For nuclear fission reactors there is no critical temperature, though they do have a temperature coefficient which makes the efficiency of the chain reaction vary slightly with temperature. This can be negative or positive, obvously a negative coefficient is preferred and is safer.
Nuclear fusion is another matter, and very high temperatures are required in tokamaks to get fusion started
A protostar is heated up by gravitational forces causing it to contract and increase in temperature. Once the core reaches a high enough temperature and pressure, nuclear fusion reactions begin, releasing energy and making the protostar shine as a star.
Neutrons are the important particles of nuclear chain reactions and the reactions depend on them. The neutrons do not really start the fission, reaction, however, because the neutrons come from fission in the fuel.The material in the fuel, typically a mix of 235U and 238U, undergoes fission spontaneously. When a fission event happens, more neutrons, typically two or three, are emitted. These bounce about from atom to atom, until they cause another atom to undergo fission, releasing more neutrons to increase the rate at which atoms undergo fission.But the neutrons needed for the chain reaction are actually produced by the fuel spontaneously, and these are produce in an ongoing manner with or without critical mass. So it is not a particle that starts the chain reaction; it is the act of putting together a critical mass.
Nuclear bombs primarily use two types of energy: fission and fusion. Fission refers to the splitting of atomic nuclei to release energy, while fusion involves combining atomic nuclei to release energy, both of which are harnessed in the explosive reactions of nuclear bombs.
Fusion reactions require high temperatures to overcome the electrostatic repulsion between positively charged atomic nuclei, allowing them to come close enough for the strong nuclear force to bind them together. The high temperature provides the particles with enough kinetic energy to overcome this repulsion and initiate the fusion process.
Stars start out as clouds of gas and dust in space. Through the process of gravitational collapse, these clouds condense and heat up, eventually forming a protostar. As the protostar continues to accumulate mass, nuclear fusion reactions begin in its core, leading to the birth of a star.
Nebula gases begin to burn primarily due to two factors: the increase in temperature and pressure that occurs as the gas clouds collapse under their own gravity. As the gas contracts, it heats up, and once the temperature reaches a critical point, nuclear fusion reactions can ignite, leading to the formation of stars. Additionally, the presence of sufficient mass is necessary to create the conditions for these processes to occur.
The core will reach between 250,000,000 to 500,000,000'C at its stable temperature. Beforehand it will rapidly gain heat from hundreds of thousands to its stable temperature, where it can begin the process of nuclear fusion. Hope that helps!
A protostar is heated up by gravitational forces causing it to contract and increase in temperature. Once the core reaches a high enough temperature and pressure, nuclear fusion reactions begin, releasing energy and making the protostar shine as a star.
The build up of temperature and pressure is greatest at the core of the forming star. This is where gravity causes atoms to be squeezed together and nuclear fusion reactions begin, releasing huge amounts of energy.
A star birth refers to the formation of a new star from a collapsing cloud of gas and dust in space. As gravity causes the cloud to contract, the core temperature rises until nuclear fusion is ignited, marking the birth of a star. These new stars eventually stabilize and begin to generate energy through nuclear reactions in their cores.
The core of the protostar reached an extremely high temperature
Hydrogen undergoes nuclear fusion to form helium at a temperature of 107 K
Gravitational attraction pulls gas and dust together in a nebula, causing it to condense and heat up. When the pressure and temperature in the core of the nebula become high enough, nuclear fusion reactions begin, initiating the process of becoming a star.
Stars begin the process of nuclear fusion when their cores reach temperatures of around 10 million degrees Celsius. At this temperature, hydrogen atoms in the core of the star are able to overcome the electrostatic repulsion between positively charged protons and fuse together to form helium.
Neutron particle is needed to begin nuclear chain reaction.
If we are just considering the "basic" nuclear reaction in a "regular" nuclear reactor, the particles of interest are the uranium-235 atoms (which are fissionable), and the neutrons, which get loose and cause fissions when they are absorbed by the U-235 atoms. We could broaden this to include some other reactions, but this is a fabulous place to begin to investigate nuclear physics.
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