The Breeders

The breeder reactor, which would produce and bum plutonium and gradually increase the inventory of fissionable material, requires reprocessing of nuclear fuel. As of 1995 only limited research and development was in progress on breeder reactors, mainly in France and Japan. 

A variation of the classical fuel cycle is the breeder cycle. Special breeder reactors are used to convert fertile isotopes iato fissile isotopes, which creates more fuel than is burned (see Nuclear reactors, reactor types). There are two viable breeder cycles U/ Pu, and Th/ U. The thorium fuels were, however, not ia use as of 1995. A breeder economy implies the existence of both breeder reactors that generate and nonbreeder reactors that consume the fissile material. The breeder reactor fuel cycle has been partially implemented ia France and the U.K. 

The recycle weapons fuel cycle rehes on the reservoir of SWUs and yellow cake equivalents represented by the fissile materials in decommissioned nuclear weapons. This variation impacts the prereactor portion of the fuel cycle. The post-reactor portion can be either classical or throwaway. Because the avadabihty of weapons-grade fissile material for use as an energy source is a relatively recent phenomenon, it has not been fully implemented. As of early 1995 the United States had purchased highly enriched uranium from Russia, and France had initiated a modification and expansion of the breeder program to use plutonium as the primary fuel (3). AH U.S. reactor manufacturers were working on designs to use weapons-grade plutonium as fuel. 

Department of Energy - has sponsored analyses of its reactors and process facilities, the risks of the breeder reactor, the risk of nuclear material transportation and disposal, and the risks of several fuel cycles. 

Mature (10-13 weeks old) premiparous females are obtained from the breeder on the day of mating (see Note 6). The day of mating is defined as gestation day 0 (GDO). 

The plutonium fuel in a breeder reactor behaves differently than uranium. Fast neutrons are required to split plutonium. For this reason, water cannot be used in breeder reactors because it moderates the neutrons. Liquid sodium is typically used in breeder reactors, and the term liquid metal fast breeder reactor (LMFBR) is used to describe it. One of the controversies associated with the breeder reactor is that it results... 

Genetic engineering is used to achieve the same goals of agronomic and quality characteristics as traditional techniques and allows the breeder to make some modifications that would not be possible through other methods... 

Fig. 31. Basic operation of the breeder reactor. The illustration does not include geometrical disposition of fuel in the core and blanket system, (General Electric)...

The isotopes of thorium include mass numbers 223-234. 232Th has a half-life of 1.39 x 1010 years, See also Radioactivity. It emits an alpha-particle and forms meso-thorium 1 (radium-228), which is also radioactive, having a half-life of 6.7 years, emitting a beta-particle. Since 2 2Th captures slow neutions to form, by a series of nuclear reactions, >>U which is fissionable, thorium can be used as a fuel for nuclear reactors of the breeder type. Thorium occurs in earth minerals, an average content estimated at about 12 ppm. Findings of hc Apollo 11 space flight indicated that thorium concentrations in some lunar rocks are about the same as the concentrations in terrestrial basalts. 

Muller, J.K., Eggert, A.-K. and Eisner, T. (2003). Nestmate recognition in burying beetles the breeder s badge as a cue used by females to distinguish their mates from male intruders. Behav. Ecol., 14, 212-220. 

Cooperate With Plant Breeders. Surely the odds run heavily against success in finding thera-peutants that can escape the resistance problem, but plant breeders face hazards as great. Perhaps, we should join hands with the breeders. Perhaps we could outwit the fungus by combining a resistance gene with a chemotherapeutant. This would multiply the odds in our favor. 

Often, however, it is necessary to resort to a more complex procedure. If none of the plants in the population of interest is resistant, the breeder must look outside that population for a source of resistance, either in another variety or in a wild relative. The resistant plants in the second population may be susceptible to a disease, may yield less than desired, have poor color or quality, or be sensitive to heat or cold. 

The breeder then contemplates releasing the line as a new commercial variety. It must be remembered that when a cross is made in which the resistant parent is a breeding line, a commercial variety from another... 

It is at this point that Darwin resorts to the two undisputahle facts from the breeders ... 

In nature there is an automatic selection which is continuously going on simply because variations exist between individual organisms (the breeders fact), and because not all can survive in a limited environment (Malthus fact). Darwin described the principle of natural selection at the end of Chapter 4 of On the Origin of Species, and it may be useful to read it in his own words ... 

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