Radiological Environmental Protection for LCLS-II High Power Operation

James Liu,Maranda Cimeno,Sayed Rokni,Jan Blaha,Ludovic Nicolas,Henry Tran,Stan Mao,Mario Santana,F Malvagi,C.M’B Diop,F Malouch,J.C Trama,J Miss

doi:10.1051/epjconf/201715303014

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 13 N, 15 O and 41 Ar, 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 15 O and 11 C circulating in LCW, 7 Be and erosion/corrosion products (22 Na, 54 Mn, 60 Co, 65 Zn, etc.) captured in resin and filters, leak detection and containment of LCW with 3 H 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.

Highlights

SLAC National Accelerator Laboratory (SLAC) is designing the LCLS-II hard X-ray free-electron-laser facility, which utilizes a new superconducting (SC) electron linac for operation with a maximum beam of 4 GeV, 240 kW average power and MHz capability
This is lower than the design goal of 1 μSv/y to Maximum Exposed Individual (MEI) from each air release point and is much lower than the design limit of 100 μSv/y
The BSY dump has small aluminum balls mixed in 39-liter of water followed by a solid Cu end-cap

Summary

Introduction

SLAC National Accelerator Laboratory (SLAC) is designing the LCLS-II hard X-ray free-electron-laser facility, which utilizes a new superconducting (SC) electron linac for operation with a maximum beam of 4 GeV, 240 kW average power and MHz capability. The LCLS-II high power operation will create higher radiological impacts to the workers, public and environment, near the beam loss points such as beam dumps and halo collimators. The main impacts to the public and environment include direct or skyshine neutron and photon radiation, effluent of radioactive air (e.g., 13N, 15O and 41Ar), and activation of groundwater (mainly tritium). Radiological design and controls for Low Conductivity Water (LCW) systems is one of the main subjects for protection of the workers, public and environment. The assessment, controls and monitoring of these hazards to satisfy the U.S Department of Energy (DOE) and SLAC requirements are described

LCLS-II facility

Skyshine radiation

Radioactive air effluent

Groundwater activation

Radiological design and controls for LCW system

Conclusions