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Topic: Thermal neutron

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	Info and facts on 'Thermal neutron' (Site not responding. Last check: 2007-10-08)
		A thermal neutron is a free neutron (additional info and facts about free neutron) with a kinetic energy (The mechanical energy that a body has by virtue of its motion) level of ca.
		After a number of collisions with nuclei, neutron (An elementary particle with 0 charge and mass about equal to a proton; enters into the structure of the atomic nucleus) s arrive at this energy level, provided that they are not absorbed.
		Thermal reactor (A nuclear reactor in which nuclear fissions are caused by neutrons that are slowed down by a moderator)
	www.absoluteastronomy.com /encyclopedia/t/th/thermal_neutron.htm (178 words)

	Encyclopedia: Neutron (Site not responding. Last check: 2007-10-08)
		The neutron and proton are instances of a nucleon.
		Neutron bombs, also called enhanced radiation bombs (ER weapons), are small thermonuclear weapons in which the burst of neutrons generated by the fusion reaction is intentionally not absorbed inside the weapon, but allowed to escape.
		The neutrons are responsible for the remaining mass of the atom.
	www.nationmaster.com /encyclopedia/Neutron (684 words)

	Neutron - Encyclopedia.WorldSearch (Site not responding. Last check: 2007-10-08)
		Outside the nucleus, neutrons are unstable and have a half-life of about 10 minutes, decaying by emitting an electron and antineutrino to become a proton.
		Particles inside the nucleus are typically resonances between neutrons and protons, which transform into one another by the emission and absorption of pions.
		The neutron, however, is unaffected by such forces; it is affected only by the very short-range strong and weak nuclear forces which comes into play when the neutron comes very close indeed to an atomic nucleus.
	encyclopedia.worldsearch.com /neutron.htm (924 words)

	Neutron moderator - Wikipedia, the free encyclopedia
		In nuclear engineering, a neutron moderator is a medium which reduces the velocity of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction.
		After sufficiently many such impacts, the velocity of the neutron will be comparable to the thermal velocities of the nuclei; this neutron is then called a thermal neutron.
		In a thermal nuclear reactor, the nucleus of a heavy fuel element such as uranium absorbs a slow-moving free neutron, becomes unstable, and then splits into two smaller atoms.
	en.wikipedia.org /wiki/Neutron_moderator (616 words)

	[No title] (Site not responding. Last check: 2007-10-08)
		A neutron emitting radioisotopic source is placed on one side of the chute or conveyor belt, and a set of gamma-ray detectors is placed on the other side or at a position adjacent to the neutron source.
		The measurement of the combination of fast and thermal neutrons is used for the establishment of the total hydrogen content of the material sample, and subsequently the moisture of the flowing material.
		Neutron detector 16 is a monitor of the fast neutron yield from the neutron generator.
	www.wipo.int /cgi-pct/guest/getbykey5?KEY=00/03237.000120&ELEMENT_SET=DECL (3758 words)

	Glossary - T
		The Thermal Decay Time Log is a record of the rate of capture of thermal neutrons in a portion of formation after it is bombarded with a burst of 14-MeV neutrons.
		The thermalized neutrons are gradually captured by elements within the neutron cloud, and, with each capture, gamma rays are emitted.
		Because chlorine is by far the strongest neutron absorber of the common earth elements, the response of the tool is determined primarily by the chlorine present (as sodium chloride) in the formation water.
	www.spwla.org /library_info/glossary/reference/glosst/glosst.htm (3376 words)

	Thermal Neutron Scattering
		The neutron by itself is "almost" stable in that it has a mean lifetime of 11 minutes before it decays (into a proton, electron and neutrino) which is a long time by particle-physics standards, and it is stabilized by combining roughly equal numbers of neutrons and protons in a nucleus of an element.
		Neutrons are produced copiously in the cores of nuclear reactors, and when particle accelerator main beams (usually protons or electrons) strike a target.
		The neutrons useful for determining magnetic ordering structures have energies corresponding to thermal equilibrium at room temperature (or colder), and those are what are produced in a nuclear reactor running at room temperature.
	www.vsu.edu /pages/488.asp (697 words)

	[No title] (Site not responding. Last check: 2007-10-08)
		As used herein, thermal neutrons are neutrons that have kinetic energy on the order of kT, where k is Boltzman's constant and T is temperature in Kelvin; fast neutrons are neutrons with kinetic energy greater that kT, typically much greater, e.
		Neutron light guide/scintillator 150, with an efficiency for detecting gamma rays of only 2 x 10-9, will typically not be alerted by modest gamma ray sources compared to the preceding security standard for neutron emission from plutonium.
		The apparatus of Claim 8, wherein the neutron scintillator comprises a thermal neutron capturing isotope coupled to a scintillation component that scintillates upon exposure of the capturing isotope to thermal neutrons.
	www.wipo.int /cgi-pct/guest/getbykey5?KEY=04/109331.041216&ELEMENT_SET=DECL (8851 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 (651 words)

	Neutron (Site not responding. Last check: 2007-10-08)
		A neutron moisture gauge consists of a source of fast (high-energy) neutrons, a thermal neutron detector, and the associated...
		Neutron scattering plays a truly unique role in that it is the only...
		In 1930 Walther Bothe and H. Becker in Germany found that if the very energetic natural alpha particles from polonium fell on certain of the light elements, specifically beryllium, boron, or lithium, an unusually penetrating radiation was produced.
	hallencyclopedia.com /Neutron (1188 words)

	Long-Term, Neutron-Monitoring Tags- (Site not responding. Last check: 2007-10-08)
		Neutrons are produced in special nuclear materials due to fission, as well as from possible (alpha, neutron) reactions.
		Including the efficiency of neutron detection and the solid angle of the detector, a total count of 103–104 is expected assuming 10 percent of the neutrons are thermalized.
		This GaAs-based thermal neutron detector is self-biased (the voltage across the junctions is sufficient to bias the detector), thus removing one of the technical challenges to implementing these detectors.
	rdc.llnl.gov /rdp/long_term.html (407 words)

	ipedia.com: Thermal neutron Article (Site not responding. Last check: 2007-10-08)
		A thermal neutron is a free neutron with a kinetic energy level of less than 0.025 eV (approx.
		They are named 'thermal' as this level of kinetic energy is similar to the average kinetic energy of a room-temperature gas.
		Many fission reactorss use a neutron moderator to slow down, or thermalize the neutrons that are emitted by nuclear fission so that they are more easily captured, causing further fission.
	www.ipedia.com /thermal_neutron.html (201 words)

	NEA Nuclear Science: WPEC - Volume 3
		Thermal nuclear constants for the primary actinides have been extensively studies, but the most recent evaluations are not in full agreement with thermal reactor calculations.
		Nowadays, the use of thorium fuel cycle in thermal neutron reactors is no longer a high priority and the physicists’ interest for thorium nuclear data is less important in the case of low energy neutron than in the fast range.
		The detailed energy-dependence of neutron cross-sections and related parameters of fissile nuclei for sub-thermal neutron energies has recently found considerable attention because of its effect on the temperature reactivity coefficient of thermal reactors [1].
	www.nea.fr /html/science/wpec/volume3/volume3.html (5532 words)

	Neutron Radiography and Neutron Activation Analysis Source
		The neutrons are attenuated by elements in the object with high thermal neutron attenuation coefficients as the beam passes through.
		The result is a negative image of the object, with the light areas indicating the greatest neutron attenuation by the object, and the dark areas indicating the least neutron attenuation.
		Neutron Activation Analysis (NAA) is a sensitive analytical technique useful for performing both qualitative and quantitative multi-element analysis of major, minor, and trace elements in samples from almost every conceivable field of scientific or technical interest.
	www.linac.com /hpg-0440.htm (529 words)

	Neutron stars
		Neutron stars are believed to form in supernovae such as the one that formed the Crab Nebula (or check out this cool X-ray image of the nebula, from the Chandra X-ray Observatory).
		Another example is thermal pair bremsstrahlung in the crust, where an electron passes by a nucleus and, instead of emitting a single photon as in standard bremsstrahlung, emits a neutrino-antineutrino pair.
		Neutrons were discovered in 1932, and very shortly afterward (in 1934) a suggestion was made by Walter Baade and Fritz Zwicky that neutron stars were formed in supernovae.
	www.astro.umd.edu /~miller/nstar.html (6455 words)

	THERMAL NEUTRON INSTRUMENTATION
		The thermal neutron instruments at the NCNR are housed in the confinement building.
		A project to modernize the older neutron scattering instruments in the confinement building will be implemented over the next few years.
		Thermal neutrons are employed at the NCNR for a wide variety of applications other than neutron scattering, such as maintaining radiation and dosimetry standards, development of radiation detectors, and neutron activation analysis studies for the Food and Drug Administration, the Federal Bureau of Investigation, and a number of other government agencies, industries, and universities.
	www.ncnr.nist.gov /instruments/therminstr.html (255 words)

	NIST Calibration Services: Neutron Sources and Neutron Dosimetry
		Neutron source emission rates are determined by the manganous sulfate bath method, in which the emission–rate of the source to be calibrated is compared to the emission–rate of NBS–1, the national standard Ra–Be photoneutron source.
		Neutron personnel instruments, both passive (e.g., dosimeters) and active (e.g., remmeters) are calibrated on the basis of a certified free–field dose–equivalent or dose equivalent rate.
		Passive neutron detectors, generally activation foils, can be irradiated to a certified neutron fluence (or average fluence–rate) in a fission neutron spectrum or by a Maxwellian thermal neutron field.
	ts.nist.gov /ts/htdocs/230/233/calibrations/ionizing-rad/neutron.htm (663 words)

	MIT Nuclear Reactor Laboratory: Facilities
		The neutron flux and fast-to-thermal flux ratio are similar to a Light Water Reactor.
		Thermal Neutron Beam: A high intensity, and low contamination thermal neutron beam is also available at MITR.
		The thermal neutron beam facility is well suited for small animal studies and for clinical studies of superficial tumors.
	web.mit.edu /nrl/www/facilities/facilities.htm (276 words)

	THERMAL NEUTRON BEAM MODIFICATION STUDIES USING AN ISOTOPE BASED NEUTRON RADIOGRAPHY FACILITY (Site not responding. Last check: 2007-10-08)
		Thermal neutron radiography is emerging as powerful non- destructive inspection technique due to very specific attenuation behaviour of thermal neutrons.
		Neutron radiographic facilities using isotopic neutron source particularly Cf-252 are being developed world wide to extend the foreseeable advantages of this techniques to more areas of interest and make facilities available for inplant use.
		The image quality obtained in thermal neutron radiography is mostly dependent on beam parameters like thermal neutron content (Nc), L/D ratio, n/r ratio etc. these parameters can be varied by changing some of the design parameters of isotope based neutron radiography facility.
	www.ndt.net /abstract/wcndt96/data2/491.htm (272 words)

	Compact accelerator neutron generators - The Industrial Physicist
		Most compact accelerator neutron tubes are loaded with 1 to 2 Ci of tritium; for comparison, a typical tritium exit sign used in an airplane or hotel might contain as much as 10 to 20 Ci of the isotope.
		In the coal industry, on-line measurements have found particular use in reporting the thermal energy and sulfur content of coal and for determining the fraction of the coal that is not hydrocarbon and will remain as ash after combustion.
		Using this information, outgoing neutrons can be identified by their emission angles and times, and used with external gamma-ray detectors and gating circuitry to acquire three-dimensional elemental information within objects (Figure 1).
	www.aip.org /tip/INPHFA/vol-9/iss-6/p22.html (1904 words)

	THERMAL NEUTRON MODERNIZATION PROGRAM
		The goal is to design the necessary safety features into the new instruments in order to accommodate new radiation safety guidelines, to substantially reduce planned exposures of personnel during normal operation, and dramatically reduce the possibility of an accidental radiation exposure.
		The triple-axis spectrometer is the work-horse for inelastic scattering studies at steady-state neutron sources.
		The current plan is to replace these with two double-focusing thermal neutron triple-axis spectrometers, one dedicated Be-filter spectrometer (FANS), and one horizontally focused sub-thermal (2-20 meV) triple axis spectrometer.
	www.ncnr.nist.gov /instruments/modernize.html (601 words)

	ne150 \| Nuclear Engineering, UC, Berkeley
		review those aspects of neutron interactions with matter that are pertinent to understanding the establishment of a chain-reaction and of the neutron space- and energy-distribution in the nuclear reactor core.
		calculate spectrum-averaged microscopic cross-sections for thermal neutrons, macroscopic cross-sections for a single isotope and for a mixture of isotopes, reaction probabilities, mean-free-path, mean time for collision, mean energy loss per elastic collision.
		Introduction to neutron diffusion theory: neutron flux and current, equation of continuity, Fick's law, transport corrections; the diffusion equation for monoenergetic neutrons, boundary conditions; elementary solutions of the steady-state diffusion equation, solutions for multiplying media, multi-group diffusion equations; solution of the two-group diffusion equation.
	www.nuc.berkeley.edu /courses/classes/ne150.html (1014 words)

	1994 Annual Symposium Paper G
		The analytical code used to model the density log was benchmarked against published calibration data and Monte Carlo calculations, while the thermal neutron porosity code had been previously benchmarked against published data.
		These interpretation problems can be particularly acute as manifested on the density/thermal neutron crossplot when invasion has progressed to the point where the flushed zone represents an infinite medium to the density tool, while the thermal neutron porosity device is still strongly influenced by the non-invaded zone.
		The effects of invasion on density/thermal neutron porosity interpretation were investigated by examining four interpretation techniques for gas-filled clean sandstone and shaly sandstone.
	www.spwla.org /library_info/abstract/sympo/1990/1994PaperG.html (370 words)

	The Distribution of Thermal Neutron Cross Sections (Yuri V. Petrov and Alexander I. Shlyakhter) (Site not responding. Last check: 2007-10-08)
		An estimate of the cross sections of nuclear reactions with thermal neutrons in terms of the average parameters of the target nucleus (the strength function, the average level spacing, and the average reaction width) is obtained.
		The probability distributions for the ratios of actual thermal neutron cross sections to their estimated values are introduced.
		They are calculated for neutron radiative capture and for inelastic neutron acceleration by the isomeric nuclei (as weell as the (n,α) reaction, etc.).
	theory.lcs.mit.edu /~ilya_shl/alex/thermal_neutron_cross_sections.html (120 words)

	Active Skim View of: 3. Thermal-Neutron and Fast-Neutron Measurements
		Thermal and epithermal neutrons have ranges of only a few meters in air and thus are produced ' + 'locally.
		Assuming that most of the neutrons originate from ' + 'a point isotropic source at the epicenter, one would expect the thermal fluence, and thus thermal activation, to decrease approximately exponentially with ' + 'distance, provided that the spectral distribution of neutrons in the epithermal and thermal region remained about the same.
		With the new measurement of fast neutrons using 63Ni, it is hoped that it will be possible to reconstruct a neutron source directly ' + 'from the fast-neutron measurements combined with the augmented thermal-neutron data.
	www.nap.edu /nap-cgi/skimit.cgi?isbn=0309075599&chap=31-59 (10394 words)

	[No title]
		In an experiment designed to measure the total cross section of lead for 10 MeV neutrons, it was found that a 1-cm-thick lead absorber attenuated the neutron flux to 84.5% of its initial value.
		A sample containing an unknown quantity of chromium is irradiated for 1 week in a thermal neutron flux of 1011 n/cm2/s.
		The reaction in this case is 50Cr + EMBED Equation.3 The thermal neutron activation cross section for 50Cr is 13.5 barns, and 50Cr forms 4.31% by number of the naturally occurring chromium atoms.
	web.mit.edu /22.04/www/pset/pset4.doc (614 words)

	Nat' Academies Press, Nuclear Wastes: Technologies for Separations and Transmutation (1996)
		Am have large thermal neutron capture cross sections and are parasitic absorbers in thermal reactors.
		Hence, for thermal neutron transmutation concepts, significant neutron emission could present problems during fuel reprocessing and refabrication, quality assurance, and performance verification.
		The work to date consists primarily of a conceptual analysis of the effects of the neutrons generated in either approach in order to estimate the benefits and hazards that would result from changing the character of the waste to be disposed.
	www.nap.edu /books/0309052262/html/51.html (989 words)

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