James S. Bogard

Application of life cycle analysis: the case of green bullets

Life‐cycle analysis (LCA) provides a general framework for assessing and summarizing all of the information important to a decision. LCA has been used to analyze the desirability of replacing lead (Pb) with a composite of tungsten (W) and tin (Sn) in projectile slugs used in small arms ammunition at US Department of Energy (DOE) training facilities for security personnel. The analysis includes consideration of costs, performance, environmental and human health impacts, availability of raw materials, and stakeholder acceptance. Projectiles developed by researchers at Oak Ridge National Laboratory (ORNL) using a composite of tungsten and tin are shown to perform as well as, or better than, those fabricated using lead. A cost analysis shows that tungsten‐tin is less costly to use than lead, since, for the current number of rounds used annually, the higher tungsten‐tin purchase price is small compared with higher maintenance costs associated with lead. The tungsten‐tin composite presents a much smaller potential for adverse human health and environmental impacts than lead. Only a small fraction of the world’s tungsten production occurs in the USA, however, and market‐economy countries account for only around 15 per cent of world tungsten production. Concludes that stakeholders would prefer tungsten‐tin on the basis of total cost, performance, reduced environmental impact and lower human toxicity. However, lead is preferable on the basis of material availability. Life cycle analysis clearly shows that advantages outweigh disadvantages in replacing lead with tungsten‐tin in small‐caliber projectiles at DOE training facilities. Concerns about the availability of raw tungsten are mitigated by the ease of converting back to lead (if necessary) and the recyclability of tungsten‐tin rounds.

Effects of thermal annealing on the radiation produced electron paramagnetic resonance spectra of bovine and equine tooth enamel: Fossil and modern

The concentration of stable radiation-induced paramagnetic states in fossil teeth can be used as a measure of sample age. Temperature excursions >100 °C, however, can cause the paramagnetic state clock to differ from the actual postmortem time. We have heated irradiated enamel from both fossilized bovid and modern equine (MEQ) teeth for 30 min in 50 °C increments from 100 to 300 °C, measuring the electron paramagnetic resonance (EPR) spectrum after each anneal, to investigate such effects. Samples were irradiated again after the last anneal, with doses of 300–1200 Gy from 60Co photons, and measured. Two unirradiated MEQ samples were also annealed for 30 min at 300 °C, one in an evacuated EPR tube and the other in a tube open to the atmosphere, and subsequently irradiated. The data showed that hyperfine components attributed to the alanine radical were not detected in the irradiated MEQ sample until after the anneals. The spectrum of the MEQ sample heated in air and then irradiated was similar to that of the heat treated fossil sample. We conclude that the hyperfine components are due to sample heating to temperatures/times >100 °C/30 min and that similarities between fossil and MEQ spectra after the 300 °C/30 min MEQ anneal are also due to sample heating. We conclude that the presence of the hyperfine components in spectra of fossil tooth enamel indicate that such thermal events occurred either at the time of death, or during the postmortem history.The concentration of stable radiation-induced paramagnetic states in fossil teeth can be used as a measure of sample age. Temperature excursions >100 °C, however, can cause the paramagnetic state clock to differ from the actual postmortem time. We have heated irradiated enamel from both fossilized bovid and modern equine (MEQ) teeth for 30 min in 50 °C increments from 100 to 300 °C, measuring the electron paramagnetic resonance (EPR) spectrum after each anneal, to investigate such effects. Samples were irradiated again after the last anneal, with doses of 300–1200 Gy from 60Co photons, and measured. Two unirradiated MEQ samples were also annealed for 30 min at 300 °C, one in an evacuated EPR tube and the other in a tube open to the atmosphere, and subsequently irradiated. The data showed that hyperfine components attributed to the alanine radical were not detected in the irradiated MEQ sample until after the anneals. The spectrum of the MEQ sample heated in air and then irradiated was similar to that of t...

Crossed-beam two-photon readout system for three-dimensional radiation dosimeters

Three-dimensional optical random access memory (3D ORAM) materials with enormous capacity and fast access speed have shown a great potential in overcoming limitations of access and storage capacity in current memory devices. As another useful development of this 3D ORAM, we have shown the application of 3D ORAM materials as a practical dosimeter. The local heating of the polymer matrix by the deposited energy of ionizing radiation is thought to contribute to the conversion of the fluorescent photochromic dye to a nonfluorescent form. The two-photon readout system is very useful in tracking the interactions of energy of ionizing radiation deposited in a polymer matrix. However, the polymer fracturing that has occurred during two-photon readout has been an obstacle in utilization of 3D ORAM materials as a dosimeter. In this work, we further evaluated the readout system using a high-energy variable attenuator in order to prevent polymer fracturing due to the strong absorption of the 1064 nm beam by the polym...

ANISOTROPY FACTORS FOR A 252Cf SOURCE

Abstract A new 252Cf source has been procured for use at the Dosimetry Applications and Research facility at the Oak Ridge National Laboratory (ORNL). This source was encapsulated by the Californium Facility at ORNL; however, the encapsulation differs from previous designs designated as SR-Cf-100. The new encapsulation, designated SR-Cf-3000, has a similar cylindrical radius to the previous generation but is 1.6 cm longer. Since the encapsulation geometries differ, the amount of internal scattering of neutrons will also differ, leading to changes in anisotropy factors between the two designs. Additionally, the different encapsulations will affect the absorbed dose and dose equivalent delivered per neutron emitted by the source since both the quantity and energy distribution of the emitted neutrons will vary with irradiation angle. This work presents the fluence anisotropy factors for the SR-Cf-3000 series encapsulation as well as absorbed dose and dose equivalent values calculated for various angles of irradiation. The fluence anisotropy factors were found to range from a maximum of 1.037 to a minimum of 0.641 for irradiation angles perpendicular and parallel to the source axis, respectively. Anisotropy in absorbed dose varied from a maximum of 1.033 to a minimum of 0.676 while anisotropy of dose equivalent varied from 1.035 to 0.657. Anisotropy in the region most commonly used was found to be +3.2% for absorbed dose and +3.3% for dose equivalent, and these effects should be included when performing dosimeter irradiations.

Measurements of continuous-in-energy neutron sources using the BC-523A capture-gated liquid scintillator

Capture-gated detectors are suitable for neutron spectroscopy in mixed neutron and gamma-ray fields. They are less prone to neutron misclassification than standard organic scintillation detectors due to additional measured information available. This information is an additional capture pulse that typically follows the initial neutron scattering pulse. One of commercially available capture-gated detectors is a BC-523A detector. This detector was tested with several continuous-in-energy neutron sources to obtain the detector response and the results are presented in this paper.

Use of Portable Gamma Spectrometers for Identifying Persons Exposed in a Nuclear Criticality Event

Abstract At the Y-12 National Security Complex, triage-style assessments are used to identify persons potentially exposed to high doses from criticality accident radiations using portable instruments by assessing the presence of activated sodium atoms in a person’s blood. Historically, simple handheld Geiger-Mueller (G-M) probes were used for these purposes although it was recognized that since these instruments contain no information on incident photon energy, it was impossible to differentiate between photons emitted by contamination on the potentially exposed worker from activation of sodium in the person’s blood. This work examines the use of a portable gamma spectrometer for assessing blood sodium activation. Irradiations of a representative phantom were performed using two neutron source configurations (unmoderated and polyethylene-moderated 252Cf), and measurements were made using the spectrometer and a G-M detector following irradiation. Detection limits in terms of personnel neutron dose are given for two neutron fields representing metal and solution criticality spectra. Both G-M and spectrometer results indicate a low minimum detectable neutron dose indicating that both instruments are useful as an emergency response instrument. The spectrometer has the added benefit of discriminating between surface contamination and blood sodium activation.

Detection of neutrons using a novel three-dimensional optical random access memory technology (3D-ORAM)

12 We report for the first time, the development of a 3D optical random access memory material for neutron dosimetry. Detection of energetic neutrons is important in many applications, spanning from radioactive waste monitoring to space exploration. These anthracene-based photochromic dosimeters show a decrease in fluorescence intensity following exposure to energetic neutrons. Unlike current neutron dosimeters, where foreknowledge of the neutron energy is necessary to determine an exposure dose, these materials can be used in unknown environments (e.g. space exploration). A readout system has also been developed to determine the radiation characteristics (e.g. neutron energy) necessary for estimating dose. The results presented in this work, demonstrate the potential of these novel materials for space exploration and other applications where foreknowledge of neutron energy is unknown and current dosimeters are incapable of providing accurate dose information.