Analytical calculation of the collimated detector response for the characterization of nuclear waste drums by segmented gamma scanning
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- Qian, N., Krings, T., Mauerhofer, E. et al. J Radioanal Nucl Chem (2012) 292: 1325. doi:10.1007/s10967-011-1601-1
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Improved methods for the reconstruction of the isotope specific activity content in nuclear waste drums with data obtained by a gamma scanning system developed at Shanghai Jiao Tong University require an analytical function of the detector response. In this work we derive an analytical detector response function for a collimated HPGe detector with a square collimation window. The model is based on a purely geometric model respecting the configuration of the collimated detector system, the positions of radioactive point sources and the absorption of γ-rays in the matrix as well as in the HPGe crystal. We show that the derived analytical detector response function is in good agreement with data simulated by MCNP5.
KeywordsNuclear wasteSegmented gamma scanningDetector response
Low and intermediate nuclear waste from nuclear power plants (NPP) in China is conditioned in 200 L drums at the NPP sites. The School of Nuclear Science and Engineering of the Shanghai Jiao Tong University develops an improved gamma scanning system to experimentally determine the isotope specific activity contents of nuclear waste drums. The gamma scanning system is mainly composed of a mechanical part to rotate a nuclear waste drum and to lift a detection system for the measurements of γ-rays. The detection system consists of a collimated HPGe detector with a square collimation window. Improved methods for the activity content reconstruction require an analytical description of the detector response to activity point sources in a waste matrix. In this work the analytical response function of the square collimated HPGe detector used at SJTU is derived according to work of Krings and Mauerhofer . For its validation the analytical detector response function is compared to simulated data obtained from MCNP5 (Monte Carlo N-Particle Code).
Illuminated active detector surface
Edge penetration correction
Simulations, results and discussions
It has been shown that MCNP5 is suitable for the simulation of efficiencies of HPGe detectors to point sources at various positions [2–4]. Therefore, the detection system as it is used at SJTU is modelled according the specifications of the detector furnisher.
It has been shown, that the here used method to analytically calculate the response of HPGe detector in the geometric setup of gamma scanning systems for the characterization of nuclear waste drums is in perfect agreement with simulated data. Thus, this analytical function can be implemented in algorithm for the accurate and reliable reconstruction of the isotope specific activity content in nuclear waste drums.
This work was supported by the National Natural Science Foundation of China (contract number: 10675084).