Radiation Dose Modeling for Niowave’s Accelerator Driven Uranium Target Assembly 3

Technical Report · Wed Dec 04 04:00:00 EST 2024

DOI:https://doi.org/10.2172/2573497· OSTI ID:2573497

Wilkerson, Blake ^[1]; Denbrock, Chad ^[2]; Grimm, Terry ^[2]; Nash, Jim ^[3]; Navarro, Jorge ^[3]; Wahlen, Robert ^[2]

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1. ORNLOak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
2. Niowave Inc., Lansing, MI (United States)
3. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Molybdenum-99 is a high-value radionuclide commonly used for medical purposes within the United States. The National Nuclear Security Administration (NNSA) seeks to reliably produce the radioisotope ⁹⁹Mo without the use of highly enriched uranium. NNSA’s Office of Material Management and Minimization (M3) provides funding and government laboratory expertise to private companies to expedite the production process domestically and currently funds designs that use low-enriched uranium or other ⁹⁹Mo production pathways. Several production designs are being explored across the industry, including uranium fission and photonuclear conversion of ¹⁰⁰Mo targets. Niowave Inc. seeks to produce ⁹⁹Mo via a high-energy electron accelerator that strikes a lead-bismuth eutectic target that ultimately produces a consistent neutron flux. The neutron flux then interacts in a subcritical reactor core configuration to produce fission in low-enriched or natural uranium targets. These fissionable targets are then processed to extract ⁹⁹Mo. The purpose of this work is to estimate the neutron and photon dose response across Niowave’s proposed facility for worker safety during operation. Owing to the size of the proposed Niowave facility and necessary shielding, unbiased Monte Carlo radiation transport is impractical, and variance reduction methods are required. This work focuses on the weight window variance reduction method to produce high confidence dose response results within a Monte Carlo radiation transport code. Specifically, an adjoint-informed weight window methodology was created to improve the dose response estimates for accelerator-driven subcritical reactor designs. This adjoint-informed methodology was implemented for Niowave’s proposed design and improved dose results at far-field locations across the facility. Acceptable dose rate contours for the proposed facility were generated across the facility and are presented in this work.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA), Office of Defense Nuclear Nonproliferation
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 2573497
• Report Number(s): ORNL/TM--2024/3646
• Country of Publication: United States
• Language: English

Related Subjects

07 ISOTOPE AND RADIATION SOURCES
73 NUCLEAR PHYSICS AND RADIATION PHYSICS