Session MJ: Applications of Nuclear Physics I

FAIR data in nuclear physics data science

Data science has transformed the field of nuclear physics, resulting in novel approaches for interdisciplinary discovery. In this work, we discuss the need to FAIR (Findability, Accessibility, Interoperability, and Reuse) principles in nuclear physical data science in order to handle the increased complexity and volume of data in the 21st century. These principles enable sustainable data use and ethical scientific advances.   

Trace-Actinide Measurements in Natural Ore and Depleted Uranium Material using Accelerator Mass Spectrometry

Detection of trace levels of ²³⁶U provides a key identification signature of uranium ore material as well as clear indication of anthropogenic contamination from reprocessing activities or weapons fallout. Although commercial mass spectrometry methods can detect high levels of contamination, only Accelerator Mass Spectrometry is sensitive enough to measure natural concentrations of ²³⁶U/U, which span from 10^-14 to 10^-10. At the University of Notre Dame’s Nuclear Science Laboratory, we have improved our detection efficiency by a factor of five, primarily through the construction of a compact ionization chamber, and have successfully demonstrated capabilities down to the 10^-10 level, with projections of the current system limit as low as 6x10^-12. Additional isotopic signatures and their sensitivities for ²³³U (10^-11), which could provide indication of irradiation from fast neutrons, as well as ²³¹Pa (10^-10), and ²³⁰Th (10^-9), decay products of ²³⁵U and ²³⁴U respectively, have also been demonstrated. Details highlighting system requirements, measurement technique, improvements to the detection system, and measurement results will be presented.   

Structural investigation of UO2 films prepared by spraying-assisted combustion synthesis

With the climate change and the energy crisis that is currently upon us, nuclear energy is in the forefront once more. Most commercial nuclear power plants use uranium dioxide (UO₂) as  the primary nuclear fuel due to its high melting point (2865 °C), its compatibility with cladding materials, as well as its high chemical and radiation stability. During reactor operations, UO₂ fuel becomes more radioactive, evolves chemically due to the ²³⁵U fission and the neutron capture of ²³⁸U followed by β-decay, and undergoes considerable morphological changes. The exact mechanisms behind these structural changes are unknown due to difficulties in investigating highly radioactive spent fuel. Ion irradiation of thin films of UO₂ is a suitable alternative for exploring such structural evolutions. However, the lack of simple, safe and efficient film deposition methods impede the irradiation-induced structural investigation of UO₂ at the nanoscale level.

I will report on a new target production method that utilizes the use of electrospray techniques to deposit chemically reactive layers that can be converted to actinide oxides by simple heat treatments. This method allows the control of the layer thicknesses while it provides excellent uniformity. Furthermore, this method  uses the very minimum in starting materials. The targets produced were tested with a 1.7 MeV Ar²⁺ beam and measurements were made of the structural changes that took place and the overall stability of the targets.  These measurements allowed us to reveal links between synthesis conditions and irradiation-driven structural changes including the origin of reduced radiation tolerance of nanoscale UO₂.

    

Impacts of Updated Mo-106 and Tc-106 Beta Decay Data

Nuclear beta decay is an area of ongoing research. Many fission isotopes have data from the National Nuclear Data Center (NNDC) that is based on experiments from over 30 years ago. Advancements in total absorption spectroscopy (TAS) have allowed for more complete knowledge of the beta decay feeding patterns of isotopes. This research looks at analysis of two fission fragments, Mo-106 and Tc-106, with cumulative fission yields of 1.92% and 3.89% for Pu-239 nuclear fuel. Experimental data for these two isotopes was obtained at Argonne National Laboratory (ANL) at the Californium Rare Isotope Breeder Upgrade (CARIBU) facility. This presentation discusses the method of analyzing the experimental data, as well as presenting the updated beta feeding intensities. Multiple new levels were discovered, as well as many pseudolevels representing tightly spaced levels at high energy. This work was done as part of the MTAS collaboration.   

Studies of Nuclear Processes in Scintillator Materials Using Event-Based Cameras

Recently developed event-based camera systems offer a novel approach for scintillator characterization and scintillator-based applications such as radiographic imaging and spectroscopy. Event-based cameras can capture the spatial and temporal information of emission light from scintillators induced by particle interactions within the scintillator. Currently (without the event-based approach), radiographic and spectroscopic signals are integrated from a multitude of events that are triggered from incident x-rays and neutrons.  Simulations of these integrated signals are challenging because of the complex nature of the processes in the scintillator. X-rays and neutrons produce secondary particles, e.g., electrons and protons, through atomic and nuclear reactions.  The secondary particles interact with scintillator materials to produce emission light.  Simulation codes like Geant4 are designed to track particles and secondaries with detailed spatial and timing information.  However, the abundance of information from detailed simulation runs are mostly useless when comparing simulated data to measured data since the events are integrated.  With event-based camera systems, where it is possible to capture the spatial and temporal information (~1.6ns) of emission light, direct comparison between detailed simulation tracks and measured tracks can be made. Nuclear reaction data plays a critical role in the new approach to scintillator characterization and modelling. This is especially true for incident particles with unique spectral characteristics.  We will present results from comparisons of Geant4 simulation runs to measured data.  We will discuss some of the open questions and highlight the gaps in the data libraries. 

 

^*This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344   

Heavy Element Complex Formation Measured by FIONA

Chemistry performed with the heaviest elements is limited due to their relatively short half-lives and lack of material. It is difficult to characterize the reaction products, thus most chemistry that has been done is inferring and comparing to their lighter element homologs. Instead, FIONA (For the Identification Of Nuclide A), at the Lawrence Berkeley National Laboratory 88- Inch Cyclotron facility, can be used for mass identification of these elements. Studies of their chemical behavior can be made with a novel gas-phase chemistry technique. The heavy nuclide is produced through a fusion-evaporation reaction, and then separated by Berkeley Gas-filled Separator. It is then collected in the radiofrequency quadrupole trap, and held for a chosen trapping time. At this point, reactive gas is injected into the system and allowed time for the chemical reaction to take place. The reaction product is then passed to FIONA for identification via a mass measurement. This has been done with ²⁵⁴No produced through ²⁰⁸Pb(⁴⁸Ca, 2n)²⁵⁴No, and preliminary analysis and results will be presented.   

ROADSTR: a Mobile Antineutrino Detector Platform for enabling Multi-Reactor Spectrum, Oscillations and Application Measurements.

The aim of the Reactor Operations Antineutrino Detection Surface Testbed Rover (ROADSTR) project is to observe and monitor electron antineutrinos from nuclear reactors. ROADSTR has been designed as a readily mobile detector, allowing measurements at multiple sites using the same instrument. Besides the clear advantages towards nuclear safeguard and verification applications, an easily redeployable detector provides also a unique chance to contribute to flux and spectrum predictions for different nuclear fuels while minimizing the detector-related systematic uncertainties. Such measurements could prove crucial to understand the different anomalies spotted in the short baseline oscillation experiments, while providing benchmark measurements for different applications. The detection technology used for ROADSTR is 6Li doped plastics with Pulse Shape Discrimination capabilities. This type of technology has been primarily developed at the LLNL and the plastics are currently being produced in a larger scale by an external collaborator. This talk will focus on the testing framework designed to characterize the plastic elements and ensure its desired functionality and response.   

Precise measurements of gamma-ray intensities for long-lived fission products

We recently demonstrated a new experimental approach to precisely determine the gamma-ray intensities following the beta decay of long-lived fission products. For national-security applications, such as stockpile stewardship and nuclear forensics, one of the most straightforward and reliable ways to determine the number of fissions that occurred in a chain reaction is done through detection of the emitted gamma rays. The focus of this talk is on recent measurements to improve the nuclear-decay data for the fission products ⁹⁵Zr, ¹⁴⁴Ce, and ¹⁴⁷Nd. Our approach consists of implanting fission-product samples into a thin carbon foil using low-energy mass-separated ion beams from the CARIBU facility and then performing beta counting using a custom-made 4-pi gas proportional counter in coincidence with gamma-ray spectroscopy using the precisely-calibrated HPGe detector at Texas A&M University. Recent results for ⁹⁵Zr, ¹⁴⁴Ce, and ¹⁴⁷Nd will be presented and future plans will be discussed.