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在核设施大气排放中,根据烟云的尺度和烟云中的放射性分布,通常采用半无限和有限烟云模式来估算γ放射性核素所致的外照射剂量。本文对采用有限烟云模式的图解法(Nomogram)和离散点近似法(DPA)估算单位源强γ放射性核素所致的空气吸收剂量率进行了比较。计算结果表明,两种方法计算的γ空气吸收剂量率相当一致,约有87%的计算结果的比值在2之内,97%在3倍以内;在稍稳定天气(E 类),计算结果的最大比值约为6倍。两种方法计算结果的不同之处,是由于输入参数及这些参数对两种方法的适应程度的不同所致。这两种方法是根据不同的需要提出的,在给定情景下,选择哪种方法取决于使用者的需要。
In atmospheric emissions of nuclear facilities, semi-infinite and limited cloud of smoke models are often used to estimate the amount of external radionuclide due to gamma-radionuclides, based on the scale of the cloud of smoke and the distribution of radioactivity in the cloud. In this paper, the air dose rates induced by γ-radionuclides per unit source were compared using the Nomogram and the discrete-point approximation (DPA) of the finite cloud model. The calculated results show that the calculated γ-air dose rates of the two methods are fairly consistent, with about 87% of the calculated values being within 2 and 97% within 3 times; in slightly stable weather (class E) The maximum ratio is about 6 times. The difference between the calculated results of the two methods is due to the different input parameters and the adaptation of these parameters to the two methods. The two methods are based on different needs, in a given scenario, the choice of which method depends on the needs of users.