无源核子料位计探测点γ场强度数值模型构建

Numerical Model Construction ofγ-Ray Intensity at the Detection Point of Passive Nucleon Level Meter

无源核子料位计利用粉煤灰自身的微量天然γ射线来检测灰斗或仓泵内的灰位,是一种新型的具有较高可靠性的非接触式料位计。探测点处的γ射线强度随粉煤灰灰位的变化规律是仪表设计、使用和标定的重要依据。首先从理论上推导出点状辐射体在吸收介质中某点的γ射线强度的计算公式,然后以此为基础,构建了粉煤灰辐射体在探测点处γ射线强度的一般化数值计算模型。在数值模型构建中,提出了更加高效的折半逼近法来计算介质对γ射线的吸收厚度。该模型的构建思想和方法适用于任意的辐射体形状和探测点位置,能够满足各种工况下的计算要求。通过与圆柱形辐射体在轴线上的准确的γ射线强度进行对比,证明了此模型的建模思路与方法是正确的,模型的精度是满足要求的。

Passive nucleon level meter uses the trace naturalγ-rays of fly ash itself to detect the ash level in the ash hopper or bin pump,which is a new type of non-contact level meter with high reliability.The variation law of the intensity ofγ-rays at the detection point with the ash level of fly ash is an important basis for the design,use and calibration of the meter.Firstly,the calculation formula ofγ-ray intensity of the point-shaped radiator at a point in the absorbing medium is derived theoretically,and then,a generalized numerical calculation model ofγ-ray intensity of fly ash radiator at the detection point is constructed.In the construction of the numerical model,a more efficient fold-and-half approximation method is proposed to calculate the absorption thickness of the medium forγ-rays.The model construction idea and method are applicable to arbitrary radiator shape and detection point location,and can meet the calculation requirements under various working conditions.By comparing with the accurateγ-ray intensity of the cylindrical radiator in the axis,it is proved that the modeling idea and method of this model are correct,and the accuracy of the model meets the requirements.