氧势对快堆不锈钢包壳管腐蚀行为的影响

EFFECTS OF OXYGEN POTENTIAL ON CORROSION BEHAVIOUR OF STAINLESS STEEL CLADDING TUBE USED FOR FBR

通过堆外模拟试验，研究了国产３１６－Ｔｉ不锈钢包壳管在４种氧势下对ＦＣＣＩ（燃料包壳化学相互作用）和ＦＰＬＭＥ（裂变产物液态金属脆化效应）的敏感性。结果表明包壳管腐蚀特征与氧势密切相关。当氧势低于Ｃｒ在不锈钢中的氧化阈值，包壳管内壁无明显侵蚀；当氧势超过Ｃｒ在不锈钢中的氧化阈值很多时，包壳管微观侵蚀形貌是基体氧化侵蚀与晶间侵蚀（ＩＧＡ）的混和。随氧势增加，晶间侵蚀深度减小，氧化侵蚀变严重。在与超化学计量混合氧化物燃料对应的高氧势下，同时发生基体氧化侵蚀，晶间侵蚀和剥离性侵蚀，侵蚀区呈“溃疡状”，由富Ｃｒ／贫Ｎｉ和富Ｎｉ／贫Ｃｒ层交替组成。

The susceptibility of domestic 316-Ti stainless steel cladding tube with respect to Fuel Cladding Chemical interaction(FCCI) and Fission Products - induced Liquid Metal Embrittlement (FPLME) under four oxygen POtentials has been investigated by out-of-pile simulation test. It is shown that the corrosion character of cladding tube strongly depends on the oxygen POtential. When the oxygen potential is lower than oxidation threshold of Cr in stainless steel, there is nonobvious attack on inner stir face of cladding, with the room temperature burst strength unchanged, the circum expansion slightly degraded, and the fracture surface of toughness character. When theoxygen Potential greatly exceeds the oxidation threshold of Cr in stainless steel, the microstructure morphology Of the attacked cladding is of matrix oxidative attack combined with IGA. With increasing of oxygen POtential, IGA depth decreases and oxidative attack becomes severe. Under high oxygen POtential correspondillg to hyperstoichiometric fuel, matrix oxidative attack, IGA as well as erosive attack occur simulaneously, with ulcer like attacked zone, consisting of rich Cr/depleted Ni and rich Ni/depleted Cr layers alternatively. The degradation of room temperature strength and expansion of attacked cladding are rather considerable; inner side of fracture surface indicats the intergranular brittle fractrure character; and there are Cs and Te in the brocken grain boundary. This fact supPOrts the POint of view that the mechanism of the focalled Fuel Adjacency Effect(FAE) is synergetic Cs and Te Fission Products-induced Liquid Metal Embrittlement.