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Annual Report

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To optimize the performance of accelerator-driven transmutation subcritical systems (ADS), engineers will need to design the system to operate with a neutron multiplication factor just below that of a critical, or self-sustaining, system. This design criterion requires particle transport codes that instill the highest level of confidence with minimal uncertainty, because larger uncertainties in the codes require larger safety margins in the design and result in a lower efficiency of the ADS transmuter. For current design efforts in the U.S., a Monte Carlo particle transport code MCNPX is used to model neutron production and transport for spallation neutron systems.

While providing a very useful research and modeling tool, uncertainties in MCNPX and associated data libraries, particularly at higher energies, require engineers to increase the safety margin in the designs of the ADS transmuter. Much of the uncertainty associated with MCNPX is thought to be due to the escape of multiple high-energy particles from the target (multiple scattering), along with uncertainties in the predictions of source term volume measurements. Determining a reliable method that measures, validates, and benchmarks the calculations of such a volumetric source term is necessary.

The primary goal of this research is to develop a detector system for the measurement of neutron production in spallation targets, to test the system in a variety of calibrated beam lines, and to produce precise, position-sensitive measurements of the volumetric neutron source term to provide data for validation of ADS design codes.


Accelerator-driven systems – Design and construction; Radioactive wastes — Transmutation; Spallation (Nuclear physics);


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