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The authors developed a real-time personal neutron dosimeter which could give neutron dose equivalent over wide energy region from thermal to 10 odd MeV by using 2 silicon detectors, fast neutron sensor and slow neutron sensor. The energy response of this dosimeter was evaluated under thermal neutron field, monoenergetic neutron field between 200keV and 15MeV, and moderated 252Cf neutron field. The neutron dose equivalent was estimated by adding neutron dose equivalent below 1MeV given by slow neutron sensor and that above 1MeV by fast neutron sensor. It was verified from various field tests that this dosimeter is able to give neutron dose equivalent within a factor of 2 margin of accuracy in reactor, accelerator, fusion research and nuclear fuel handling facilities. This dosimeter has more than one order higher sensitivity than conventional personal neutron dosimeters and is insensitive to γ-rays up to about 500 mSv/h. This dosimeter will soon be commercially available as a personal dosimeter which gives neutron and γ-ray dose equivalents simultaneously by installing γ-ray silicon sensor.

There is a great interest to find nuclear accidents as soon as possible and/or to carry out daily monitoring and control for nuclear facilities from a distance. In order to satisfy these requirements, a direction finding gamma-ray detector has been developed as a monitor of gamma-ray leakage from such facilities. The detector comprises three scintillators made of the same material of sodium iodine with thallium NaI(Tl). Computer simulations and laboratory experiments show the possibility of direction finding of gamma rays with reasonable accuracy.