Different reaction taking place simultaneously, along with nuclear fission.
What do you mean with "intermediate reactions"? Radioactive decay of fission products? Activation and damage of structural materials with neutrons? Dynamics of xenon-135? Please specify as each one is a whole different issue (and I can answer only about a few of them).
Do you think about neutron scattering, neutron capture and activation of nuclei, giant resonance ? I´ve no idea what your question is aiming.
In order to turn nuclear fission into electrical energy, nuclear power plant operators have to control the energy given off by the enriched uranium and allow it to heat water into steam.
Enriched uranium typically is formed into inch-long (2.5-centimeter-long) pellets, each with approximately the same diameter as a dime. Next, the pellets are arranged into long rods, and the rods are collected together into bundles. The bundles are submerged in water inside a pressure vessel. The water acts as a coolant. Left to its own devices, the uranium would eventually overheat and melt.
To prevent overheating, control rods made of a material that absorbs neutrons are inserted into the uranium bundle using a mechanism that can raise or lower them. Raising and lowering the control rods allow operators to control the rate of the nuclear reaction. When an operator wants the uranium core to produce more heat, the control rods are lifted out of the uranium bundle (thus absorbing fewer neutrons). To reduce heat, they are lowered into the uranium bundle. The rods can also be lowered completely into the uranium bundle to shut the reactor down in the event of an accident or to change the fuel.
The uranium bundle acts as an extremely high-energy source of heat. It heats the water and turns it to steam. The steam drives a turbine, which spins a generator to produce power.
In some nuclear power plants, the steam from the reactor goes through a secondary, intermediate heat exchanger to convert another loop of water to steam, which drives the turbine. The advantage to this design is that the radioactive water/steam never contacts the turbine. Also, in some reactors, the coolant fluid in contact with the reactor core is gas (carbon dioxide) or liquid metal (sodium, potassium); these types of reactors allow the core to be operated at higher temperatures.
Despite all the cosmic energy that the word "nuclear" invokes, power plants that depend on atomic energy don't operate that differently from a typical coal-burning power plant. Both heat water into pressurized steam, which drives a turbine generator. The key difference between the two plants is the method of heating the water.
While older plants burn fossil fuels, nuclear plants depend on the heat that occurs during nuclear fission, when one atom splits into two and releases energy. Nuclear fission happens naturally every day. Uranium, for example, constantly undergoes spontaneous fission at a very slow rate. This is why the element emits radiation, and why it's a natural choice for the induced fission that nuclear power plants require.
Uranium is a common element on Earth and has existed since the planet formed. While there are several varieties of uranium, uranium-235 (U-235) is the one most important to the production of both nuclear power and nuclear bombs.
U-235 decays naturally by alpha radiation: It throws off an alpha particle, or two neutrons and two protons bound together. It's also one of the few elements that can undergo induced fission. Fire a free neutron into a U-235 nucleus and the nucleus will absorb the neutron, become unstable and split immediately. As soon as the nucleus captures the neutron, it splits into two lighter atoms and throws off two or three new neutrons (the number of ejected neutrons depends on how the U-235 atom splits). The process of capturing the neutron and splitting happens very quickly.
The decay of a single U-235 atom releases approximately 200 MeV (million electron volts). That may not seem like much, but there are lots of uranium atoms in a pound (0.45 kilograms) of uranium. So many, in fact, that a pound of highly enriched uranium as used to power a nuclear submarine is equal to about a million gallons of gasoline.
The splitting of an atom releases an incredible amount of heat and gamma radiation, or radiation made of high-energy photons. The two atoms that result from the fission later release beta radiation (superfast electrons) and gamma radiation of their own, too.
But for all of this to work, scientists have to first enrich a sample of uranium so that it contains 2 to 3 percent more U-235. Three-percent enrichment is sufficient for nuclear power plants.
medium-term operation for Xe-135 concentration control in Nulcear Reactor?
You do not "control" reactions in a reactor. They are governed by the reaction cross sections, which are a physical property of individual nuclei. In the presence of neutrons these reactions will take place. The cross sections are energy-dependent. Therefore, cou cannot "control" the reactions, but you can influence them by the design - i.e. by the presence or absence of a particular meterial, or by influencing the neutron energy distribution (the neutron spectrum). For a more detailed answer you will have to provide amore detailed description of what you actually want to do.
I think that the indermedite reaction for thermal reactors is the diffusion reaction with the moderator that can be controled by the property of water (density, temperarure, ...).
what I understand for your question is the side reaction taking place while irradiating samples in nuclear reactor. Various type of reactions (n,g) (n, Alpha), (n, p) are possible depending upon the cross section of element for a particular reaction. So, its difficult to avoid the side reactions if you want either of these reactions.
Well, I guess you meant "controlling reactor power". Immediate reaction means when control rods are inserted into the reactor, power distribution shows immediate change. On the other hand, when boron injection that is called "boration" is conducted, it has 10 to 15 mins of lag time till power distribution change because circulation of boron water in a nuclear power plant takes normally 10 to 15 mins. Boration is used to change lagged power distribution change while control rod insertion is to immediate power change. This is the characteristic of a system.
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