Needs and performance requirements for neutron monitoring in the nuclear power industry

Neutrons do not contribute greatly to the collective occupational dose at Ontario Hydro's nuclear generating stations. Nonetheless, there is a need to monitor workers' exposure to neutrons in some locations. At present, neutron area surveys and personal dosimetry are both performed using integrating rem meters (of the Andersson-Braun design), which workers take with them when they will be working in an area where neutrons are known to be present This is not a satisfactory method for neutron monitoring or dosimetry, both because of the inconvenience of carrying around a large, heavy instrument, and because rem meters are known to be inaccurate in many situations. There is a further problem associated with the calibration of the rem meters, which is done in a fast neutron field quite unlike the neutron fields found in nuclear generating stations. However, rem meters continue to be used, owing to the lack of suitable alternatives and also to the low priority neutron dosimetry has traditionally received in the company. The properties of an ideal neutron dosemeter and of an ideal survey meter for use in nuclear generating stations are described. These properties are compared with those of currently available dosemeters and instruments, and it is shown where changes and improvements are needed. The need for a calibration field that is more representative of the energy spectra to be measured in practice is also discussed.