Nuclear reactor

[[image:AKW-LeibstadtCH.jpg|thumb|150pix|right|Nuclear power station at Leibstadt, Switzerland, Switzerland. The nuclear reactor is inside the dome-shaped containment building.]] A nuclear reactor is a device in which nuclear chain reactions are initiated, controlled, and sustained at a steady rate (as opposed to a nuclear explosion, where the chain reaction occurs in a split second). Nuclear reactors are used for many purposes, but the most significant current uses are for the generation of electrical power and for the production of plutonium for use in nuclear weapons. Currently all commercial nuclear reactors are based on nuclear fission. For experiments on reactors based on nuclear fusion, see fusion power. There are other devices in which nuclear reactions occur in a controlled fashion, including radioisotope thermoelectric generators, which generate heat and power by passive radioactive decay, and Farnsworth-Hirsch fusors, in which controlled nuclear fusion is used to produce neutron radiation. == Applications == *Nuclear power: **heat for electricity generation **heat for domestic and industrial heating **desalination *Nuclear propulsion: **nuclear marine propulsion **proposed nuclear thermal rockets *Transmutation of elements: **production of plutonium, often for use in nuclear weapons **creating various radiation isotopes, such as americium for use in smoke detectors *research applications including: **providing a source of neutron and positron radiation **development of nuclear technology == History == Enrico Fermi and Le� Szil�rd were the first to build a nuclear pile and demonstrate a controlled chain reaction. In 1955 they shared a joint patent for the nuclear reactor, issued by the U.S. Patent Office. The first nuclear reactors were used to generate plutonium for nuclear weapons. Additional reactors were used in the navy (see United States Naval reactor) to propel submarines and aircraft carriers. In the mid-1950s, both the Soviet Union and western countries were expanding their nuclear research to include non-military uses of the atom. However, as with the military program, much of the non-military work was done in secret. On December 20, 1951, electric power from a nuclear powered generator was produced for the first time at EBR-I (EBR-1) located near Arco, Idaho. On June 27, 1954, the world's first nuclear power plant generated electricity but no headlines--at least, not in the West. According to the Uranium Institute (London, England), the first reactor to generate electricity for commercial use was at Obninsk, Kaluga Oblast, Russia. The Shippingport Reactor (in Pennsylvania) was the first commercial nuclear generator to become operational in the United States. The Shippingport reactor was ordered in 1953 and began commercial operation in 1957. Even before the 1979 Three Mile Island accident, new orders for nuclear plants in the U.S. had ceased for economic reasons primarily related to greatly extended construction times. As of 2004, no new nuclear plants have been ordered in the USA since 1978 [http://www.pbs.org/wgbh/pages/frontline/shows/reaction/maps/chart2.html], although it is possible that the first nuclear power plant in the United States since 1978 may be installed in the remote town of Galena Nuclear Power Plant [the City Council itself has approved the idea, and Toshiba has proposed to install its Toshiba 4S "nuclear battery" in Galena free of charge as a test]. The negative influence of the 1986 Chernobyl accident increased regulations which increased the costs of operating a reactor. In 1997, a total of 78 reactors were either under construction, planned, or indefinitely deferred. These units have a combined power of 67,484 MWe, approximately 25 % of the total power already in existence. However, only 45 reactors were under construction worldwide. The remaining 33 units are either being planned or indefinitely deferred. Three U.S. units are not projected to come on-line. Some experts have predicted that Watts Bar 1, which came on-line in 1997, will be the last U.S. commercial nuclear reactor to go on-line. Other experts, however, predict that electricity shortages will renew the demand for nuclear power plants. As of 2004, the immediate future of the industry in many countries still appeared uncertain, the most notable exceptions being Japan, China and India, all actively developing both fast and thermal technology, South Korea, developing thermal technology only, and South Africa, developing the Pebble bed reactor (PBMR). Finland and France actively pursue nuclear programs and both have new reactors planned for the very near future. In the U.S., three consortia responded in 2004 to the U.S. Department of Energy's solicitation under the Nuclear Power 2010 Program and were awarded matching funds. As of the early 21st century, nuclear power is of particular interest to both China and India to serve their rapidly growing economies. See also future energy development. The first organization to develop utilitarian nuclear power, the United States Navy, is the only organization worldwide with a totally clean record. This is perhaps because of the stringent demands of Admiral Hyman G. Rickover, who was the driving force behind nuclear marine propulsion. The U.S. Navy has operated more nuclear reactors than any other entity, other than the Soviet Navy, with no publicly known major incidents. Two U.S. nuclear submarines, the USS Scorpion (SSN-589) and USS Thresher (SSN-593), have been lost at sea, though for reasons not related to their reactors, and their wrecks are situated such that the risk of nuclear pollution is considered low. In 1995, a 17-year-old Boy Scout named David Hahn attempted to build a small nuclear reactor in a potting shed in his back yard. This reactor was far too small to be critical, but it included a neutron source and neutron moderator. He collected sufficient quantities of radioactive materials that the US EPA had to be called in to saw up and dispose of the entire potting shed in a radioactive waste dump. David's parents had already secretly disposed of some of the most dangerous material by throwing it in the garbage. The reactor was built with radium (from old paint) and americium (from smoke detectors) as sources of alpha particles, which struck aluminum and beryllium to produce fast neutrons. The resulting neutrons were used to irradiate thorium (from gas mantles) and uranium (obtained as samples from a Czech company). The required information to obtain the elements and design the reactor were obtained by the simple expedient of writing letters to various organizations, claiming to be working on a merit badge or as "Professor Hahn" teaching a high-school physics class. The event received little publicity at the time but was investigated and written up three years later in ''The Radioactive Boy Scout'', a Harper's Weekly article by Ken Silverstein (who also wrote a book of the same title; see below). == Method of operation == All commercial nuclear reactors produce heat through ''nuclear fission''. In this process, the nucleus of an element such as uranium splits into two smaller atoms. This occurs naturally in radioactive elements, but it can be induced artificially by making some atoms absorb a neutron. This causes the nucleus to become unstable and makes it split apart very quickly. The fission process for a uranium atom yields two smaller atoms, one to three fast neutron, and energy. Uranium fission therefore releases more neutrons than it requires, and the reaction can become self sustaining if conditions are appropriate. This is called a chain reaction. When a neutron is captured by a fissionable nucleus, it may cause fission immediately, or it may lead to an unstable species which undergoes fission a short time later. 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 mass is said to be prompt critical if the immediate fission events are sufficient to carry on a chain reaction. A prompt critical mass will rapidly release an exponentially increasing amount of heat and cannot be controlled. Nuclear reactors are (with the exception of certain speculative subcritical reactors) designed to contain critical masses that are not prompt critical, so that control systems can react quickly enough to maintain a steady rate of heat production. The neutrons released by fission are moving quickly. Such "fast neutrons" are not easily absorbed by fissionable nuclei. Some reactors are designed to work with these neutrons, but most reactors use a neutron moderator to slow these neutrons down so that they are more easily absorbed. Such neutrons are often slowed until they are in thermal equilibrium with the reactor core; as a result, they are called thermal neutrons (or slow neutrons). The amount of heat produced by a reactor is a crucial parameter. It may be controlled by adjusting the amount of neutron moderator in the reactor core, control rods consisting of neutron absorbers may be used to control the output, or the physical arrangement of the fuel may be changed. The Doppler broadening effect also serves to reduce the rate of fission as the temperature increases. Many reactors use several methods, both for control and for emergency shutdown. ===Reactor design=== ''See also Nuclear_power_plant#Fission_reactors'' A nuclear reactor is designed to carry out nuclear fission reactions on a large scale. This produces heat, fission products, and intense neutron radiation. In a nuclear power plant, that heat is used to do useful work. Some reactors, whether experimental or military, are designed with no concern for making use of the generated heat, as their goal is to make use of the neutron radiation to transmutation elements. In either case, for all current nuclear reactors, it is essential that a nuclear chain reaction be continually sustained. In a sustained nuclear chain reaction, the fission of a single fuel nucleus releases a few neutrons. These neutrons initially carry a great deal of energy (and are therefore called fast neutrons). These neutrons may be captured immediately by another fuel nucleus, or they may interact with a neutron moderator or a neutron absorber. The likelihood that a fast-moving neutron is captured by a fuel nucleus is relatively low, so it is often necessary to slow down the neutrons. This is done by allowing the neutrons to scatter off nuclei of a neutron moderator. After a few such scattering events, the neutron radiation has a thermal energy spectrum (that is, they are moving with the same average energy as a gas at the same temperature as the reactor core) and is much more easily captured by a fuel nucleus. A nuclear reactor that uses a moderator is called a slow or thermal reactor, and it is normally categorized according to the type of moderator. Common moderators are heavy water and ordinary light water. Some reactors also use graphite, although it has a number of problems (see, for example, the Windscale fire and the Chernobyl accident). A reactor that is not moderated is called a fast reactor. The higher neutron flux allows some nuclear reactions to occur that are difficult to arrange in a slow reactor. In particular, it is possible to transmute thorium and other isotopes into usable fuel isotopes. Such a reactor can potentially produce more fuel than it consumes; for this reason fast reactors are sometimes called "breeder reactors". When a neutron is captured by a fuel nucleus, the nucleus may undergo fission immediately, it may remain in an unstable state for a short while before undergoing fission, or it may fail to undergo fission at all. Fission events that occur immediately are called "prompt" fission events, and if there are enough prompt events for the reaction to be self-sustaining without the delayed fission events, then the reactor is said to be prompt critical. In such a situation, the amount of fission in the reactor will grow exponentially and very quickly; the result would be a large explosion (although not one comparable to a nuclear weapon). Thus a stable nuclear reactor must be maintained in a critical but not prompt critical state. Controls are also essential to ensure that the temperature does not rise so high that the reactor is damaged or destroyed. A nuclear reactor is controlled by adjusting the configuration of neutron absorbers in and around the core, the configuration of the neutron moderator (if any), and the sometimes the configuration of the fuel itself. The most common arrangement is to include neutron-absorbing control rods which can be partially inserted into the reactor in order to damp its reaction. Such control rods normally require sophisticated monitoring equipment, so a number of advanced reactor designs (such as the pebble-bed reactor) have tried to build in passive safety systems which require no action by electronic, mechanical, or human agents to prevent plant overheating. In any nuclear reactor, some sort of cooling is necessary. In a nuclear power plant, the cooling system must be designed so that it can make use of the heat released. Most nuclear reactors use water as a coolant, either in a pressurized liquid form or by boiling into steam. Since water acts as a moderator, fast reactors cannot be cooled with water. Molten sodium or sodium salts are in current use. Reactors designed for transmutation only may simply release the heat to the environment. === Safety === As part of the design of any nuclear reactor provisions ought to be made for operator errors or failure of critical equipment. For this reason the "Defense in Depth" concept is employed to ensure operability of all systems when required for safety. All systems in nuclear plants have three main safety objectives: * Control of Reactivity (ability to control the amount of neutron flux in the fuel mechanically or chemically), * Maintenance of Core Cooling (maintaining an adequate supply and backup supply of coolant to the core region) and * Maintenance of Barriers to Release of Radiation (fuel cladding, primary barrier, containment and attenuation devices). Where Systems, Structures and Components (SSC) are required to perform any duties supporting the three safety functions, they are provided with frequent inspection, operational or functional tests, and increased design, purchase and repair scrutiny as part of a Quality Assurance (QA) plan. Part of the design of these SSC includes redundancy (having multiple backup components), provision of independent systems (such as a requirement to have two or more separate systems performing the same function in parallel)"voting" on an interpretation of a signal, fail-safe design (knowing how a SSC will fail and what effect it will have on companion SSC) monitoring instrumentation and protection against "Common Mode Failure". Common Mode Failure prevents a single failure from affecting both "trains" or systems of independent, redundant equipment. Engineering performance is tested on a frequent basis (surveillance) to provide assurance (QA) of readiness to perform its designed function. It should be noted that many of these same design features are mandated on commercial airliners. On detection of process (pressure, temperature, radiation, flow, etc) indications outside of a normal range an alarm will sound and be "acknowledged" in the control room, where an operator makes adjustments. If the alarming parameters exceed set points further, the reactor, turbine or generator may provide a fault signal which automatically places the system in a safer (lower energy) mode and may terminate operations without operator control. In the case of a generator or turbine fault, steam will be limited or shut off and the turbine will slow. If the problem is not corrected quickly, a SCRAM (from the origins of atomic power) or Safety Control Rod Actuation Mechanism will occur inserting the control rods (moderators) into the reactor core and significantly slowing the neutron flux. The plant must then be restarted after an investigation is completed. Each facility operates to a set of license conditions (Final Safety Evaluation Report, or FSAR) specific to the units' design, location and environment. The license conditions, condensed in a set of Technical Specifications, describes the limits of power, certain process parameters, staff, training and qualifications, minimum available equipment and other physical and administrative requirements which must be in place in order to operate the reactor. Violation of the license conditions may result in fines and inability to operate the facility. == Types of reactors == [[image:Pulstar2.jpg|thumb|right|NC State's PULSTAR Reactor is a 1 MW pool-type research reactor with 4% enriched, pin-type fuel consisting of UO₂ pellets in zircaloy cladding.]][[image:Pulstar1.jpg|thumb|right|The control room of NC State's Pulstar Nuclear Reactor.]] A number of reactor technologies have been developed. Fission reactors can be divided roughly into two classes, depending on the energy of the neutrons that are used to sustain the fission chain reaction. *''thermal reactor'' use slow or thermal neutrons. These are characterised by having neutron moderator which are intended to slow the neutrons until they approach the average kinetic energy of the surrounding particles, that is, until they are ''thermalised''. Thermal neutrons have a far higher probability of fissioning U-235, and a lower probability of capture by U-238 than the faster neutrons that result from fission do. As well as the moderator, thermal reactors have fuel (fissionable material), containments, pressure vessels, shielding, and instrumentation to monitor and control the reactor's systems. Most power reactors are of this type, and the first plutonium production reactors were thermal reactors using graphite as the moderator. Some thermal power reactors are more thermalised than others; Graphite (ex. Russian RBMK reactors) and heavy water moderated plants (ex. Canadian CANDU reactors) tend to be more thoroughly thermalised than PWRs and BWRs, which use light water (normal water) as the moderator. *''fast neutron reactor'' use fast neutrons to sustain the fission chain reaction, and are characterised by the lack of moderating material. They require highly enriched fuel (sometimes weapons-grade), or plutonium in order to reduce the amount of U-238 that would otherwise capture fast neutrons. Some are capable of producing more fuel than they consume, usually by converting U-238 to Pu-239. Some early power stations were fast reactors, as are some Russian naval propulsion units, and construction of prototypes is continuing, see fast breeder, but overall the class has not achieved the success of thermal reactors in any application. An example of this type of reactor is the Fast Breeder Reactor (FBR). Thermal power reactors can again be divided into three types, depending on whether they use pressurised fuel channels, a large pressure vessel, or gas cooling. *Pressure vessels holding steam heated by the reactor are used by most commercial and naval reactors. This serves as a layer of shielding and containment. *Pressurised channels are used by the RBMK and CANDU_reactor reactors. Channel-type reactors can be refuelled under load, which has advantages and disadvantages discussed under CANDU_reactor . *Gas-cooled reactors are cooled by a circulating inert gas, usually helium, but nitrogen and carbon dioxide have also been used. Utilisation of the heat varies, depending on the reactor. Some reactors run hot enough that the gas can directly power a gas turbine. Older designs usually run the gas through a heat exchanger to make steam for a steam turbine. The pebble bed reactor uses a gas-cooled design. Since water serves as a moderator, it cannot be used as a coolant in a fast reactor. Most designs for fast power reactors have been cooled by liquid metal, usually molten sodium. They have also been of two types, called pool and loop reactors. ===Current families of reactors=== *Pressurized water reactor *Boiling water reactor *Fast breeder *CANDU reactor *D2G reactor ===Obsolescent types still in service=== *Magnox *Advanced gas-cooled reactor *RBMK ===Advanced reactors=== More than a dozen advanced reactor designs are in various stages of development. Some are evolutionary from the PWR, BWR and CANDU_reactor designs above, some are more radical departures. The former include the Advanced Boiling Water Reactor, two of which are now operating with others are under construction. The best-known radical new design is the Pebble bed reactor (PBMR), a high temperature gas cooled reactor. Other possible designs exist on the drawing board, notably the energy amplifier, awaiting political support and funding. Some, such as the Integral Fast Reactor, have been cancelled due to a political climate unfavorable to nuclear power. == Nuclear fuel cycle == ''Main article: nuclear fuel cycle'' Thermal reactors generally depend on refined and enriched uranium. Some nuclear reactors can operate with a mixture of plutonium and uranium (see MOX). The process by which uranium ore is mined, processed, enriched, used, possibly nuclear reprocessing and disposed of is known as the nuclear fuel cycle. Uranium is sampled and mining as other metals are, via open-pit mining or leach mining. Raw uranium ore found in the United States ranges from 0.05% to 0.3% uranium oxide. Uranium ore is not rare; the largest probable resources, extractable at a cost of US$80 per kilogram or cheaper, are located in Australia, Kazakhstan, Canada, South Africa, Brazil, Namibia, Russia, and the United States. The raw ore is then milled, where it is ground and chemically leached. The resulting powder of natural uranium oxide is called "yellowcake". The yellowcake powder is then converted to uranium hexafluoride to prepare for enrichment. Since under 1% of the uranium found in nature is the easily fissionable U-235 isotope, the uranium must be enriched to about 4% U-235, usually by means of gaseous diffusion or gas centrifuge. The enriched result is then converted into uranium dioxide powder, which is pressed and fired onto pellet form. These pellets are stacked into tubes which are then sealed and called fuel rods. Many of these fuel rods are used in each nuclear reactor. === Fueling of nuclear reactors === The amount of energy in the reservoir of nuclear fuel is frequently expressed in terms of "full-power days," which is the number of 24-hour periods (days) a reactor is scheduled for operation at full power output for the generation of heat energy. The number of full-power days in a reactor's operating cycle (between refueling outage times) is related to the amount of fissile uranium-235 (U-235) contained in the fuel assemblies at the beginning of the cycle. A higher percentage of U-235 in the core at the beginning of a cycle will permit the reactor to be run for a greater number of full-power days. At the end of the operating cycle, the fuel in some of the assemblies is "spent," and is discharged and replaced with new (fresh) fuel assemblies. The fraction of the reactor's fuel core replaced during refueling is typically one-fourth for a boiling-water reactor and one-third for a pressurized-water reactor. Not all reactors need to be shut down for refueling; for example, pebble bed reactors, molten salt reactors and CANDU reactors allow fuel to be shifted through the reactor while it is running. In a CANDU reactor, this also allows individual fuel elements to be moved about within the reactor core to places that are best suited to the amount of U-235 in the fuel element. The amount of energy extracted from nuclear fuel is called its "burn up," which is expressed in terms of the heat energy produced per initial unit of fuel weight. Burn up is commonly expressed as megawatt days thermal per metric ton of initial heavy metal. === Waste Management === The final stage of the nuclear fuel cycle is the management of the still highly radioactive, "spent" fuel, which constitutes the most problematic component of the nuclear waste stream. After fifty years of nuclear power the question of how to deal with this material remains fraught with safety concerns and technical problems, and one of the most important lines of criticism of the industry is based on the long-term risks and costs associated with dealing with the waste. Management of the spent fuel can include various combinations of storage, reprocessing, and disposal. In practice storage has been the primary modality so far. Typically the spent fuel rods are stored in a pool of water which is usually located on-site. The water provides both cooling for the still-decaying uranium, and shielding from the continuing radioactivity. nuclear reprocessing is attractive in principle because (1) it can recycle nuclear fuel and (2) it can prepare the waste material for disposal. Considerable experience with reprocessing in France however, has indicated that a one way fuel cycle based on extracting and processing fresh supplies of uranium and storing the spent fuel is more economical than reprocessing. == Natural nuclear reactors == A natural nuclear fission reactor can occur under certain circumstances that mimic the conditions in a constructed reactor. The only known natural nuclear reactor formed 2 billion years ago in Oklo, Gabon, Africa. [http://www.ans.org/pi/np/oklo] Such reactors can no longer form on Earth: radioactive decay over this immense time span has reduced the proportion of U-235 in naturally occurring uranium to below the amount required to sustain a chain reaction. The natural nuclear reactors formed when a uranium-rich mineral deposit became inundated with groundwater that acted as a neutron moderator, and a strong chain reaction took place. The water moderator would boil away as the reaction increased, slowing it back down again and preventing a meltdown. The fission reaction was sustained for hundreds of thousands of years. These natural reactors are extensively studied by scientists interested in geologic radioactive waste disposal. They offer a case study of how radioactive isotopes migrate through the earth's crust. This is a significant area of controversy as opponents of geologic waste disposal fear that isotopes from stored waste could end up in water supplies or be carried into the environment. == Related articles== * Nuclear Reactor Operator Badge * United States Naval reactor * List of nuclear reactors == See also== * Nuclear power * Nuclear fission * Nuclear fusion * Nuclear power plant * Nuclear meltdown * Power plant * Nuclear waste * Electricity generation * Nuclear physics * Enrico Fermi * Manhattan Project * Nuclear marine propulsion * Technology assessment * List of nuclear accidents * Energy amplifier * Future energy development ==References and links== *[http://eia.doe.gov Energy Information Administration] provides lots of statistics and information on the industry. *[http://www.antenna.nl/wise/uranium/efac.html World Nuclear Fuel Facilities] *[http://www.uic.com.au/ The Uranium Information Centre] provided some of the original material in this article. *[http://www.nrc.gov/ The US Nuclear Regulatory Commission] supervises the US Nuclear industry *The Idaho National Engineering and Environmental Laboratory developed nuclear reactor technology in the United States - [http://newsdesk.inel.gov/press_releases/2001/05-21EBR_I_summer_tours.htm INEL Newsdesk - Experimental Breeder Reactor-I opens for summer tours] *The International Atomic Energy Agency (IAEA) works with its Member States and multiple partners worldwide to promote safe, secure and peaceful nuclear technologies. **[http://www.iaea.org/ IAEA Website] **[http://www.iaea.org/programmes/a2/ IAEA's Power Reactor Information System (PRIS)] **[http://www.iaea.org/inis/aws/htgr/ IAEA's Knowledge Base] on Gas Cooled Reactors **[http://www.iaea.org/inis/ws/ IAEA's Web directory of nuclear related resources on the Internet] *[https://www.pbmr.co.za/ The Pebble Bed Modular Reactor] - [http://whyfiles.org/130nukes/3.html Whyfiles.org - On a bed of pebbles] *[http://www.world-nuclear.org World Nuclear Association] - A pro nuclear site *[http://www.greenpeace.org/~nuclear/ Greenpeace Nuclear Campaign] - An anti-nuclear site *[http://www.democracynow.org/article.pl?sid=04/09/24/1359225 A Debate: Is Nuclear Power The Solution to Global Warming?] *[http://www.ecolo.org Environmentalists for Nuclear Power, pro nuclear site] *[http://www.sckcen.be SCK.CEN Belgian Nuclear Research Centre - pro nuclear site] *[http://www.phyast.pitt.edu/~blc/book/BOOK.html The Nuclear Energy Option] by Bernard Cohen. Pro nuclear book which compares risks of nuclear power with other methods of energy generation. *[http://www.ucsusa.org/clean_energy/nuclear_safety/page.cfm?pageID=1408 Union of Concerned Scientists, Concerns re: US nuclear reactor program] Patents * US[http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=/netahtml/srchnum.htm&r=1&f=G&l=50&s1=2708656.WKU.&OS=PN/2708656&RS=PN/2708656 2708656] -- ''Neutronic reactor'' -- E. Fermi et. al. Energy conversion Nuclear technology Electric power

Nuclear reactor

==Integral Fast Reactor== IMHO we need to build a section on the IFR. It is an extreamly important advanced design and it was shut down for political reasons. Combined with this we need to talk about High Temperature Electrolysis and what this can mean for the hydrogen economy... since it can be up to 55% efficient. This has the potential to replace steam reformation which can currently produce hydrogen at about 0.65 per lbs. We currently have a hydrogen source from steam reformation, however it is less energy efficient than just buring the methane. Not only this, the methane source IS NOT GOING TO BE THERE. Here is why I say this. Canada produces about 6.3TCF per year and exports about 55% to the USA. Source - BP statistical review. Please look it up and correct my figures if they are not correct. Now Tar Sands operations are expected to ramp up to about 5 million barrels per day by 2015-2020. In order for this to happen they need a source of hydrogen which in the past has been steam reformation (or taken straight from the methane... I need to check this). In fact Tar Sands by my esitmates (which will need to be recalculated) the amount of NG required will be fully 1/2 of Canada's expected production by 2020. This means that Canada has to completely eliminate NG exports to the USA in order to produce the synthetic crude. Since the USA is already short of natural gas, another option might be to try to wean the lion's share of Canadian current consumption in order to make some gas available to the USA. A third alternative is LNG imports and perhaps we can import what we need. However, we do have the nuclear option and the IFR combined with high temp electolysis supporting tar sands operations would be a very attractive option. The waste heat can be turned into process steam and tar sands needs this as well. If we do this, then we are taking the first steps into the hydrogen economy. It is just that we are hooking the hydrogen up to carbon atoms and storing it as synthetic oil instead of trying to store it in a tank by itself. CANDU can be used in place of IFR but the temps are about 300C instead of the 850C required by the High Temp Electrolysis process. By simply increasing the pressure we can raise the tmep but I was unable to find out if this is compatible with the High Temp Electrolyiss process. In any event, all of this should be written up into a series of articals. We should definately delinate the short sighteness of the political reasoning of 1994 when congress shut down the IFR program at Argonne Labs. If as I expect we start to see a MAJOR energy crisis develope then having these reasons written up will provide excellent background information of why people are freezing their butts off in the dark and why we are building up nuclear wastes when we clearly have excellent alternatives like burning up the damn actinides in an IFR. :Can you give us some good references on that? I found one [http://www.nationalcenter.org/NPA378.html], written by a fan, but a few with more technical details and criticisms would be helpful. --User:Aarchiba 08:18, Dec 24, 2004 (UTC) :Ok I wrote Integral Fast Reactor. Go to town. --User:Aarchiba 01:47, Feb 3, 2005 (UTC) ==Natural Reactors== Can someone add information on the "natural nuclear reactors" that sometimes form in Uranium deposits.. I know there's at least one somewhere in Africa.. I'll try to find a source, but I'm sure someone out there right now knows exactly what I'm talking about. --User:Dante Alighieri 22:22 Dec 5, 2002 (UTC) :Gabon I think is the only site yet discovered. I'll add something when I have a moment, or do a search on "gabon fossil nuclear reactor" or similar. Or there's a link to some info in Talk:Plutonium User:Andrewa 21:54 Mar 17, 2003 (UTC) I have just been studying the topic and have a little information from "Radiochemistry and Nuclear Methods of Analysis" a text by Ehmann and Vance (Chemical Analysis volume 116 Wiley-Interscience Publication 1991). The possible site of the natural nuclear reactor was in the Oklo Mine in Gabon, Africa. Some of the evidence which points to the existance of a natural reactor are higher than average decreases in isotopic enrichment of U-235 (used as fuel), higher than average decreases in isotopic enrichment of isotopes of other elements that are neutron absorbersw (i.e. the isotopes that were neutron absorbers are decreased with respect to those that are not),and soil containing sufficient water to slow cosmic neutrons to acceptable energies for initiation of a fission reaction. ---- ==Danger of NP== Copied from the danger of nuclear power. I think most of the points are already in the article. Nuclear power is considered to be unsafe by some, who claim: *There is no solution to the problems related to disposal of highly radioactive waste. *There is no solution and often no money to safely decommission a nuclear reactor. *The mining, processing and handling of nuclear materials is spreading radioactive waste into our environment. *The plants are potential terrorist targets. *Many plants have had accidents in which radioactive materials have been leaked into the environment. *During regular operation of these plants, many different radionuclides are released into the environment. *The fuel and waste from the plants has facilitated the spread of nuclear weapons across the planet. :I didn't notice before, but that last comment is particularly controversial. There have been dual-use plants, certainly, but nobody has yet produced a bomb by diverting material from a plant built purely as a power reactor, and there are good reasons for thinking nobody ever will. :This whole section was POV, in my opinion. In hindsight there is also some possibility that the attempt to redefine the term LWR to include Chernobyl, which I addressed below, was politically motivated. User:Andrewa 09:03 30 Jun 2003 (UTC) ----- Most of these points are false. The idea of no solution for radioactive wastes is a perfect example because we have fuel re-processing in Europe and Japan which gets rid of the Pu, then we have spallation and IFR technology literally sitting on the door step. About the only criticm that is valid is that when you have vast amounts of energy in a small place then any problems can take on a sinister new meaning. This is true of any concentrated energy sources such as explosives, oil tankers and expecially the LNG tankers, big bottles of propane and so forth. It isn't the nuclear character which is the problem - it is the concentration of the energy. ----- Actually, in regards to the danger of nuclear power, most of these points are correct, verifiable and with historical precedent. I would also like to point out that fuel re-processing is neither a solution for nuclear waste, nor as you erroneously stated, does it get rid of Pu. None of the technologies you mentioned either reduce the radioactive hazard of nuclear waste or provide a solution for it's long term storage. I think that it's extremely important to be objective about this type of article, but ignoring proven facts just because they don't fit with your own view of nuclear energy or because they are sometimes spouted by radical environmental groups shouldn't preclude them from this article. I think it would be highly pertinent, for example, to include links to the websites of such groups in the interest of balance and to allow the reader to make their own conclusions. ==LWR vs RBMK vs PWR know your terminology== I hope I have not been too harsh in my comment, calling what I have corrected a "major error". The original said a light water reactor was so called because of its *cooling*. It is in fact called a light water reactor because of its *moderator*. I thought it very important to make it clear because it's a common mistake, and some people even confidently tell me that Chernobyl was a PWR. Of course it was not, it was not an LWR at all. It *was* light water cooled, but the RBMK has very little in common with a PWR (more in common with a BWR maybe, but still not a lot). User:Andrewa 21:54 Mar 17, 2003 (UTC) == Economics == The economic discussion is misleading. Current production costs (fuel+O&M+capital and, for nuclear, + D&D) of electricity from nuclear power plants are in the $15-$17/MWhrE range, coal in the mid $20's, and natural gas in the $40's and climbing every day with gas prices. Should check the facts against recent FERC reporting. : Added this information. The main problem isn't the cost per megawatt, the problem is the total cost per plant. User:Roadrunner 21:53, 1 Apr 2004 (UTC) :: added this problem: reconversion of several millions of tons of uraniumhexafluoride worldwide. who`s gonna pay for that?? repaint the steel containers every 50 years for the next some billion years ?now think about and let us know. TREE, 3 april ::added this problem : tritium (radioactive hydrogen) concentration in public drinking water has a tenfold increase(~1945-2003),tendency rising. hydrogen is essential for genetic "language". how do you calculate the cost of a cripple?? ten cripples? lots of them? TREE, 3april * Energy Balance of NPP: http://www.elstatconsultant.nl/ :I cut the above link out of the article because the site is not very well done, hard to navigate and I am not sure how good the study actually is. But it seems to go into some technical detail and may be of value - so I am pasting it here for reference, and maybe someone can glean some information from it and include the information into the article and then use the study as a reference. Until then I say we keep it off of the article page. User:Trelvis ---- * During regular operation of these plants, radiation is released into local environments. that is how you call it. it is definitely wrong and misleading.correct term is: "radioactive matter" and not just "radiation" you should be educated enough to recognize the difference.plus you are supposed not to tell lies.now please re-add my link to the stormsmith(elstatconsultant) website and let the people judge themselves. the work is profound and very well done . let me add ,that i`ve been in the nukebusiness myself. like mine,your head is round,to give way for thoughts to change direction sometimes . yours TREE ::If the work on the stormsmith site is profound and very well done, then by all means work the material into this article, and cite that page. If you think parts of this article are wrong or misleading, please change them and help us make this article more accurate. If you simply want to complain while questioning other contributor's educations and head shapes, then you will be frustrated to learn you will for the most part be ignored. User:Trelvis 17:01, Apr 2, 2004 (UTC) ==Cooling Tower== For a change from the wrangling: Practically every analytic geometry book has a picture of a nuclear reactor cooling tower as an example of a hyperboloid of revolution. We have one here, in this article. Why are the cooling towers that shape? Are they actually that shape in most plants? --User:Aarchiba 07:11, Apr 25, 2004 (UTC) :I think most reactors are sited near some body of water - river, lake, ocean - which they use as a heat sink, but yes, those that have cooling towers do use this shape. I don't know the math, but the shape plus the heat from the reactor creates a strong draft in the chimney so that fans aren't needed to move air through the tower. Altough large, the structure is relatively cheap because, as the ''hyperboloid of revolution'' shows, it can be built out of straight pieces. --User:Wwoods 17:33, 3 May 2004 (UTC) :The "nuclear" cooling tower is an effective way to increase the convection cooling of a liquid. The cloud coming out of the tower is always water vapor (not steam) and the inside of the cooling tower is quite cold. Cooling towers are used in any temperature difference driven power generator (basically everything but hydroelectric and some solar). This is because the effeciency of a generator is proportional to the difference in temperatures between the engine and the coolant. People often see a cooling tower and assume that the power plant is nuclear, but this usually isn't the case. --User:Ignignot 13:28, Sep 1, 2004 (UTC) == Gabon reactor == If it is not too late to comment, there are many articles on the OKLO (Gabon) reactors (there were more than one) listed on the web - a good one to start with was prepared by the American Nuclear Society It is at http://www.ans.org/pi/np/oklo/. There is still research going on in analysing the neutronics of the reactor. Dave Eissenberg eissenbd@sover.net ---- Quote from the article: "seawater has enough uranium to power the world's current industrial civilization until the sun becomes a red giant" This is not true. Current industrial civilisation needs about 10 TW of power. Even if we can get 10¹⁴ J out of 1 kg of uranium (slightly more than the total energy released by fission), we would need 0.1 kg of uranium per second, or about 1.6 × 10¹⁶ kg in 5 billion years, the estimated time till sun becomes a red giant. According to webelements [http://www.webelements.com/webelements/elements/text/U/geol.html], there are 3.3 ppb per weight uranium in seawater. So we would need about 4.8 × 10²⁴ kg seawater, which is more than three quaters of the earth's mass. There is not that much seawater on earth. With a volume of the oceans of about 10⁹ km³ there's about 10²¹ kg of water in the oceans. With a more realistic estimate of how much energy one can get out of uranium, the 10 TW could only be produced for a few 10⁵ years. User:193.171.121.30 18:56, 30 Jun 2004 (UTC) :While the quote ''is'' overblown, the amount of U that can be extracted from seawater is much larger than the amount currently in solution in seawater. Water circulates through the upper crust and can dissolve more. Not necessarily the most cost-effective method of mining it, but hey...
--User:Wwoods 19:31, 30 Jun 2004 (UTC) ::True, but then it was at least misleading because it said "... seawater has enough uranium ...". User:193.171.121.30 21:43, 12 Jul 2004 (UTC) Um...wow... This article is bad, but I've no idea how to fix it. Issues: 1. Blatantly POV at the end, in the nonproliferation section...Not to mention contradictory. First ir says the US "claims" NK has nuclear weapons. Then it says the NPT "clearly" has not prevented NK from producing them. 2. "This seems like good public policy, because of the good safety record of commercial aircraft." Whether it is or isn't (and I think it is), how is this NPOV? --User:Penta 23:32, 1 Jul 2004 (UTC) The NPOV phrases Penta mentions probably shouldn't be in this article at all - the article is about nuclear reactors, and there is a separate article (which this article links to) on nuclear proliferation. If proliferation is mentioned here, it should be strictly in terms of how it relates to the operation of (civilian or military) nuclear reactors. --User:Dachannien 20:30, 2 Nov 2004 (UTC) ---- The article lists Pebble bed reactors as the most common type of modern gas-cooled reactor -- am I wrong in my belief that there are no operational PBR's other than research reactors? Are there any PBR's that are actually providing power to residential/industrial/governmental users? Not attacking the concept of PBR's, just questioning the use of "common" in this context. :If I recall correctly, South Africa is producing commercial PBR's. --User:Ignignot 13:35, Sep 1, 2004 (UTC) The end of the article needs to be cleaned up. I'm not even sure the natural nuclear reactors section deserves its own heading; the "proponents say..." paragraph is completely inane and sounds like it was made up on the spot. With that paragraph removed the entire section is a couple sentences. ==Ongoing Edits== Over the next week or so I'll be editing this article to improve it. I'm shocked at how poorly written it is. Almost every sentence in the first section has its own paragraph. The entire article seems to focus more on the debate about use of nuclear power instead of the process of producing energy from a nuclear reaction, which should be the main thrust. The entire thing needs to be reorganized, and much needs to be rewritten into better prose. Please post any comments about my edits here. I'll put up a sign saying I'm editing when I have the page open. --User:Ignignot 13:40, Sep 1, 2004 (UTC) == Number of active reactors. == "In 2000, there were 438 [...] In 2001, there were 104" Is this really true? Do we have references?User:Rich Farmbrough 10:54, 6 Oct 2004 (UTC) :As of September 30, 2004: 438 worldwide, 103 USA :http://www.uic.com.au/reactors.htm :Background: Throughout the World, there were 438 commercial nuclear generating units with a total capacity of about 351 gigawatts. :http://www.eia.doe.gov/cneaf/nuclear/page/nuc_reactors/reactsum2.html : Introduction: As of August 3, 2004, there are 104 commercial nuclear generating units that are fully licensed by the U.S. Nuclear Regulatory Commission (NRC) to operate in the United States. :http://www.eia.doe.gov/cneaf/nuclear/page/nuc_reactors/reactsum.html :User:Wwoods 15:23, 6 Oct 2004 (UTC) ==Removed text== From the bullet point on ''fast reactors'': ''This type of reactor is used in some mobile applications, where space constraints are a major concern, '' I don't think that's true. The thermalised units used by the US navy are at least as successful as the liquid metal cooled fast reactors of the Soviet navy. There may be advantages to this class of propulsion unit, but they have yet to be proven. User:Andrewa 06:22, 26 Nov 2004 (UTC) ==Obsolete v. Obsolescent== The UK still has several active Magnox Reactors, and the one at Wylfa has several more years left. The AGRs have no announced closure programme. The article as a whole is too US-centred. User:Linuxlad 08:56, 26 Nov 2004 (UTC) :[http://www.hyperdictionary.com/dictionary/obsolescent Hyperdictionary] defines ''obsolescent'' as ''becoming obsolete''. This seems an accurate description of the three classes of reactor listed. All are still in service, but it is doubtful that any new ones will be built as power stations. I add that disclaimer because North Korea has built several Magnox plants apparently as part of a weapons project. In hindsight the AGR project was doomed from the start because the proposed beryllium based fuel cladding failed under neutron irradiation (the work that showed this was done here in Australia at HIFAR). :Wikipedia has a chronic problem with US-centricity, and always will IMO. By all means correct the balance. But IMO if the UK was to order more NPPs right now, they'd be PWRs just like the last one was. User:Andrewa 19:55, 26 Nov 2004 (UTC) ==New article== This article currently covers a great breadth of subjects, from types of nuclear reactor to nuclear power stations. I've replaced the redirect at nuclear power plant by a stub, and propose to progressively move material from this article to more suitable places, including the new stub. Help of course welcome! User:Andrewa 21:09, 26 Nov 2004 (UTC) -you should use that article for discussion of the nuclear fission reactor, and not redirect Nuclear Power here - that should be a disambuguation page pointing to Nuclear Power Plant or History of Nuclear Power. Any thoughts (User:Ricjl) ==Nuclear Reactor Types== Can someone add the different types or make it more clear. This article talks about a type IV reactor.

Researchers from the US Government's Idaho National Engineering and Environmental Laboratory (INELL) and the private company Ceramatec say a computer model shows they could separate hydrogen from hot water by using a nuclear reactor.
The method would yield more hydrogen than does electrolysis, which runs electricity through water to separate hydrogen and oxygen.
The researchers say the conversion rate of water into hydrogen ranges between 45 and 50 per cent in high temperatures, compared with about 30 per cent in electrolysis.
"This is a breakthrough ... [and] a crucial first step toward large-scale production of hydrogen from water, rather than from fossil fuels," said Stephen Herring, consulting engineer at INELL.
Mr Herring says the nuclear reactor method should be cheaper and more environmentally friendly.
However, the method would work with Generation IV nuclear reactors, which the United States no longer makes.

[http://www.abc.net.au/news/newsitems/200411/s1255053.htm Using Reactors to Extract hydrogen] Thanks --User:Llbbl 15:21, 30 Nov 2004 (UTC) i need someone really bad! ==Trigor's edit== I have erased claim that nuclear waste is stored in unprotected place and that is vulnerable to terror attack in most plants. No offense but that is not truth because this waste has containment and most often it is in reactor containment itself. I have added the link. Also I have added some data about terrorist attacks as well as link. I have pointed out that there is no proof that low level radiation is harmful. I have also pointed out that there are uses for depleted uranium. Please write if you are unpleased with edit. :Thanks for the references; I cleaned up the formatting and grammar a bit. Please do be careful to avoid duplicating content; a few of the things that were added were there just a paragraph before. To be fair, the article is already full of duplication and needs cleanup, but let's try not to make it any worse... --User:Aarchiba 03:59, Feb 2, 2005 (UTC) I agree with all of your comments save one. One regarding low level radiation. ICRP said in theirs recommendations that low levels of radiation to general population are not concern and that there is indeed no proof that they can cause any injury. If one 1mSv is problem than perhaps people should also know that someone who lives in Balkan will receive 2mSv, someone in Sweden 4mSv and someone in Dower 7msV but to make it simple I have just put what I did. Do you think that that is biased and why? Thanks for your help :) TRIGOR :(changed indentation for clarity) :I said that the dangers of low-dose radiation are controversial because they are. There have been a bunch of studies on radiation hormesis that suggest that low doses may actually be ''beneficial''; there are agencies (often coalitions of nuclear power companies, who may be biased but may also know more) who claim it's not dangerous; and there are (many!) groups who claim it's very dangerous no matter the level (the linear no-threshold model). So this is a subject in which one good reference is not enough; you'd need several on each side, and this is not necessarily the place for that. So I flagged it as controversial (regardless of what I, personally, believe). :In practical terms, also, if this article says "it's safe", people will be forever coming in and changing it to "no it's not"; if we say "it's dangerous", people will forever be changing it to "it's perfectly safe". At least if we flag it as controversial and take a neutral point of view, some of them will stop and think. --User:Aarchiba 02:00, Feb 3, 2005 (UTC). Official stance of IAEA, ICRP and Association of world's nuclear operators and many others is that it is safe. That is official position based on conclusive and verifiable body of evidence. No official government and international agency has claimed that it is dangerous. Debate between small and sometimes pseudo scientific groups should not have place in this article. I believe that if you reject to say it is safe than you could at least cite opinion of ICRP and NRC. These agencies do not see controversy and that can be read on their respectful websites. Sincerely Trigor I have to agree with User:Aarchiba. We should probably list LNT, hormesis and the worst than LNT theorys. This should probably be at Ionizing radiation, this article is already getting a little long. User:Pstudier 03:52, 2005 Feb 3 (UTC) == Old "Reactor design section" == In the vast majority of the world's nuclear power plants, heat energy generated by fissioning uranium fuel is collected in purified water and is carried away from the reactor's core either as steam in boiling water reactors or as superheated water in PWR. In a pressurized-water reactor, the high temperature water in the primary cooling loop is used to transfer heat energy to a secondary loop for the creation of steam. In either a boiling-water or pressurized-water installation, steam under high pressure is the medium used to transfer the nuclear reactor's heat energy to a turbine that mechanically turns an electric generator. Boiling-water and pressurized-water reactors are called light water reactors, because they utilize ordinary water as the neutron moderator. In all light water reactors to date, this water is also used to transfer the heat from reactor to turbine in the electricity generation process. In other reactor designs, the heat may be transferred by light water, pressurized heavy water, helium, liquid sodium, or another substance. ==Energy development WikiProject== Please add Wikipedia:WikiProject Energy development to your Watchlists and participate in any polls and discussion there. Thanks in advance. We really need some additional input. We are kind of at a standstill on some issues. User:Hawstom 05:50, Feb 26, 2005 (UTC) ==Operational Safety== What about operational safety? For example, I've been reading the us government accident reports on criticality accidents alone, and they're pretty disturbing. For example, the technicians responsible for the Tokaimura incident weren't even informed what a criticality was! Public information archived before it was "yanked" by 9/11 hysteria can be found here:http://www.fas.org/sgp/othergov/doe/lanl/index.html Tokaimura was not a nuclear reactor facility. I am not defending anything, but it wouldn't belong in a Nuclear reactor article. I had a quick scan through the article lists but couldn't see any really relevant ones; can you be more specific. User:Dabbler 12:35, 28 Feb 2005 (UTC) ==Gas / Vapor Core Reactors== Why is there no mention of Gas Core or Vapor Core reactors? I have heard of these ideas several times from other sources. I guess I should just be bold and start it. :Perhaps you are thinking of Gaseous fission reactors, a kind of nuclear thermal rocket? They're still very speculative. :Currently, this page is focused on reactors used for commercial power; much of the information belongs on nuclear power plant. This page could then be generalized to discuss all sorts of nuclear reactors. --User:Aarchiba 19:51, Mar 10, 2005 (UTC) == Separate nuclear power == Shouldn't we have a seperate article for nuclear power where the theoretical process is described? This article should be about the reactors themselves, their commercial applications and all that. User:Karmosin 13:24, Mar 30, 2005 (UTC) :Well, we currently have a page for nuclear power plant which seems to be what you are talking about. I'm not sure what's wrong about the current article, except perhaps the section on their technical workings could be scaled down a bit and shifted to another article (sort of how nuclear weapons design is an offshoot of nuclear weapon). --User:Fastfission 17:35, 30 Mar 2005 (UTC) ::Well, if there's a nuclear power plant, then this article should definetly be nuclear power and nuclear reactor should be a redirect to nuclear power plant. Doesn't that seem logical to you? User:Karmosin 20:56, Mar 30, 2005 (UTC) :::Hmm, it sounds like some refactoring is in order. We want nuclear power, nuclear power plant, and nuclear reactor articles (or redirects). It seems to me that nuclear reactor ought to cover all types of nuclear reactor, including those for electrical power generation, vehicle propulsion, research, and plutonium production (for example, the Windscale reactor that caught fire was incapable of producing electrical or other power, as the cooling air was vented directly to the chimney). Nuclear power plant ought to contain information on those aspects of nuclear reactors specific to nuclear power generation (cooling towers, gas turbines, proliferation risks, when was the first nuclear power station built). Nuclear power should be on the idea of nuclear power generation, its history and politics, environmental impact, etcetera. :::Does this sound reasonable? I think the most important point is that nuclear reactor should not be restricted to those used for power generation. Maybe the other two should be a single article, although I think they are notionally different enough to warrant two articles. :::As for where the text currently at this article belongs, that's a different question, which we can't answer until we figure out what should go where. --User:Aarchiba 22:18, Mar 30, 2005 (UTC) :::I created nuclear power; all three pagesneed tidying. --User:Aarchiba 23:10, Mar 30, 2005 (UTC) == David Hahn's nuclear reactor == The contraption that David Hahn built was in fact a nuclear reactor - not a critical one, nor did it carry out chain reactions, but it did produce (some) fissile material by direct exposure to neutron radiation. It certainly produced other radioactive material by neutron activation as well. I think this is semantics: by the definition we give, a nuclear reactor need not have a critical mass; all that needs to happen is that nuclear transformations need to happen in a controlled way. But the fact remains that as described in the Harper article, his machine could and did produce (some) fissile materials. Do you have another reference? --User:Aarchiba 21:25, Apr 26, 2005 (UTC) Well, there are Subcritical reactor so I won't quibble about it being critical. However, his neutron source was radium/polonium and aluminum/beryllium based. From Neutron source ''Neutrons are liberated when beryllium is hit by alpha particles at about 30 neutrons/million alpha particles''. Not enough neutrons to transmute any significant amount of material. The book reported that the radioactivity steadily increased, but this was from the buildup of daughters of thorium (see http://www.uic.com.au/neAp2.htm): Th-232 -> Ra-228 + alpha, half life 14 billion years Ra-228 -> Ac-228 + beta, half life 5.8 years Ac-228 -> Th-228 + beta, half life 1.9 years Th-228 -> Pb-208 + 5 alphas + 2 beta, chain of several reactions, max half life 3.6 days A fresh sample of Thorium a couple weeks old would be pure Th-232. Over the next several years all these daughters would build up, increasing the radioactivity of the sample. The book is very confused on this point. Apparently, the author does not understand physics. User:Pstudier 22:17, 2005 Apr 26 (UTC) :So a reactor is just a neutron source and a fissile target? That sounds like a pretty loose definition of the term... if that were the case, then Fermi invented the reactor in 1934, not 1942. (And really, since no "subcritical reactors" have ever yet been created, why use them as the baseline for our definition?) --User:Fastfission 22:50, 26 Apr 2005 (UTC) ::Well, a chemical reactor is just a vessel used to carry out chemical reactions, so it seems natural to call the analogous thing a nuclear reactor. It's not a nuclear ''fission'' reactor (in any significant way), although a plutonium-based RTG is fission-based even though there are no significant chain reactions. ::Maybe we should have a stricter definition, but remember that there aren't any chain reactions or any fission in a fusion reactor (whether a tokamak, an inertial confinement machine, or a Farnsworth-Hirsch fusor). Granted, this article is not about those, but they are called nuclear reactors. On the other hand, giant particle accelerators used for making new elements are not usually called nuclear reactors... ::Anyway, whether to call it a nuclear reactor or not is not very relevant. ::The real question we should sort out is whether David Hahn actually produced any significant neutron activation. He should have been able to tell; simply (say) exposing a piece of aluminum to the output of his "neutron gun" and then measuring the induced radioactivity would be enough. ::I don't think simple aging of the thorium is sufficient to account for the high (and increasing) levels of radioactivity - after all, the thorium was from gas mantles, and if that was the only effect, his levels of radioactivity should not have increased much faster than those of the gas mantles (which people habitually store for years). ::On the other hand, many of the produced neutrons will have hit non-thorium and non-uranium atoms, activating them. ::What's more, he had a lot of radium, initially mostly shut up in the lead box, but I imagine he tracked it (and other radioactives) around a lot. This is almost certainly why "radiation could be detected as far away as the neighbors' house". ::Let's do a calculation: 10 g of radium, say, is 370 GBq, mostly alphas. That's about 10 million neutrons/sec (using the beryllium number above). Multiply by 2.5 million seconds (about a month) and that's 2.5x10^13 neutrons. If they all made U-233, that would be

2.5\times 10^13 \times \ln 2 / (159200\times 3.16\times 10^7) = 3

decays per second. So the radioactivity certainly wasn't due to U-233 (or U-238, which has an even longer half-life). Whether you consider 10 ng of U-233 a significant quantity or not is up to you. ::I can't find a reference for that 30/million number, but [http://www.sciner.com/Neutron/Neutron_Generators_Basics.htm one page on neutron generators] claims that isotopic neutron generators are suitable for neutron fluxes < 10^8 per second, so it's quite plausible. There are many pages describing experiments inducing measurable radioactivity from isotopic sources, such as [http://academic.brooklyn.cuny.edu/physics/sobel/Nucphys/radlab.html this one describing a class demonstration], and [http://www.orau.org/ptp/collection/medalsmementoes/dimes.htm this one describing irradiated dimes]. ::So I think we can say: ::* He did generate neutrons ::* He generated tiny amounts of fissile materials ::* He produced some radioactivity by neutron activation ::* He spread radioactive contamination all over the place ::What the article should actually say is up for debate. --User:Aarchiba 08:02, Apr 27, 2005 (UTC) :::10 grams of radium would have killed him. IIRC, at 1 meter, this would be a dose of 10,000 mR/hr. 30 hours near this would have made him sick. In contrast, a radium alarm clock on Ebay was claimed to have 0.6mR/hr on the faceplate, which would probably be about 0.006mR/hr at one meter. More importantly, by your calculations, the induced radioactivity was 3 decays per second compared to 370 billion decays per second, or one hundred billionth of the source. This is not significant! ::::I was trying to get an upper bound. He did find a bottle of radium paint in an old clock, which is how he got so much. How do you get 10,000 mR/hr at 1 meter? Radium yields mostly alphas, which are easily stopped; plus he knew enough to put the stuff in a lead box. ::::From [http://www.ead.anl.gov/pub/doc/radium.pdf] we find that the daughter Pb-214 has a 0.25Mev gamma, and Bi-214 has a 1.5Mev gamma. This source also mentions the use of sealed sources for cancer treatment. I can't find a reference for 1,000 mR/hr at 1 meter for 1 gram of radium. Note that 1 gram of radium is about 1 curie. [http://web.princeton.edu/sites/ehs/ssradtraining/workingsafely/workingsafely.htm] gives the value of 370mR/hr for Cs-137, whose daughter has a 0.66Mev gamma, so I claim my figure is plausible. User:Pstudier 21:02, 2005 Apr 27 (UTC) ::::The induced radioactivity was probably not alpha particles, but you're probably right that it was negligible compared to what he started with. --User:Aarchiba 19:11, Apr 27, 2005 (UTC) :::From the decay chain one finds that old thorium will have 10 times the number of decays per second as pure Th-232. Very approximately, 6 year old thorium will have about 5 times the number of decays per second as fresh. ::::The thorium he got was likely to be old, but it's probably a factor. --User:Aarchiba 19:11, Apr 27, 2005 (UTC) :::Usually, the definition of reactor includes a significant amount of reaction. Changing a few atoms doesn't count, IMHO. Therefore I am reverting. User:Pstudier 18:33, 2005 Apr 27 (UTC) ::::Hmm, fair enough. I might go in and edit it a bit, but I won't try to claim it was a reactor. --User:Aarchiba 19:11, Apr 27, 2005 (UTC) I would be much more comfortable disagreeing with the Harper's article if we could find a reference to support our claims. --User:Aarchiba 19:11, Apr 27, 2005 (UTC) ::Ha... 10g of radium? That's was about the world supply of the stuff, isolated, in 1920... remember that Madame Curie had to have an international fundraiser to buy her own gram! --User:Fastfission 03:38, 28 Apr 2005 (UTC) :::::Didn't David Hahn get in the US Navy nuclear power program for that stunt? Edit: Crap. I forgot my sig, again. --User:Admiral Roo 11:43, Jun 16, 2005 (UTC) ==US Navy clean== "The first organization to develop utilitarian nuclear power, the U.S. Navy, is the only organization worldwide with a totally clean record. " Do we have any references for this, because it's open to some interpretation. What do we mean by "totally clean"? Never had a radiation leak? Also the British Navy has a pretty good reactor safety record. User:DJ Clayworth 21:38, 26 Apr 2005 (UTC)

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