[en] The main aspects of advanced thorium cycles in LWRs and HWRs are reviewed. New concepts include the seed blanket close packed heavy water breeder, the light water seed blanket thorium burner and self-induced thorium cycle in CANDU type reactors. (author)

[en] A new type of light water seed blanket with the seed having 20% enrichment and the blanket a special combination of elements of natural uranium and thorium, relatively close packed, but sufficient spacing for heat transfer purpose is described. The blanket would deliver approximately half the total energy for about 10,000 MWDIT, so this type of core would be just as economical or better in uranium ore consumation as present cores. (author)

[en] The nuclear reactor with spatially separate breeding and fission zones and pressurized water cooling has a Pu compensation in the fission zones like that occurring in light water reactors after a life of about 35,000 MWD/to. The geometry of the breeding to the fission zone is selected so that an epithermal neutron spectrum is produced. The fission zones preferably contain 8 to 14% by weigth of Pu and the breading zones contain 2 to 6% by weight of Pu. (orig./DG)

[en] This patent describes a light water receptor (LWR) for breeding fissile material using a uranium-plutonium cycle. It comprises: a prebreeder section having plutonium fuel containing a Pu-241 component, the prebreeder section being operable to produce enriched plutonium having an increased Pu-241 component; and a breeder section for receiving the enriched plutonium from the prebreeder section, the breeder section being operable for breeding fissile material from the enriched plutonium fuel. This patent describes a method of operating a light water nuclear reactor (LWR) for breeding fissile material using a uranium-plutonium cycle. It comprises: operating the prebreeder to produce enriched plutonium fuel having an increased Pu-241 component; fueling a breeder section with the enriched plutonium fuel to breed the fissile material

[en] A neutronic flow meter which uses a neutron source surrounded by a moderator at cryogenic temperatures and neutron detectors located upstream and downstream of the source to measure the fluid flow rate through a pipe and alternately a ships speed is described. (U.S.)

[en] A reference design was developed for a close packed pressurized heavy water cooled and moderated breeder core, operating on the uranium plutonium cycle. The seed-blanket concept was found to be most advantageous. The core is composed of a large number of identical seed-blanket units, each of which is controlled by moving the seed, which is zoned in such a way as to vary the leakage of neutrons between the seed and blanket. The control method is known as Geometry Control. In order to assure a negative void coefficient at all times during life it was necessary to dilute the heavy water with 20% light water. Initial fuel loading was approximately 4700 kg of fissionable plutonium of recycle composition. This leading was sufficient for approximately a two-year lifetime, at the end of which the Fissile Inventory Ratio (FIR) was 1.05. (FIR is the ratio of fissile fuel in the core at any time to that at the beginning of core life). A thermal hydraulic analysis indicated that the core could fit into the pressure vessel of a standard pressurized light reactor and would meet safety requirements in case of a LOCA

[en] This paper presents an optimization of the seed blanket concept for the burning of thorium; present uranium requirements in commercial reactors would be reduced about 75%. Only natural thorium and natural and moderately enriched uranium would be utilized which would be difficult or impossible to use in weapons. Advantages of the proposed core design are presented: minimum amount of fissile fuel, feasibility of ''geometry control''. Approximately 75% of the total core energy will be obtained from the natural thorium if irradiated to its radiation limit of about 50,000 MWD/T or more, the rest coming essentially from the seed. The enrichment of the seed will be set as low as possible consistent with other objectives since the lower the enrichment, the less suitable is the seed fuel for weapons use. From a safety standpoint, the seed/blanket concept is superior to uniformly enriched cores. After the blanket irradiation limit is reached, the blanket can be stored, until such time as it is economic to reprocess and reuse the U-233 and thorium. The seed elements, which will be almost completely depleted, need not be reprocessed. (B.G.)

[en] This invention provides a method of operating a nuclear reactor, and a reactor construction enabling such operation, in which a significant portion of the total core power is derived from burning natural thorium, rather than uranium. Because of the relatively high thermal absorption and low resonance capture of irradiated thorium, as compared to natural uranium, applying the invention to heavy-water moderated reactors would remove the present positive void coefficient of such reactors. Such a reactor construction and operation would have the further advantage of producing substantial savings in the requirements of uranium

[en] The aim of this project is to make a breakthrough in nuclear energy technology by designing a core meeting the following requirements no fuel required in initial loading or produced which can be utilized for nuclear weaponry; use of tried and proved light water nuclear technology. The vast majority of the world's commercial nuclear power reactors are of the light water type; production of most the core energy from thorium. Since thorium is much more plentiful than uranium, this will ensure enough nuclear fuel for many centuries. It will be unnecessary to utilize sodium cooled fast breeders which have high capital costs and difficult maintenance and safety problems. (author). 7 figs

No abstract available