Abstract
Boise State University (BSU), in collaboration with the Nuclear Science User Facilities (NSUF), has two Thermo Scientific P385 neutron generators with deuterium-deuterium (D-D) and deuterium-tritium (D-T) accelerator heads ready for deployment at BSU. However, in order to operate the generators at BSU, the Nuclear Regulatory Commission (NRC) required that a neutron laboratory provide sufficient shielding to limit personnel dose [1, 2].
Through an iterative design process, MCNP [3] was used to model a neutron science laboratory with sufficient shielding to stay within the NRC’s annual dose limits for both operators [4] and the general public in adjacent labs and hallways [5]. The goal was to design a shielding plan that allowed for 100 hours of annual neutron generator operation at highest energy (14 MeV at 3x10^8 n/s for the D-T accelerator head).
The laboratory space was modeled using the MCNP plotter with architectural features such as walls, windows, and concrete support pillars constraining the shielding design. An accurate MCNP model of the neutron generator with the D-T accelerator head was obtained from Thermo Scientific and used as the source terms for the models. Tally cells of human muscle tissue were placed at strategic locations within the neutron science laboratory and in adjacent laboratories and hallways to predict the total dose received by a person at those locations. Cell tallies included both neutron and gamma ray contributions. Optimization of the shielding design placed smaller volumes of highly-effective, more expensive materials closest to the neutron generator, while using less effective, lower cost materials in larger quantities to provide adequate shielding.
For the final shielding design, neutron generators were contained within a cylinder of 5% borated high-density polyethylene with lead lining. Water bricks below the neutron generator provided necessary shielding for people in the laboratory directly below the neutron sciences laboratory. The experimental area was contained within a concrete masonry unit (CMU) labyrinth, and an additional CMU wall shielded members of the general public in the adjacent laboratory. In this finalized design, the dose to all human analogues fell within both the NRC’s dose limits and the building’s load limits.
Original language | American English |
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State | Published - 16 Jul 2021 |
Event | 1st Annual 2021 MCNP User Symposium - Virtual Duration: 16 Jul 2021 → … |
Conference
Conference | 1st Annual 2021 MCNP User Symposium |
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Period | 16/07/21 → … |
EGS Disciplines
- Materials Science and Engineering