tailieunhanh - Ebook Power plant technology: Part 2

(BQ) Part 2 book "Power plant technology" has contents: Fast breeder reactors and powerplants, geothermal energy, solar energy wind energy, energy from the oceans, energy storage, environmental aspects of power generation. | ELEVEN FAST-BREEDER REACTORS AND POWERPLANTS 11-1 INTRODUCTION The growth of nuclear power in the world s electric utility industry to date has primarily relied upon water-cooled and gas-cooled thermal neufron reactors. These are burners that in effect consume fissionable fuel with low conversion ratios Sec. 11-2 . The expected continued growth in the use of nuclear power and consequent consumption of available nuclear fuels have prompted the reevaluation of long-term goals. Ways of conserving uranium reserves and of keeping fuei-cycle costs down as fuel costs go up are therefore being sought. The fast-breeder reactor is the logical step in that direction. Fast reactors are those whose neuttons are not slowed down to thermal energies by a moderator. Coolant and other reactor materials however moderate the neuưons to a certain extent in a fast reactor so that theheutron spectrum extends from fission energies that may be as high as 17 MeV but average about 2 MeV down to about or MeV. A hard-spectrum fast reactor is one in which the neutron density distribution extends over a narrow range nearer the high end of the energy spectrum. A soft-spectrum fast reactor on the other hand is one in which more moderation occurs such as by liquid sodium and oxide fuels hence the distribution extends to lower energies. A breeder reactor is one in which more fissionable fuel is produced than is consumed or one that has a conversion or breeding ratio greater than 1. Present-day burner reactors produce some Pu239 from the u238 in their fuel. Some of this plutonium is burned during the life of the core but some remains. The remainder can be used to fuel initial fast-breeder reactors in a reactor mix until a self-supporting fast-breeder-reactor system is at hand. Such a system would convert the abundant u238 453 Í54 POWERPLANT TECHNOLOGY percent of all natural uranium to fissionable Pu239 and hence extend our fu H reserves for centuries to come. Table 1Ỉ-1 lists the . .