Search NASA⌕ Search

SEARCH · Search NASA

Results for “Dose Characterization”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

Detailed characterization of the 1087 MeV/nucleon iron-56 beam used for radiobiology at the alternating gradient synchrotron

We report beam characterization and dosimetric measurements made using a 56Fe beam extracted from the Brookhaven National Laboratory Alternating Gradient Synchrotron (AGS) with a kinetic energy of 1087 MeV/nucleon. The measurements reveal that the depth-dose distribution of this beam differs significantly from that obtained with a 600 MeV/nucleon iron beam used in several earlier radiobiology experiments at the Lawrence Berkeley National Laboratory's BEVALAC. We present detailed measurements of beam parameters relevant for radiobiology, including track- and dose-averaged linear energy transfer (LET), fragment composition and LET spectra measured behind sample holders used in irradiations of biological samples. We also report measurements of fluence behind three depths (1.94, 4.68 and 9.35 g cm(-2)) of polyethylene targets with the 1087 MeV/nucleon beam, and behind 1.94 g cm(-2) of polyethylene with a 610 MeV/nucleon beam delivered by the AGS. These results are compared to earlier measurements with the 600 MeV/nucleon beam at the BEVALAC.

NASA Discipline Radiation Health↗
NASA NTRS2013

Monte-Carlo Simulations of Heavy Ions Track Structures and Applications

In space, astronauts are exposed to protons, high ]energy heavy (HZE) ions that have a high charge (Z) and energy (E), and secondary radiation, including neutrons and recoil nuclei produced by nuclear reactions in spacecraft walls or in tissue. The astronauts can only be partly shielded from these particles. Therefore, on travelling to Mars, it is estimated that every cell nucleus in an astronaut fs body would be hit by a proton or secondary electron (e.g., electrons of the target atoms ionized by the HZE ion) every few days and by an HZE ion about once a month. The risks related to these heavy ions are not well known and of concern for long duration space exploration missions. Medical ion therapy is another situation where human beings can be irradiated by heavy ions, usually to treat cancer. Heavy ions have a peculiar track structure characterized by high levels of energy ]deposition clustering, especially in near the track ends in the so ]called eBragg peak f region. In radiotherapy, these features of heavy ions can provide an improved dose conformation with respect to photons, also considering that the relative biological effectiveness (RBE) of therapeutic ions in the plateau region before the peak is sufficiently low. Therefore, several proton and carbon ion therapy facilities are under construction at this moment

Plante, Ianik↗
NASA NTRSDate not supplied

Retrospectives: Intersection of Spaceflight Stressors and Microbial Risk to Crew and Craft

OVERVIEW The spaceflight environment has several unique stressors that affect the health of both the crew and the spacecraft. An area of continued, albeit incomplete, study is the interaction of these stressors on microbial populations inherent to both astronauts and spacecraft surfaces and systems. A primary concern is the potential for the spaceflight environment to perturb the phenotype of these populations towards negative outcomes for crew and craft. In order to effectively mitigate these potential risks, they must first be characterized. We performed a retrospective literature analysis to assess the current state of knowledge regarding the affects of ionizing radiation and elevated CO2 on relevant microbial populations. The results of these retrospectives will guide next steps in the decisions of what (if any) further studies should be pursued and to guide decisions of the need for countermeasures. STRESSORS Ionizing radiation. The health risk involved with increased exposure to cosmic radiation has been studied in crew for 35+ years, with human health and cancer risk being the main focus. However, space radiation could also affect both the resident microorganisms aboard the ISS and the normal, healthy astronaut microbiomes that are of direct concern for crew health. A retrospective review of over 250 publications was accomplished looking at the impact of cumulative ionizing radiation doses lower than 3 Gy (chronic or acute) on microbial populations. Elevated CO2. The health risk involved with elevated atmospheric CO2 in spacecraft, primarily focusing on human toxicological risks, is understudied. The current Spaceflight Maximum Allowance Concentration for 24-hour average CO2 is 0.4% (3 mm Hg), which is significantly higher than terrestrial levels (0.04%). Whether these elevated ambient CO2 levels aboard spacecraft influence the diversity and phenotypic responses of the resident microbial communities from both the spacecraft environment (air, surface, water) and crew members (gut, nasal,skin microbiomes) is not known. A retrospective review was accomplished looking at the impact of chronic CO2 exposure up to 0.7% (5 mm Hg) for up to 6 months and acute exposure up to 2.6% (20 mm Hg) for up to 24 hours. CONCLUSIONS: MICROBIOME OF THE BUILT ENVIRONMENT The microbiome of the built spacecraft environment has been sampled consistently over the course of human spaceflight and significant advancements have been made in identifying microbial populations on the ISS. The dominant source of microbes on spacecraft surfaces are human-derived. Once in the spacecraft built environment,the extreme environment selects for features that enhance survival. While efforts to understand potential antibiotic resistance and pathogenicity of ISS isolates is robust, there is little to no understanding of which spaceflight environmental stressors, to include ionizing radiation or elevated CO2, drive the evolutionary trajectory of spacecraft-associated microbial populations. CONCLUSIONS: MICROBE-HOST INTERACTIONS The host-microbiome field has emerged as an important factor in human health on Earth as well in spaceflight. The field is struggling with the complexity of the system under investigation as there is substantial taxonomic and functional heterogeneity in these communities, making it difficult to establish clear stimulus-response dynamics.Taxonomic characterization is the norm; however, the functional role of each community member is key to linking environmental perturbations to potential dysbiosis. For both ionizing radiation and elevated CO2, the likely target of the perturbation is the host tissue, not the microbes themselves.. Any resulting changes to the microbial community composition and/or function is likely a result of adapting to those changes in the host physiology. RECOMMENDATIONS Emphasize functional characterization as opposed to taxonomic characterization of microbial communities.Increase the number of investigations using chronic, spaceflight-relevant doses of ionizing radiation. MoBE studies should move away from observational studies towards predictive modeling of community dynamics. Continue to develop scale-down models, such as tissues-on-a-chip & defined microbial communities. Focus on the crew response to elevated CO2 over MoBE considerations. Assess how direct contact with the hypercapnic environment affects skin microbiome dynamics.

Countermeasures↗
NASA NTRS1999

Characterization of Treefoil Peptide Genes in Iron-Ion or X-Irradiated Human Cells

The gastrointestinal (GI) tract is especially sensitive to ionizing radiation, probably because of its high rate of cell turn over. Most of the data in the literature concerns the histological/anatomical description of damage rather than functional studies. In fact, previous reports in humans have shown that, at doses of 2 Gy or more, functional abnormalities appear indicating that in radiation sensitive tissues the effects of radiation are not limited to cell death. GI functions are controlled in particular by GI peptides. One hypothesis is that ionizing radiation may modulate the synthesis and release of these peptides and consequently may contribute largely to abnormalities in GI function. However, no previous studies have been concerned with GI-specific gene expression in irradiated GI tissues. The family of human trefoil peptides comprises three members thus far, all of which are expressed in specific regions of the GI tract. In addition, two trefoil peptides, pS2 (TFFI) and HITF (TFF2) are expressed in breast tissue. Their exact function in GI and breast tissues is unclear but mucosal integrity, repair, mucin secretion and responsiveness to hormones have been shown. We recently isolated and characterized pS2 as a novel p53- and estrogen receptor-independent gene whose MRNA expression in several cells lines was found to be delayed 4 to 7 days after irradiation with X-rays, fission neutrons or 1 GeV/n Fe-ions. The aim of the present study was to determine whether pS2 and HITF have a similar induction kinetics in irradiated gastric and breast cell lines, and whether they have the phorbol ester (TPA) responsive element (TRE).

Balcer-Kubiczek, E. K.↗
DOE OSTI2016

TH-CD-201-09: High Spatial Resolution Absorbed Dose to Water Measurements Using Optical Calorimetry in Megavoltage External Beam Therapy

Purpose: To develop and implement a high spatial resolution calorimeter methodology to measure absorbed dose to water (ADW) using phase shifts (PSs) of light passing through a water phantom and to compare measurements with theoretical calculations. Methods: Radiation-induced temperature changes were measured using the PSs of a He-Ne laser beam passing through a (10×10×10) cm{sup 3} water phantom. PSs were measured using a Michelson interferometer and recording the time-dependent fringe patterns on a CCD camera. The phantom was positioned at the center of the radiation field. A Varian 21EX was used to deliver 500 MU from a 9 MeV beam using a (6×6) cm{sup 2} cone. A 127cm SSD was used and the PSs were measured at depths ranging from of 1.90cm to 2.10cm in steps of 0.05cm by taking profiles at the corresponding rows across the image. PSs were computed by taking the difference between pre- and post-irradiation image frames and then measuring the amplitude of the resulting image profiles. An amplitude-to-PS calibration curve was generated using a piezoelectric transducer to mechanically induce PSs between 0.05 and 1.50 radians in steps of 0.05 radians. The temperature dependence of the refractive index of water at 632.8nm was used to convert PSs to ADW. Measured results were compared with ADW values calculated using the linac output calibration and commissioning data. Results: Milli-radian resolution in PS measurement was achieved using the described methodology. Measured radiation-induced PSs ranged from 0.10 ± 0.01 to 0.12 ± 0.01 radians at the investigated depths. After converting PSs to ADW, measured and calculated ADW values agreed within the measurement uncertainty. Conclusion: This work shows that interferometer-based calorimetry measurements are capable of achieving sub-millimeter resolution measuring 2D temperature/dose distributions, which are particularly useful for characterizing beams from modalities such as SRS, proton therapy, or microbeams.

60 APPLIED LIFE SCIENCES↗
NASA NTRS2016

Cosmic Radiation Dose Measurements from the RaD-X Flight Campaign

The NASA Radiation Dosimetry Experiment (RaD-X) stratospheric balloon flight mission obtained measurements for improving the understanding of cosmic radiation transport in the atmosphere and human exposure to this ionizing radiation field in the aircraft environment. The value of dosimetric measurements from the balloon platform is that they can be used to characterize cosmic ray primaries, the ultimate source of aviation radiation exposure. In addition, radiation detectors were flown to assess their potential application to long-term, continuous monitoring of the aircraft radiation environment. The RaD-X balloon was successfully launched from Fort Sumner, New Mexico (34.5 degrees North, 104.2 degrees West) on 25 September 2015. Over 18 hours of flight data were obtained from each of the four different science instruments at altitudes above 20 kilometers. The RaD-X balloon flight was supplemented by contemporaneous aircraft measurements. Flight-averaged dosimetric quantities are reported at seven altitudes to provide benchmark measurements for improving aviation radiation models. The altitude range of the flight data extends from commercial aircraft altitudes to above the Pfotzer maximum where the dosimetric quantities are influenced by cosmic ray primaries. The RaD-X balloon flight observed an absence of the Pfotzer maximum in the measurements of dose equivalent rate.

Mertens, Christopher J.↗
DOE OSTI2020

Development of a Conditioned System-Level Groundwater Model to Evaluate Long-Term Groundwater Impacts within a Performance Assessment - 20115

A preliminary performance assessment (PA) of single-shell tank Waste Management Area (WMA) A-AX located at the U.S. Department of Energy (DOE)'s Hanford Site in southeastern Washington is being conducted to satisfy the requirements of DOE Order 435.1 [1] as it relates to closure of the single-shell radioactive waste tanks in the WMA A-AX tank farms. A PA assesses the fate, transport, and impacts of radionuclides within a low-level radioactive waste disposal facility in its assumed closure configuration and the subsequent potential doses to humans over a 1,000-year compliance period and a 10,000-year performance evaluation period. The WMA A-AX preliminary PA evaluation is structured around the complementary use of process-level and system-level models to calculate the facility performance against established DOE Order 435.1 [1] performance objectives. Process-level models are those that represent a detailed phenomenological representation of processes of concern in the PA. Process models typically only represent one or a few of the components of the PA, such as groundwater flow and transport, and must be integrated with other modeling elements to perform PA calculations. System-level models are those that are abstracted from the process models, retaining the essential features of the process model, while allowing integration of all aspects of the PA in a single modeling framework. System-level models are often characterized by coarser numerical discretization, lower dimensionality, or other similar simplifications compared to the process-level model. Traditionally, a three-dimensional (3-D) process-level model is utilized primarily to evaluate the long-term impact on groundwater and the potential doses to individuals who consume contaminated groundwater. System-level models are also utilized to evaluate the groundwater pathway in PAs. These models typically have reduced dimensionality (1-D) and are conditioned utilizing flow fields (Darcy fluxes) and moisture content distributions that are abstracted from the process level models. The abstraction approach assures that the flow field in both models is consistent for a specific set of input parameters for flow, differing only in the discretization and dimensionality of the two models. The preliminary WMA A-AX PA incorporates a detailed representation of the geological system and hydraulic properties within the 3-D model STOMP{sup C} numerical code so that the effects of relevant features and processes on water flow and radionuclide transport in the subsurface can be evaluated. The complementary system-level model is developed utilizing the GoldSim{sup C} code to implement a simplified, 1-D equivalent model to represent the groundwater pathway. Contaminant transport through the vadose zone and unconfined aquifer for Tc-99 and I-129 were evaluated in each of the models. Adjustments to the saturated portion of the GoldSim{sup C} 1-D model were required to mimic the dispersion effect captured with the 3-D STOMP{sup C} model. Once this conditioning was conducted, highly similar results for the transport of Tc-99 and I-129 were achieved at the point of calculation, located 100 m downgradient from the WMA A-AX fenceline. These radionuclides represent elements that are regarded as primary dose drivers in the PA groundwater pathway analysis. The high degree of conformance between the two models suggests that the use of the equivalent 1-D system model is suitable for evaluating the full suite of radionuclides that will be released from the tank sources within WMA A-AX over the 1,000-year compliance period and over the 10,000-year evaluation period. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2019

Crystallization kinetics of rapid spray plasma processed multiple cation perovskites in open air

Rapid Spray Plasma Processing (RSPP) is a high throughput, scalable, and open-air route toward manufacturing perovskite solar modules. The plasma exposure is dosed such that the perovskite precursor solution is cured in milliseconds using a combination of rapid heating, reactive species, and UV photons. We implemented in situ wide angle X-ray scattering (WAXS) to characterize the crystal growth in multiple cation, mixed halide perovskite thin films—Cs x (MA z FA 1-z ) 1-x Pb(Br 0.17 I 0.83 ) 3 for 0.05 ≤ x ≤ 0.25—fabricated in open air. The use of synchrotron radiation and high detector speeds resolved the formation and dissolution of a transient intermediate crystalline phase during the tens of milliseconds when the perovskite crystallized. Increasing the mole fraction of cesium and methylammonium resulted in a decrease in the intermediate phase and an increase in the average grain diameter. Increasing the cesium fraction suppressed phase segregation, as observed in photoluminescence. Calculations showed the refractive index decreased and the extinction coefficient increased with cesium fraction. Based on the rapid crystallization kinetics, RSPP perovskite films exhibit residual stress values >5× lower than spin coated films. Understanding the kinetics of perovskite formation enables the design of perovskite films with improved thermomechanical and operational stability.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Development of a bright MeV photon source with compound parabolic concentrator targets on the National Ignition Facility Advanced Radiographic Capability (NIF-ARC) laser

Compound parabolic concentrator (CPC) targets are utilized at the National Ignition Facility Advanced Radiographic Capability (NIF-ARC) laser to enhance the acceleration of electrons and production of high energy photons, for laser durations of 10 ps and energies up to 2.4 kJ. A large enhancement of mean electron energy (>2 ×) and photon brightness (>10×) is found with CPC targets compared to flat targets. Using multiple diagnostic techniques at different spatial locations and scaling by gold activation spatial data, photon spectra are characterized for E photon = 0.5-30 MeV. Beam width and pointing variations are given. The efficient production of MeV photons at I laser ≈ 2 x 10 18 W/cm 2 with CPCs is observed, with doses of >10 rad in air at 1 m for E photon > 0.5 MeV; these exceed those previously reported with laser-driven sources. Using this source, sub-mm resolution radiographs are generated through large areal density radiograph objects. Hence these results are promising for the development of bright MeV x-ray and particle sources on Petawatt class laser systems.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

Terpenes modulate bacterial and fungal growth and sorghum rhizobiome communities

ABSTRACT Terpenes are among the oldest and largest class of plant-specialized bioproducts that are known to affect plant development, adaptation, and biological interactions. While their biosynthesis, evolution, and function in aboveground interactions with insects and individual microbial species are well studied, how different terpenes impact plant microbiomes belowground is much less understood. Here we designed an experiment to assess how belowground exogenous applications of monoterpenes (1,8-cineole and linalool) and a sesquiterpene (nerolidol) delivered through an artificial root system impacted its belowground bacterial and fungal microbiome. We found that the terpene applications had significant and variable impacts on bacterial and fungal communities, depending on terpene class and concentration; however, these impacts were localized to the artificial root system and the fungal rhizosphere. We complemented this experiment with pure culture bioassays on responsive bacteria and fungi isolated from the sorghum rhizobiome. Overall, higher concentrations (200 µM) of nerolidol were inhibitory to Ferrovibrium and tested Firmicutes. While fungal isolates of Penicillium and Periconia were also more inhibited by higher concentrations (200 µM) of nerolidol, Clonostachys was enhanced at this higher level and together with Humicola was inhibited by the lower concentration tested (100 µM). On the other hand, 1,8-cineole had an inhibitory effect on Orbilia at both tested concentrations but had a promotive effect at 100 µM on Penicillium and Periconia . Similarly, linalool at 100 µM had significant growth promotion in Mortierella , but an inhibitory effect for Orbilia . Together, these results highlight the variable direct effects of terpenes on single microbial isolates and demonstrate the complexity of microbe-terpene interactions in the rhizobiome. Importance Terpenes represent one of the largest and oldest classes of plant-specialized metabolism, but their role in the belowground microbiome is poorly understood. Here, we used a “rhizobox” mesocosm experimental set-up to supply different concentrations and classes of terpenes into the soil compartment with growing sorghum for 1 month to assess how these terpenes affect sorghum bacterial and fungal rhizobiome communities. Changes in bacterial and fungal communities between treatments belowground were characterized, followed by bioassays screening on bacterial and fungal isolates from the sorghum rhizosphere against terpenes to validate direct microbial responses. We found that microbial growth stimulatory and inhibitory effects were localized, terpene specific, dose dependent, and transient in time. This work paves the way for engineering terpene metabolisms in plant microbiomes for improved sustainable agriculture and bioenergy crop production.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Dosimetric and biological impact of activity extravasation of radiopharmaceuticals in PET imaging

The increasing use of nuclear medicine and PET imaging has intensified scrutiny of radiotracer extravasation. To our knowledge, this topic is understudied but holds great potential for enhancing our understanding of extravasation in clinical PET imaging. This work aims to (1) quantify the absorbed doses from radiotracer extravasation in PET imaging, both locally at the site of extravasation and with the extravasation location as a source of exposure to bodily organs and (2) assess the biological ramifications within the injection site at the cellular level. A radiation dosimetry simulation was performed using a whole-body 4D Extended Cardiac-Torso (XCAT) phantom embedded in the GATE Monte Carlo platform. A 10-mCi dose of 18 F-FDG was chosen to simulate a typical clinical PET scan scenario, with 10% of the activity extravasated in the antecubital fossa of the right arm of the phantom. The extravasation volume was modeled as a 5.5 mL rectangle in the hypodermal layer of skin. Absorbed dose contributions were calculated for the first two half-lives, assuming biological clearance thereafter. Dose calculations were performed as absorbed doses at the organ and skin levels. Energy deposition was simulated both at the local extravasation site and in multiple organs of interest and converted to absorbed doses based on their respective masses. Each simulation was repeated ten times to estimate Monte Carlo uncertainties. Biological impacts on cells within the extravasated volume were evaluated by randomizing cells and exposing them to a uniform radiation source of 18 F and 68 Ga. Particle types, their energies, and direction cosines were recorded in phase space files using a separate Geant4 simulation to characterize their entry into the nucleus of the cellular volume. Subsequently, the phase space files were imported into the TOPAS-nBio simulation to assess the extent of DNA damage, including double-strand breaks (DSBs) and single-strand breaks (SSBs). Organ-level dosimetric estimations are presented for 18 F and 68 Ga radionuclides in various organs of interest. With 10% extravasation, the hypodermal layer of the skin received the highest absorbed dose of 1.32 ± 0.01 Gy for 18 F and 0.99 ± 0.01 Gy for 68 Ga. The epidermal and dermal layers received absorbed doses of 0.07 ± 0.01 Gy and 0.13 ± 0.01 Gy for 18 F, and 0.14 ± 0.01 Gy and 0.29 ± 0.01 Gy for 68 Ga, respectively. In the extravasated volume, 18 F caused an average absorbed dose per nucleus of 0.17 ± 0.01 Gy, estimated to result in 10.58 ± 0.50 DSBs and 268.11 ± 12.43 SSBs per nucleus. For 68 Ga, the absorbed dose per nucleus was 0.11 ± 0.01 Gy, leading to an estimated 6.49 ± 0.34 DSBs and 161.24 ± 8.12 SSBs per nucleus. Absorbed doses in other organs were on the order of micro-gray (µGy). The likelihood of epidermal erythema resulting from extravasation during PET imaging is low, as the simulated absorbed doses to the epidermis remain below the thresholds that trigger such effects. Moreover, the organ-level absorbed doses were found to be clinically insignificant across various simulated organs. The minimal DNA damage at the extravasation site suggests that long-term harm, such as radiation-induced carcinogenesis, is highly unlikely.

DNA strand breaks↗
DOE OSTI2016

Calibration of a Passive Neutron Counter with {sup 242}Pu Standards - 16450

At the Los Alamos National Laboratory TA 55 facility, a large quantity of Heat Source (HS) and MT42 (primarily {sup 242}Pu) has been designated for disposal as TRU waste. The waste, to be packaged in either 55 gal drums or Pipe Overpack Containers (POCs), is scheduled to be assayed with the TA 55 HENC 3 system. The system is owned and operated by the Nuclear Waste Partnership (NWP) under a contract with the Carlsbad DoE field office. The HENC 3 is a combined passive neutron/gamma assay system. The neutron component of the system was previously calibrated up to 21.9 g of {sup 240}Pu effective. This corresponds to approximately 9 g of typical HS plutonium and 13 g of MT42 waste. In order to reduce packaging efforts and radiation dose for waste handling personnel, LANL has requested an increase in the HENC 3 calibration limit to approximate the maximum allowable shipping and storage limits for TRU waste. To increase the limits, NWP has obtained the use of well characterized MT42 source materials. The sources, developed and owned by LANL, range from to 5 g to 200 g of plutonium enriched to 86.6% {sup 242}Pu. Using these sources in combination, multiple measurements were performed with both 55-gal drums and POCs to determine their suitability for extending the neutron calibration range of the system. The results of the measurements were (1) compared to the existing calibration for consistency and (2) used to extend the calibration range to 307 g of {sup 240}Pu effective. This report will discuss the elements of the neutron component of the HENC 3 system, the calibration extension effort, problems encountered, and the results of the measurements. As a result of the extension, HS and MT42 materials can be assayed in 55-gal drums and POCs up to their allowable shipping limits. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

Characterizing Fluence as a Function of Areal Density for 1 and 14 MeV Neutrons Transported Through Air

Computing neutron dosimetry involves transporting neutrons [n] from a source to a sink, determining the neutron heating within the sink and multiplying the neutron heating by a quality factor to compute the dose equivalent. The space and energy dependent neutron fluence is a measure of the amount of neutrons crossing a particular surface area, about a particular energy and is given in units of [n/cm{sup 2}]. Microscopic cross sections are given in units of area and vary by isotope and reaction type as a function of energy. The product of the atom density of a particular atom in a specie and the microscopic cross section of a particular reaction results in the macroscopic cross section of a particular reaction, given in units of per length [1/cm] as a function of energy. Summing the macroscopic cross sections of all isotopes, and all collisions resulting in heating, within a volume, results in a total collision heating macroscopic cross section for that volume. The product of the energy and spatial dependent collision heating macroscopic cross section and the energy and spatial dependent fluence, within an energy group, results in a collision heating reaction density for that particular reaction in that energy group. Weighting each energy group's collision heating reactions, with the corresponding energy dependent particle damage per collision heating event (usually biological damage), and then integrating over energy and volume results in the delivered dose. Therefore understanding dose delivery involves examining the spatial and energy (and time) dependent fluence behavior. Because of the coupled energy and space dependence of the heating weighting and macroscopic cross sections, the fluence is not so easily separable in energy and space; however, the energy integrated fluence can be used as a first order approximation of the relative magnitude of reactions as a function of space. Here we examine the first part in the dosimetry calculation process, transporting neutrons from source to sink, as applied to neutron transport in air, examining characteristics of the fluence. Presented here is analysis regarding the nature of the fluence peak between 10 g/cm{sup 2} and 100 g/cm{sup 2} for a typical air transport calculation. Due to the high concentration of nitrogen and oxygen isotopes of these elements, these isotopes tend to dominate the transport. From the analysis presented here, the fluence peak is the result of scatter back and forth across the peak regime, and (n,2n) has a minimal (<4%) contribution. Further evidence of minimal (n,2n) impact in the 10-100 g/cm{sup 2} span includes the 1 MeV fluence peak being so much larger than the 14 MeV peak; where 1 MeV is not above the (n,2n) threshold. Also presented here is the usefulness of using tally tagging with cell flagging to further dissect the nature of the fluence. These technologies allow us to understand the originating volume that makes a contribution to a scoring regime. (authors)

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2016

SU-F-T-570: Comparison of Synthetic Diamond, Microionization Chamber, and Radiochromic Film for Absolute Dosimetry of VMAT Radiosurgery

Purpose: Patient specific quality assurance of stereotactic radiosurgery (SRS) plans is challenging because of small target sizes and high dose gradients. We compared three detectors for dosimetry of VMAT SRS plans. Methods: The dose at the center of seventeen targets was measured using a synthetic diamond detector (2.2 mm diameter, 1 µm thickness), a 0.007 cm{sup 3} ionization chamber, and radiochromic film. Measurements were made in a PMMA phantom in the clinical geometry – all gantry and table angles were delivered as planned. The diamond and chamber positions were offset by 1 cm from the film plane, so the isocenter was shifted accordingly to place the center of the target at the detector of interest. To ensure accurate detector placement, the phantom was positioned using kV images. To account for the shift-induced difference in geometry and differing prescription doses between plans, the measurements were normalized to the expected dose calculated by the treatment planning system. Results: The target sizes ranged from 2.8 mm to 34.8 mm (median 14.8 mm). The mean measurement-to-plan ratios were 1.054, 1.076, and 1.023 for RCF, diamond, and chamber, respectively. The mean difference between the chamber and film was −3.2% and between diamond and film was 2.2%. For targets larger than 15 mm, the mean difference relative to film was −0.8% and 0.1% for chamber and diamond, respectively, whereas for targets smaller than 15 mm, the difference was −5.3% and 4.2% for chamber and diamond, respectively. The difference was significant (p=0.005) using the two-sample Kolmogorov-Smirnov test. Conclusion: The detectors agree for target sizes larger than 15 mm. Relative to film, for smaller targets the diamond detector over-responds, whereas the ionization chamber under-responds. Further work is needed to characterize detector response in modulated SRS fields.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Development of a novel photoaffinity probe for labeling nocistatin receptor

Highlights: • Biotin-(AC{sub 5}){sub 2}-[Y{sup 6},azF{sup 14}]bNST is a novel nocistatin photoaffinity probe. • Biotin-(AC{sub 5}){sub 2}-[Y{sup 6},azF{sup 14}]bNST inhibits the tactile pain allodynia. • Biotin-(AC{sub 5}){sub 2}-[Y{sup 6},azF{sup 14}]bNST-binding proteins are observed at 58 and 64 kDa. Nocistatin (NST) is a neuropeptide produced from the same precursor protein of opioid peptide nociceptin/orphanin FQ, and it is involved in a broad range of central functions including pain transmission in the nervous system. However, the composition and structure of the receptor(s) for NST remain unclear. Here, we developed NST photoaffinity probe to identify NST receptor. The NST photoaffinity probe contains an azide moiety for the tagging of the binding protein as well as biotin for protein detection. Intrathecal administration of a NST photoaffinity probe, biotin-(AC{sub 5}){sub 2}-[Y{sup 6},azF{sup 14}]bNST, inhibited the nociceptin/orphanin FQ-evoked tactile pain allodynia in a manner similar to that of NST. The biotin-(AC{sub 5}){sub 2}-[Y{sup 6},azF{sup 14}]bNST-binding proteins were primarily localized in the gray matter of the spinal cord. After photo-crosslinking of the protein complex with biotin-(AC{sub 5}){sub 2}-[Y{sup 6},azF{sup 14}]bNST, two dominant binding protein bands were observed at 58 and 64 kDa. Thus, biotin-(AC{sub 5}){sub 2}-[Y{sup 6},azF{sup 14}]bNST has pharmacological activity and is useful for characterizing the NST receptor.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Nevada National Security Site Environmental Report 2016

This Nevada National Security Site Environmental Report (NNSSER) was prepared to satisfy DOE Order DOE O 231.1B, “Environment, Safety and Health Reporting.” Its purpose is to (1) report compliance status with environmental standards and requirements, (2) present results of environmental monitoring of radiological and nonradiological effluents, (3) report estimated radiological doses to the public from releases of radioactive material, (4) summarize environmental incidents of noncompliance and actions taken in response to them, (5) describe the National Nuclear Security Administration Nevada Field Office (NNSA/NFO) Environmental Management System and characterize its performance, and (6) highlight significant environmental programs and efforts. This NNSSER summarizes data and compliance status for calendar year 2016 at the Nevada National Security Site (NNSS) and its two Nevada-based support facilities, the North Las Vegas Facility (NLVF) and the Remote Sensing Laboratory–Nellis (RSL-Nellis). It also addresses environmental restoration (ER) projects conducted at the Tonopah Test Range (TTR) and the Nevada Test and Training Range (NTTR). NNSA/NFO directs the management and operation of the NNSS and six sites across the nation. In addition to the NNSA itself, the six sites include two in Nevada (NLVF and RSL-Nellis) and four in other states (RSL-Andrews in Maryland, Livermore Operations in California, Los Alamos Operations in New Mexico, and Special Technologies Laboratory in California). Los Alamos, Lawrence Livermore, and Sandia National Laboratories are the principal organizations that sponsor and implement the nuclear weapons programs at the NNSS. National Security Technologies, LLC (NSTec), is the current Management and Operating contractor accountable for the successful execution of work and ensuring that work is performed in compliance with environmental regulations. The six sites all provide support to enhance the NNSS as a location for its multiple missions. The three major NNSS missions include National Security/Defense, Environmental Management, and Nondefense. The major programs that support these missions are Stockpile Stewardship and Management, Nonproliferation and Counterterrorism, Nuclear Emergency Response, Strategic Partnership Projects, Environmental Restoration, Waste Management, Conservation and Renewable Energy, Other Research and Development, and Infrastructure. The major facilities that support the programs include the U1a Facility, Big Explosives Experimental Facility (BEEF), Device Assembly Facility, Dense Plasma Focus Facility, Joint Actinide Shock Physics Experimental Research Facility, Radiological/Nuclear Countermeasures Test and Evaluation Complex, Nonproliferation Test and Evaluation Complex (NPTEC), Radiological/Nuclear Weapons of Mass Destruction Incident Exercise Site, the Area 5 Radioactive Waste Management Complex (RWMC), and the Area 3 Radioactive Waste Management Site (RWMS).

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRSDate not supplied

Retrospectives: Current State of Knowledge on the Intersection of Spaceflight Stressors and Microbial Risks to Crew and Craft

OVERVIEW The spaceflight environment has several unique stressors that affect the health of both the crew and the spacecraft. An area of continued, albeit incomplete, study is the interaction of these stressors on microbial populations inherent to both astronauts and spacecraft surfaces and systems. A primary concern is the potential for the spaceflight environment to perturb the phenotype of these populations towards negative outcomes for crew and craft. In order to effectively mitigate these potential risks, they must first be characterized. We performed a retrospective literature analysis to assess the current state of knowledge regarding the affects of ionizing radiation and elevated CO2 on relevant microbial populations. The results of these retrospectives will guide next steps in the decisions of what (if any) further studies should be pursued and to guide decisions of the need for countermeasures. STRESSORS Ionizing radiation. The health risk involved with increased exposure to cosmic radiation has been studied in crew for 35+ years, with human health and cancer risk being the main focus. However, space radiation could also affect both the resident microorganisms aboard the ISS and the normal, healthy astronaut microbiomes that are of direct concern for crew health. A retrospective review of over 250 publications was accomplished looking at the impact of cumulative ionizing radiation doses lower than 3 Gy (chronic or acute) on microbial populations. Elevated CO2. The health risk involved with elevated atmospheric CO2 in spacecraft, primarily focusing on human toxicological risks, is understudied. The current Spaceflight Maximum Allowance Concentration for 24-hour average CO2 is 0.4% (3 mm Hg), which is significantly higher than terrestrial levels (0.04%). Whether these elevated ambient CO2 levels aboard spacecraft influence the diversity and phenotypic responses of the resident microbial communities from both the spacecraft environment (air, surface, water) and crew members (gut, nasal, skin microbiomes) is not known. A retrospective review was accomplished looking at the impact of chronic CO2 exposure up to 0.7% (5 mm Hg) for up to 6 months and acute exposure up to 2.6% (20 mm Hg) for up to 24 hours. CONCLUSIONS: MICROBIOME OF THE BUILT ENVIRONMENT The microbiome of the built spacecraft environment has been sampled consistently over the course of human spaceflight and significant advancements have been made in identifying microbial populations on the ISS. The dominant source of microbes on spacecraft surfaces are human-derived. Once in the spacecraft built environment, the extreme environment selects for features that enhance survival. While efforts to understand potential antibiotic resistance and pathogenicity of ISS isolates is robust, there is little to no understanding of which spaceflight environmental stressors, to include ionizing radiation or elevated CO2, drive the evolutionary trajectory of spacecraft-associated microbial populations. CONCLUSIONS: MICROBE-HOST INTERACTIONS The host-microbiome field has emerged as an important factor in human health on Earth as well in spaceflight. The field is struggling with the complexity of the system under investigation as there is substantial taxonomic and functional heterogeneity in these communities, making it difficult to establish clear stimulus-response dynamics. Taxonomic characterization is the norm; however, the functional role of each community member is key to linking environmental perturbations to potential dysbiosis. For both ionizing radiation and elevated CO2, the likely target of the perturbation is the host tissue, not the microbes themselves.. Any resulting changes to the microbial community composition and/or function is likely a result of adapting to those changes in the host physiology. RECOMMENDATIONS Emphasize functional characterization as opposed to taxonomic characterization of microbial communities. Increase the number of investigations using chronic, spaceflight-relevant doses of ionizing radiation. MoBE studies should move away from observational studies towards predictive modeling of community dynamics. Continue to develop scale-down models, such as tissues-on-a-chip & defined microbial communities. Focus on the crew response to elevated CO2 over MoBE considerations. Assess how direct contact with the hypercapnic environment affects skin microbiome dynamics.

retrospective↗