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Topic: Critical mass (nuclear)

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Critical mass - Wikipedia, the free encyclopedia The critical mass of a fissionable material depends upon the nuclear (eg the nuclear fission cross-section) and physical properties of the material, its geometry (shape), and its purity, as well as whether it is surrounded by a neutron reflector or interrupted by an absorber. In the case of a sphere surrounded by a neutron reflector the critical mass is about 15 kg for uranium-235 (20 to 25 kg for a gun-type assembly) and 10 kg for plutonium-239. The realisation that a supercritical assembly is not necessarily prompt critical is attributed to Enrico Fermi, and made the construction of a nuclear reactor using a fission chain reaction possible. en.wikipedia.org /wiki/Critical_mass

Critical mass - Wikipedia, the free encyclopedia The critical mass of fissile material is the amount needed for a sustained nuclear chain reaction. In the case of a sphere surrounded by a neutron reflector the critical mass is about 15 kg for uranium-235 (20 to 25 kg for a gun-type assembly) and 10 kg for plutonium-239. The realisation that a supercritical assembly is not necessarily prompt critical is attributed to Enrico Fermi, and made the construction of a nuclear reactor using a fission chain reaction possible. en.wikipedia.org /wiki/Critical_mass_(nuclear)   (1964 words)

Uranium-235 Chain Reaction A fission chain reaction produces intermediate mass fragments which are highly radioactive and produce further energy by their radioactive decay. A critical chain reaction can be achieved at low concentrations of U-235 if the neutrons from fission are moderated to lower their speed, since the probability for fission with slow neutrons is greater. If the reaction will sustain itself, it is said to be "critical", and the mass of U-235 required to produced the critical condition is said to be a "critical mass". hyperphysics.phy-astr.gsu.edu /hbase/nucene/u235chn.html   (141 words)

Public Citizen Critical Mass Energy and Environment Program Critical Mass Energy and Environment Program - House Republicans' Desperate Push to Force Passage of Regressive Energy Legislation: Even in its pared-down form, the energy bill would be a windfall for the oil, gas, and nuclear industries, but a disaster for consumers, taxpayers, and the environment. Will provide $1.1 billion  for an experimental nuclear plant in Idaho that would cogenerate electricity and hydrogen, undermining hydrogen’s clean potential Allocates $865 million  for research and development of nuclear reprocessing technologies www.stopenergybill.org   (141 words)

Energy Citations Database (ECD) - Energy and Energy-Related Bibliographic Citations Propulsion systems based on critical mass devices are clearly feasible, so the primary problem is to reduce the size of the explosive devices so that a critical mass is not required. If pulse nuclear fusion propulsion can become a reality then the performance is enough to complete manned missions to the inner planets in weeks and the outer planets in months. Concepts based on inertial confinement fusion are heavier than those that use antiprotons for the trigger due to the mass associated with the lasers, or particle beams and their power supplies. www.osti.gov /energycitations/product.biblio.jsp?osti_id=20506850   (421 words)

Prompt critical - Wikipedia, the free encyclopedia Indeed, one of the problems to be overcome in constructing a plutonium-fueled bomb is to achieve prompt criticality and an explosion before the energy released by the reaction in an assembly that is merely supercritical destroys the bomb. Thus, a prompt critical mass is a supercritical mass that is supercritical without needing the contribution of neutrons whose release is delayed after the triggering of each fission event. Prompt criticality must be avoided in the operation of a nuclear reactor, and reactors are designed to make it as unlikely as possible that it will occur. en.wikipedia.org /wiki/Prompt_critical   (899 words)

Remarks as prepared for delivery by Director of Central Intelligence George J. Tenet at Georgetown University February 5, 2004 This was critical when the Libyans approached British and US intelligence about dismantling their chemical, biological and nuclear weapons programs.  They came to the British and American intelligence  because they knew we could keep the negotiations secret. In the Estimate, all agencies agreed that Saddam wanted nuclear weapons.  Most were convinced that he still had a program and if he obtained fissile material he could have a weapon within a year.  But we detected no such acquisition. Most agencies believed that Saddam had begun to reconstitute his nuclear program, but they disagreed on a number of issues such as which procurement activities were designed to support his nuclear program. www.cia.gov /cia/public_affairs/speeches/2004/tenet_georgetownspeech_02052004.html   (4513 words)

Nuclear Weapons Program - North Korea Since 20-kiloton standard nuclear warhead has 8 kilograms of critical mass, this amounts to mass of material of nuclear fission out of which about 3 nuclear warheads could be extracted. The two 1,000 MW light-water nuclear reactors would be safer and would produce much less plutonium, in order to help boost the supply of electricity in the North, which is now in a critical shortage. In the 1970s it focused study on the nuclear fuel cycle including refining, conversion and fabrication. fas.org /nuke/guide/dprk/nuke   (2849 words)

Nuclear Weapons Program - North Korea Since 20-kiloton standard nuclear warhead has 8 kilograms of critical mass, this amounts to mass of material of nuclear fission out of which about 3 nuclear warheads could be extracted. The two 1,000 MW light-water nuclear reactors would be safer and would produce much less plutonium, in order to help boost the supply of electricity in the North, which is now in a critical shortage. At least two of the estimates are said to be based on the assumption that North Korea removed fuel rods from the 5-MW(e) reactor and subsequently reprocessed the fuel during slowdowns in the reactor's operations in 1990 and 1991. fas.org /nuke/guide/dprk/nuke   (2849 words)

Public Citizen Critical Mass Energy and Environment Program - Critical Mass Energy and Environment Program Public Citizen's Critical Mass Energy and Environment Program works to protect citizens and the environment from the dangers posed by nuclear power and seeks policies that will lead to safe, affordable and environmentally sustainable energy. Critical Mass Energy and Environment Program - Critical Mass Energy and Environment Program We also advocate creation of an agricultural and food distribution system that guarantees safe, wholesome food produced in a humane and sustainable manner, and work to protect the world's fragile water resources from commodification, privatization, and mass diversion. www.citizen.org /cmep   (2849 words)

Nuclear Weapon Design These were later replaced with weapons designed to a goal of less than a 1 in a 1 million chance of the weapon delivering more than 4 pounds of nuclear yield if the high explosives were detonated at the single most critical possible point. Fission weapons require a system to assemble a supercritical mass from a sub-critical mass in a very short time. Nuclear weapons are particularly destructive, with immediate effects including blast and thermal radiation and delayed effects produced by ionizing radiation, neutrons, and radioactive fallout. www.fas.org /nuke/intro/nuke/design.htm   (3646 words)

An Analysis of Al-Qaida Tradecraft Mass attrition attack remain another possibility--use of some Weapon of Mass Destruction (nuclear, chemical, biological, radiological) to kill large numbers of the population, critical population segments (financial, early responders, etc.), or deny critical locations (Wall Street and other exchanges, Silicon Valley, etc.). By no means is this a complete, or even an ordered (most important or greatest priority first), list; see Hunting the Sleepers for applicable rules of thumb for this sort of work. Capture of documents, secrets, and armaments is higher risk than one would assume for sleepers. www.metatempo.com /analysis-alqaida-tradecraft.html   (3646 words)

Yorkshire CND - Los Alamos National Laboratory Adds New Element to Nukes - 20/10/02 The experiment, 12 years in the making, was completed in late September and gives nuclear scientists for the first time a clear indication of how much neptunium is needed to create a critical mass, or a nuclear chain reaction. The uranium helped drive the neptunium to a critical mass, and the scientists could carefully control the reaction's rate by raising or lowering the neptunium and uranium assembly away from the fixed uranium shells to prevent the reaction from going "supercritical." That's when nuclear chain reactions become explosive. Los Alamos National Laboratory has announced it was the first lab in the Western Hemisphere, and possibly the world, to use a radioactive material other than plutonium or uranium to achieve a nuclear chain reaction, which can lead to a nuclear explosion if it is not controlled. cndyorks.gn.apc.org /news/articles/lanlnewelement.htm   (759 words)

Public Citizen Critical Mass Energy and Environment Program Critical Mass Energy and Environment Program - Tritium Leaks at Nuclear Power Plants Contaminate Groundwater In February 2006, a tritium leak was discovered at the Byron Nuclear Generating Station, another Exelon plant in Illinois. The tritium levels in vaults along pipes that transport waste water were at four times the EPA standard. It is not yet clear whether these elevated tritium levels have reached the groundwater. The Dresden Generating Station in Grundy County, Illinois is a third Exelon nuclear plant that has had recent tritium leaks. A 2004 test following the October discovery of a pipeline leak revealed groundwater tritium levels at 500 times the federal limit. Even worse, nuclear energy companies have kept the discoveries of these leaks from the public, sometimes for several years. Tritium is a byproduct of nuclear generation and can enter the body through ingestion, absorption or inhalation. www.citizen.org /cmep/energy_enviro_nuclear/nuclear_power_plants/reactor_safety/articles.cfm?ID=15089   (638 words)

nptarget.html The scientists suggested that such a reaction could be initiated by assembling a critical mass--an amount of nuclear explosive adequate to sustain it--either by firing two subcritical masses of plutonium or uranium 235 together or by imploding (crushing) a hollow sphere made of these materials with a blanket of high explosives (Tolman). Financial aid@to development of nuclear reactor rather than to yet uncertain atomic bomb.[A. Lyman, J. Briggs, A. Sachs, L. ilard, E. Teller and E. Wigner] 1939.10 [England] An idea by J. Chadwick for an atomic bomb utilizing@natural uranium based on a paper by R.Peierls, mass needed for critical@state: 30-40 tons. Today, our enemies see weapons of mass destruction as weapons of choice.The greater the threat, the greater is the risk of inaction -- and the more compelling the case for taking anticipatory action to defend ourselves, even if uncertainty remains as to the time and place of the enemy's attack. www.ask.ne.jp /~hankaku/english/nptarget.html   (638 words)

Prompt neutron - Wikipedia, the free encyclopedia If a nuclear reactor happened to be prompt critical - even very slightly - the number of neutrons would increase exponentially and very quickly the reactor would become uncontrollable. However, thanks to the delayed neutrons, it is possible to run a reactor subcritically as far as only prompt neutrons are concerned: the delayed neutrons come a moment later, just in time to sustain the chain reaction when it is going to die out. In nuclear engineering, a prompt neutron is a neutron immediately emitted by a nuclear fission event, as opposed to a delayed neutron which is emitted by one of the fission products anytime from a few milliseconds to a few minutes later. en.wikipedia.org /wiki/Prompt_neutron   (410 words)

Nuclear Weapon Design The minimum mass of fissile material that can sustain a nuclear chain reaction is called a critical mass and depends on the density, shape, and type of fissile material, as well as the effectiveness of any surrounding material (called a reflector or tamper) at reflecting neutrons back into the fissioning mass. Nuclear weapons are particularly destructive, with immediate effects including blast and thermal radiation and delayed effects produced by ionizing radiation, neutrons, and radioactive fallout. Nuclear weaponry has advanced considerably since 1945, as can be seen at an unclassified level by comparing the size and weight of “Fat Man” with the far smaller, lighter, and more powerful weapons carried by modern ballistic missiles. www.fas.org /nuke/intro/nuke/design.htm   (3646 words)

Public Citizen Critical Mass Energy and Environment Program Critical Mass Energy and Environment Program - The Nuclear Burden on Mississippi The health effects of routine operation of a nuclear plant require more thorough investigation. It will produce high-level nuclear waste that will stay in Mississippi indefinitely. [6] Vision 2020 – Nuclear Energy and the Nation’s Future Prosperity, Nuclear Energy Institute, p. www.citizen.org /cmep/energy_enviro_nuclear/newnukes/grandgulf/articles.cfm?ID=13476   (363 words)

Nuclear Weapon Design The minimum mass of fissile material that can sustain a nuclear chain reaction is called a critical mass and depends on the density, shape, and type of fissile material, as well as the effectiveness of any surrounding material (called a reflector or tamper) at reflecting neutrons back into the fissioning mass. Nuclear weaponry has advanced considerably since 1945, as can be seen at an unclassified level by comparing the size and weight of �Fat Man� with the far smaller, lighter, and more powerful weapons carried by modern ballistic missiles. Nuclear weapons are particularly destructive, with immediate effects including blast and thermal radiation and delayed effects produced by ionizing radiation, neutrons, and radioactive fallout. www.fas.org /nuke/intro/nuke/design.htm   (363 words)

Nuclear Weapon Design The minimum mass of fissile material that can sustain a nuclear chain reaction is called a critical mass and depends on the density, shape, and type of fissile material, as well as the effectiveness of any surrounding material (called a reflector or tamper) at reflecting neutrons back into the fissioning mass. Nuclear weaponry has advanced considerably since 1945, as can be seen at an unclassified level by comparing the size and weight of “Fat Man” with the far smaller, lighter, and more powerful weapons carried by modern ballistic missiles. Nuclear weapons are particularly destructive, with immediate effects including blast and thermal radiation and delayed effects produced by ionizing radiation, neutrons, and radioactive fallout. www.fas.org /nuke/intro/nuke/design.htm   (363 words)

Domain Leader Dot Com! this article is about the public event of bicyclists taking over roadways for the concept in nuclear physics critical mass critical mass is an event held typically on the last friday of every month in city cities around the world where bicycle bicyclists and self-propelled people take to the streets nuts is an acronym meaning neils unix talk server nuclear utilization target selection counterpart to mutual assured destruction mad nuclear use theorists more properly formatted nuts nomenclature of territorial units for statistics new ulm trebuchet society minnesota see also nut disambig MANYOO EYE RAMOSSeville right-back Sergio Ramos Garcia is a target for Manchester United say the Mirror, with Sir Alex of Ferguson reportedly eyeing him as Gazza Neville#39;s long-term replacement. www.domain-leader.com /?mode=history&date=2005-3-19   (13676 words)

Nuclear reactor - the free encyclopedia Nuclear reactors are (with the exception of certain speculative subcritical reactors) designed to contain critical masses that are not prompt critical, so that controlsystems can react quickly enough to maintain a steady rate of heat production. A mass of fissionable material is said to be a critical mass if each fission event leads to one or more fission events on average. A prompt critical mass will rapidly release an exponentially increasing amount of heat and cannot becontrolled. www.encyclopedia-of-knowledge.com /?t=NR   (3833 words)

Nuclear Data Project The nuclear structure evaluation effort has been redirected from mass-chain evaluation to horizontal evaluation of selective nuclear properties and/or selective nuclei, particularly nuclei in the far-from-stability regions which are directly related to local on-going research programs. The nuclear structure evaluation procedure involves the critical analysis of all literature on nuclei under study. The NDP has been responsible for collecting and evaluating nuclear structure data for 56 mass chains in the mass region A>200. www.phy.ornl.gov /ndp   (808 words)

Neptunium Goes Critical At Los Alamos During the experiment, measurements are taken as the lower section is raised and brought closer and closer to the upper section until sufficient mass of fissile materials is present and criticality is achieved. Prior to this experiment, the critical mass of neptunium was only estimated with computer models from data based on earlier experiments using much smaller amounts of the element in less than optimal configurations. The experiment has yielded preliminary data that show the critical mass of neptunium is actually less than previously predicted. www.spacedaily.com /news/energy-tech-02s.html   (1231 words)

Nuclear Materials Experience with small nuclear devices indicates that it is impossible to make a nuclear device with a total mass less than the bare sphere critical mass of the fissile material used. The presence of neutrons during the assembly of a supercritical mass leads to a premature nuclear reaction, an inefficient release of energy, even a near total weapon failure in some cases. Due to the rapid recent growth of the world wide nuclear power industry, reactor grade uranium is currently being generated by commerical operations at a rate of 75 tonnes/yr. nuclearweaponarchive.org /Nwfaq/Nfaq6.html   (1231 words)

Nuclear salt-water rocket -- Facts, Info, and Encyclopedia article These would be stored in tanks that would prevent a (The minimum mass of fissionable material that can sustain a chain reaction) critical mass from forming by some combination of geometry or (An elementary particle with 0 charge and mass about equal to a proton; enters into the structure of the atomic nucleus) neutron absorption. The rocket would be powered by a nuclear-thermal reaction when the water was injected into a reaction chamber. Zubrin, "Nuclear Salt Water Rockets: High Thrust at 10,000 sec ISP", Journal of the British Interplanetary Society 44, 371-376 (1991) www.absoluteastronomy.com /encyclopedia/N/Nu/Nuclear_salt-water_rocket.htm   (167 words)

Remarks as prepared for delivery by Director of Central Intelligence George J. Tenet at Georgetown University February 5, 2004 This was critical when the Libyans approached British and US intelligence about dismantling their chemical, biological and nuclear weapons programs.  They came to the British and American intelligence  because they knew we could keep the negotiations secret. In the Estimate, all agencies agreed that Saddam wanted nuclear weapons.  Most were convinced that he still had a program and if he obtained fissile material he could have a weapon within a year.  But we detected no such acquisition. It was only when we convinced them we knew Libya’s nuclear program was a weapons program, that they showed us their weapon design. www.cia.gov /cia/public_affairs/speeches/2004/tenet_georgetownspeech_02052004.html   (4513 words)

Critical mass - Wikipedia, the free encyclopedia The realisation that a supercritical assembly is not necessarily prompt critical is attributed to Enrico Fermi, and made the construction of a nuclear reactor using a fission chain reaction possible. The critical mass of fissile material is the amount needed for a sustained nuclear chain reaction. In the case of a sphere surrounded by a neutron reflector the critical mass is about 15 kg for uranium-235 (20 to 25 kg for a gun-type assembly) and 10 kg for plutonium-239. en.wikipedia.org /wiki/Critical_mass   (2060 words)

Nuclear weapon - Wikipedia, the free encyclopedia In fission weapons, a mass of fissile material (enriched uranium or plutonium) is rapidly assembled into a critical mass, in which a chain reaction begins and grows exponentially, releasing tremendous amounts of energy. Nuclear weapons have been at the heart of many national and international political disputes, and have played a major part in popular culture since their dramatic public debut in the 1940s, and have usually symbolized the ultimate ability of mankind to utilize the strength of nature for destruction. Nuclear weapons were symbols of military and national power, and nuclear testing was often used both to test new designs as well as to send political messages. en.wikipedia.org /wiki/Nuclear_weapon   (2384 words)

The First Nuclear Chain Reaction This quantity of uranium necessary for a chain reaction under given conditions is known as the critical mass, or more commonly, the "critical size" of the particular pile. These facts implied the possibility of a chain reaction, similar in certain respects to the reaction which is the source of the sun's energy. An atomic chain reaction may be compared to the burning of a rubbish pile from spontaneous combustion. hep.uchicago.edu /cp1.html   (4322 words)

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