Neutron ray measured in Tokyo — Uranium-235 found in Chiba — Can’t be detected by most geiger counters (PHOTO & VIDEO) TOKYO, Oct. 19 — A Neutron ray was measured in Toranomon, Tokyo on October 18, reports Mochizuki of Fukushima Diary. Neutron rays are emitted by uranium-235. Also, in Kashiwa, Chiba citizens detected uranium-235 beside a bench at Matsuba Daiichi Park on October 11. The Uranium-235