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A radionuclide intake happens when a radioactive material enters the body through inhalation or ingestion or through a wound. Because the radiation produced by some materials (such as plutonium, americium, uranium, and tritium) cannot leave the body, we look for the materials themselves in urine samples.
A series of outdoor shots were conducted at the HERMES III facility in November 2016. There were several goals associated with these experiments, one of which is an improved understanding of the courtyard radiation environment. Previous work had developed parametric fits to the spatial and temporal dose rate in the area of interest. This work explores the inter-shot variation of the dose in the courtyard, updated fit parameters, and an improved dose rate model which better captures high frequency content. The parametric fit for the spatial profile is found to be adequate in the far-field, however near-field radiation dose is still not well-understood.
This report presents the preliminary work for IER 484, the characterization of the leakage radia tion field from the TRIGA reactor at the Armed Forces Radiobiology Research Institute (AFRRI). The purpose of the dose characterization is to establish the reference dose needed to execute a NAD inter-comparison exercise. During the week of August 20th, a team from Lawrence Livermore National Laboratory (LLNL), Sandia National Laboratory (SNL), and Institut de Radioprotection et de Sûreté Nucléaire (IRSN) performed various measurements in AFRRI’s TRIGA ER1 (Exposure Room 1) with Passive Neutron Spectrometer (PNS) spheres and nuclear accident dosimeters (NADs) mounted on Bottle Manikin Absorption (BOMAB) phantoms (to simulate doses received by people) and additional NADs mounted on aluminum plates (to simulate doses in free air). Without Atomic Weapons Establishment (AWE), LLNL became responsible for measuring the neutron spectrum using PNS spheres. SNL is responsible for providing photon dose data. LLNL, SNL, and IRSN each deployed their own NADs, which will be compared to the reference dose measured. Final characterization of the dose field based on analyzed data will be presented in the CED4a report.
This report presents an analytical function as the reference neutron and photon dose (normalized to an ion chamber integral) for future nuclear accident dosimeter (NAD) exercise at the Armed Forces Radiobiology Research Institute (AFRRI). Various dosimeters and equipment were positioned within exposure room 1 (ER1) and irradiated using a 1.1 MW Training, Research, Isotope, General Atomics (TRIGA) Mark-F nuclear reactor. An ion chamber located in ER1 was used as a normalization factor in Equation 2. This allows for a quick calculation of neutron and photon dose based on the ion chamber data. Currently, AFRRI is in preparation to host a NAD exercise this summer.
Abstract not provided.
The IER-602 3b document (Angus, et al. 2024) reported the initial, 24-hour results of the international nuclear accident intercomparison, which took place at the Armed Forces Radiobiological Research Institute during June 24-28, 2024. This report provides updated results and further analysis of the intercomparison.
Abstract Context: Computational fluid dynamics (CFD) simulations of airflows coupled with physiologically based pharmacokinetic (PBPK) modeling of respiratory tissue doses of airborne materials have traditionally used either steady-state inhalation or a sinusoidal approximation of the breathing cycle for airflow simulations despite their differences from normal breathing patterns. Objective: Evaluate the impact of realistic breathing patterns, including sniffing, on predicted nasal tissue concentrations of a reactive vapor that targets the nose in rats as a case study. Materials and methods: Whole-body plethysmography measurements from a free-breathing rat were used to produce profiles of normal breathing, sniffing and combinations of both as flow inputs to CFD/PBPK simulations of acetaldehyde exposure. Results: For the normal measured ventilation profile, modest reductions in time- and tissue depth-dependent areas under the curve (AUC) acetaldehyde concentrations were predicted in the wet squamous, respiratory and transitional epithelium along the main airflow path, while corresponding increases were predicted in the olfactory epithelium, especially the most distal regions of the ethmoid turbinates, versus the idealized profile. The higher amplitude/frequency sniffing profile produced greater AUC increases over the idealized profile in the olfactory epithelium, especially in the posterior region. Conclusions: The differences in tissue AUCs at known lesion-forming regions for acetaldehyde between normal and idealized profiles were minimal, suggesting that sinusoidal profiles may be used for this chemical and exposure concentration. However, depending upon the chemical, exposure system and concentration and the time spent sniffing, the use of realistic breathing profiles, including sniffing, could become an important modulator for local tissue dose predictions.
The β + -emitting radionuclide 86 gY (t 1/2 = 14.7 h) forms a matched-pair with the β – -emitting therapeutic radionuclide 90Y (t 1/2 = 2.7 d) for theranostic application in medicine. This approach demands a precise knowledge of the positron emission probability of the PET nuclide which was until recently rather uncertain for 86 gY. In this work, an 86 gY source of high radionuclidic purity was prepared and a direct measurement of the positron emission intensity per 100 decay of the parent (hereafter “positron emission intensity”) was performed using high-resolution HPGe detector γ-ray spectroscopy. The electron capture intensity was also determined as an additional check by measuring the K α and K β X-rays of energies 14.1 and 15.8 keV, respectively, using a low energy HPGe detector. From those measurements, normalized values of 27.2 ± 2.0% for β + -emission and 72.8 ± 2.0% for EC were obtained. These results are in excellent agreement with values recently reported in the literature based on a detailed decay scheme study.
This paper reports results from the first measurements made on the exterior of a LEO spacecraft of mean dose equivalent rate and average quality factor as functions of shielding depth for shielding less than 1 g/cm2 Al equivalent. Two sets of measurements were made on the outside of the Mir Orbital Station; one near solar maximum in June 1991 and one near solar minimum in 1997. Absorbed dose was measured using stacks of TLDs. LET spectrum from charged particles of LET infinity H2O > o r= 5keV/micrometers was measured using stacks of CR-39 PNTDs. Results from the TLD and PNTD measurements at a given shielding depth were combined to yield mean total dose rate, mean dose equivalent rate, and average quality factor. Measurements made near solar maximum tend to be greater than those made during solar minimum. Both mean dose rate and mean dose equivalent rate decrease by nearly four orders of magnitude within the first g/cm2 shielding illustrating the attenuation of both trapped electrons and low-energy trapped protons. In order to overcome problems with detector saturation after standard chemical processing, measurement of LET spectrum in the least shielded CR-39 PNTD layer (0.005 g/cm2 Al) was carried out using an atomic force microscope. c2002 Elsevier Science Ltd. All rights reserved.
Passive radiation dosimeters were exposed aboard the Mir Orbital Station over a substantial portion of the solar cycle in order to measure the change in dose and dose equivalent rates as a function of time. During solar minimum, simultaneous measurements of the radiation environment throughout the habitable volume of the Mir were made using passive dosimeters in order to investigate the effect of localized shielding on dose and dose equivalent. The passive dosimeters consisted of a combination of thermoluminescent detectors to measure absorbed dose and CR-39 PNTDs to measure the linear energy transfer (LET) spectrum from charged particles of LET infinity H2O > or = 5 keV/micrometers. Results from the two detector types were then combined to yield mean total dose rate, mean dose equivalent rate, and average quality factor. Contrary to expectations, both dose and dose equivalent rates measured during May-October 1991 near solar maximum were higher than similar measurements carried out in 1996-1997 during solar minimum. The elevated dose and dose equivalent rates measured in 1991 were probably due to a combination of intense solar activity, including a large solar particle event on 9 June 1991, and the temporary trapped radiation belt created in the slot region by the solar particle event and ensuing magnetic storm of 24 March 1991. During solar minimum, mean dose and dose equivalent rates were found to vary by factors of 1.55 and 1.37, respectively, between different locations through the interior of Mir. More heavily shielded locations tended to yield lower total dose and dose equivalent rates, but higher average quality factor than did more lightly shielding locations. However, other factors such as changes in the immediate shielding environment surrounding a given detector location, changes in the orientation of the Mir relative to its velocity vector, and changes in the altitude of the station also contributed to the variation. Proton and neutron-induced target fragment secondaries, not primary galactic cosmic rays, were found to dominate the LET spectrum above 100 keV/micrometers. This indicates that in low earth orbit, trapped protons in the South Atlantic Anomaly are responsible for the major fraction of the total dose equivalent. c2002 Elsevier Science Ltd. All rights reserved.
A new type of real-time radiation monitoring device, RRMD-III, consisting of three double-sided silicon strip detectors (DSSDs), has been developed and tested on-board the Space Shuttle mission STS-84. The test succeeded in measuring the linear energy transfer (LET) distribution over the range of 0.2 keV/micrometer to 600 keV/micrometer for 178 h. The Shuttle cruised at an altitude of 300 to 400 km and an inclination angle of 51.6 degrees for 221.3 h, which is equivalent to the International Space Station orbit. The LET distribution obtained for particles was investigated by separating it into galactic cosmic ray (GCR) particles and trapped particles in the South Atlantic Anomaly (SAA) region. The result shows that the contribution in dose-equivalent due to GCR particles is almost equal to that from trapped particles. The total absorbed dose rate during the mission was 0.611 mGy/day; the effective quality factor, 1.64; and the dose equivalent rate, 0.998 mSv/day. The average absorbed dose rates are 0.158 mGy/min for GCR particles and 3.67 mGy/min for trapped particles. The effective quality factors are 2.48 for GCR particles and 1.19 for trapped particles. The absorbed doses obtained by the RRMD-III and a conventional method using TLD (Mg(2)SiO(4)), which was placed around the RRMD-III were compared. It was found that the TLDs showed a lower efficiency, just 58% of absorbed dose registered by the RRMD-III.
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Abstract Not Provided
Here we want to give our student readers a good picture of what it is like to work in various types of organizations and possibly aid them in choosing a career that’s a good fit for them, we have introduced a new series in this section of the newsletter. We will be chatting with young professionals working in different settings— national laboratories, academia, hospitals, and industries—about their back - ground, their responsibilities, what they like about working for their employer, and what suggestions they have for students aspiring to a similar career. In the first installment of the series, I talked to John Klumpp of Radiation Protection Services Group at Los Alamos National Laboratory about his experiences.
Presentation describes advanced dosimetric grading scheme to include radiographic chain elements.
With the many advances in semiconductor manufacturing, the pool of available materials for use in their production also continues to broaden. One such example is aluminum antimonide (AlSb). Its promising properties for radiation detection have attracted multiple researchers, and allow for the possibility that it may be a high resolution, room temperature x-ray/gamma detector. Antimony has an atomic number of 51 (Z=51) and is responsible for the majority of photon interactions. Furthermore, the mass attenuation coefficient is comparable with other well-known solid state gamma detectors such as CZT. With a band gap of 1.6 eV (CZT=1.5 eV), low leakage current at room temperature is expected, and high charge carrier statistics from radiation interactions can be expected. Charge carrier statistics are driven by high charge mobility (μ) and lifetime (τ). μτ for CZT is on the order of 5x10{sup -3} cm{sup 2}/V for electrons, but two orders of magnitude smaller for holes. This results in large variations in detector pulse height depending on the location of interaction (close to the anode vs. close to the cathode). Theoretically, AlSb should exhibit much more symmetric electron and hole properties near 5x10{sup -3} cm{sup 2}/V. According to the Hecht relation, this should produce a more uniform detector response and increase the number of generated charge carriers, improving resolution. An added benefit is that AlSb can be grown directly onto Si substrates, enabling fully integrated circuit board-level sensors. However, several characteristic properties remain unknown and inconsistent published results due to difficulties in producing the material. Difficulties in bulk growth methods (material interactions with growth hardware such as crystals and air) resulted in high levels of defects. The use of AlSb in optoelectronics from thin film growth methods has been documented, including growth directly onto Si, and provides the potential for much more controlled material. In our work we use thin film growth of AlSb geared towards high quality material for understanding the properties for radiation detection. (authors)
The University of Washington (UW) Clinical Neutron Therapy System (CNTS) generates a fast neutron beam using 50.5 MeV protons incident on a beryllium target. The CNTS is mainly used for fast neutron therapy in the treatment of cancer but is also used for radiation effects testing and the production of rare isotopes, or isotopes with a short half-life, for medical imaging and therapy. The accelerator and treatment head is modeled using the MCNP6 Monte Carlo code to enable beam characterization (neutron and photon fluence, linear energy transfer, secondary particle production), study the behavior of neutron dosimeters and ionization chamber (IC) responses, and to conduct first principle studies of the relative biological effectiveness (RBE) of fast neutrons compared to {sup 60}Co γ-rays. Measurements of neutron dose in selected CNTS fields were made using a model-17 ion chamber (IC-17) flowing methane-based, tissue-equivalent (TE) gas. As a first approximation, we compared IC-17 measurements to the MCNP calculated dose in a thin layer of water at selected locations along the central axis of the beam. To examine the impact of the composition of the chamber fill-gas and the chamber design characteristics, we also developed a high-resolution (∼ 50 μm) MCNP model of the IC-17 from a computerized tomography (CT) scan. Initial results indicate that the dose response of the IC-17 ion chamber is up to 30% larger (smaller?) compared to the dose to water for neutrons with energies >20 MeV. Differences in chamber and water response as large as 800% occur for neutrons with kinetic energies below 1 keV. The simulations of IC-17 response (and dose to water) for CNTS fast neutron spectra match measured doses within 4.6% for all field sizes and irradiation geometries considered. This reported studies provide additional evidence establishing use of the IC-17 ion chamber model or a thin layer of water as a reasonable surrogate for CNTS fast neutron dose calculations.