Post, August 10, 2021 • We use nuclear data, e.g., dosimetry cross sections, to support the characterization of the neutron environment in our radiation test facilities. We also use neutron benchmark fields to validate the dosimetry cross sections. We have provided detailed characterization data for the neutron environments in various fields produced, using spectrum-modifying “buckets”,...
Activities
Characterization of Neutron Response of Reactor Ionizing Dose Dosimeters
Post, August 10, 2021 • CaF2:Mn TLD thermoluminescence response, alanine EPR signal, and radiochromic film response are all used to characterize the ionizing dose in radiation environments. When these dosimeters are used in mixed neutron/photon environments, it can be hard to capture the difference in response due to the neutrons and photon energy deposition. The...
Combined Environment Radiation Effects (Ionizing Dose and Displacement Damage)
Post, August 10, 2021 • Our previous research has look at radiation damage to semiconductors caused by both ionization and by displacement. Since some devices can be sensitive to both damage processes, we are actively looking at combined radiation effects and establishing models to quantify any synergistic effects. We have developed a set of definitions...
Defect Evolution and Neutron Fluence Rate Effects from Neutron Exposure
Post, August 10, 2021 • Our interest in nuclear data extends from the nuclear interaction itself into the results from the subsequent electronic interactions of the recoil products. Thus, we have research efforts that investigate the evolution of more complex defects from the initial recoil atoms using molecular dynamics (MD) and density functional theory (DFT)....
Development of Low Neutron Response Dosimeters for Use in Research Reactors, e.g., EPR-based Teflon and Polyethylene Dosimeters
Post, August 10, 2021 • As we investigate the neutron response of the dosimeters we use in the mixed neutron/photon reactor environments that support our radiation testing, we are active in developing new dosimeters that minimize their neutron response. Rather than trying to compensate for the neutron contribution, we have looked at developing a dosimeter...
Dose Enhancement in Radiation Testing
Post, August 10, 2021 • Dose enhancement effects from material interfaces with different atomic number elements can affect ionization and the resulting material response. Scattered photon contributions with the higher photoelectric cross section from low energy photons can significantly affect the dose at a point near an interface. This can be an important effect in...
Effect of Nuclear Data Uncertainty on Radiation Damage Metrics
Post, August 10, 2021 • Effect of Nuclear Data Uncertainty on Radiation Damage Metrics It is critical that we understand the uncertainty in our nuclear data and how this uncertainty influences our applications. Sandia has done extensive work to understand the uncertainty contributors. Recent work has focused on the uncertainty in the silicon damage metrics...
Improved/Expanded Nuclear Data Processing with NJOY-2016
Post, August 10, 2021 • Improved/Expanded Nuclear Data Processing with NJOY-2016 In support of our application of nuclear data to mission areas, we use and build upon nuclear data processing codes such as NJOY-2016, FRENDY, and LISTEF. As one example of this, Sandia has tailored a version of the LANL-developed NJOY-2016 code to: a) permit...
Interface of Fission Product Delayed n/γ Environments with Nuclear Effects Codes
Post, August 10, 2021 • Since a research reactor radiation environment has both prompt and delayed fission components for the neutron and photon fields and we are often investigating a transient response of a material in a radiation environment, we are faced with having to use diagnostic measurements to deconvolute the radiation environment based on...
Neutron Dosimetry Cross Sections
Post, August 10, 2021 • We have engaged with the international community through a series of IAEA-sponsored Coordinated Research Projects (CRP) and Data Development Projects (DDP) that focus on nuclear data. Primary thrusts have been to refine the cross sections of reactions used to support dosimetry applications, quantify the energy-dependent uncertainty in the cross sections...
Radiation Damage to Materials
Post, August 10, 2021 • All aspects of radiation damage to materials are of interest in our research. While there is an interest in designing radiation hard materials, such as materials that are resistant to embrittlement for use in reactor pressure vessels, there is also an interest in designing radiation soft materials for use as...
Research Reactor Radiation Diagnostic Development
Post, August 10, 2021 • We have developed advanced diagnostics that can be used in our radiation facilities to support applications and to validate nuclear data. One example is the development of diamond and GaAs-based photoconducting detectors (PCD) used to capture the transient radiation in pulses generated in reactor and accelerator radiation environments. These diagnostics...
Validation of Thermal Neutron Silicon Displacement Damage Metrics
Post, August 10, 2021 • We try to validate our modeling using experiments under a wide range of neutron/photon radiation conditions. One aspect of particular interest is material damage from thermal neutrons. There have been several reports of silicon displacement damage from thermal neutrons not following the normal damage metrics, i.e., large capture kerma values...