[en] Since the inception of multisphere neutron spectrometers (Bramblett et al. 1960), EML scientists have been involved in the development of these spectrometers (O'Brien et al. 1965), various applications in radiation protection (Weinstein 1970), the development of unfolding codes (Sanna and O'Brien 1971), and the calculation of their response functions (Sanna 1973). These traditions continue at EML, and we have what one might call the state-of-the-art instrumentation and data analysis techniques. The essence of the Bonner sphere method is to expose the detectors to neutron radiation fields and take successive counts with thicker and thicker moderators surrounding a neutron capture detector. For example, for a given medium energy of neutrons the count rate increases and then drops as the moderator thickness increases. The spectral shape may be inferred from the relative responses of the detector in the variously-sized moderating spheres. This kind of spectrometer has been used extensively in radiation protection practice to determine neutron spectral distributions around particle accelerators (Awschalom 1966), nuclear power stations (Hajnal et al. 1979), and other nuclear facilities (Awschalom and Sanna 1985), as well as in cosmic ray neutron research (Hajnal et al. 1971, Nakamura et al. 1987). This spectrometer system has proven to be very useful since it is simple, portable, has an isotropic response and covers a wide energy range (Cross and Ing 1987). The data can be unfolded and interpreted fairly easily using one of the EML-developed unfolding codes