Study On Monte Carlo Simulation & Deconvolution Overlapping Peaks Of Gamma-ray Spectra In NaI(Tl) Detector

With the development of the Nuclear Power and the application of the Nuclear Method, the probability ofradioactivity contamination is growing. These have been drawn more and more attention in radiationprotection research by the public and government. NaI(Tl) multichannel spectrometer are widly used inairborne & in-situ gama-ray survey because of its much characteristic: high sensitivity, working in normalsituation and so on . But its lower resolution than HPGe (high pure Ge) detector results in some peaksoverlapping, specially peaks of 0.662 MeV, 0.583 Mev and 0.609MeV. So this research makes sense inlearning and application.This paper has simulated peaks of spectrum in NaI(Tl) multichannel spectrometer by Monte CarloMethod(MCNP4B program), including 3 parts: 137Cs in air, natural nuclide( 238U,232Th,40K)in soil , 137Csdistributing in soil. Meanwhile, contrast between simulations and experiment has been taken. The conclusionsare follow.(1) The results of simulations and experiment are agree with in -32.68~27.32% for 137Cs thatconcentration is about 5×10-5Bq in air. The contrast of simulations and experiment for natural nuclide insoil is well agree with in shape and channel, but has much discrepancy in intensity.(2) The simulated results for 137Cs distributing in soil indicate that , during 0~50cm depth, the gamma-rayis absorbed as Y=0.00139·e-0.2578x, and during 20~150cm horizon distance, Y=4291.3·X-2.0232. Fromthese formula, we can detertmine the detection limits in depth and horizon distance , respectively, 30cm and70cm.(3) Discussing the deconvolved method for low energy information of spectrum in NaI(Tl) multichannelspectrometer.