Breeding ratio

An important parameter of any breeder is the breeding ratio (BR) defined as the ratio of the fissile atoms produced to the fissile atoms consumed and given by the simple relation... 

Breeding ratio (BR), 17 586 Bremsstrahlung X-radiation, 24.101-102 external, 21 312 internal, 21 309, 310t in fine art examination/conservation, 11 403... 

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. 

The Li nucleus can absorb a fast (above 3 MeV) neutron to produce a tritium nucleus, an alpha particle, and a slower neutron. A moderated neutron can be absorbed by a Li nucleus to produce a tritium and an alpha. Neutronic calculations indicate that a thick sphere of natural lithium could breed about 1.8 tritium atoms for each tritium atom burned in a fusion reaction (1 ). Structure and portions of the volume left open for fueling or driver beams reduce the 1.8 tritium breeding ratio. If the ratio falls below 1.0, it may be increased by addition of a neutron multiplier such as Be or Pb, and by isotopically enriching the Li in °Li. 

For lithium temperatures of 500°C, the liquid metal heat exchanger requires 3.3 to 8.0 m of area per MWj-(10,600 to 25,600 m for a 1-GWg plant). The wall thickness will be about 0.65 mm to 1.3 mm for a Cr-1 Mo heat exchanger. For a 30% tritium burn fraction and a 1.75 tritium breeding ratio, 19.5 mg/sec of tritium are added to a 1-GWg HYLIFE plant s liquid metal wall, and the same amount must diffuse out. The permeability constant for tritium diffusing through 2 1 Cr-1 Mo steel is (21)... 

Hydrogen Pressure Ranges for Liquid-Only or Vapor-Only Tritium Recovery for IMW IGF Reactors. For a 2700-MWf IGF reac-tor with a 600-m chamber, a 30% tritium bum fraction and a 1.75 tritium breeding ratio, 19.5 mg/s of tritium are added to the reaction chamber. If tritium is to be recovered from only the liquid, a maximum loss through the vacuum system of 1% (0.2 mg/s) is assumed to be acceptable. With a laser driver (26), the vacuum system might operate at a 1.3 Pa (10 2 Torr) with about 10% of the vapor being pumped per second. Then, about 3.5 mPa (2.6 x 10 Torr) of tritium, or 10 times the pressure associated with 0.2 mg tritium, is allowable. 

The total breeding ratio in the Creys-Malville reactor was 1.24. In BN-350 a breeding ratio of 1.5 can be obtained because it has less neutron absorbing materials. Still higher breeding gain can be achieved in fast reactors at some sacrifice of safety control. 

Second, there are the characteristics that depend on the neutron distribution in the system. These characteristics also have, usually, a direct dependence on the material densities. Examples of characteristics of this type, to be referred to as nucleonic characteristics, are breeding ratio, total power, power shape factor, and reactivity worth. The variation of the functional fiV/], denoting a general nucleonic characteristic, caused by a small but otherwise arbitrary variation 5N in the density distribution of the ith material, is... 

The advent of perturbation theory for altered systems (see Section V,F) opens a new field for the application of perturbation theory—the field of perturbation sensitivity studies. This is the study of changes in effects of perturbations, or system alterations, caused by uncertainties or variations in input parameters. Examples are (1) the uncertainty of the change in an integral parameter (such as the breeding ratio) resulting from design variations due to uncertainties in cross sections, (2) nonlinear effects of cross-section uncertainties, and (3) the effects of data uncertainties, approximations in computational models, or design variations on the detector response in a deep-penetration problem that is solved with a flux-difference or an adjoint-difference method (see Section V,E). 

Average burnup Cladding material Cladding outer diameter/thickness Blanket thickness Upper / lower / radial Breeding ratio ... 

Presently, the availability of great amounts of fissile plutonium produced by thermal reactors and that released from now-redundant nuclear weapons in the USA, the Russian Federation, the European Union, and in some other countries with significant nuclear power sector and relatively slow primary energy consumption growth, has eliminated the initial requirements of short doubling time and high breeding ratio. 

Ductless fuel assemblies are used in the core. Each of three radial zones of the core consists of fuel pins with different diameters (9.1/9.6/10.4mm) with the same fuel composition and fuel pin pith small pins in central and big in outer zone. A rather large fuel pin to pin distance (13.6 mm) provides the large coolant flow cross section, suitable core hydraulic resistance. To reach core breeding ratio equal one, MOX fuel was replaced by U-Pu nitride. 

A measured breeding ratio of 1.16, which resulted in the loading of the first fuel assembly made with reprocessed plutonium in 1980. 

I am much indebted to W. HMele for the remark that C. B. Mills and N. M. Smith (AECD-3973), gave already in 1951 a similarly high estimate for the contribution of the (n,2n) reaction to the breeding ratio. Dr. H fele also made a very careful evaluation of this contribution which will appear as ORNL-2779. He further pointed to the adverse effect of the Li , formed in the (w,a) process, on the breeding ratio. 

You will note that the breeding ratio of the mixed fast-thermal breeder is lower than that of the fast breeder, which may reach the value 2. The purpose... 

The breeding ratio values given in the fifth column of 50 Table I are based on the nuclear properties of plutonium and uranium and take into account neutrons lost by leakage from the reactor as well as those neutrons lost by capture in the coolant and in the metallic protective jacket enclosing the fission metal. It is assumed that the 65 coolant has an absorption cross section per cubic centimeter which is about that of natural uranium, and that the absorption cross section per cubic centimeter of the jacket metal is about that of natural uranium. 

The modem BN-800"reactor design" has a breeding ratio equal to unit, uses MOX-fiiel on the basis of power plutonium and meets all safety requirements. 

Calculations indicate that a large HTGR operating with a fuel permitting rapid withdrawal of the gaseous fission products could achieve a breeding ratio as high as 1.1. 

Studies on the gas-cooled, fast-spectrum reactor have shown that a potential advantage of carbide fuel over oxide is derived from its increased conductivity, increased heavy metal density, and decreased moderating effect. The improved conductivity of the carbide over the oxide may allow the maximum heat removal per foot of fuel element to be raised from 20 to about 40 kW/ft. Increased heavy metal density and decreased moderating effect of the carbide allow the possibility of a harder neutron spectrum and therefore an increase of about 10% in the breeding ratio. 

The combination of analytical methods and of nuclear data used as the basis for the parametric studies in this work was selected so as to be consistent with the safety philosophy, that is, to give reasonable probability of under-predicting Doppler effect and breeding ratio, and of overpredicting sodium void effect. 

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