# Gamma-ray Full Spectrum Analysis for Environmental Radioactivity by HPGe Detector

• Jeong, Meeyoung ;
• Lee, Kyeong Beom ;
• Kim, Kyeong Ja ;
• Lee, Min-Kie ;
• Han, Ju-Bong
• Accepted : 2014.12.04
• Published : 2014.12.15
• 100 60

#### Abstract

Odyssey, one of the NASA's Mars exploration program and SELENE (Kaguya), a Japanese lunar orbiting spacecraft have a payload of Gamma-Ray Spectrometer (GRS) for analyzing radioactive chemical elements of the atmosphere and the surface. In these days, gamma-ray spectroscopy with a High-Purity Germanium (HPGe) detector has been widely used for the activity measurements of natural radionuclides contained in the soil of the Earth. The energy spectra obtained by the HPGe detectors have been generally analyzed by means of the Window Analysis (WA) method. In this method, activity concentrations are determined by using the net counts of energy window around individual peaks. Meanwhile, an alternative method, the so-called Full Spectrum Analysis (FSA) method uses count numbers not only from full-absorption peaks but from the contributions of Compton scattering due to gamma-rays. Consequently, while it takes a substantial time to obtain a statistically significant result in the WA method, the FSA method requires a much shorter time to reach the same level of the statistical significance. This study shows the validation results of FSA method. We have compared the concentration of radioactivity of $^{40}K$, $^{232}Th$ and $^{238}U$ in the soil measured by the WA method and the FSA method, respectively. The gamma-ray spectrum of reference materials (RGU and RGTh, KCl) and soil samples were measured by the 120% HPGe detector with cosmic muon veto detector. According to the comparison result of activity concentrations between the FSA and the WA, we could conclude that FSA method is validated against the WA method. This study implies that the FSA method can be used in a harsh measurement environment, such as the gamma-ray measurement in the Moon, in which the level of statistical significance is usually required in a much shorter data acquisition time than the WA method.

#### Keywords

gamma-ray full spectrum analysis;gamma-ray spectrometer;lunar orbiter payload;anticoincidence background suppression

#### References

1. Hendriks PHGM, Limburg J, De Meijer RJ, Full-spectrum analysis of natural $\gamma$-ray spectra, JER 53, 365-380 (2001). http://dx.doi.org/10.1016/S0265-931X(00)00142-9 https://doi.org/10.1016/S0265-931X(00)00142-9
2. Khandaker MU, High purity germanium detector in gammaray spectrometry, IJFPS 1, 42-46 (2011).
3. Lee KB, Lee JM, Park TS, Lee SH, Construction of classical confidence regions of model parameters in nonlinear regression analyses, Applied Radiation and Isotopes 68, 1261-1265 (2010). http://dx.doi.org/10.1016/j.apradiso.2009.11.013 https://doi.org/10.1016/j.apradiso.2009.11.013
4. Lee KB, Park TS, Lee JM, Oh P-J, Lee S-H, Development of a low-level background gamma-ray spectrometer by KRISS, Applied Radiation and Isotopes 66, 845-849 (2008). http://dx.doi.org/10.1016/j.apradiso.2008.02.083 https://doi.org/10.1016/j.apradiso.2008.02.083
5. LNHB (Laboratoire National Henri Becquerel), Atomic & Nuclear Data [Internet], cited 2014 Aug 02, available from: http://www.nucleide.org/NucData.htm
6. Maphoto KP, Determination of natural radioactivity concentrations in soil: a comparative study of Windows and Full Spectrum Analysis, M. Sc. (Dept. of Physics, Faculty of Natural Sciences), University of the Western Cape (2004).
7. Murray AS, Marten R, Johnston A, Martin P, Analysis for naturally occuring radionuclides at environmental concentrations by gamma spectrometry, JRNC 115, 263-288 (1987). http://dx.doi.org/10.1007/BF02037443 https://doi.org/10.1007/BF02037443
8. Nuttall PM, A Handbook of Radioactivity Measurement Procedures, IJRB 37, 351-352 (1980). http://dx.doi.org/10.1080/09553008014550431 https://doi.org/10.1080/09553008014550431
9. Quittner P, Gamma-ray spectroscopy, with particular reference to detector and computer evaluation techniques (London, Hilger, 1972)
10. Wieser ME, Atomic weights of the elements 2005 (IUPAC Technical Report), Pure and Applied Chemistry 78, 2051-2066 (2006). http://dx.doi.org/10.1351/pac200678112051 https://doi.org/10.1351/pac200678112051