Download or read book Characterization of the Neutron Fields in the Lawrence Livermore National Laboratory LLNL Radiation Calibration Laboratory Low Scatter Facility written by and published by . This book was released on 2009 with total page 135 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Characterization of the Neutron Fields in the Lawrence Livermore National Laboratory LLNL Radiation Calibration Laboratory Low Scatter Calibration Facility written by and published by . This book was released on 2009 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt: In June 2007, the Department of Energy (DOE) revised its rule on Occupational Radiation Protection, Part 10 CFR 835. A significant aspect of the revision was the adoption of the recommendations outlined in International Commission on Radiological Protection (ICRP) Report 60 (ICRP-60), including new radiation weighting factors for neutrons, updated internal dosimetric models, and dose terms consistent with the newer ICRP recommendations. ICRP-60 uses the quantities defined by the International Commission on Radiation Units and Measurements (ICRU) for personnel and area monitoring including the ambient dose equivalent H*(d). A Joint Task Group of ICRU and ICRP has developed various fluence-to-dose conversion coefficients which are published in ICRP-74 for both protection and operational quantities. In February 2008, Lawrence Livermore National Laboratory (LLNL) replaced its old pneumatic transport neutron irradiation system in the Radiation Calibration Laboratory (RCL) Low Scatter Calibration Facility (B255, Room 183A) with a Hopewell Designs irradiator model N40. The exposure tube for the Hopewell system is located close to, but not in exactly the same position as the exposure tube for the pneumatic system. Additionally, the sources for the Hopewell system are stored in Room 183A where, prior to the change, they were stored in a separate room (Room 183C). The new source configuration and revision of the 10 CFR 835 radiation weighting factors necessitate a re-evaluation of the neutron dose rates in B255 Room 183A. This report deals only with the changes in the operational quantities ambient dose equivalent and ambient dose rate equivalent for neutrons as a result of the implementation of the revised 10 CFR 835. In the report, the terms 'neutron dose' and 'neutron dose rate' will be used for convenience for ambient neutron dose equivalent and ambient neutron dose rate equivalent unless otherwise stated.
Download or read book Characterisation of the Neutron Field at the ANSTO Instrument Calibration Facility written by Haider Meriaty and published by . This book was released on 2009 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt: "ANSTO's Instrument Calibration Facility provides calibration services to radiation monitors, used in radiation protection applications." "Determination of the free field (direct) and scattered components of neutron field in a calibration room was essential to obtain an accurate response of the neutron monitor under testing. The free field fluence response and the fractional room return scatter, caused by the interaction of neutron fluence with the room structure, were determined."--P. 3.
Download or read book Energy Research Abstracts written by and published by . This book was released on 1993 with total page 906 pages. Available in PDF, EPUB and Kindle. Book excerpt: Semiannual, with semiannual and annual indexes. References to all scientific and technical literature coming from DOE, its laboratories, energy centers, and contractors. Includes all works deriving from DOE, other related government-sponsored information, and foreign nonnuclear information. Arranged under 39 categories, e.g., Biomedical sciences, basic studies; Biomedical sciences, applied studies; Health and safety; and Fusion energy. Entry gives bibliographical information and abstract. Corporate, author, subject, report number indexes.
Download or read book Studies of Background Levels for the NIF Yield Diagnostics from Neutron and Gamma Radiation written by and published by . This book was released on 2007 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) is nearing completion of construction and is preparing for the National Ignition Campaign (NIC) with potentially significant yield in 2010. The design of a wide range of yield diagnostics in and outside the target-bay of the NIF must consider scattered background neutrons and neutron-induced gamma rays to measure neutrons and x-rays from target. The large and complex target chamber and facility make the calculation of scattered neutrons and gamma rays extremely challenging. The NIF was designed with shielded locations for many of the yield diagnostics including the neutron alcove and four diagnostic mezzanines. Accurate calculation of the background levels in these shielded locations requires advanced Monte Carlo techniques, e.g., variance reduction. Placement, size, and materials of collimators on the line of sight (LOS) through the shielding must be evaluated to trade off signal levels and unwanted backgrounds. The background at these locations is also affected by neutrons that pass through the laser beam tubes and scatter off of structures and walls in the switch yards. Detailed 3D Monte Carlo analyses are performed to determine neutron and gamma fluxes for some of the yield diagnostics.
Download or read book Calibration of a Neutron Log in Partially Saturated Media Part II Error Analysis written by and published by . This book was released on 1981 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Four sources or error (uncertainty) are studied in water content obtained from neutron logs calibrated in partially saturated media for holes up to 3 m. For this calibration a special facility was built and an algorithm for a commercial epithermal neutron log was developed that obtains water content from count rate, bulk density, and gap between the neutron sonde and the borehole wall. The algorithm contained errors due to the calibration and lack of fit, while the field measurements included uncertainties in the count rate (caused by statistics and a short time constant), gap, and density. There can be inhomogeneity in the material surrounding the borehole. Under normal field conditions the hole-size-corrected water content obtained from such neutron logs can have an uncertainty as large as 15% of its value.
Download or read book Neutron Spectrum Measurements for Radiation Protection Purposes written by and published by . This book was released on 1978 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The energy spectra of low-intensity neutron sources used for calibrating personnel neutron dose-rate meters and dosimeters and for characterizing the neutron fields to which personnel are exposed were measured. Several detector-analyzer systems that will measure in the energy range 50 keV to 20 MeV at intensities from 10−1 to 105 n/cm2-s are described. The systems include NE213 and stilbene organic scintillators as well as H2, 3He, and CH4 proportional counters. Also described are pulse-height analysis and pulse-shape discrimination systems. An unfolding code, NUTSPEC, reduces the pulse-height data to an absolute differential neutron flux phi(E) for the above detectors. The code uses a derivative unfolding method for the scintillation detectors, and for the proportional counters it calculates a response matrix and uses an iterative unfolding method to determine phi(E). The unfolded flux distribution combined with published conversion factors produces differential neutron dose-equivalent and kerma rates. Spectral segments obtained with different detectors from several measurements merge into a single differential flux spectrum over the range 50 keV to 20 MeV, together with the corresponding differential kerma and neutron dose-equivalent distributions. Also reported are spectrum measurements near 252Cf and 238PuBe sources with various moderators.
Download or read book Evaluation of the Neutron Dose Received by Personnel at the LLNL written by and published by . This book was released on 1982 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This report was prepared to document the techniques being used to evaluate the neutron exposures received by personnel at the LLNL. Two types of evaluations are discussed covering the use of the routine personnel dosimeter and of the albedo neutron dosimeter. Included in the report are field survey results which were used to determine the calibration factors being applied to the dosimeter readings. Calibration procedures are discussed and recommendations are made on calibration and evaluation procedures.
Download or read book Measurement of Neutron Flux and Spectra for Physical and Biological Applications written by National Committee on Radiation Protection and Measurements (U.S.) and published by . This book was released on 1960 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Measurement of Neutron Flux and Spectra for Physical and Biological Applications written by National Committee on Radiation Protection and Measurements (U.S.) and published by . This book was released on 1960 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Government Research Directory written by and published by . This book was released on 2009 with total page 666 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fusion Energy Update written by and published by . This book was released on 1986 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Upgrade of the PNNL TEPC and Multisphere Spectrometer written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Pacific Northwest National Laboratory (PNNL) has used two types of instruments, the tissue equivalent proportional counter (TEPC) and the multisphere spectrometer for characterizing neutron radiation fields in support of neutron dosimetry at the Hanford site. The US Department of Energy recently issued new requirements for radiation protection standards in 10 CFR 835 which affect the way that neutron dose equivalent rates are evaluated. In response to the new requirements, PNNL has upgraded the analyses used in conjunction with the TEPC and multisphere. The analysis software for the TEPC was modified for this effort, and a new analysis code was selected for the multisphere. These new analysis techniques were implemented and tested with measurement data that had been collected in previous measurements. In order to test the effectiveness of the changes, measurements were taken in PNNL's Low Scatter Room using 252Cf sources in both unmoderated and D2O-moderated configurations that generate well-characterized neutron fields. The instruments were also used at Los Alamos National Laboratory (LANL), in their Neutron Free-in-Air calibration room, also using neutron sources that generate well-characterized neutron fields. The results of the software modifications and the measurements are documented in this report. The TEPC measurements performed at PNNL agreed well with accepted dose equivalent rates using the traditional analysis, agreeing with the accepted value to within 13% for both unmoderated and moderated 252Cf sources. When the new analysis was applied to the TEPC measurement data, the results were high compared to the new accepted value. A similar pattern was seen for TEPC measurements at LANL. Using the traditional analysis method, results for all neutron sources showed good agreement with accepted values, nearly always less than 10%. For the new method of analysis, however, the TEPC responded with higher dose equivalent rates than accepted, by as much as 25%. The reason for the overresponse is that there is very little attenuation of the neutrons by tissue, so it cannot match the effect of attenuation by 1 cm of tissue called for in the new standards. This could be corrected with a modified instrument with a thicker wall, or by analytical means that would need to be developed. The multisphere spectrometer performed reasonably well both at PNNL and at LANL. It could produce a neutron spectrum that was similar to the accepted spectrum, and total flux values were usually within 15% of the accepted values. Dose equivalent rates were usually within 18% of the accepted values. The average energies, however, were usually lower than the accepted values. The performance of this instrument could be much better than seen in this study. If PNNL were to add some moderating spheres to its measurement set and calculate a new set of instrument response functions, performance could be improved. The multisphere could then be a more useful instrument for assessing the dose equivalent rate in the workplace.
Download or read book INIS Atomindex written by and published by . This book was released on 1988 with total page 948 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Characterization of a Neutron Calibration Range written by Daniel Isidoro Menchaca and published by . This book was released on 1995 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Improved Method for Measuring the Absolute DD Neutron Yield and Calibrating Neutron Time of flight Detectors in Inertial Confinement Fusion Experiments written by Caleb Joseph Waugh and published by . This book was released on 2014 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the establishment of nuclear physics in the early 1900's and the development of the hydrogen bomb in the 1950's, inertial confinement fusion (ICF) has been an important field in physics. Funded largely though the U.S. National Nuclear Security Agency (NNSA), the Laboratory for Laser Energetics (LLE), Sandia National Laboratories (SNL) and Lawrence Livermore National Laboratory (LLNL) have advanced ICF as a platform for stockpile stewardship and weapons physics, but also have contributed to basic science in high energy density regimes and for pursuing fusion an energy source. One of the primary goals of the ICF research program is to produce a thermonuclear burn in an ICF capsule where the power balance of the reaction is net positive. This criterion is often referred to as ignition. One of the most common metrics for gauging progress towards ignition in an ICF implosion is the ITFX parameter (similar to the Lawson Criterion) and is primarily a function of the implosion areal density (pR) and fusion yield. An ITFX value greater than one indicates net energy production. In deuterium/tritium fuel mixtures the yield is determined by measuring the reactant 14.0 MeV neutrons. Subsequently, the ability to obtain highly accurate absolute neutron yield measurements is vital to determining the ITFX and hence progress toward ignition. Although ignition implosions all use deuterium/tritium fuel mixes, other capsule fuel mixes such as pure deuterium and deuterium/helium 3 are also used to improve understanding of capsule performance. At the LLE and LLNL, neutron time-of-flight (nTOF) detectors routinely measure the absolute neutron yield from laser-driven ICF implosions. Although originally calibrated through a series of cross-calibrations with indium and copper neutron activation systems, an alternative method has been developed for measuring the DDn yield that provides a more accurate calibration by directly calibrating nTOF in situ to CR-39 range filter (RF) proton detectors. A neutron yield can be inferred from the CR-39 RF proton measurement since the DD proton and DD neutron branching ratio is well characterized and close to unity. By obtaining highly accurate DDp yields from a series of exploding pusher campaigns on OMEGA, an excellent absolute DDn yield measurement was obtained and used to calibrate the 3m nTOF detector. Data obtained suggest the existing OMEGA nTOF calibration coefficient to be low by 9.0 1.5 % based on the inferred CR-39 DD neutron yield. In addition, comparison across multiple exploding pusher campaigns indicate that significant reduction in charged particle flux anisotropies can be achieved on shots where capsule bang time occurs significantly (on the order of 500ps) after the end of the laser pulse. This is important since the main source of error in the RF DDp yield measurement is due to particle flux anisotropies. Results indicate that the CR-39 RF/nTOF in situ calibration method can serve as a valuable platform for measuring the DDn yield from ICF implosions and for calibrating and reducing the uncertainty of calibration coefficients of nTOF detector systems on OMEGA and other larger facilities such as the National Ignition Facility (NIF).
Download or read book Neutron Source Strength Calibrations written by E. Dale McGarry and published by . This book was released on 1988 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt:
