PWR失水事故工况下燃料包壳与水蒸汽反应研究

STUDY OF FUEL CLADDING-STEAM REACTION UNDER A LOSS OF COOLANT-ACCIDENT (LOCA)

文章描述PWR失水事故工况下燃料包壳与水蒸汽的氧化反应行为。国产Zr-4包壳管在900-1500℃流动水蒸汽中的等温反应速率在1000℃以上遵循抛物线规律,ZrO_2层、α-Zr(O)层和ZrO_2+α-Zr(O)层的成长在此温度以上也遵循抛物线规律,其速率常数分别为:K,(O_2)=4.98 ×10~5exp(-20907/T),mg^2·cm^4·s^(-1);K,(ZrO_2)=0.0104exp(-17592/T),cm^2·s^(-1);K,(α-Zr(O))=0.6407exp(-23207/T),cm^2·s^(-1);K,(ξ)=0.3025exp(-20194/T),cm^2·s^(-1)。高温水中形成的氧化膜使1100℃以下的锆合金与水蒸汽的反应速率降低,不同表面处理和热处理对其影响极小。Zr-2和Zr-4在高温水中的氧化速率无明显差异,Zr-2.5Nb抗高温水蒸汽的氧化能力优于Zr-2和Zr-4。Zr-4合金在高温水蒸汽中的氧化增重超过35mg·cm^(-2)时,氧化膜易出现剥落和破裂。

The isothermal reaction rate of domestic Zircaloy--4 in flowing steam is measured in the temperaurerange of 900--1500℃. The reaction rate measured from the weight gain of the sample follows theparabolic law above 1000℃, the growth rates of ZrO_2 layer, oxygen--stablized alpha phase α--Zr (O)layer and ZrO_2 + α--Zr (O)layer are also parabolic above 1000℃. The parabolic rate constants are K_p(O_2) = 4.98×10~5exp(--20907/ T ), mg^2·cm^(-4)·s^(-1); K_p (ZrO_2) = 0. 0104 exp(--17592/ T ),cm^2·s^(-1); K_p(α--Zr (O) ) = 0.6407exp(--23207/ T ),cm^2·s^(-1); K_p(ξ) = 0. 3025exp(--20194/ T), cm^2·s^(-1). The oxide film produced in high temperature water decreases Zircaloy--steam reaction ratesat 1100℃ or less. Different surface treatments(pickling and polishing)and different heat treatments (αannealing and β quenching) have small or neglible effects. Oxidation rates of Zircaloy--2 and Zircaloy--4in high temperature steam haven't distinct difference, but the high tempetature steam oxidation resis-tance of Zr--2.5Nb is superior to that of Zircaloy--4 and Zircaloy--2. It is found that when the oxideweight gain of Zircaloy--4 in high tempetature steam in larger than 35mg·cm^(-2), the oxide film easilyseperates and spalls.