50 research outputs found
Evaluating the Effectiveness of Shielding Material, Vehicle Shape and Astronaut Position for Deep Space Travel
Background: As future crewed, deep space missions are being planned, it is important to assess how spacecraft design can be used to minimize radiation exposure. Collectively with shielding material, vehicle shape and astronaut position must be used to protect astronauts from the two primary sources of space radiation: Galactic Cosmic Rays (GCRs) and Solar Particle Events (SPEs).
Methods: The On-Line Tool for the Assessment of Radiation in Space (OLTARIS) version 4.1 analysis package is used to evaluate and analyze this detailed radiation field. Developed by the National Aeronautics and Space Administration\u27s (NASA) Langley Research Center, the tool enables engineering and research related space radiation calculations. Each configuration is evaluated in whole body effective dose equivalent (ED). This research evaluates 70 aerospace materials, 2 vehicle shapes and 3 astronaut positions.
Results and Conclusions: The material analyses show that for metals, aluminum outperforms and therefore is the most feasible metal for deep space travel. But when evaluating all materials, polyethylene outperforms all feasible aerospace materials.
The vehicle shape and astronaut position analyses show that moving a human phantom closer to a wall does significantly decrease the ED. This pattern is not dependent on material nor boundary condition, but the mean shielding thickness a source ray must travel through for the GCR boundary condition. For shielding thicknesses greater than 30 g/cm 2 for polyethylene and 100g/cm 2 for aluminum, the results suggest that having astronauts’ habitats and work areas located further from the center will help protect astronauts longer from deep space radiation.https://scholarscompass.vcu.edu/gradposters/1067/thumbnail.jp
Affine Toda Solitons and Vertex Operators
Affine Toda theories with imaginary couplings associate with any simple Lie
algebra generalisations of Sine Gordon theory which are likewise
integrable and possess soliton solutions. The solitons are \lq\lq created" by
exponentials of quantities which lie in the untwisted affine
Kac-Moody algebra and ad-diagonalise the principal Heisenberg
subalgebra. When is simply-laced and highest weight irreducible
representations at level one are considered, can be expressed as
a vertex operator whose square vanishes. This nilpotency property is extended
to all highest weight representations of all affine untwisted Kac-Moody
algebras in the sense that the highest non vanishing power becomes proportional
to the level. As a consequence, the exponential series mentioned terminates and
the soliton solutions have a relatively simple algebraic expression whose
properties can be studied in a general way. This means that various physical
properties of the soliton solutions can be directly related to the algebraic
structure. For example, a classical version of Dorey's fusing rule follows from
the operator product expansion of two 's, at least when is
simply laced. This adds to the list of resemblances of the solitons with
respect to the particles which are the quantum excitations of the fields.Comment: Imperial/TP/92-93/29 SWAT/92-93/5 PU-PH-93/1392, requires newma
Irradiation Experiment for Living Insect-Based Radiological Dispersal Device
People generally associate fear with “nuclear”, “radioactive” and “insects”. It is speculated that a release of radioactive living insects would instill more fear into the general public than a “traditional” style radiological dispersion device (RDD). This paper evaluates the potential threat of an insect-based RDD using experimental data. The results of this project found that insect-based RDDs are an insignificant threat due to the challenges in making insects radioactive enough to pose any danger to humans without killing the insects
Development of a Real-Time Detection Strategy for Material Accountancy and Process Monitoring During Nuclear Fuel Reprocessing Using the Urex+3A Method
Reprocessing nuclear fuel is becoming more viable in the United States due to the anticipated increase in construction of nuclear power plants, the growing stockpile of existing used nuclear fuel, and a public desire to reduce the amount of this fuel. However, a new reprocessing facility in non-weapon states must be safeguarded and new reprocessing facilities in weapon states will likely have safeguards due to political and material accountancy reasons. These facilities will have state of the art controls and monitoring methods to safeguard special nuclear materials, as well as to provide real-time monitoring. The focus of this project is to enable the development of a safeguards strategy that uses well established photon measurement methods to characterize samples from the UREX+3a reprocessing method using a variety of detector types and measurement times.
It was determined that the errors from quantitative measurements were too large for traditional safeguards methods; however, a safeguards strategy based on qualitative gamma ray and neutron measurements is proposed. The gamma ray detection equipment used in the safeguard strategy could also be used to improve the real-time process monitoring in a yet-to-be built facility. A facility that had real-time gamma detection equipment could improve product quality control and provide additional benefits, such as waste volume reduction. In addition to the spectral analyses, it was determined by Monte Carlo N Particle (MCNP) simulations that there is no noticeable self shielding for internal pipe diameters less than 2 inches, indicating that no self shielding correction factors are needed. Further, it was determined that HPGe N-type detectors would be suitable for a neutron radiation environment. Finally, the gamma ray spectra for the measured samples were simulated using MCNP and then the model was extended to predict the responses from an actual reprocessing scenario from UREX+3a applied to fuel that had a decay time of three years. The 3-year decayed fuel was more representative of commercially reprocessed fuel than the acquired UREX+3a samples.
This research found that the safeguards approach proposed in this paper would be best suited as an addition to existing safeguard strategies. Real-time gamma ray detection for process monitoring would be beneficial to a reprocessing facility and could be done with commercially available detectors
Khalifa University Reachback Program Supporting Prevention of Illicit Nuclear and Radiological Material Smuggling in the United Arab Emirates
Trafficking of Illicit nuclear or radiological materials is a global threat which can involve and adversely affect any country. Ultimately, it is the responsibility of each state to prevent and combat illicit nuclear trafficking by screening all cargo and travelers entering, exiting, and transiting through its borders. As a part of the national radiation detection infrastructure of the United Arab Emirates (UAE), a reachback program was established at Khalifa University (KU) to provide capabilities for adjudication of radiation alarms at Khalifa Port and other radiation portal monitor (RPM) locations. In addition to the main mission, KU Reachback aims to educate and prepare local talent to lead these vital efforts in the future. This is particularly important because the UAE, similar to other newcomers to the nuclear industry, faces human capital challenges which can be addressed using domestic or regional solutions
Exact S-Matrices with Affine Quantum Group Symmetry
We show how to construct the exact factorized S-matrices of 1+1 dimensional
quantum field theories whose symmetry charges generate a quantum affine
algebra. Quantum affine Toda theories are examples of such theories. We take
into account that the Lorentz spins of the symmetry charges determine the
gradation of the quantum affine algebras. This gives the S-matrices a non-rigid
pole structure. It depends on a kind of ``quantum'' dual Coxeter number which
will therefore also determine the quantum mass ratios in these theories. As an
example we explicitly construct S-matrices with symmetry.Comment: Latex file, 21 page
Renormalization group trajectories from resonance factorized S-matrices
We propose and investigate a large class of models possessing resonance
factorized S-matrices. The associated Casimir energy describes a rich pattern
of renormalization group trajectories related to flows in the coset models
based on the simply laced Lie Algebras. From a simplest resonance S-matrix,
satisfying the ``-property'', we predict new flows in non-unitary
minimal models.Comment: (7 pages) (no figures included
Solitons, Tau-functions and Hamiltonian Reduction for Non-Abelian Conformal Affine Toda Theories
We consider the Hamiltonian reduction of the two-loop
Wess-Zumino-Novikov-Witten model (WZNW) based on an untwisted affine Kac-Moody
algebra \cgh. The resulting reduced models, called {\em Generalized
Non-Abelian Conformal Affine Toda (G-CAT)}, are conformally invariant and a
wide class of them possesses soliton solutions; these models constitute
non-abelian generalizations of the Conformal Affine Toda models. Their general
solution is constructed by the Leznov-Saveliev method. Moreover, the dressing
transformations leading to the solutions in the orbit of the vacuum are
considered in detail, as well as the -functions, which are defined for
any integrable highest weight representation of \cgh, irrespectively of its
particular realization. When the conformal symmetry is spontaneously broken,
the G-CAT model becomes a generalized Affine Toda model, whose soliton
solutions are constructed. Their masses are obtained exploring the spontaneous
breakdown of the conformal symmetry, and their relation to the fundamental
particle masses is discussed.Comment: 47 pages. LaTe
Integrability of Coupled Conformal Field Theories
The massive phase of two-layer integrable systems is studied by means of RSOS
restrictions of affine Toda theories. A general classification of all possible
integrable perturbations of coupled minimal models is pursued by an analysis of
the (extended) Dynkin diagrams. The models considered in most detail are
coupled minimal models which interpolate between magnetically coupled Ising
models and Heisenberg spin-ladders along the discrete series.Comment: 23 pages, four figure
Affine Toda field theories related to Coxeter groups of non-crystallographic type
We propose affine Toda field theories related to the non-crystallographic
Coxeter groups H_2, H_3 and H_4. The classical mass spectrum, the classical
three-point couplings and the one-loop corrections to the mass renormalisation
are determined. The construction is carried out by means of a reduction
procedure from crystallographic to non-crystallographic Coxeter groups. The
embedding structure explains for various affine Toda field theories that their
particles can be organised in pairs, such that their relative masses differ by
the golden ratio.Comment: 28 pages LaTe