
	Where results make sense

Topic: Neutron moderator

Related Topics

Fast neutron

Thermal neutron

Neutron

Chain reaction

Pressurized water reactor

Nuclear power plant

Moderator

Heavy water

Radioisotope

Alcohol fuel

Hydrogen

Electronvolt

David Hahn

Carbon

Buckyball

In the News (Fri 27 Nov 09)

Northern Trust

Marvin Harrison

Peter Chernin

Gary Locke

Match Play

Penelope Cruz

Mickey Rourke

AR Rahman

Danny Boyle

Hugh Jackman

	ASQ Home Page Template
		Thermal neutrons are extracted to the experimental areas in 4 sectors of the target block.
		This "cold neutron source" is situated in a horizontal insert inside the moderator tank and near the target, where the thermal neutron flux has its maximum.
		The vertical and horizontal inserts of the cold neutron source are enclosed in vacuum for thermal insulation and in a protective gas enclosure for prevention of potentially explosive hydrogen-oxygen mixtures in case of a leak in the system.
	asq.web.psi.ch /ASQ/facilities/SINQSYSTEMS.html (1289 words)

	Neutron Activation of Silver
		Thermal neutrons, which are neutrons in thermal equilibrium with their surroundings, can be produced by passing neutrons through materials containing a high concentration of light nuclei.
		After neutron irradiation, the foil is removed from the neutron flux and the induced activity (beta decay) is measured using a thin-walled Geiger counter.
		However, the neutron source should be well shielded from the counter, and at a sufficient distance so that the background count is not raised appreciably by gamma rays from the radium.
	www.fas.harvard.edu /~scidemos/QuantumRelativity/NeutronActivationofSilver/NeutronActivationofSilver.html (1264 words)

	Neutron moderator - Definition, explanation
		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 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.
		Because more free neutrons are released from a uranium fission event than are required to initiate the event, the reaction can become self sustaining--a chain reaction --under controlled conditions, thus producing a tremendous amount of energy.
	www.calsky.com /lexikon/en/txt/n/ne/neutron_moderator.php (299 words)

	Glossary
		Alpha particles are helium nuclei, with 2 protons and 2 neutrons.
		Deuterium: "Heavy hydrogen", a stable isotope having one proton and one neutron in the nucleus.
		Moderator: A material such as light or heavy water or graphite used in a reactor to slow down fast neutrons by collision with lighter nuclei so as to expedite further fission.
	www.world-nuclear.org /info/inf51.html (2742 words)

	NIST Center for Neutron Research
		Neutron tomography gives 3D images of water in a proton exchange membrane fuel cell.
		Neutron interferometry, neutron radiography, and fundamental physics using neutrons are active research areas at the NCNR
		The project comprises development of a new cold neutron moderator, and a new guide hall with five state-of-the-art instruments.
	www.ncnr.nist.gov (278 words)

	Energy: Explore & Exploit...
		In this case the chain reaction is sustained by fast neutrons, without the use of moderators.
		The fuel is 20% plutonium dioxide and 80% uranium dioxide.
		The reactor core is surrounded with clean uranium-238, which, by neutron capturing and by two beta decays, turns into plutonium, later processed and used as fuel.
	library.thinkquest.org /05aug/01522/nuclear5.html (824 words)

	Method and apparatus for measuring the concentration of a component, for instance iron, in a material - Patent 4028267
		This process is called moderation and the hydrogen containing material in the plug 15 and the container 5 consequently serves as a moderator for the neutrons which get an energy distribution which considerably increases the probability of the desired capture of neutrons in the material 10 to be measured.
		The thermal neutrons from the moderators are captured by (and stay in) the nuclei of the material 10 and thereby immediately produce an emission of gamma rays, the energy of which (or wave length) is characteristic of the emitting nucleus (basic element).
		Neutron radiation may in certain processes give rise to disturbing signals from the detector and such influence may be suppressed by the boron-containing plastic 22 in the vessel 21.
	www.freepatentsonline.com /4028267.html (3009 words)

	SINQ
		Neutron scattering is one of the most effective ways to obtain information on both, the structure and the dynamics of condensed matter.
		Beside thermal neutrons, a cold moderator of liquid deuterium (cold source) slows neutrons down and shifts their spectrum to lower energies.
		These neutrons have proved to be particularly valuable in materials research and in the investigation of biological substances.
	sinq.web.psi.ch (185 words)

	Low Energy Neutron Source (LENS): Indiana University Cyclotron Facility
		The standard LENS moderator is capable of accurately condensing various gas mixtures, and the facility is capable of characterizing any moderator prototype that can fit within the 50cm diameter/50 cm tall cylindrical water reflector volume (assuming compatibility with the standard Be target geometry is maintained).
		The emphasis on cold and very cold neutrons makes it suitable for materials research, particularly in the area of nanoscale structures which are a research focus of many universities in the region.
		LENS is a neutron scattering facility with a three-fold mission: to conduct materials research with neutrons, develop new neutron instrumentation for both fundamental and applied research, and to enhance education in the science and technology of neutrons at all levels.
	www.iucf.indiana.edu /lens (1612 words)

	Neutron Reflection from H/D containing materials
		The specular reflection, measured as a function of the scattering vector Q perpendicular to the reflecting surface, is related to the neutron refractive index profile normal to the interface or surface.
		The essence of a neutron reflection experiment is to measure the neutron reflectivity (or reflected intensity) as a function of the scattering vector, Q, perpendicular to the reflecting surface.
		A model consistent with both the neutron reflectivity and NRA gives a structure with polystyrene rich phases which wet both the air and substrate interfaces and are separated by a polybutadiene rich phase.
	www.isis.rl.ac.uk /largescale/Crisp/documents/neut_refl_HD.htm (4065 words)

	Reference.com/Encyclopedia/Neutron moderator
		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.
		Because more free neutrons are released from a uranium fission event than are required to initiate the event, the reaction can become self sustaining — a chain reaction — under controlled conditions, thus liberating a tremendous amount of energy.
		Some pebble-bed reactor's moderators are not only simple, but also inexpensive: the nuclear fuel is embedded in spheres of reactor-grade pyrolytic carbon, roughly of the size of tennis balls.
	www.reference.com /browse/wiki/Neutron_moderator (940 words)

	RTFTechnologies Neutron Detector (Site not responding. Last check: )
		The detection and quantification of neutron output from an IEC fusor is critical for proving that fusion is occurring.
		Since neutrons have no charge, they can not be counted by conventional instruments that detect the presence of ionizing particles, such as geiger counters or ionization chambers.
		Neutrons must be quantified by their interaction with other nuclei in a detection system.
	www.rtftechnologies.org /physics/neutron-detector.htm (795 words)

	neutron_moderator - The Wordbook 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.
		Because more free neutrons are released from a uranium fission event than are required to initiate the event, the reaction can become self sustaining — a chain reaction — under controlled conditions, thus liberating a tremendous amount of energy.
		The newly-released fast neutrons, moving at roughly 10% the vacuum speed of light, must be slowed down or "moderated", typically to speeds of a few kilometers per second, if they are likely to cause further fission in neighbouring uranium nuclei and hence continue the chain reaction.
	www.thewordbook.com /neutron_moderator (963 words)

	Cylindrical neutron generator - Patent 6907097
		The cylindrical neutron generator of claim 23 wherein the extracting means comprises a cylindrical extraction electrode on the outer or inner surface of the ion source and having a plurality of axially extending slots.
		The cylindrical neutron generator of claim 24 wherein the extracting means comprises a cylindrical plasma electrode inside and spaced apart from the extraction electrode and having a plurality of axially extending slots aligned with the slots in the extraction electrode.
		In one embodiment the plasma generator is in the center and the neutron target is on the outside, and in the second embodiment, the plasma generator is on the outside and the target is on the inside.
	www.freepatentsonline.com /6907097.html (4617 words)

	NUKEFACTS ... and fictions
		The neutron generation time is the time interval required by a generation of fictious neutrons to traverse one life cycle, which consists of six distinct interactions that occur in sequence over time.
		The neutron generation time starts at the instant of fission, when the generation of neutrons is born, and ends at the instant these neutrons create fissions to initiate the next generation of neutrons.
		Since neutrons may be classifed by more than one criterion, including time of appearance after fission, energy at the time of release, average lifetime of the neutron, and the emitting entity or event, special care must taken to ensure that only one correct answer is provided.
	www.pipeline.com /~rstater/nrcneutron.html (1519 words)

	New pulsed cold neutron beam line for fundamental nuclear physics at LANSCE Journal of Research of the National ...
		The brightness of the moderator was estimated by MCNP modeling [5,6].
		During the moderation process, neutrons in a thermal energy range experience more than one collision with hydrogen molecules in the moderator and with particles in the Be-reflector that surrounds the moderator.
		Neutrons from the moderator enter the 21 m long straight m = [[theta].sub.c]/[[theta].sub.c]([.sup.nat]Ni) = 3 SM neutron guide [9], where [[theta].sub.c] is the critical angle of reflection.
	www.findarticles.com /p/articles/mi_m0IKZ/is_3_110/ai_n15397385 (912 words)

	Brazilian Journal of Physics - A direct measurement of the neutron-neutron scattering length (Site not responding. Last check: )
		A neutron moderator is installed in the central through channel and the scattered neutrons are detected at a distance of 12 m from the reactor.
		The neutrons collide in a neutron interaction chamber, which we denote as the nn-cavity, and the scattered neutrons are detected externally.
		Neutron activation studies were performed to measure the thermal neutron densities inside cylindrical converters inserted into the YAGUAR reactor channel.
	www.scielo.br /scielo.php?pid=S0103-97332005000500036&script=sci_arttext&tlng=en (1849 words)

	Dictionary of Nuclear Terms
		Neutrons travelling with a speed close to that with which they were ejected from the fissioning nucleus, typically about 20,000 km s-1.
		A proton or a neutron, the particles from which all atomic nuclei are composed.
		In neutron radiography, a beam of thermal neutrons is used.
	www.arrowtechinc.com /dictionary_terms.htm (3750 words)

	(S-8) Nuclear Energy
		Free neutrons are not found in nature (they would decay into protons and electrons), but they can be released from atoms of beryllium by bombarding them with alpha particles from radioactive materials, or by other methods.
		Neutrons produced in a rod generally escape into the moderator, and by the time they hit another rod, they are moving very slowly: such slow neutrons are gobbled up much more avidly by U-235 than by U-238, so that even in a rod containing only 0.7% U-235, the U-235 atoms make most of the "catches.
		It should be added that many neutrons are also lost--escaping from the edges of the reactor into the surrounding material, or being absorbed inside it by the " wrong " nuclei, the ones which do not undergo fission.
	www-istp.gsfc.nasa.gov /stargaze/Snuclear.htm (3299 words)

	Lunar & Planetary Lab at The University of Arizona
		As it turns out, hydrogen is a very good moderator of neutrons and hence the detector is quite sensitive to the presence of hydrogen on the surface (to a depth of about one meter) of Mars.
		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)

	PSU Neutron Beam Group (NBG) - Neutron Beam Laboratory Expansion
		The Neutron Beam Laboratory (NBL) is one of the experimental facilities at the RSEC.
		Well-collimated beams of neutrons, thermalized by a D 2 0, are passed into the NBL for use in various neutron beam techniques.
		In steady state operation at 1 MW, the thermal neutron flux is 1x10 13 n/cm 2 sec at the edge of the core and 3x10 13 n/cm 2 sec at the central thimble.
	www.engr.psu.edu /nbg/NeutronBeamPortModeling.htm (1119 words)

	An Exceptional Nuclear Glossary
		Delayed neutrons account for approximately 0.75% of the neutron output from fission and this is an important aspect of controlling the increase in energy output of reactors.
		Absorption of a neutron by an atomic nucleus.
		Neutrons in one generation that are successfully moderated and that induce further fission reactions produce a new generation of neutrons.
	www.dataenabled.com /nuclearglossary/suites/nuclearglossary_neutrons.html (706 words)

	(S-8) Nuclear Energy
		Free neutrons are not found in nature (they would decay into protons and electrons), but they can be released from atoms of beryllium by bombarding them with alpha particles from radioactive materials, or by other methods.
		Neutrons produced in a rod generally escape into the moderator, and by the time they hit another rod, they are moving very slowly: such slow neutrons are gobbled up much more avidly by U-235 than by U-238, so that even in a rod containing only 0.7% U-235, the U-235 atoms make most of the "catches.
		It should be added that many neutrons are also lost--escaping from the edges of the reactor into the surrounding material, or being absorbed inside it by the " wrong " nuclei, the ones which do not undergo fission.
	www-spof.gsfc.nasa.gov /stargaze/Snuclear.htm (3299 words)

	Instrument Systems - Instruments - Elastic Spectrometers - Magnetism Reflectometer (Site not responding. Last check: )
		Neutrons from the moderator are guided to the sample position at a distance of 18.5 m via a combination of a short channel beam bender and a tapered neutron guide.
		Neutrons that are reflected/diffracted by the sample will be counted by a two-dimensional multidetector at a 20 m distance from the moderator.
		Besides the conventional use of a neutron reflectometer to analyze the structural and magnetic depth profiles of thin film structures, complementary kinetic studies (for example, probing the dynamic behavior of magnetic domains) are feasible.
	www.sns.gov /users/instrument_systems/instruments/elastic/magnet.shtml (741 words)

	New pulsed cold neutron beam line for fundamental nuclear physics at LANSCE Journal of Research of the National ...
		Energetic neutrons from the spallation process are moderated with water or cold-hydrogen moderators.
		Since the sensitivity of the NPDGamma experiment is determined by the neutron statistics, we decided to measure the brightness of the FP12 moderator.
		When this system is moved farther from the beam axis, neutrons have to have larger glancing angles in order to enter the detector: they go through a number of reflections in the guide.
	findarticles.com /p/articles/mi_m0IKZ/is_3_110/ai_n15397385 (895 words)

	H2Incidents: Liquid Hydrogen Neutron Moderator Leak
		A liquid hydrogen neutron moderator developed a leak between the canister that contains liquid hydrogen and the insulating vacuum jacket.
		The moderator canister is constructed of aluminum and is approximately five inches wide, five inches high, and two inches deep.
		Since the moderator is constrained and not readily accessible by personnel, inspections could not be performed to determine the exact location or cause of the leak.
	www.h2incidents.org /incident.asp?inc=68 (256 words)

Try your search on: Qwika (all wikis)