a fission of uranium produces 4×10^-11 joules how many fissions is needed to produce 40kw
Answers
Explanation:
An integer number of neutrons, for example, either two, three or four, are emitted in the reactions leading to different pairs of fission products described in reaction (1). The average number is 2.43. Some of the neutrons in reaction (1) can be used to induce fission in another 235U nucleus, thus continuing a controlled, self-perpetuating nuclear chain reaction. Some fraction of the remaining neutrons from reaction (1) are utilized in reaction (2) to produce 239Pu. The rest are absorbed in other nuclei without further effect.
The isotope 232Th, although not fissionable with thermal neutrons, is a possible energy source because it absorbs thermal neutrons to produce long-lived 233U, which also undergoes thermal neutron fission with a high probability. Thus the "big three" readily fissionable nuclei are: 235U, 239Pu, and 233U.
Fig. 14-2. The reactor vessel of a commercial reactor is inside this containment building.
A typical pressurized (or boiling) water nuclear reactor consists of a core of fissionable material (UO2, enriched to 3.3% to 4% in 235U) in which the chain reaction takes place. A picture of a reactor is shown in Fig. 14-2. The energy released in the fission process, which is primarily in the form of the kinetic energy of the fission fragments, heats the water. The water serves both as a neutron moderator (it slows down the fission neutrons to thermal energies), and as a heat transfer fluid. The chain reaction is controlled by rods of neutron-absorbing material inserted into the core. The thermal energy is removed from the core by the water to an external thermal-energy converter. In the pressurized water reactor (PWR), the thermal energy produces steam for the turbine through the use of a heat exchanger, whereas in a boiling water reactor (BWR), the steam is produced for direct use in the turbine.