NSUF 23-4750: Time-Resolved Neutron Damage Characterization using In Situ Positron Annihilation Spectroscopy
The main objective of this experiment is to develop a novel positron annihilation spectroscopy based technique to measure in situ and ex situ, via a reactor spectrum of neutrons, the presence of vacancy defects in bulk reactor structural materials using Coincidence Doppler Broadening Positron Annihilation Spectroscopy (CDB-PAS). Such measurements have never been performed before. We will measure the shape of the 511 keV peak from the annihilation of positrons in samples of ½”-diameter 316L stainless steel rods. Using the Ohio State University Fast Beam Facility (OSURR FBF), we will establish neutron-driven CDB-PAS as a technique for measuring ex situ bulk defect chemistry in pre-irradiated samples, and we will test the use of a neutron beam to perform CDB-PAS in situ as the neutron beam produces defects. The measurements will provide for an understanding of the defect chemistry that develops in situ within reactor structural materials in a reactor environment.
In PAS, positrons thermalize within a sample material and annihilate with bound electrons. The resulting two annihilation photons share the total 1.022 MeV of energy of the electron/positron pair, though the detected energy of each individual photon depends upon the component of the crystal momentum of the annihilating electron in the direction towards the detectors. The exact spectral shape of the measured annihilation peak is sensitive to the average defect chemistry in the sample. The detection limits of PAS can be down to concentrations of 10-7 and sizes of angstroms, making it ideal for characterizing atomic level defects during the early stages of irradiation damage. Ex situ PAS studies include additively manufactured (AM) alloy components, low dose irradiated graphite, 3D printed UO2 annular slugs, irradiated silicon carbide (SiC) samples’ thermal properties, quality control of experiments before inserting into the Advanced Test Reactor (ATR) core for early damage detection, operational life prediction of low dose neutron irradiation for pressure vessels, gas bubbles in neutron irradiated metals, neutron irradiated 3C-SiC, and neutron irradiated tungsten.
This experiment will require 2 weeks of beam time at the OSURR FBF. Two days of beam time will be dedicated to measuring the CDB-PAS spectrum from non-irradiated and pre-irradiated samples, and 8 days of beam time will be dedicated to measuring the evolution of the shape of the 511 keV peak in situ during irradiation. We have already simulated this experiment on the beamline, and we anticipate the rate of detected 511 keV coincidence photons will be sufficient to bin this data hourly. We expect negligible detector damage from fast neutrons, and the overall gamma rate on the detectors will be well-within typical operational parameters.
Additional Info
| Field | Value |
|---|---|
| Abstract | The main objective of this experiment is to develop a novel positron annihilation spectroscopy based technique to measure in situ and ex situ, via a reactor spectrum of neutrons, the presence of vacancy defects in bulk reactor structural materials using Coincidence Doppler Broadening Positron Annihilation Spectroscopy (CDB-PAS). Such measurements have never been performed before. We will measure the shape of the 511 keV peak from the annihilation of positrons in samples of ½”-diameter 316L stainless steel rods. Using the Ohio State University Fast Beam Facility (OSURR FBF), we will establish neutron-driven CDB-PAS as a technique for measuring ex situ bulk defect chemistry in pre-irradiated samples, and we will test the use of a neutron beam to perform CDB-PAS in situ as the neutron beam produces defects. The measurements will provide for an understanding of the defect chemistry that develops in situ within reactor structural materials in a reactor environment. In PAS, positrons thermalize within a sample material and annihilate with bound electrons. The resulting two annihilation photons share the total 1.022 MeV of energy of the electron/positron pair, though the detected energy of each individual photon depends upon the component of the crystal momentum of the annihilating electron in the direction towards the detectors. The exact spectral shape of the measured annihilation peak is sensitive to the average defect chemistry in the sample. The detection limits of PAS can be down to concentrations of 10-7 and sizes of angstroms, making it ideal for characterizing atomic level defects during the early stages of irradiation damage. Ex situ PAS studies include additively manufactured (AM) alloy components, low dose irradiated graphite, 3D printed UO2 annular slugs, irradiated silicon carbide (SiC) samples’ thermal properties, quality control of experiments before inserting into the Advanced Test Reactor (ATR) core for early damage detection, operational life prediction of low dose neutron irradiation for pressure vessels, gas bubbles in neutron irradiated metals, neutron irradiated 3C-SiC, and neutron irradiated tungsten. This experiment will require 2 weeks of beam time at the OSURR FBF. Two days of beam time will be dedicated to measuring the CDB-PAS spectrum from non-irradiated and pre-irradiated samples, and 8 days of beam time will be dedicated to measuring the evolution of the shape of the 511 keV peak in situ during irradiation. We have already simulated this experiment on the beamline, and we anticipate the rate of detected 511 keV coincidence photons will be sufficient to bin this data hourly. We expect negligible detector damage from fast neutrons, and the overall gamma rate on the detectors will be well-within typical operational parameters. |
| Award Announced Date | 2023-09-14T13:40:17.193 |
| Awarded Institution | None |
| Facility | None |
| Facility Tech Lead | Raymond Cao |
| Irradiation Facility | Ohio State University Research Reactor |
| PI | Connor Harper |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | None |