沸水式反應爐爐心噴灑管路組件劣化研究

Study on BWR Core Spray Pipeline Component Degradation

本文說明沸水式反應爐爐心噴灑測試管路組件劣化（薄化）分析個案，管件材質為低碳鋼。劣化分析進行完成之熱室檢驗，包含目視檢驗、X光繞射分析、化學成分分析、金相檢驗、管壁厚度量測、微硬度測試、掃瞄電子顯微鏡觀察及X光能譜成分分析。檢驗結果顯示，劣化管件內壁披覆濃厚黑色結瘤狀沉積物，沉積物下方有沿著管材枕木形織構成長之蝕孔。分析顯示微生物腐蝕為管件薄化（及穿孔）肇因，機制為結瘤與沉積物孔蝕。

This paper presents a degradation (wall-thinning) analysis done on the BWR core-spray 3-inch testing pipeline component. Hot-cell examination performed included visual inspection, X-ray diffraction, chemical compositions analysis, metallographic test, wall-thickness measurement, hardness test, and scanning electron microscopic observation. Results obtained showed that the inside surface of the wall-thinned piping component was covered with a wide range of black tubercle-type deposits. Localized pitting corrosion beneath each of the tubercle deposits, which occurred and grew along the stringer texture of the material matrix, was identified. It was concluded that the microbiologically-induced corrosion was responsible for the wall-thinning (and perforation) degradation of the core-spray testing piping component. Tuberculation together with under-deposit pitting (or MIC-pitting) were considered the degradation mechanism.