就地γ谱仪核素深度分布测量模式灵敏度研究

Method-sensitivity of in-situ γ Spectrometry to Determine the Depth-distribution of Artificial Radionuclides in Soil

通过理论推导和数值计算,对＂多能峰模式＂、＂峰谷比模式＂和＂准直器模式＂三种就地γ谱仪核素深度分布测量模式灵敏度进行研究。＂多能峰模式＂采用152Eu 244、1 408 keVγ射线,＂峰谷比模式＂采用137Cs 662 keVγ射线,＂准直器模式＂采用137Cs 662 keVγ射线和就地计数系统（ISOCS）30°、90°~180°准直器。研究表明,总体上灵敏度大小依次为＂峰谷比模式＂〉＂多能峰模式＂〉〉＂准直器模式＂。

The main limitation of in-situ γ spectrometry lies in determining the depth-distribution of the artificial radionuclide in soil.So,many researchers have developed methods and models aimed at deducing the depth-distribution information from in-situ spectrum itself.Until now,there are three main methods studied and established,which includes ＂Multiple photopeak method＂,＂Peak-to-valley ratio method＂ and ＂Collimated or lead plate method＂.This paper presented the theoretical study on the method-sensitivity comparison.The experimental methods for Multiple photopeak,Peak-to-valley ratio and Collimated or lead plate are at the energy of 244 keV and 1 408 keV γ-rays of 152Eu,662 keV γ-ray of 137Cs,662 keV γ-ray of 137Cs,respectively,and the ISOCS was employed in Collimated or lead plate method.Results indicated that the sequence of method-sensitivity from the maximum to the minimum was as following： Peak-to-valley method,Multiple photopeak method,and Collimated or lead plate method,and the sensitivity of Collimated or lead plate method was far less than Multiple photopeak method.