基于LaBr_(3)(Ce)闪烁体的γ能谱测井仪性能提升研究

Performance improvement of gamma ray spectrum logging tool based on LaBr_(3)(Ce) scintillation crystals

地处南部非洲纳米比亚的湖山铀矿的主要含矿岩石为白岗岩,其矿石中放射性元素钍含量较高,对γ测井结果影响较大。为了解决钍元素对γ测井结果的影响,采用了高分辨率LaBr_(3)(Ce)闪烁探测器、交叉谱段法以及分离射线谱技术,研制了新型γ能谱测井仪,极大地提高了钍、铀、钾核素的计数率、仪器的量程以及测井速度,并能有效区分钍、铀、钾核素,实现了铀含量的定量测量,该测井仪器的实验和校准测试是在控制孔、爆破孔、国家标准铀模型中进行的,验证了其测量精度、范围、速度适用性、稳定性、重复性等。新型γ能谱测井仪在测量范围及测井速度方面,达到γ测井规范要求,即铀含量测量上限达到5.0%eU,测井速度达到0.067 m·s^(−1)。能够直接解释出钍、铀、钾含量,提高了矿石铀品位测量的准确性。使用该γ能谱测井仪成功实现了湖山矿爆破孔矿石铀品位的快速定量测量,并可精确估算铀矿量。

[Background]The main ore-bearing rock of the Husab Uranium Mine in Namibia,southern Africa,is white granite,and the radioactive element thorium content in the ore is high,which has a greater impact on theγray logging results.[Purpose]This study aims to solve the problem of thorium's interference on theγray logging results by developing aγray spectrum logging instrument.[Methods]A high-resolution LaBr_(3)(Ce)scintillation detector was employed to build a new type ofγray spectrum logging tool.Combined with cross-segment method ofγray spectrum and techniques for separating theγray spectrum,the counting rates of thorium,uranium and potassium nuclides were greatly improved,so did the measuring range of the tool and logging speed.Experiment and calibration tests of this logging instrument were conducted on control holes,blast holes,national standard uranium calibration pit,etc.,to verify its range,speed applicability,stability,repeatability,etc.[Results]Tests results show that theγray spectrum logging achieves upper limit of uranium content measurement of 5.0%eU,and the logging speed of 0.067 m·s^(−1),satisfying the rapid quantitative measurement of uranium grades in the blast holes of the Husab Mine and accurately estimated the amount of uranium with superior measuring accuracy to theγray logging method.[Conclusions]Theγray logging tool of this study reaches specification requirements ofγray logging.It can effectively distinguish thorium,uranium and potassium nuclides,realizing the quantitative measurement of uranium content.