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首页> 外文学位 >Decreasing the fission track analysis detection limit of plutonium concentrations in human excreta by utilizing two distinct neutron energy spectra.
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Decreasing the fission track analysis detection limit of plutonium concentrations in human excreta by utilizing two distinct neutron energy spectra.

机译：通过利用两个不同的中子能谱来降低人类排泄物中p浓度的裂变径迹分析检测极限。

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摘要

Environmental Pu239 arises from the development, production and testing of nuclear weapons. Fallout of this weapon debris has produced an average worldwide Pu239 level of about 1 ppb. Traditional methods are available to measure Pu239 at fCi levels, but these methods are unable to detect Pu239 at environmental levels (100 aCi). Such an ultra sensitive method chemically separates Pu239 from naturally occurring uranium and other fissile isotopes. Then the technique is applied to the Pu239 burden effluent.;Fissile samples are exposed to distinct neutron spectra to achieve quantitative analysis of each fissile isotope using fission track analysis without chemical separation. The University of Utah's 100 kW TRIGA reactor was used to deliver thermal and epithermal neutron fluences. Each isotope has a unique fission cross-section for different neutron energy ranges. It was possible to differentiate between the isotopes based on the number of fission tracks produced. The proposed technique can measure the amount of Th232, U235, and Pu239 in the sample simultaneously. Samples containing known amounts of Pu239, natural uranium (U235 and U238) were deposited on the polycarbonate Lexan detectors and irradiated in different positions in the reactor core. They were chemically etched and fission tracks were counted. The concentrations were calculated using the computer code COG and the mathematical correlations for the two irradiators. NU=-2.754 0+/-0.25x1011 T1+1.9654+/-0.24 x1012T2 NPu=3.3 861+/-0.27x107 T1-1.4973+/-0.25 x108T2 aU,1= 6.2479+/-0.17x10-13 ,aU,2= 1.1304+/-0.23x10-13 aPu,1= 8.1976+/-0.16x10-11 ,aPu,2= 1.1492+/-0.23x10-11;T1 and T2 are the number of tracks counted from samples when exposed to a known neutron spectra. Without chemical processing, the detection limit of ∼120 aCi/g can easily be achieved. Calculated amounts ranged within a factor of two to three from a known quantity deposited on the Lexan detectors. The uncertainties associated with this method stem from the differences in theoretical and actual neutron flux in the irradiators, the inefficiencies with etching process, and errors with the track counting activity.
机译：环保Pu239源于核武器的开发，生产和测试。该武器碎片的尘埃产生的全球平均Pu239水平约为1 ppb。传统方法可用于在fCi水平上测量Pu239，但是这些方法无法在环境水平（100 aCi）下检测Pu239。这种超灵敏的方法将Pu239与天然存在的铀和其他易裂变同位素化学分离。然后将该技术应用于Pu239负荷流出物；将易裂变样品暴露于不同的中子光谱中，使用裂变径迹分析无需化学分离即可对每个裂变同位素进行定量分析。犹他大学的100 kW TRIGA反应堆用于传递热和超热中子注量。对于不同的中子能量范围，每个同位素都有一个独特的裂变截面。根据产生的裂变径迹的数量，可以区分同位素。所提出的技术可以同时测量样品中Th232，U235和Pu239的量。将包含已知量的Pu239，天然铀（U235和U238）的样品沉积在聚碳酸酯Lexan检测器上，并在反应堆堆芯的不同位置进行辐照。对它们进行了化学蚀刻，并计算了裂变径迹。使用计算机代码COG和两个照射器的数学相关性计算浓度。 NU = -2.754 0 +/- 0.25x1011 T1 + 1.9654 +/- 0.24 x1012T2 NPu = 3.3 861 +/- 0.27x107 T1-1.4973 +/- 0.25 x108T2 aU，1 = 6.2479 +/- 0.17x10-13，aU， 2 = 1.1304 +/- 0.23x10-13 aPu，1 = 8.1976 +/- 0.16x10-11，aPu，2 = 1.1492 +/- 0.23x10-11; T1和T2是暴露于样品时从样品计数的轨道数已知的中子光谱。如果不进行化学处理，则可以轻松实现约120 aCi / g的检测限。计算的量与沉积在Lexan检测器上的已知量的2到3倍不等。与该方法相关的不确定性源于辐照器中理论中子通量和实际中子通量的差异，蚀刻过程的效率低下以及径迹计数活动的误差。

著录项

  • 作者

    Choe, Dong-Ok.;

  • 作者单位

    The University of Utah.;

  • 授予单位 The University of Utah.;
  • 学科 Engineering Nuclear.;Environmental Sciences.
  • 学位 Ph.D.
  • 年度 2000
  • 页码 177 p.
  • 总页数 177
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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