Сonditions of uranium fission
In the separation of uranium has emerge excess neutrons, twenty or more as the ratio of neutrons N in the nucleus of uranium to the number of protons in its Z
N / Z = 1,59, and from it formed two atoms of elements the middle of the periodic table that fall in its region of stability with the ratio N / Z = 1,2-1,4 after their neutron radiation.
Розпад урану-238 відбувається за такими напрямами:
α-розпад в 234Th (ймовірність 100 % [1], енергія розпаду 4 269,7(29) кеВ [2]):
енергія α-частинок, що випускаються 4 151 кеВ (у 21% випадків) и 4 198 кеВ (у 79% випадків)[3].
Спонтанний поділ (імовірність 5,45(7)×10−5 %)[1];
Подвійний β−-розпад у 238Pu (ймовірність 2,2(7)×10−10 %[1], енергія розпаду 1 144,2(12) кеВ[2])
Розпад урану-232 відбувається за такими напрямами:
α-розпад в 228Th (ймовірність 100 %[1], енергія розпаду 5 413,63(9) кеВ[2]):
енергія випускаємих α-частинок 5 263,36 кеВ (в 31,55 % випадків) и 5 320,12 кеВ (в 68,15 % випадків)[3].
Спонтанне ділення (ймовірність менше 1×10−12 %)[1];
Кластерний розпад з утворенням нукліду 28Mg (ймовірність розпаду менше 5×10−12 %)[1]:
Кластерний розпад з утворенням нукліду 24Ne (ймовірність розпаду 8,9(7)×10−10 %)[1]:
3. Critical mass
Critical mass is the amount of fissile material needed to sustain nuclear fission.
Factor of multiplication
Multiplication factor may refer to:
Neutron multiplication factor, in a nuclear chain reaction
Multiplication factor, a term used in digital photography
Multiplication factor or gas gain in gas ionization detectors used in Nuclear and Particle Physics.
Typical nuclear fission reactions
Uranium and plutonium fission
4. Basic elements of nuclear reactor structure: moderator, fuel rods, coolant agent, tamper, steering rods
Neutron moderator- medium that reduces the velocity of fast neutrons, for example in a nuclear reactor
Fuel rods - composed of the fuel material, mixed with structural, neutron-moderating, or neutron-reflecting materials.
A coolant - a fluid which flows through or around a device to prevent its overheating, transferring the heat produced by the device to other devices that use or dissipate it. An ideal coolant has high thermal capacity, low viscosity, is low-cost, non-toxic, and chemically inert, neither causing nor promoting corrosion of the cooling system. Some applications also require the coolant to be an electrical insulator.
A similar envelope can be used to reduce the critical size of a nuclear weapon, but here the envelope has an additional role: its very inertia delays the expansion of the reacting material. For this reason such an envelope is often called a tamper.
The weapon tends to fly to bits as the reaction proceeds and this tends to stop the reaction, so the use of a tamper makes for a longer lasting, more energetic, and more efficient explosion. The most effective tamper is the one having the highest density; high tensile strength is unimportant because no material remains intact under the extreme pressures of a nuclear weapon. Coincidentally, high density materials are excellent neutron reflectors.
Control rods (steering rods )- used in nuclear reactors to control the fission rate of uranium and plutonium.