear-grade materials.Tests were conducted at 90℃to simulate the coastal service environment of the Qinshan Nuclear Power Station.[Results]The analysis of seawater composition revealed that the seawater near the Qinshan Nuclear Power Station is diluted by freshwater,as it is located near the Yangtze River estuary.Despite this dilution,a comparison with the global average sodium content of seawater indicated that the seawater near the Qinshan Nuclear Power Station retains the typical characteristics of normal seawater.The design results for the harmful salt solution indicated that,based on the total chloride content of substitute ocean water according to the ASTM D1141-98 standard(2021 edition),the concentration of each compound in the seawater near the Qinshan Nuclear Power Station must be multiplied by 4.07526 for amplification.This adjustment allows the formulation of a harmful salt simulation solution for salt spray deposition that complies with ASTM standards.The experimental results of harmful salt deposition on the surface of nuclear-grade material at 90℃indicated the following:By setting the sedimentation rate of the salt spray at 1.75 mL/(h·80 cm2)and establishing a single salt spray period as“1 min of salt spray followed by 15 min of standing,”one salt spray period was necessary for the average harmful salt concentration on the surface of the sample to reach 0.1 g/m2(using thin slice samples measuring 100 mm×100 mm×0.1 mm).To achieve a concentration of 1.0 g/m2,12 salt spray cycles were required(using flat samples measuring 50 mm×25 mm×2 mm).Finally,112 salt spray cycles were needed to reach a concentration of 10.0 g/m2(also using flat samples measuring 50 mm×25 mm×2 mm).[Conclusions]The seawater near the Qinshan Nuclear Power Station retains the characteristics of normal seawater.This paper proposes a laboratory design concept and serves as a reference for evaluating the service life and performance of materials used in nuclear power plants operating in actual service environments.