Shielding calculations at dismantled synchrocyclotron

The Space Radiation Effects Laboratory (SREL) located in Newport News, Virginia, was operated by the College of William and Mary for the National Aeronautics and Space Administration (NASA). A synchrocyclotron was formerly in operation in this building and a primary beam of 600 MeV protons and secondary beams of 400 MeV pions and muons were produced for the purpose of studying the effects of radiation on materials, components, and systems planned for use in space. The synchrocyclotron and its accessory equipment were removed in 1980. At several locations, the scattered synchrocyclotron beam caused an induced radioactivity within the walls of the cyclotron room. The concrete shields surrounding the synchrocyclotron have been removed from the building and stored adjacent to the radiochemistry laboratory. The facility is no longer operational; it has been decided to decommission the synchrocyclotron. In 1985, the Oak Ridge National Laboratory Radiological Survey Activities (ORNL/RASA) group was invited to perform a radiological survey to determine the amount of residual radioactivity on the walls and the floor, calculate the dose to potential occupants working in the building, and make recommendations to minimize exposures from the residual radioactivity on the walls and the floor of the cyclotron room. In this paper, accelerator decommissioning is reviewed, and criteria for decommissioning of accelerators is discussed. The survey method is described, and the findings at the SREL are presented