Radiological Environmental Protection for LCLS-II High Power Operation

SLAC National Accelerator Laboratory, Menlo Park, CA, 95125, USA

^* Corresponding author: james@slac.stanford.edu

Published online: 25 September 2017

Abstract

The LCLS-II superconducting electron accelerator at SLAC plans to operate at up to 4 GeV and 240 kW average power, which would create higher radiological impacts particularly near the beam loss points such as beam dumps and halo collimators. The main hazards to the public and environment include direct or skyshine radiation, effluent of radioactive air such as ¹³N, ¹⁵O and ⁴¹Ar, and activation of groundwater creating tritium. These hazards were evaluated using analytic methods and FLUKA Monte Carlo code. The controls (mainly extensive bulk shielding and local shielding around high loss points) and monitoring (neutron/photon detectors with detection capabilities below natural background at site boundary, site-wide radioactive air monitors, and groundwater wells) were designed to meet the U.S. DOE and EPA, as well as SLAC requirements. The radiological design and controls for the LCW systems [including concrete housing shielding for ¹⁵O and ¹¹C circulating in LCW, ⁷Be and erosion/corrosion products (²²Na, ⁵⁴Mn, ⁶⁰Co, ⁶⁵Zn, etc.) captured in resin and filters, leak detection and containment of LCW with ³H and its waste water discharge; explosion from H₂ build-up in surge tank and release of radionuclides] associated with the high power beam dumps are also presented.