Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “GAMMA”

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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Method and system for calibrating gamma radiation flux levels in a solid state gamma radiation detection system

One aspect of the present disclosure comprises a method for calibrating a drive level of a non-radioactive calibration source. Another aspect of the present disclosure comprises a method for using a non-radioactive calibration source to verify correct operation of a radiation detector. Another aspect of the present disclosure comprises a radiation detection system that comprises a radiation detector and a non-radioactive calibration source that is used to verify correct operation of the radiation detector.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2017

Measuring the Charged Pion Polarizability in the $\gamma\gamma\rightarrow\pi^{+{}}\pi^{-{}}$ Reaction

A new measurement of the charged pion polarizability ????? is approved to run at Jefferson Lab using the GlueX detector in experimental Hall D. The charged pion polarizability ranks among the most important tests of low-energy QCD presently unresolved by experiment. Analogous to precision measurements of ?0??? that test the intrinsic odd-parity (anomalous) sector of QCD, the pion polarizability tests the intrinsic even-parity sector of QCD. The ????+?? cross section will be accessed via the Primakoff mechanism on a nuclear target. The linearly polarized photon source in Hall D will allow the separation of the Primakoff cross section from coherent ?0(770) production. An additional detector will also need to be constructed to help distinguish ?+?? and ?+?? events. An update on the status of the experiment will be given.

Lawrence, David↗
DOE OSTI2017

Validation of Methodology to Simulate Gamma Doses from Historical Weapons Tests

The United States tested nuclear weapons in the atmosphere (aboveground) from 1945 until 1963, when the nation became a signatory to the Partial Test Ban Treaty. During those tests, gamma doses were often measured within kilometers of the point of detonation. Additional gamma dose measurements were made in and around the location of any personnel conducting the test, possibly with personal dosimeters. These gamma dose measurements have been declassified to provide the personnel involved with an estimate of the total dose they received while involved with the aboveground testing program. Several years ago, interest in these gamma doses was renewed by organizations that would need to provide the public with dose estimates in the event of a radiological or nuclear weapon terrorist attack on the United States. This work provides an initial validation of the computational methods used to simulate dose from a radiological or nuclear weapon. This initial work will focus on dose from gamma rays. The sources of gamma rays from a nuclear weapon include prompt fission gammas, gammas generated via neutron interactions (capture, inelastic scattering, and activation), and gammas produced by the decay of fission products. All of these gamma ray sources for a nuclear weapon are also potential sources of gammas from a radiological weapon. However, the sources of gamma rays from a radiological weapon depend on the material present in the device, and prompt fission gammas will mostly come from spontaneous fission instead of induced fission. This paper focuses on validation using gamma ray dose measurements from nuclear detonations, which is adequate to validate the requisite transport methodologies, source term generation, and cross sections needed to model gamma doses delivered by most radiological weapons. The 1961 report on Operation Plumbbob provides an overview of how the total gamma dose delivered by a nuclear weapon is broken down by the different sources specified above. The prompt fission gamma rays contribute about 5% of the total gamma dose. The gamma rays produced by neutron interactions usually deliver the largest portion of the total gamma dose, which is typically between 55% and 85% of the total. The remainder of the total gamma ray dose is attributed to decay of fission products.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2018

Neutron Capture Energies for Flux Normalization and Approximate Model for Gamma-Smeared Power

The Consortium for Advanced Simulation of Light Water Reactors (CASL) Virtual Environment for Reactor Applications (VERA) neutronics simulator MPACT has used a single recoverable fission energy for each fissionable nuclide assuming that all recoverable energies come only from fission reaction, for which capture energy is merged with fission energy. This approach includes approximations and requires improvement by separating capture energy from the merged effective recoverable energy. This report documents the procedure to generate recoverable neutron capture energies and the development of a program called CapKappa to generate capture energies. Recoverable neutron capture energies have been generated by using CapKappa with the evaluated nuclear data file (ENDF)/B-7.0 and 7.1 cross section and decay libraries. The new capture kappas were compared to the current SCALE-6.2 and the CASMO-5 capture kappas. These new capture kappas have been incorporated into the Simplified AMPX 51- and 252-group libraries, and they can be used for the AMPX multigroup (MG) libraries and the SCALE code package. The CASL VERA neutronics simulator MPACT does not include a gamma transport capability, which limits it to explicitly estimating local energy deposition from fission, neutron, and gamma slowing down and capture. Since the mean free path of gamma rays is typically much longer than that for the neutron, and the total gamma energy is about 10% to the total energy, the gamma-smeared power distribution is different from the fission power distribution. Explicit local energy deposition through neutron and gamma transport calculation is significantly important in multi-physics whole core simulation with thermal-hydraulic feedback. Therefore, the gamma transport capability should be incorporated into the CASL neutronics simulator MPACT. However, this task will be timeconsuming in developing the neutron induced gamma production and gamma cross section libraries. This study is to investigate an approximate model to estimate gammasmeared power distribution without performing any gamma transport calculation. A simple approximate gamma smearing model has been investigated based on the facts that pinwise gamma energy depositions are almost flat over a fuel assembly, and assembly-wise gamma energy deposition is proportional to kappa-fission energy deposition. The approximate gamma smearing model works well for single assembly cases, and can partly improve the gamma smeared power distribution for the whole core model. Although the power distributions can be improved by the approximate gamma smearing model, still there is an issue to explicitly obtain local energy deposition. A new simple approach or gamma transport/diffusion capability may need to be incorporated into MPACT to estimate local energy deposition for more robust multi-physics simulation.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗