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Robotics & Remote Systems
The Mission of the Robotics and Remote Systems Division is to promote the development and application of immersive simulation, robotics, and remote systems for hazardous environments for the purpose of reducing hazardous exposure to individuals, reducing environmental hazards and reducing the cost of performing work.
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Utility Working Conference and Vendor Technology Expo (UWC 2024)
August 4–7, 2024
Marco Island, FL|JW Marriott Marco Island
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The Standards Committee is responsible for the development and maintenance of voluntary consensus standards that address the design, analysis, and operation of components, systems, and facilities related to the application of nuclear science and technology. Find out What’s New, check out the Standards Store, or Get Involved today!
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NRC engineers share their expertise at the University of Puerto Rico
Robert Roche-Rivera and Marcos Rolón-Acevedo are licensed professional engineers who work at the U.S. Nuclear Regulatory Commission. They are also alumni of the University of Puerto Rico–Mayagüez (UPRM) and have been sharing their knowledge and experience with students at their alma mater since last year, serving as adjunct professors in the university’s Department of Mechanical Engineering. During the 2023–2024 school year, they each taught two courses: Fundamentals of Nuclear Science and Engineering, and Nuclear Power Plant Engineering.
Vedant K. Mehta, Michael W. D. Cooper, Robert B. Wilkerson, Dan Kotlyar, Dasari V. Rao, Sven C. Vogel
Nuclear Science and Engineering | Volume 195 | Number 6 | June 2021 | Pages 563-577
Technical Paper | doi.org/10.1080/00295639.2020.1851632
Articles are hosted by Taylor and Francis Online.
Yttrium hydride is being considered as a moderator material for microreactor concepts because of its excellent hydrogen retainment capacity at high temperatures. These types of reactors, operating at thermal to epithermal neutron energies, require accurate thermal scattering laws (TSLs) for yttrium hydride to predict and optimize moderator performance. Currently, TSL evaluations exist only for stoichiometric YH2. To perform high-certainty neutronics calculations and to improve the criticality safety of yttrium hydride–moderated reactors, evaluations of substoichiometric yttrium dihydride TSLs are necessary. Ab initio density functional theory (DFT) was used to generate the phonon density of states for yttrium and hydrogen under harmonic approximation in yttrium hydride (). To obtain substoichiometric yttrium dihydride, vacancies in the YH2 crystal were created using special quasi-random structures (SQS). Using NJOY2016, the TSLs for yttrium hydride were constructed from the DFT results as a function of stoichiometry and temperature. Our TSLs for the stoichiometric composition YH2 were in excellent agreement with the ENDF/B-VIII.0 evaluations. As such, this study extends the yttrium hydride TSLs for compositions between YH1.31 to YH1.91 with the interval of H/Y ≈ 0.1 for use in the MCNP code. The substoichiometric yttrium hydride scattering cross sections deviated by as much as 30% (elastic) and 60% (inelastic) when compared to the YH2 TSLs, underlining the necessity to have the TSLs presented here available, e.g., for safety-related reactor calculations. For the validation of the underlying DFT results of our model, quasi-harmonic approximation was used to compute the thermal lattice strain and constant pressure heat capacity for YH2. Neutron diffraction experiments were also carried out to characterize thermophysical properties that were adopted for stoichiometric and substoichiometric model validation. Additional properties such as heat capacity cv, and thermal displacement parameters were also computed for yttrium hydride () and compared to experimental results. Neutron diffraction validation of the YH2-x material properties and ENDF/B-VIII.0 verification of YH2 TSLs provide a very strong basis on the accuracy of the extended yttrium hydride TSL evaluations at thermal energies.