Second Target Station Bunker Shielding with Populated and Unpopulated Neutron Beamlines: Preliminary Design

Abstract

At the U.S. Department of Energy’s Oak Ridge National Laboratory, the Second Target Station (STS) beamline sources for preliminary design have been used to perform a shielding analysis of the bunker. Prompt total effective dose rates (i.e., neutron plus photon effective dose rates when the proton beam is on) were calculated on top of the bunker roof and outside the bunker wall. These areas outside the bunker will be generally accessible, so the prompt total dose rate in these areas should not exceed 2.5 μSv‧h⁻¹ (0.25 mrem‧h⁻¹). This paper presents the required shielding thicknesses to meet this dose rate limit. In one instance, this dose rate limit is not met: For a combination of populated and unpopulated beamlines, the prompt total dose rate outside the bunker across from the unpopulated beamline, which has less shielding because of the lack of beamline shielding, slightly exceeds 2.5 μSv‧h⁻¹. Once more details are known regarding the STS high-density concrete density and composition, a future analysis will investigate the shielding modifications required to reduce the calculated prompt total dose rates for this configuration to less than 2.5 μSv‧h⁻¹.

Keywords:

• Spallation
• bunker shielding
• neutron beamline

Acknowledgments

The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).

Disclosure Statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE; Basic Energy Sciences).