Thermal breeder-reactor

J. R. Lamarsh, Introduction to Nuclear Engineering, Addison-Wesley, Reading, MA, 1975 A. M. Perry, A. M. Weinberg, Thermal Breeder Reactors, Annu. Rev. Nucl. Sci. 22, 317 (1972)... 

In the thermal breeder reactor, is produced from Th. The reactor may be designed either with a core containing a mixture of Th and or with a central zone core) of surrounded by an outer layer blanket) of Th. However, it is necessary to minimize parasitic neutron capture in structmal materials including monitoring systems, control rods, etc. Calculations have shown that a conversion ratio of 1.06 should be possible. 

E. D. Arnold et al.. Preliminary Cost Estimation Chemical Processing and Fuel Costs for a Thermal Breeder Reactor Station, US. EG Report ORNL-1761, Oak Ridge National Laboratory, Jan. 27, 1955. 

With the lower inventories of the thermal breeders it is possible, however, to install much more capacity in this reactor type as compared with the fast breeders, using the same amount of fissile material. This leads to much higher penetration rates into the total system nuclear capacity for the thermal breeders, or, in other words, a much higher fraction of the total system nuclear capacity will consist of thermal breeders. Furthermore, the low inventories of the thermal breeder reactors make it possible to start these reactors with even though this results in a higher... 

Fig. 5. Radioactivity after shutdown per watt of thermal power for A, a Hquid-metal fast breeder reactor, and for a D—T fusion reactor made of various stmctural materials B, HT-9 ferritic steel C, V-15Cr-5Ti vanadium—chromium—titanium alloy and D, siUcon carbide, SiC, showing the million-fold advantage of SiC over steel a day after shutdown. The radioactivity level after shutdown is also given for E, a SiC fusion reactor using the neutron reduced...

Boron-10 has a natural abundance of 19.61 atomic % and a thermal neutron cross section of 3.837 x 10 m (3837 bams) as compared to the cross section of 5 x 10 m (0.005 bams). Boron-10 is used at 40—95 atomic % in safety devices and control rods of nuclear reactors. Its use is also intended for breeder-reactor control rods. 

Many of the fission products formed in a nuclear reactor are themselves strong neutron absorbers (i.e. poisons ) and so will stop the chain reaction before all the (and Pu which has also been formed) has been consumed. If this wastage is to be avoided the irradiated fuel elements must be removed periodically and the fission products separated from the remaining uranium and the plutonijjm. Such reprocessing is of course inherent in the operation of fast-breeder reactors, but whether or not it is used for thermal reactors depends on economic and political factors. Reprocessing is currently undertaken in the UK, France and Russia but is not considered to be economic in the USA. 

Y. S. Tang. Ph.D has more than 35 years of experience in the field of thermal and fluid flow. His research interests have covered aspects of thermal hydraulics that are related to conventional and nonconventional power generation systems, with an emphasis on nuclear reactor design and analysis that focuses on liquld-meta -cooled reactors. Dr. Tang is co-author of Radioactive Waste Management published by Taylor 8 Francis, and Thermal Analysis of Liquid Metal Fast Breeder Reactors, He received a B5. from National Central University In China and an MS. in mechanical engineering from the University of Wisconsin. He earned his Ph.D. 

In fast (neutron) reactors, the fission chain reaction is sustained by fast neutrons, unlike in thermal reactors. Thus, fast reactors require fuel that is relatively rich in fissile material highly enriched uranium (> 20%) or plutonium. As fast neutrons are desired, there is also the need to eliminate neutron moderators hence, certain liquid metals, such as sodium, are used for cooling instead of water. Fast reactors more deliberately use the 238U as well as the fissile 235U isotope used in most reactors. If designed to produce more plutonium than they consume, they are called fast-breeder reactors if they are net consumers of plutonium, they are called burners . 

PWR - thermal pressurised water reactors BR - fast breeder reactors ... 

Shortages of oil and coal will be followed by one of uranium. The nuclear industry knows that the fuel of today s thermal nuclear reactors (U235) is exhaustible and therefore in a few decades they plan to shift to breeder reactors. They say little to the public, except that this conversion would make nuclear power inexhaustible. This is true, because the conventional "slow neutron" thermal reactors are "once through" (in the sense that they consume their uranium fuel), while fast neutron breeder reactors make more fuel than they use. 

I have devoted more space to explaining the dangers of nuclear power than to the consequences of using fossil fuels, because while the consequences of carbon emission are well understood, the inexhaustible nature of thermal power and the implications of terrorists using breeder reactor fuel for military purposes are largely unknown. 

The concluding fifth chapter compares the energy options available to mankind. It provides quantitative data on the present trends of C02 emissions, energy consumption and population growth and on the consequences of continued reliance on exhaustible (fossil and nuclear) energy sources. I also explain why dependence on thermal nuclear energy is likely to lead to dependence on plutonium-fueled breeder reactors. The chapter calculates the costs and time needed to convert to a totally renewable energy economy and also discusses the consequences of inaction. 

Mixtures of uranium and plutonium may be used instead of weakly enriched uranium in thermal reactors and are applied in fast breeder reactors, which are operated with the aim of producing more fissile material than is consumed by fission. The main fissile nuclide is Pu, which is continuously reproduced according to reaction (11.4) from In fast breeder reactors operating with about 6 tons of Pu and about 100 tons of U a net gain of fissile Pu may be obtained. The bum-up is about 10 MW d per ton of fuel, and reprocessing with the aim to recover the plutonium is expedient. 

Pu02 is also well suited as a nuclear fuel. It is often used in the form of a UO2/ PUO2 mixture ( mixed oxides MOX) containing up to about 20% PUO2. UO2/ PUO2 mixtures may be applied in thermal reactors instead of enriched uranium, or in fast breeder reactors. Pellets of Th02 can be used in thermal converters for production of... 

The main advantage of UC is the high thermal conductivity. On the other hand, the low chemical resistance is a major disadvantage UC is decomposed by water below 100 °C, which is prohibitive for its use in water-cooled reactors. However, UC may be applied in gas-cooled reactors or in the form of UC/PuC mixtures in fast sodium-cooled breeder reactors. 

Solvent extraction can be carried out in pulsated extraction columns, in mixer-settlers or in centrifuge extractors. Organic compounds such as esters of phosphoric acid, ketones, ethers or long-chain amines are applied as extractants for U and Pu. Some extraction procedures are listed in Table 11.11. The Purex process has found wide application because it may be applied for various kinds of fuel, including that from fast breeder reactors. The Thorex process is a modification of the Purex process and has been developed for reprocessing of fuel from thermal breeders. 

When more them one solute is involved in the consideration of the process design, the situation becomes much more complex since the extraction behaviours of the different solutes will usually be interdependent. In the case of irradiated thermal reactor fuels the solvent extraction process will be dealing with uranium containing up to ca. 4% of fission products and other actinides. These will have only a minor effect on uranium distribution so that a single-solute model may be adequate for process design. However, in some cases nitric acid extraction may compete with U02 extraction and a two-solute model may be needed. In the case of breeder reactor fuels the uranium may contain perhaps 20% of plutonium or thorium. Neptunium or protactinium levels in such fuels may also not be negligible and, under these circumstances, the single-solute... 

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