Speaker
Description
The Second Target Station (STS) facility at Oak Ridge National Laboratory’s Spallation Neutron Source will receive a 700 kW, 1.3 GeV proton beam with a pulse frequency of 15 Hz, delivered by the Ring to Second Target Beam Transport (RTST). Spanning approximately 220 meters, the RTST includes 56 quadrupole magnets and 15 dipole magnets. According to the STS Project Radiation Safety Policy and Plan [1], radiation exposures in generally accessible areas must not exceed 0.25 mrem/hr during normal facility operations.
The radiation transport model geometry, created using constructive solid geometry (CSG), includes the entire beamline downstream of the accumulator ring to the STS target building. This encompasses the beam vacuum tubing, magnets, tunnel structure, and surrounding components like the soil berm, truck access tunnel, shield walls, and labyrinths. The MCNP6 [2,3] general-purpose Monte Carlo radiation transport code was utilized to estimate dose rates in accessible regions, accounting for contributions from 1 W/m beam losses and backscatter from the beam striking the rotating STS tungsten target. Custom MCNP6 subroutines were developed to represent the beam losses along the RTST and the primary beam on the target. The ADVANTG [4] code facilitated the generation of optimized weight windows to converge dose rates in areas of interest.
This work offers an overview of the passive radiation shielding design for the RTST facility. It encompasses methodologies for calculating expected dose rates in generally accessible regions and discusses technical design challenges along with their respective solutions.
References:
- Second Target Station (STS) Project Radiation Safety Policy and Plan, S01030100-PN0001, Second Target Station, Oak Ridge National Laboratory, October 2020.
- Werner, C. J., et al., MCNP User’s Manual – Code Version 6.2, LA-UR-17-29981, Los Alamos National Laboratory, October 2017.
- Werner, C. J., et al., MCNP6.2 Release Notes, LA-UR-18-20808, Los Alamos National Laboratory, February 2018.
- Mosher, S. W., Bevil, A. M., Johnson S. R., et al. ADVANTG―An Automated Variance Reduction Parameter Generator, ORNL/TM-2013/416, Rev. 1, Oak Ridge National Laboratory, August 2015.
