In this study, we explored the potential of a NaI(Tl) scintillator-based gamma spectrometer for the accurate determination of burial dose rates in natural geological samples using a full spectrum analysis (FSA) approach. In this method, an iterative reweighted least-square regression is used to fit calibration standard spectra (⁴⁰K, and ²³⁸U and ²³²Th series in equilibrium) to the sample spectrum, after subtraction of an appropriate background. The resulting minimum detection limits for ⁴⁰K, ²³⁸U, and ²³²Th are 4.8, 0.4 and 0.3 Bq·kg^–1, respectively (for a 0.23 kg sample); this is one order of magnitude lower than those obtained with the three-window approach previously reported by us, and well below the concentrations found in most natural sediments. These improved values are also comparable to those from high-resolution HPGe gamma spectrometry. Almost all activity concentrations of ⁴⁰K, ²³⁸U, and ²³²Th from 20 measured natural samples differ by ≤5% from the high resolution spectrometry values; the average ratio of dose rates derived from our NaI(Tl) spectrometer to those from HPGe spectrometry is 0.993 ± 0.004 (n=20). We conclude that our scintillation spectrometry system employing FSA is a useful alternative laboratory method for accurate and precise determination of burial dose rates at a significantly lower cost than high resolution gamma spectrometry.

中文翻译：

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全光谱分析在NaI（Tl）γ谱仪中确定埋葬剂量率的应用

在这项研究中，我们探索了基于NaI（Tl）闪烁体的伽马能谱仪使用全光谱分析（FSA）方法准确确定自然地质样品中掩埋剂量率的潜力。在此方法中，减去适当的背景后，使用迭代的加权最小二乘回归将校准标准光谱（平衡时为⁴⁰ K，²³⁸ U和²³² Th系列）与样品光谱拟合。结果得出的⁴⁰ K，²³⁸ U和²³² Th的最低检测限为4.8、0.4和0.3 Bq·kg ^–1，分别（对于0.23千克的样品）；这比我们先前报道的三窗法所获得的浓度低一个数量级，并且远低于大多数天然沉积物中的浓度。这些改进的值也可以与高分辨率HPGeγ谱仪的值相媲美。几乎所有活动浓度为⁴⁰ K，²³⁸ U和²³²20个测量的自然样品中的Th与高分辨率光谱值相差≤5％；从我们的NaI（Tl）光谱仪得出的剂量率与从HPGe光谱法得出的剂量率的平均比率为0.993±0.004（n = 20）。我们得出的结论是，采用FSA的闪烁光谱系统是一种有用的替代实验室方法，可比高分辨率的伽马光谱法以更低的成本准确而准确地确定埋葬剂量率。