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However, the liquid–vapor boundary terminates in an endpoint at some critical temperature T c and critical pressure p c. This is the critical point. The critical point of water occurs at 647.096 K (373.946 °C; 705.103 °F) and 22.064 megapascals (3,200.1 psi; 217.75 atm; 220.64 bar). [3]
Using careful control rod movements, it is thus possible to achieve a supercritical reactor core without reaching an unsafe prompt-critical state. Once a reactor plant is operating at its target or design power level, it can be operated to maintain its critical condition for long periods of time.
A transcritical cycle is a closed thermodynamic cycle where the working fluid goes through both subcritical and supercritical states. In particular, for power cycles the working fluid is kept in the liquid region during the compression phase and in vapour and/or supercritical conditions during the expansion phase.
As already mentioned before, k = (Neutrons produced in one generation)/(Neutrons produced in the previous generation). In other words, when the reactor is critical, k = 1; when the reactor is subcritical, k < 1; and when the reactor is supercritical, k > 1. Reactivity is an expression of the departure from criticality. δk = (k − 1)/k.
Note that subcritical and supercritical describe the stability of the outer lines of the pitchfork (dashed or solid, respectively) and are not dependent on which direction the pitchfork faces. For example, the negative of the first ODE above, x ˙ = x 3 − r x {\displaystyle {\dot {x}}=x^{3}-rx} , faces the same direction as the first picture ...
Hydraulic jump in a rectangular channel, also known as classical jump, is a natural phenomenon that occurs whenever flow changes from supercritical to subcritical flow. In this transition, the water surface rises abruptly, surface rollers are formed, intense mixing occurs, air is entrained, and often a large amount of energy is dissipated.
In most types of critical reactors, there exist circumstances in which the rate of fission can increase rapidly, damaging or destroying the reactor and allowing the escape of radioactive material (see SL-1 or Chernobyl disaster). With a subcritical reactor, the reaction will cease unless continually fed neutrons from an outside source.
A numerical measure of a critical mass depends on the effective neutron multiplication factor k, the average number of neutrons released per fission event that go on to cause another fission event rather than being absorbed or leaving the material. A subcritical mass is a mass that does not have the ability to sustain a fission chain reaction ...