半干旱地區(qū)天然黃土包氣帶中氚的運(yùn)移特征

摘要： 通過(guò)氚在黃土包氣帶現(xiàn)場(chǎng)示蹤試驗(yàn)結(jié)果的分析，發(fā)現(xiàn)3H縱向分布在相對(duì)濃度較大時(shí)是對(duì)稱(chēng)的，而相對(duì)濃度較小時(shí)則不對(duì)稱(chēng)。通過(guò)對(duì)橫向遷移數(shù)據(jù)的處理，得到了3H在天然黃土中的橫向濃度分布方差σ2y分別為68.4cm2(A坑，t=780d，埋深76cm處)和138.5cm2(B坑，t=779d，埋深110cm處)。橫向擴(kuò)散參數(shù)約為縱向擴(kuò)散參數(shù)的1/3。在埋深較大的B坑中，快成分份額f(t,Uq)隨時(shí)間變化不大，相對(duì)速度Uq(t,xq)隨時(shí)間的變化也不大。在此前提下，按快成分計(jì)算出關(guān)心地點(diǎn)的濃度在某些情況下大于常規(guī)計(jì)算結(jié)果。這表明，以質(zhì)心運(yùn)動(dòng)速度為代表的常規(guī)計(jì)算在某些情況下是不保守的。 Abstract： Through analyses of the field tracer migration test results oftritium in unsaturated loess located in semi-arid area,it is found that the longitudinal concentration distributions of 3H are symmetry at higher relative concentration and non-symmetry at lower relative concentration.From processing of the migration test data the lateral concentration distribution variances (σ2y) of 3H are obtained.σ2y is 68.4 cm2 (in pit A,at t=780 d and depth of 76 cm) and 138.5 cm2(in pit B,at t=779 d and depth of 110 cm),respectively.The lateral diffusion parameter is about one third of the longitudinal diffusion parameter.It is found from analyzing faster component of diffusion of 3H that the changes of both the faster component fractions,f(t,Uq),and the relative velocities,Uq,with time in pit B are not significant.Under the prerequisite,the concentrations calculated by faster component at point concerned are larger than that by conventional calculation under some conditions.It shows that it is not conservative to use the velocity of the center of mass as representative to conduct conventional calculation under some conditions. 作 者： 王志明    楊月娥   作者單位： 中國(guó)輻射防護(hù)研究院，山西 太原 030006  期 刊： 原子能科學(xué)技術(shù)  ISTICEIPKU   Journal： ATOMIC ENERGY SCIENCE AND TECHNOLOGY  年，卷(期)： 2001, 35(1)  分類(lèi)號(hào)： X830.1  關(guān)鍵詞： 黃土包氣帶    氚    現(xiàn)場(chǎng)示蹤試驗(yàn)    運(yùn)移    濃度分布方差    擴(kuò)散參數(shù)   

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