Neutron Meters

Neutron meters measure neutron radiation dose rate and fluence. They give radiation protection officers, nuclear facility personnel, and CBRN operators quantitative data on neutron exposure levels. These instruments operate in environments where fission reactions and special nuclear materials produce significant neutron fields.

Neutrons carry no electric charge. They do not ionize matter directly. As a result, neutron meters use nuclear reactions to convert neutron interactions into measurable electrical signals. He-3 proportional counter tubes detect thermal neutrons at efficiencies above 70%. The reaction n + He-3 → p + T produces proton and triton ions that ionize the detector gas. Polyethylene moderator shells slow fast neutrons to thermal energies before they reach the detector. This maximizes detection efficiency across the full neutron energy spectrum. Furthermore, Li-6 and boron-lined proportional counters provide viable He-3 alternatives for portal monitoring and handheld instruments.

Dose rate display covers ranges from 0.1 µSv/h to 10 Sv/h. This spans background monitoring through high-dose emergency response scenarios. Energy-compensated assemblies correct count rate readings for varying neutron biological effectiveness. They display dose equivalent in µSv/h or mSv/h directly without manual conversion. Additionally, rem meters such as the Ludlum 42-40 use tissue-equivalent moderator geometries. These produce flat neutron energy response from thermal to fast — meeting IAEA and ANSI personnel dose monitoring requirements.

Audible count rate outputs notify operators of neutron field entry. Alarm set points trigger on dose rate threshold crossings. Moreover, data logging stores dose rate and accumulated dose readings with timestamps for regulatory compliance documentation.

These meters serve Pakistan’s PAEC nuclear facilities, Pakistan Army CBRN units, Pakistan Customs at Karachi Port and Torkham, and university nuclear physics departments in Lahore and Islamabad.