Radiation safety design for the Linac Coherent Light Source (LCLS), which provides ultra fast intense X-ray FEL, was performed at SLAC national accelerator laboratory. The LCLS has specific layout, i.e, an experimental area having through holes sits in front of intense high energy electron beam. For this condition extensive simulations and experiments had been carried out during several years to find out solutions to meet requirements of radiation dose rates under normal operation, mis-steering condition and system failure. In this effort, prompt dose rate in accessible area and ground water activity were estimated for shielding structure of 17 GeV, 5 kW main dump. To obtain dose rate in the experimental area, production of muon and high energy bremsstrahlung were estimated for beam losses of a bending magnet and thin insertion devices at more than 70 m upstream of the area. Dose rates for failure cases of beam containment system and personal protection system were estimated to ensure that the dose rate in accessible area is kept below the limit under these conditions. The accuracy of the design was confirmed during commissioning phase through field measurements prior to user runs.
