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Reactivity Worth
A dollar is a unit of reactivity for a nuclear reactor, calibrated to the interval between the conditions of criticality and prompt criticality. Prompt criticality will result in an extremely rapid power rise, with the resultant destruction of the reactor, unless it is specifically designed to tolerate the condition. A cent is of a dollar. In nuclear reactor physics discussions, the symbols are often appended to the end of the numerical value of reactivity, such as 3.48$ or 21 ¢. Reactivity (denoted ρ or ΔK/K) is related to the effective neutron multiplication factor (''keff''), the average number of all neutrons from one fission that cause another fission. ρ = But in nuclear physics, it useful to talk about the reactivity contributed by just the prompt neutrons. This is the reactivity in dollars or cents. Reactivity in its most general sense would not be measured in dollars or cents. This is because keff measures the total value of reactivity, a summation of the reacti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Reactor
A nuclear reactor is a device used to initiate and control a Nuclear fission, fission nuclear chain reaction. They are used for Nuclear power, commercial electricity, nuclear marine propulsion, marine propulsion, Weapons-grade plutonium, weapons production and Research reactor, research. Fissile material, Fissile nuclei (primarily uranium-235 or plutonium-239) absorb single neutron, neutrons and split, releasing energy and multiple neutrons, which can induce further fission. Reactors stabilize this, regulating Neutron absorber, neutron absorbers and neutron moderator, moderators in the core. Fuel efficiency is exceptionally high; Enriched uranium#Low-enriched uranium (LEU), low-enriched uranium is 120,000 times more energy dense than coal. Heat from nuclear fission is passed to a working fluid Nuclear reactor#By coolant, coolant. In commercial reactors, this drives Turbine, turbines and electrical generator shafts. Some reactors are used for district heating, and isotopes, isoto ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Doubling Time
The doubling time is the time it takes for a population to double in size/value. It is applied to population growth, inflation, resource extraction, consumption of goods, compound interest, the volume of malignant tumours, and many other things that tend to grow over time. When the relative growth rate (not the absolute growth rate) is constant, the quantity undergoes exponential growth and has a constant doubling time or period, which can be calculated directly from the growth rate. This time can be calculated by dividing the natural logarithm of 2 by the exponent of growth, or approximated by dividing 70 by the percentage growth rate (more roughly but roundly, dividing 72; see the rule of 72 for details and derivations of this formula). The doubling time is a characteristic unit (a natural unit of scale) for the exponential growth equation, and its converse for exponential decay is the half-life. As an example, Canada's net population growth was 2.7 percent in the year 202 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Doppler Broadening
In atomic physics, Doppler broadening is broadening of spectral lines due to the Doppler effect caused by a distribution of velocities of atoms or molecules. Different velocities of the emitting (or absorbing) particles result in different Doppler shifts, the cumulative effect of which is the emission (absorption) line broadening. This resulting line profile is known as a Doppler profile. A particular case is the thermal Doppler broadening due to the thermal motion of the particles. Then, the broadening depends only on the frequency of the spectral line, the mass of the emitting particles, and their temperature, and therefore can be used for inferring the temperature of an emitting (or absorbing) body being spectroscopically investigated. Derivation (non-relativistic case) When a particle moves (e.g., due to the thermal motion) towards the observer, the emitted radiation is shifted to a higher frequency. Likewise, when the emitter moves away, the frequency is lowered. In th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Research Reactor
Research reactors are nuclear fission-based nuclear reactors that serve primarily as a neutron source. They are also called non-power reactors, in contrast to power reactors that are used for electricity production, heat generation, or maritime propulsion. Purpose The neutrons produced by a research reactor are used for neutron scattering, non-destructive testing, analysis and testing of materials, production of radioisotopes, research and public outreach and education. Research reactors that produce radioisotopes for medical or industrial use are sometimes called isotope reactors. Reactors that are optimised for beamline experiments nowadays compete with spallation sources. Technical aspects Research reactors are simpler than power reactors and operate at lower temperatures. They need far less fuel, and far less fission products build up as the fuel is used. On the other hand, their fuel requires more highly enriched uranium, typically up to 20% U-235, although some use 93 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boiling Water Reactor
A boiling water reactor (BWR) is a type of nuclear reactor used for the generation of electrical power. It is the second most common type of electricity-generating nuclear reactor after the pressurized water reactor (PWR). BWR are thermal neutron reactors, where water is thus used both as a coolant and as a moderator, slowing down neutrons. As opposed to PWR, there is no separation between the reactor pressure vessel (RPV) and the steam turbine in BWR. Water is allowed to vaporize directly inside of the reactor core (at a pressure of approximately 70 bars) before being directed to the turbine which drives the electric generator. Immediately after the turbine, a heat exchanger called a condenser brings the outgoing fluid back into liquid form before it is sent back into the reactor. The cold side of the condenser is made up of the plant's secondary coolant cycle which is fed by the power plant's cold source (generally the sea or a river, more rarely air). The BWR was developed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pressurized Water Reactor
A pressurized water reactor (PWR) is a type of light-water nuclear reactor. PWRs constitute the large majority of the world's nuclear power plants (with notable exceptions being the UK, Japan, India and Canada). In a PWR, water is used both as a neutron moderator and as coolant fluid for the reactor core. In the core, water is heated by the energy released by the fission of atoms contained in the fuel. Using very high pressure (around 155 bar: 2250 psi) ensures that the water stays in a liquid state. The heated water then flows to a steam generator, where it transfers its thermal energy to the water of a secondary cycle kept at a lower pressure which allows it to vaporize. The resulting steam then drives steam turbines linked to an electric generator. A boiling water reactor (BWR) by contrast does not maintain such a high pressure in the primary cycle and the water thus vaporizes inside of the reactor pressure vessel (RPV) before being sent to the turbine. Most PWR designs ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SPERT Reactor
The Special Power Excursion Reactor Test Program (SPERT) was a series of tests focusing on the safety of nuclear reactors.Nuclear Safety — A review of Recent Developments. Volume 2, Number 3. pgs. 15-16. It was commissioned in 1954 by the U.S. Atomic Energy Commission, to be run by the Phillips Petroleum Company Phillips Petroleum Company was an American oil company incorporated in 1917 that expanded into petroleum refining, marketing and transportation, natural gas gathering and the chemicals sectors. It was Phillips Petroleum that first found oil in th .... Reactors SPERT-I The SPERT-I reactor became operational in July 1955, with the first tests being performed in September.W. E. Nyer, S. G. ForbesSPERT I Reactor Safety Studies./ref> SPERT-II The SPERT-II reactor became operational in March 1960. References External links * by SPERT researcher Nuclear safety and security {{nuclear-energy-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Weapon
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission or atomic bomb) or a combination of fission and fusion reactions (thermonuclear weapon), producing a nuclear explosion. Both bomb types release large quantities of energy from relatively small amounts of matter. Nuclear bombs have had yields between 10 tons (the W54) and 50 megatons for the Tsar Bomba (see TNT equivalent). Yields in the low kilotons can devastate cities. A thermonuclear weapon weighing as little as can release energy equal to more than 1.2 megatons of TNT (5.0 PJ). Apart from the blast, effects of nuclear weapons include firestorms, extreme heat and ionizing radiation, radioactive nuclear fallout, an electromagnetic pulse, and a radar blackout. The first nuclear weapons were developed by the Allied Manhattan Project during World War II. Their production continues to require a large scientific and industrial complex, pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reactor Accident
A nuclear and radiation accident is defined by the International Atomic Energy Agency (IAEA) as "an event that has led to significant consequences to people, the environment or the facility." Examples include lethal effects to individuals, large radioactivity release to the environment, or a reactor core melt. The prime example of a "major nuclear accident" is one in which a reactor core is damaged and significant amounts of radioactive isotopes are released, such as in the Chernobyl disaster in 1986 and Fukushima nuclear disaster in 2011. The impact of nuclear accidents has been a topic of debate since the first nuclear reactors were constructed in 1954 and has been a key factor in public concern about nuclear facilities. M.V. Ramana. Nuclear Power: Economic, Safety, Health, and Environmental Issues of Near-Term Technologies, ''Annual Review of Environment and Resources'', 2009, 34, p. 136. Technical measures to reduce the risk of accidents or to minimize the amount of rad ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
