Breeding irradiation

Plutonium en Rdacteur Rapide). The partners in this experiment are CEA (F), JRC/ITU, FZK (D) and AEA/BNFL (UK). The goal of these irradiation experiments is to demonstrate basic properties, nuclear efficiency and safety behaviour of new fuel types, which are either defined by a very high content of plutonium (> 40 wt%), together with uranium and minor actinides (MA) or by the complete absence of uranium (in order to avoid additional breeding). Irradiation of a mixed (U, Pu)02 fuel pin with 45 wt% Pu started in July 1995 at HFR Petten and that of mixed (U,Pu,Np)02 and (Pu,Ce)02 fuel pins in December 1995. 

The economic scale of the application of radiation in the field of agriculture in Japan was estimated from public documents to be about 964 million in 1997. The economic scale survey in food irradiation and mutation breeding was extended to the United States for a direct comparison to the situation in Japan. The maximum estimation amounted to 3.2 billion for food irradiation and 11.2 billion for mutation breeding. The economic scale for products in selected agricultural fields was 14.5 billion for the United States and about 0.8 billion for Japan, implying that the former is larger in magnitude by a factor of about 18 [5]. 

Maekawa, M. et al.. Differential responses to UV-B irradiation of three near isogenic lines carrying different purple leaf genes for anthocyanin accumulation in rice Oryza sativa L.), Breeding Sci., 51, 27, 2001. 

A second approach, when a diverse gene pool is available, is to interbreed species with appropriate traits by standard seed-breeding processes. This has been done very effectively with species of brassica to yield the modem oilseed rape (canola). If necessary, the gene pool can be extended by mutation resulting from chemical treatment or from irradiation. This may produce novel varieties with interesting traits and is the basis of the low-linolenic lines from linseed, and other examples are described in Section 9.3. 

But wouldn t we expect animals to breed faster if faced with a threat to their survival These findings may be no more than an ecological equivalent of the faster rate of bacterial replication in response to irradiation, or our own urge to find a sexual partner in the last few minutes after a nuclear warning. Certainly the evidence is supportive of the disposable soma theory, but it is far from proof. Can the relationship be emulated in the laboratory, with minimal exposure to predators or other life-shorten-ing factors ... 

Genetic differences in net photosynthesis have indicated that it is possible to use such physiological parameters in breeding for low irradiance and temperature tolerant cultivars. 

Transuranium elements are artificially created. The (n, y) reaction, first used successfully for the production of neptunium (Z = 93), works only up to fermium (Z = 100). It ends at Fm due to the short half-life of this isotope (e.g., Seaborg and Loveland 1990). With neutron irradiation, transuranium elements can be produced in weighable amounts by breeding in high flux reactors because the cross sections are of the order of barns, neutron fluxes are high, and the usable target thickness is large. 

The irradiation of solids with fast neutrons results in the displacement of atoms from their lattice sites the resultant interstitials and vacancies can cause various radiation damage phenomena. In addition, the determination of H and He gas production as well as the neutron multiplication by 14 MeV-neutron-induced (n,p), (n,a) and (n,2n) reactions, respectively, in the construction materials of fusion reactors is very important. Studies on the tritium breeding and outgassing efficiency for different blanket materials are also important tasks. 

In one significant respect, U-233 is better than uranium-235 and plutonium-239 its higher neutron yield per neutron absorbed. Given a start with some other fissile material (U-235 or Pu-239), a breeding cycle similar to but more efficient than that with U-238 and plutonium (in slow-neutron reactors) can be set up. The Th-232 absorbs a neutron to become Th-233, which normally decays to protactinium-233 and then U-233. The irradiated fuel can then be unloaded from the reactor, the U-233 separated from the thorium, and fed back into another reactor as part of a closed fuel cycle. 

Fresh mixed-oxide fuels consist of a UO2 matrix with a content of 3 to 4% fissile plutonium, with the plutonium concentrated in the master-mixture grains. During irradiation, fission product and transuranium elements are built up in the same manner as in uranium fuel the newly formed transuranium elements are homogeneously distributed in the fuel matrix with the exception of the preferential plutonium breeding in the outermost zone of the pellet. The plutonium constituent has little effect on the chemical conditions in the fuel therefore, both types of fuels are quite similar with regard to the chemistry environment of the fission products under the operating conditions of light water reactors. 

See also i ricultural Science Animal Breeding and Husbandry Cell and Tissue Engineering Egg Production Fisheries Science Food Preservation Genetically Modified Food Production Genetically Modified Organisms Nutrition and Dietetics Pasteurization and Irradiation Plant Breeding and Propagation. 

Hajika, M., Igita, K. and Kitamura, K. (1991) A line lacking all the seed lipoxygenase isozymes in soybean [Glycine max (L.) Merrill] induced by gamma-ray irradiation. Jpn. J. Breed. 41, 507-509. 

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