What is an example of a nuclear family?
It is a family that includes only parents (of any genders) and children (if any). It can also be comprised of a single parent and children or a child. The point that differentiates it from other types of families (i.e. extended families) is that it does not and should not include any other possible flavors of relatives. No grandparents, uncles, aunts, cousins, great-uncles and great-grandparents.It does not mean the people included into a nuclear family need to be orphans. It just denotes the smallest family unit in existence that can function and be treated as an independent whole. Extended families are formed out of these nuclear families and other individuals. For example, if 2 brothers each has a wife and some kids, they form two nuclear families that can be parts of an extended family which includes their families, their parents and other relatives.
How does a nuclear power plant work?
I'll give a short, basic answer because this question has been asked on Quora several times and there are full answers to the question already. Basically, a nuclear fission power plant operates much like a coal-fired power plant. You heat water in a boiler, it turns to steam, and the steam is used to drive turbine generators that generate electricity.The main difference then, is how the heat is generated. Nuclear fission gives off this heat primarily through the fission of Uranium-235 nuclei. When there are enough U-235 nuclei close to each other, and you have a substance (such as water) that can thermalize neutrons (slow them down), then a high probability exists for U-235 nuclei to absorb one of these neutrons, fission, and give off neutrons to also be thermalized, absorbed in other nuclei and continue the chain reaction. The net effect of this is heat is produced and transferred to the coolant. Not all reactor designs use water as coolant, but most do.The heated water either boils directly in the reactor vessel (Boiling Water Reactor or BWR), or it is kept under pressure and transfers heat to a separate system in a steam generator (Pressurized Water Reactor or PWR). Either way, the steam is then used to run turbine generators and produce electricity.The fission reaction is controlled through various means. The most direct control is either positioning fuel rods at various levels in the reactor core, or by withdrawing and inserting control rods. Control rods are made of neutron-absorbing materials that effectively interrupt the fission chain reaction. Reactivity in the reactor is also controlled by added "poisons" (which absorb neutrons, such as boron), and by the moderator itself. Most moderators have what is called a negative temperature coefficient for reactivity. Using water as an example (since that is what most reactors use as a moderator/coolant), as water gets hotter, it becomes more likely that a neutron zooming into it will just pass through and not be slowed down. Less neutrons being slowed down means less fissions, so reactor power decreases. As water cools, you then get more neutrons thermalized, and thus more fissions and power goes up.Anyway, that is a basic explanation. Years ago, I studied from books on the subject so thick, if you dropped one on your foot you'd probably end up with a broken foot. So it's safe to say, there is a lot more to discuss on the matter!
Why are nuclear power stations just glorified steam engines, can’t we use a better technology?
That's like saying why do we still use moving air to fly airplanes. Turbo-fan engines (aka gas turbine engines) are just glorified propeller planes; can't we do better?There is an old joke in power generation.A mechanical engineer was working at a nuclear power plant run by a company dominated by nuclear specialists. This poor mechanical engineer was constantly ignored and belittled for being just a mechanical engineer.One day during a meeting where his input was once again ignored he finally said:“Do you know the point of all of this?”“Huh?”“The point, the reason you are here, the reason this whole damn facility exists?”“Why is that?”“Your real job is to turn that mechanical generator, and I’m the only person in this room who knows how it works; the rest of you are just here to help me do my job because if the generator doesn't turn the entire facility and everyone in it is worthless.”…The truth is, the fundamental technologies used to make power haven't changed much because they are quite well understood.However, the reliability and efficiency of these systems has increased exponentially and that has made our power-plants exponentially more intricate and complex than they used to be.While the fundamental thermodynamic and electromechanical concepts involved haven't changed significantly, it's not correct to say that a modern nuclear (or coal) power plant is at all similar to a simple steam engine.In particular, the creation of reliable turbine engines (gas or steam driven), that can be used at scale, is one of the most efficient ways known to extract large amounts of rotational energy from a supply of heat and pressure (created by exploding gas or steam).Now the key phrase here is “at scale,” and the scale we’re talking about is one where the turbine is probably bigger than your home… we're talking about systems so complex and highly refined that it can literally take several days just to start a coal or nuclear power plant and the emergency stop system is a complex computer-driven shutdown sequence.Comparing a steam engine to a steam turbine is like comparing a propeller plane to a jet fighter. Technically, they are both just “moving air,” but the performance differences are incomparable.
Explain how the heat energy is converted into mechanical energy.?
You cannot fully convert heat energy into mechanical energy without loosing some as waste heat. There exists a maximum efficiency possible based on the temperature of the hot and cold regions. In general, heat is converted to mechanical energy and some heat rejection, via several processes involving temperature or phase change as well as pressure change of a working fluid. Here are numerous examples: Nuclear power plant: Hot region is the nuclear fuel rods. Cold region is the cooling tower or river water condenser. This heat engine uses the Rankine cycle with steam and liquid water as the working fluid. Coal power plant: Hot region is the flame and boiler. Cold region is the cooling tower or river water condenser. This heat engine uses the Rankine cycle with steam and liquid water as the working fluid. Internal combustion engine: Hot region is the fuel being burned in a compressed volume of air. Cold region is the atmosphere. This heat engine uses the Otto cycle or the Diesel cycle, it can be modeled with air as the working fluid. Jet engine: Hot region is the stabilized flame in the combustion chamber. Cold region is the atmosphere. This heat engine uses the Brayton cycle, it can be modeled with air as the working fluid.
What are the main functions of the different parts of a nuclear reactor?
There are several components common to most types of reactors:Fuel. Uranium is the basic fuel. Usually pellets of uranium oxide (UO2)are arranged in tubes to form fuel rods. The rods are arranged into fuel assemblies in the reactor core.Moderator. Material in the core which slows down the neutrons released from fission so that they cause more fission. It is usually water, but may be heavy water or graphite.Control rods. These are made with neutron-absorbing material such as cadmium, hafnium or boron, and are inserted or withdrawn from the core to control the rate of reaction, or to halt it. (Secondary control systems involve other neutron absorbers, usually boron in the coolant – its concentration can be adjusted over time as the fuel burns up.)Coolant. A fluid circulating through the core so as to transfer the heat from it. In light water reactors the water moderator functions also as primary coolant. There is secondary coolant circuit where the water becomes steam.Pressure vessel or pressure tubes. Usually a robust steel vessel containing the reactor core and moderator/coolant, but it may be a series of tubes holding the fuel and conveying the coolant through the surrounding moderator.Steam generator. Part of the cooling system of pressurised water reactors (PWR & PHWR) where the high-pressure primary coolant bringing heat from the reactor is used to make steam for the turbine, in a secondary circuit. Essentially a heat exchanger like a motor car radiator*. Reactors have up to six 'loops', each with a steam generator.Containment. The structure around the reactor and associated steam generators which is designed to protect it from outside intrusion and to protect those outside from the effects of radiation in case of any serious malfunction inside. It is typically a metre-thick concrete and steel structure.
What is an external combustion engine?
*An external combustion engine (EC engine) is a heat engine where an internal working fluid is heated, often from an external source, through the engine wall or a heat exchanger. The fluid then performs work during expansion and by acting on the mechanism of the engine provides useable motion and useable work. The fluid is then cooled (closed cycle) or dumped and cool fluid pulled in (open cycle). Burning fuel with an oxidizer, or any other heat source can supply the external heat, hence "external combustion". The internal fluid is quite often an inert gas. The fluid can be any liquid or more commonly, any gas, as well as mixtures. In the case of the steam engine, the fluid changes phases between liquid and gas. *Examples: A steam turbine is a good example of an external-combustion engine. Heat from a burning fuel/oxidizer mix, or from a nuclear reactor changes water in a device called a boiler to steam. Pipes carry the steam into the turbine, which has a series of bladed wheels attached to a shaft. The high-temperature steam expands as it rushes through the turbine and so pushes on the blades and causes them to turn the shaft. Steam leaving the turbine has a much lower temperature. The spinning shaft can drive an electric generator, move a ship's propeller, or do other useful work. *Stirling engine is also external combustion engine. *http://en.wikipedia.org/wiki/Stirling_engines *http://en.wikipedia.org/wiki/External_combustion_engine *http://www.stirling-tech.com/stirlingengine.htm For images , please click: www.thefreedictionary.com/steam%20engi... www.colrich.pwp.blueyond.../hotairengi... http://www.stirling-tech.com/images/st5.jpg
What are the applications of nuclear fission?
There are various applications of nuclear fission:It can be used in a nuclear power plant to make electricity.It can be used in a nuclear propulsion system to drive ships or submarines.It can be used to make neutrons for sensitive elemental analysis.It can be used to make neutrons for industrial purposes.It can be used in a nuclear weapon.It can be used as a very sensitive neutron detector.It can be used to make radioisotopes for industrial use.It can be used to make radioisotopes for therapeutic or diagnostic medial purposes.