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Topic: Neutron flux

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Flux

	Neutron flux - Wikipedia, the free encyclopedia
		Neutron flux is the term applied to the measurement of neutrons passing though a given region of space.
		A flow of neutrons is often used to initiate the fission of unstable large nuclei.
		The flux shape is the term applied to the density or relative strength of the flux as it moves around the reactor.
	en.wikipedia.org /wiki/Neutron_flux (305 words)

	Neutron star - Wikipedia, the free encyclopedia
		A newborn neutron star can rotate several times a second; sometimes, when they orbit a companion star and are able to accrete matter from it, they can increase this to several thousand times per second, distorting into an oblate spheroid shape despite their own immense gravity (an equatorial bulge).
		Neutron stars may "pulse" due to particle acceleration near the magnetic poles, which are not aligned with the rotation axis of the star.
		Although a neutron star could logically be classed as an exotic atom, since the bulk of the star is one huge atomic nucleus and electrical neutrality forces it to have a thin shell of electrons surrounding it, it is generally more useful to consider such objects as stars.
	en.wikipedia.org /wiki/Neutron_star (1568 words)

	Neutron source - Wikipedia, the free encyclopedia
		Neutron source is a general term referring to a variety devices that emit neutrons, irrespective of the mechanism used to produce the neutrons.
		Cf-252 and all other spontaneous fission neutron sources are produced by irradiating uranium or another transuranic element in a nuclear reactor, where neutrons are absorbed in the starting material and its subsequent reaction products, transmuting the starting material into the SF isotope.
		This nuclear reaction can be used to construct a neutron source by intermixing a radioisotope that emits alpha particles such as radium or polonium with a low atomic weight isotope, usually in the form of a mixture of powders of the two materials.
	en.wikipedia.org /wiki/Neutron_source (627 words)

	Neutron spectra
		The distribution of neutron energies in a reactor differs from the fission neutron spectrum due to the slowing down of neutrons in elastic and inelastic collisions with fuel, coolant and construction material.
		Hence, the contribution of these neutrons to the overall neutron flux in a sub-critical system with a typical neutron multiplication of ~25 will be marginal.
		Consequently, the average neutron energy in the nitride core is as large as 160 MeV, with a median energy of 220 keV.
	www.neutron.kth.se /courses/transmutation/Spectra/Spectra.html (1210 words)

	Portable Neutron Generators
		Neutron emission from the d-d reaction is slightly peaked in the forward (along the axis of the ion beam) direction.
		The neutron tube is, in turn, enclosed in a metal housing, the accelerator head, which is filled with a dielectric media to insulate the high voltage elements of the tube from the surroundings.
		Neutron generator with built in alpha particle detector uses an interesting physical property of the deuterium-tritium reaction, namely that the target emits an alpha particle simultaneously with, and at exactly at 180 degrees opposite to, each fast 14 MeV neutron produced.
	www.sciner.com /Neutron/Neutron_Generators_Basics.htm (1805 words)

	NEUTRON ACTIVATION ANALYSIS
		Neutron Activation Analysis (NAA) is a quantitative and qualitative method of high efficiency for the precise determination of a number of main-components and trace elements in different types of samples.
		But, as the neutron flux is rather low in comparison to a nuclear reactor their use in NAA is limited to the determination of elements of high activation cross section which are present in major concentrations.
		In the case of nuclear reactions induced by neutrons the radioactivity of the examined isotope depends on the flux of the neutrons and the cross section of the given nuclear reaction.
	www.reak.bme.hu /nti/Education/Wigner_Course/WignerManuals/Budapest/NEUTRON_ACTIVATION_ANALYSIS.htm (2941 words)

	[No title] (Site not responding. Last check: 2007-10-30)
		Neutron induced threshold reaction cross-sections and double differential cross-sections for non-elastic reactions were obtained using the geometry dependent hybrid exciton and evaporation models.
		Neutron flux and nuclear response calculations The main purpose of the IFMIF facility is to produce a neutron environment similar to a future fusion device in order to provide reasonable material irradiation conditions.
		This means, the neutron flux spectrum calculated at a given spatial point in the test cell is used to estimate the damage parameters at this point, as if there would be a differential small volume element of the material of interest.
	www.ubka.uni-karlsruhe.de /vvv/fzk/5868/5868.text (19993 words)

	NIST - Absolute Neutron Fluence Determination (Site not responding. Last check: 2007-10-30)
		It was recognized from the outset that the required accuracy for determination of neutron flux (or density) was among the most formidable challenges of the neutron lifetime project.
		The neutron monitor employed in the neutron decay measurement is designed to measure the neutron density in the beam.
		The neutron radiometer measures neutron flux by detecting the power produced by nuclear capture reactions in a target which totally absorbs an incident neutron beam.
	physics.nist.gov /Divisions/Div846/Gp3/FunPhys/fluence.html (1090 words)

	Method and apparatus for neutron radiation monitoring - Patent 4498007
		The neutron flux responsive element 14 comprises a series of four intrinsic silicon radiation sensors 20 connected in series between external terminals 16 and 18.
		Flux sensor 14 could be a single flux responsive element 20 instead of the illustrated series of four.
		Cumulative neutron flux is preferably detected while in an unpowered state since the neutron induced crystal damage is independent of applied bias.
	www.freepatentsonline.com /4498007.html (3117 words)

	Core Neutronics
		Core neutron flux level and distribution are passed to the NIS (Nuclear Instrumentation System) Model which simulates the source range (SRM), intermediate range (IRM) and local power range (LPRM) detectors and instrument channels.
		If the detector resides within the reactor core, the reconstructed flux level signal of the detector is multiplied by a fixed detector efficiency constant to convert the flux signal into a counts per second (cps) signal (for SRM detectors) or a percentage power signal (for IRM detectors).
		Note that this neutron flux, whether thermal or total, must be consistent with the neutron flux used to generate the previously (Section II) noted core averaged cross sections and reactivity worths.
	www.exitech.com /Models/core_neutronics.htm (3205 words)

	Lunar & Planetary Lab at The University of Arizona
		A second independent measure of epithermal neutrons is provided by the downward facing prism because it is shielded from the outside by sheets of cadmium and the other three prisms.
		Neutrons lose energy in the detector through multiple scattering collisions with the hydrogen and carbon nuclei that compose the scintillator.
		Because the neutron and the proton have the same mass, most of the energy is lost to proton recoils as a neutron scatters off a hydrogen nucleus.
	grs.lpl.arizona.edu /content/about/neutron (649 words)

	Compact Neutron Generators
		When pulsed neutron beams are used to examine a sample, it is possible to separate the different types of neutron-nuclei interactions after each neutron pulse.
		Accelerator-based neutron generators have been proposed for treating tumors via brachytherapy but the high energy accelerators necessary for the procedure are typically too large for hospital environments.
		Neutrons are emitted at all angles from the spherical generator.
	www.lbl.gov /Tech-Transfer/techs/lbnl1764.html (1281 words)

	CCC-0112: SAND-2, Neutron Flux Spectra from Multiple Foil Activation Experiment
		Neutron energy spectra are determined by an analysis of experimental activation detector data.
		The calculational procedure consists of the selection of a known flux spectrum form to serve as the initial approximation to the solution, and subsequent iteration to a form acceptable as an appropriate solution.
		The solution is specified either as time-integrated flux (fluence) for a pulsed environment or as a flux for a steady-state neutron environment.
	www.nea.fr /abs/html/ccc-0112.html (800 words)

	High Flux Isotope Reactor
		In the fuel element flux trap, a hydraulic rabbit tube provides access to the high thermal-neutron flux in the reactor for short-term irradiations, and other positions are ideal for fast-neutron irradiation-damage studies.
		The large flux of neutrons in the reflector outside the fuel of such a reactor may be tapped by extending empty "beam" tubes into the reflector, thus allowing neutrons to be beamed into experiments outside the reactor shielding.
		The HFIR is unique in the sense that it provides one of the highest steady-state neutron fluxes available in any of the world's reactors, and neutron currents from the four horizontal beam tubes are among the highest available.
	www.ornl.gov /sci/rrd/pages/hfir.html (2088 words)

	Neutron Flux
		neutrons are traveling through the material and how many centimeters they travel each second.
		all neutrons in one cubic centimeter during one second.
		The term neutron flux in some applications (for example, cross section measurement) is used
	www.tpub.com /content/doe/h1019v1/css/h1019v1_119.htm (323 words)

	neutron
		Neutron guides work exactly like fiber optic guides—they are rectangular conduits, typically, 5 × 10 centimeters (2 × 4 inches), whose inside surfaces may be coated with multiple layers of nickel that will reflect any neutrons that strike the surface at a glancing angle, if they are not traveling too fast.
		Because neutrons are now so important to so many fields of science and engineering, the upgrade program is carefully planned to minimize the time that the HFIR will be out of service and to complete the work before the HFBR at Brookhaven shuts down for a planned upgrade of its own.
		Neutron scattering investigations show that in healthy bones, collagen molecules form a regular nearby periodic array with an average spacing of about 1.5 nanometers, and minerals deposit in spaces along this array every 87 nanometers.
	www.ornl.gov /info/ornlreview/rev29-12/text/neutron.htm (2999 words)

	The Neutron Source : a high flux reactor
		The thermal neutron flux, in equilibrium with the heavy water moderator (300 K), has a peak in the Maxwellian distribution at 1.2 Å.
		In the reactor hall (see photo), neutron beams are available from thermal, hot and cold beam ports and from one cold neutron guide connected with the horizontal cold source.
		The vertical service tube is sufficiently large to incorporate a vertical neutron guide of 7 cm diameter constructed of aluminium and lined with a thin (0.15 mm) nickel tube.
	www.ill.fr /General/Reactor.html (731 words)

	Minimum activation martensitic alloys for surface disposal after exposure to neutron flux - Patent 4533406
		All elements will activate upon neutron bombardment, and only a relatively few elements have daughter radionuclides that decay quickly enough or are weak enough such that they could be disposed of as surface waste.
		Furthermore, it is established that austenitic steels increase in volume during exposure to a neutron flux, and swelling of austenitic steels is presently considered to be outside the acceptable design limits for dimension changes in nuclear reactors.
		Each additive to the melt must be analyzed, e.g., by neutron activation analysis or similarly sensitive spectrophotometry to determine the levels of the impurities in the additives to the melt, whereby final impurity levels are generally predetermined.
	www.freepatentsonline.com /4533406.html (3005 words)

	1
		–– With collisions with the moderator, neutrons are in thermal equilibirum.
		, of neutrons in thermal equilibrium is defined as
		Flux distribution is obtained by multiplying the neutron density distribution by the neutron speed as:
	www.nuc.berkeley.edu /waste/NE124/Section1.3.1/Section1.3.1.html (192 words)

	Neutron Flux Distributions in the Materials Testing Reactor. Part II. The 5 x 5 Loading - Storming Media
		Abstract: Flux distribution measurements have been made in the Materials Testing Reactor with the fuel elements arranged in a Symmetrica1 5 x 5 loading.
		Three-dimensional thermal neutron flux distribution maps were made for both clean, cold fuel elements and depleted, poisoned fuel elements.
		A qualitative comparison of the flux distribution is made between the 5 x 5 loading and the 3 x 9 north slab loading.
	www.stormingmedia.us /12/1271/A127123.html (130 words)

	Westinghouse Electric Company \| Products & Services (Site not responding. Last check: 2007-10-30)
		Flux maps are produced by successively passing a neutron-sensitive detector axially through the reactor core.
		Self-powered neutron detectors are located spatially throughout the reactor core in dedicated thimbles.
		Continuous in-core flux monitoring with a redundant controller to process the detector signals and provide flux data to the plant computer and operator displays.
	www.westinghousenuclear.com /C3b2a.asp (554 words)

	European Neutron-Muon Portal
		The continuous spallation neutron source SINQ - the first of its kind worldwide - began commissioning in December 1996.
		SINQ is the first, and up to now only, running neutron source which was consequently designed for and equipped with supermirror coated neutron guides.
		This together with the fact that the cold D2-source (recently upgraded with a re-entrant hole) contrary to reactors is placed in the flux maximum results in a cold neutron flux at the instruments far beyond that of neutron sources with a comparable thermal neutron flux.
	neutron.neutron-eu.net /n_about/n_where/europe/271 (269 words)

	Instinct Training Ltd. - Nuclear Plant Theory - Neutron Flux Distribution
		Explain the term 'relative flux shape' and sketch the radial and axial flux shapes for a homogeneous cylindrical reactor of constant K
		Indicate how the basic radial neutron flux shape is modulated by the periodic lattice structure of a heterogeneous reactor.
		will distort the axial flux shape, noting in particular the effect on the position and magnitude of the peak neutron flux, and the condition for the worst distortion.
	www.instinct-training.co.uk /nuclear/fd.htm (300 words)

	APOD: 2002 March 15 - Neutron Mars (Site not responding. Last check: 2007-10-30)
		As cosmic rays from interplanetary space penetrate the thin martian atmosphere and reach the surface they interact with elements in the upper layer of soil, scattering neutrons back into space.
		Tracking variations in absorption, neutron detectors can map changes in surface hydrogen content from orbit.
		Hydrogen content is taken as a surrogate measure of frozen water (H20), the most likely form of hydrogen close to the martian surface.
	antwrp.gsfc.nasa.gov /apod/ap020315.html (159 words)

	neutron flux - Storming Media
		Neutron and Electromagnetic Emissions During the 1990 May 24 Solar Flare Date: 13 DEC 96
		A Pressure Ionization Chamber for the Measurement of Neutron Fluxes at Tolerance Level in Portable Instruments Date: OCT 45
		Effect Of The Temperature Of The Moderator on The Velocity Distribution of Neutrons With Numerical Calculations For H As Moderator Date: 14 SEP 44
	www.stormingmedia.us /keywords/neutron_flux.html (449 words)

	Fast neutron flux spectrum aboard Mars Odyssey during cruise
		The energy spectrum of fast neutrons generated by interactions between galactic cosmic rays and the Mars Odyssey spacecraft during quiet interplanetary conditions is determined.
		The estimated ratio of this component of spacecraft neutron background to the Martian leakage flux in Mars orbit is expected to amount to between 0.30 and 0.34.
		The fast neutron flux between 0.7 and 6 MeV should only contribute 0.40 Roentgen Equivalent Man (rem) per year to the total radiation dose aboard a Mars Odyssey class spacecraft at solar maximum.
	www.agu.org /pubs/crossref/2002.../2001JA000295.shtml (315 words)

	Calcium - Wikipedia, the free encyclopedia
		Ca, has a nucleus of 20 protons and 20 neutrons.
		Its electron configuration is: 2 electrons in the K shell (principal quantum number 1), 8 in the L shell (principal quantum number 2), 8 in the M shell (principal quantum number 3), and 2 in the N shell (principal quantum number 4).
		Most of its production is in the upper metre or so of the soil column where the cosmogenic neutron flux is still sufficiently strong.
	en.wikipedia.org /wiki/Calcium (1403 words)

	NEA-0900: TPHEX, MultiGroup Neutron Flux in Homogeneous Hexagonal LWR Cells
		The flux at each cell interface is divided azimuthally into 60-degree sectors, with two components (an incomplete P1 expansion) in each sector.
		The interface fluxes are connected by transmission of uncollided neutrons through the cell.
		However, since 48 variables are needed to describe the flux and source in each cell and group, and since many coefficients are also needed, large problems (more than about 225 cells) may require lots of memory, even though only data for one group at a time are held in memory.
	www.nea.fr /abs/html/nea-0900.html (1062 words)

	Neutron Flux Spectrum Summary
		The neutron flux spectrum for the fast energy region of a thermal reactor has a
		shape similar to that of the spectrum of neutrons emitted by the fission process.
		The neutron flux spectrum for the slow region of a thermal reactor contains a
	www.tpub.com /content/doe/h1019v1/css/h1019v1_141.htm (222 words)

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