Development of Detection and Direction Estimation Techniques of Neutron Sources

Tohn Takahashi - JAEA
Mitsuo Koizumi - JAEA
Takanori Mochimaru - JAEA
Kota Hironaka - JAEA
Hirokuni Yamanishi - Kindai University
Genichiro Wakabayashi - Kindai University
In order to prevent nuclear terrorism at major public events, it is essential to prevent the bringing in nuclear and radioactive materials to the event site, and to detect and nuclear and radioactive materials quickly even if they are brought in. In particular, when detecting nuclear materials and neutron sources, it may be more effective to detect fast neutrons which have higher shielding difficulty than gamma-rays. In this study, we have started technology development of detection using a plastic scintillator that has sensitivity to fast neutrons and is easy to process and handle. Since plastic scintillators are sensitive to both fast neutrons and gamma-rays, signals from gamma-rays interfere those from neutrons. EJ-276 plastic scintillator can distinguish neutrons from gamma-rays by using Pulse Shape Discrimination (PSD) technique. We introduced the rod-shaped EJ-276 (25mm×25mm×250mm) for the purpose of developing a system for detecting fast neutrons. Through measurements of Cf-252 neutron source, we verified that neutrons and gamma-rays can be discriminated by PSD. Since the introduced scintillator is rod-shaped, the sensitivity is angle-dependent. At Kindai University we have performed some experiments for performance evaluation of the detector. The detector showed the angular dependence and good match with PHITS simulation result. By combining this with PSD technique, it is possible to develop a detector that is effective for detecting a direction of a neutron source. More detail results will be presented.