Nuclear Reactors

One worst case scenario would be a meltdown in which an explosion puts the entire contents of the reactor into the atmosphere. As bad as the Chernobyl disaster was, only a part of the material in the reactor got into the atmosphere. This was in large part because several people went into a water pool below the reactor to drain it, knowing the job would quickly kill them. If the molten metals in the reactor had got into the water, the steam explosion would have sent a large part of it into the air.

We know there were agricultural losses as far away (and upwind) as Scotland, and complete losses of herds in Finland, many hundreds of miles from the plant. We know that thousands of square miles of land were rendered unfit for use for years, and many square miles almost permanently. Estimates for the economic loss from Chernobyl run as high as a trillion 1995 dollars. Twenty years after the event, Belarus was still putting 20% of its money into cleanup. Clearly, a worse disaster would be very bad. An equivalent failure in the US would cost a multiple of the amount of money.

The spent fuel pools of US reactors are considered a weak part of plant design and cause considerable anxiety over security. Of the 103 plants currently operating, only six have spent fuel pools hardened against impact of a six ton aircraft, and only one is hardened against impact of a large commercial airliner. The US has not decided how to deal with nuclear waste, and, as a result, most of the waste is in spent fuel pools. Impact of a large commercial airliner into one of these structures might cause a "worst case scenario" of scale similar to Chernobyl. This is an object of widespread discussion in public forums on nuclear energy, such as town meetings currently happening in Vermont over whether the Vermont Yankee plant should have its license renewed. There have been rumors that the 9-11 terrorists considered hitting such a plant, but decided against it because it would cause to much harm to their cause.

The short answer is that at least the fuel melts, but if it can melt anything else, it does, including concrete.

There are different types of meltdowns. At Three Mile Island, the meltdown happened when hot steam reacted with the zirconium cladding of reactor rods. This allowed uranium fuel pellets to come into contact and melt together. Upwards of half of the fuel in the reactor melted.

A worse case is if the reactor itself melts, so the nuclear fuel can go through it. In Chernobyl, the reactor was opened by a series of explosions caused by steam and chemical reactions. Molten fuel escaped the reactor, and there was a threat that when it melted through the concrete floor the reactor stood on, it would fall into a water containment below. If this had happened it almost certainly would have caused another explosion and a much worse disaster.

Fortunately for all of us who are alive, a number of people went into the area of the disaster, knowing they would be killed as a result, to get the water out of the containment under the reactor. The molten fuel combined with other materials, and was diluted in the process, finally solidifying in the area under the reactor.

As a matter of interest, other people also worked to contain the radioactive material, knowing the work would kill them. Some of these people lived as long as six weeks in the hospital, and some hospital workers came down with radiation poisoning as a result of this exposure. The disaster workers who died were buried in graves over 300 feet deep to isolate the radiation in their bodies.

Neutron absorption is the key to the operation of a nuclear reactor as this is what perpetuates the chain reaction. Neutrons can be absorbed by a number of things within the core of an operating reactor, but when a fuel atom absorbs a neutron, it becomes unstable and fissions. The fission event releases fission fragments, energy, and more neutrons, which will, when absorbed, continue the chain reaction.

The dangerous condition caused by overheating inside a nuclear reactor is known as a meltdown. This occurs when the core overheats to the point where the fuel rods are damaged, leading to the release of radioactive materials. Meltdowns can potentially result in the breach of containment structures and severe environmental consequences.

The nuclear fuel is found in the fuel rods. These fuel rods are formed into fuel bundles called fuel assemblies, and together they make up the reactor core.

Control rods are neutron absorbing materials used the check the operation of a nuclear reactror.

Some examples: Ag-Cd-In (especially for CANDU reactors), boron carbide and other boron compounds, lanthanides compounds, hafnium compounds, etc.

In a nuclear reactor, nuclear reactions create heat by splitting atoms or combining them. This heat is used to produce steam, which drives a turbine connected to a generator. The generator then converts mechanical energy into electricity that can be distributed to power homes and businesses.

Yes, potassium is sometimes used as a coolant in liquid metal fast breeder reactors. It has good heat-transfer properties and low neutron absorption, making it suitable for this application. However, its reactivity with water and air limits its use in some reactor designs.

A nuclear weapon requires highly enriched U-235 or Pu-239, whilst reactors usually don't contain fuel with more than 5 percent fissile material, this is for the vast majority true and for all power reactors. There are some small research ones that may have up to 20 percent U-235 but still not enough for a weapon. The other point is that a weapon requires a critical assembly to be put together in a very short time to get an explosion, whilst in a reactor the fissile material is spread out in an array of fuel assemblies, it could not be suddenly brought together in one mass. The worst that can happen in a reactor is overheating and melting of the fuel, which is a commercial disaster but the reactor design should contain the results in the secondary containment, with only small release of activity outside the plant boundaries. At Chernobyl the design did not have secondary containment, but it's important to realise that the explosion there was due to a surge in steam pressure, not a nuclear explosion, though fuel melting did then occur. That design would never be approved in the US or the EU areas.

: Main article: Thorium fuel cycle Thorium, as well as uranium and plutonium, can be used as fuel in a nuclear reactor. Although not fissile itself, 232Th will absorb slow neutrons to produce (233U), which is fissile. Hence, like 238U, it is fertile. Problems include the high cost of fuel fabrication due partly to the high radioactivity of 233U which is a result of its contamination with traces of the short-lived 232U; the similar problems in recycling thorium due to highly radioactive 228Th; some weapons proliferation risk of 233U; and the technical problems (not yet satisfactorily solved) in reprocessing. Much development work is still required before the thorium fuel cycle can be commercialised, and the effort required seems unlikely while (or where) abundant uranium is available. Nevertheless, the thorium fuel cycle, with its potential for breeding fuel without fast neutron reactors, holds considerable potential long-term benefits. Thorium is significantly more abundant than uranium, and is a key factor in sustainable nuclear energy. One of the earliest efforts to use a thorium fuel cycle took place at Oak Ridge National Laboratory in the 1960s. An experimental reactor was built based on Molten Salt Reactor technology to study the feasibility of such an approach, using thorium-fluoride salt kept hot enough to be liquid, thus eliminating the need for fabricating fuel elements. This effort culminated in the Molten-Salt Reactor Experiment that used 232Th as the fertile material and 233U as the fissile fuel. Due to a lack of funding, the MSR program was discontinued in 1976.

A nuclear reactor generates heat by controlled nuclear fission. Primary coolant carries this heat away to make steam. If a reactor is not cooled, it will overheat. Even if it is shut down immediately, the radioactive fragments of fission in the core will still be undergoing radioactive decay. This will continue to generate a lot of what we call decay heat. This heat can be sufficient to melt the metal that forms the fuel elements if cooling is not maintained, and the result is a nuclear meltdown with various consequences.

A boiling water nuclear reactor delivers steam to the turbine blades. The heated water in the reactor boils and produces steam, which is then used to drive the turbine blades and generate electricity.

A nuclear reactor primarily emits electromagnetic radiation in the form of gamma rays. These gamma rays are released during the nuclear fission process that occurs in the reactor core. Additionally, reactors may also release some neutron radiation through reactions with the reactor's components.

When we talk about the reactor cooling system, the meaning is usually the system for removing the reactor thermal output and transferring it to the steam raising units. This is obviously the way the reactor power is utilised. There are other cooling systems though, the most important being the emergency cooling system which can remove the reactor after heat, after it has been shutdown. This system can be powered by back up diesel generators if the connection to the grid has been lost. There will also be an emergency cooling system for the secondary containment, should there be a large loss of coolant accident, though this is very unlikely to happen.

Question incomplete. Pu-241 is formed from Pu-240, the longer the fuel is irradiated in the reactor the more of the higher mass Pu isotopes are formed. This is why to produce weapons grade Pu, which must be mostly Pu-239, the fuel has to be irradiated only for a limited period. Pu-241 is fissile, so could be used in a weapon, but I believe the disadvantage is that it fissions spontaneously which can lower the weapons efficiency. I suggest you (a) complete the question, and (b) put it in the Nuclear Weapons category, possibly also Nuclear Physics, rather than Nuclear Energy which I take to be about civil use of nuclear power.

It is called a nuclear meltdown when fuel rods in a nuclear power plant generate so much heat that they start to melt. This can lead to the release of radioactive material and poses a serious threat to both human health and the environment.

Nuclear reactors can be harmful if not managed properly, such as in the case of accidents or leaks. However, when operated safely and within regulatory guidelines, nuclear reactors provide clean energy and help reduce greenhouse gas emissions. Strict safety measures and regulations are in place to minimize risks associated with nuclear power generation.

1. meltdown
2. generation of hydrogen gas when water contacts overheated zirconium alloy on fuel pellets, possible hydrogen explosion (chemical not nuclear)
3. warping of fuel rods
4. warping of control rods making it impossible to move them to regulate the reactor
5. structural failures
6. etc.

About 70% of France's electricity is generated from nuclear power, making it one of the largest users of nuclear energy in the world. France has 56 nuclear reactors in operation across 19 nuclear power plants.

control rods

There are 100 nuclear power reactors operating in USA besides five under construction as of July 2014.

There were no operational nuclear reactors in 1934 as the first functioning nuclear reactor, the Chicago Pile-1, was not built until 1942 as part of the Manhattan Project.