[2N12-16] Environment Measurement/Nuclear Material

[2N14] Applicability of multiple gamma-ray detection to long-lived radioactive nuclide determination in environmental samples

*Masumi Oshima¹, Jun Goto², Yurie Ikebe¹, Hirofumi Seto¹, Shigeru Bamba¹, Hirofumi Shinohara¹, Takao Morimoto¹, Keisuke Isogai¹ (1. Japan Chemical Analysis Center, 2. Niigata University)

Keywords:multiple gamma-ray detection method, determination of long-lived radioactive nuclides

Gamma-gamma coincidence measurement utilized in gamma-ray spectroscopy experiments is well known to be effective for the improvement of signal-to-noise ratio in a gamma-ray spectrum. We study its applicability to determination of long-lived radioactive nuclides in environmental samples. The gamma-ray simulation code Geant 4.10.2 was used. A conventional and effective detector system comprising seven Ge detectors was assumed. We took up thirty five nuclides which need to be determined for the evaluation of fission product leakage at the nuclear accident in the Fukushima nuclear power plants in Japan. Among them twelve nuclides emit gamma-rays and five nuclides of ⁶⁰Co, ⁹⁴Nb, ¹³⁴Cs, ¹⁵²Eu and ¹⁵⁴Eu can be the objectives of the multiple gamma-ray detection method. The simulation results indicate that the signal-to-noise ratio can be improved by a factor between 1 and 300, and the detection limit between 2.6 and 8.2 relative to the singles measurement, implying that the method can be well applied to the determination of the long-lived radioactive nuclides and will provide a quick and non-destructive analysis method.