Lawrence Berkeley National Laboratory

Accelerator-produced radiation levels at the perimeter of the Ernest Orlando Lawrence Berkeley National Laboratory (the Berkeley Laboratory) reached a maximum in 1959. Neutrons produced by the Bevatron were the dominant component of the radiation field. Radiation levels were estimated from measurements of total neutron fluence and reported in units of dose equivalent (rem). Accurate conversion from total fluence to dose equivalent demands knowledge of both the energy spectrum of accelerator-produced neutrons and the appropriate conversion coefficient functions for different irradiation geometries. At that time (circa 1960), such information was limited, and it was necessary to use judgment in the interpretation of measured data. The Health Physics Group of the Berkeley Laboratory used the best data then available and, as a matter of policy, reported the most conservative (largest) values of dose equivalent supported by their data.Since the early sixties, significant improvements in the information required to compute dose equivalent, particularly in the case of conversion coefficients, have been reported in the scientific literature. This paper reinterprets the older neutron measurements using the best conversion coefficient data available today. It is concluded that the dose equivalents reported in the early sixties would be reduced by at least a factor of two using current methods of analysis.