Breeding reactor

Discuss the differences between a light water and a heavy water nuclear fission reactor. What are the advantages of a breeds reactor over a conventional nuclear fission reactor ... 

The composition of boron carbide is approximately 80 atomic percent boron. The material is often considered as a source of boron, without the high reactivity of the latter. Like boron, B4C has a high neutron capture cross-section for thermal neutrons and a low secondary gamma radiation. As such, it provides an excellent neutron absorber and is used extensively to control the neutron flux in nuclear fission reactors, such as the boiling water, pressurized water, and fast breeding reactors. It is also used for the compact storage of spent fuel rods.l l... 

Fig. 3. The Earth s energy reserves. The dotted line in the block representing nuclear fusion refers to reserves of uranium and thorium in the land masses, calculated for breeding reactors.

Tobias, I., Breeding Reactors, USAEC Report CF-55-6-157, Oak Ridge, National Laboratory. June 7, 1955. 

A D—T fusion reactor is expected to have a tritium inventory of a few kilograms. Tritium is a relatively short-Hved (12.36 year half-life) and benign (beta emitter) radioactive material, and represents a radiological ha2ard many orders of magnitude less than does the fuel inventory in a fission reactor. Clearly, however, fusion reactors must be designed to preclude the accidental release of tritium or any other volatile radioactive material. There is no need to have fissile materials present in a fusion reactor, and relatively simple inspection techniques should suffice to prevent any clandestine breeding of fissile materials, eg, for potential weapons diversion. 

Tritium is produced in heavy-water-moderated reactors and sometimes must be separated isotopicaHy from hydrogen and deuterium for disposal. Ultimately, the tritium could be used as fuel in thermonuclear reactors (see Fusionenergy). Nuclear fusion reactions that involve tritium occur at the lowest known temperatures for such reactions. One possible reaction using deuterium produces neutrons that can be used to react with a lithium blanket to breed more tritium. 

The role of the reactor may be either as a converter, which produces some plutonium by neutron absorption in uranium-238 but depends on uranium-235 for most of the fission, or as a breeder, which contains a large amount of plutonium and produces more fissile material than it consumes. Breeding is also possible using uranium-233 produced by neutron absorption in thorium-232. 

This reaction offers the advantage of a superior neutron yield of in a thermal reactor system. The abiHty to breed fissile from naturally occurring Th allows the world s thorium reserves to be added to its uranium reserves as a potential source of fission power. However, the Th/ U cycle is unlikely to be developed in the 1990s owing both to the more advanced state of the / Pu cycle and to the avadabiHty of uranium. Thorium is also used in the production of the cx-emitting radiotherapeutic agent, Bi, via the production of Th and subsequent decay through Ac (20). 

The only large-scale use of deuterium in industry is as a moderator, in the form of D2O, for nuclear reactors. Because of its favorable slowing-down properties and its small capture cross section for neutrons, deuterium moderation permits the use of uranium containing the natural abundance of uranium-235, thus avoiding an isotope enrichment step in the preparation of reactor fuel. Heavy water-moderated thermal neutron reactors fueled with uranium-233 and surrounded with a natural thorium blanket offer the prospect of successful fuel breeding, ie, production of greater amounts of (by neutron capture in thorium) than are consumed by nuclear fission in the operation of the reactor. The advantages of heavy water-moderated reactors are difficult to assess. 

The net yield of thermal neutrons from the fission of is higher than from that of and, furthermore, Th is a more effective neutron absorber than As a result, the breeding of is feasible even in thermal reactors. Unfortunately the use of the Th/ U cycle has been inhibited by reprocessing problems caused by the very high energy y-radiation of some of the daughter products. 

Along with these power plants, the U.S. could build up a fuel reprocessing capability to allow spent nuclear fuel to be reused which would lower fuel cost and eliminate the storage of high-level nuclear waste. Fuel for the reactors has been estimated to be available for 1,000 years using standard reactors with high breeding ratios and breeder reactors where more fuel is produced than consumed. 

France has the largest implementation of breeder reactors with its 250-MW Phenix reactor and 1200-MW Super-Phenix. The Phenix went into operation in 1973 and the Super-Phenix in 1984. Japan has its 300-MW Monju reactor which was put into service in 1994. While India has the 500-MW PFBR and 13.2-MW FBTR. These reactors produce about 20% more fuel than they consume. Optimum breeding allows about 75% of the energy in natural uranium to be used compared to 1% in a conventional light water reactor. 

Breeder reactors were developed to utilize the 97% of natural uranium that occurs as nonfissionable U-238. The idea behind a breeder reactor is to convert U-238 into a fissionable fuel material, plutonium. A reaction to breed plutonium is... 

Bose-Einstein Condensate phase of matter that is created just above absolute zero when atoms lose their individual identity Boyle s Law law that states volume of a gas is inversely related to its pressure Breeder Reactor type of nuclear reactor that creates or breeds fissionable plutonium from nonfissionable U-238 Buckministerfullerene Cg, allotrope of carbon consisting of spherical arrangement of carbon, named after architect Buckmin-ister Fuller, Invertor of geodesic dome Buffer a solution that resists a change in pH... 

One of the fascinating features of fission power is the breeding of fission fuel from nonfissionable uranium-238. Breeding occurs when small amounts of fissionable isotopes are mixed with uranium-238 in a reactor. Fission liberates neutrons that convert the relatively abundant nonfissionable uranium-238 to uranium-239, which beta-decays to neptunium-239, which in turn beta-decays to fissionable plutonium-239. So in addition to the abundant energy produced, fission fuel is bred from relatively abundant uranium-238 in the process. 

The fast breeder reactor derives its name from its ability to breed, that is. to create more fissionable material than it consumes. This ability stems from... 

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