Patent Application
20160012922
Plenty thorium resources have been found in the PRC as shown in Table 1 below.
It is estimated that the potential energy contained in its thorium resources, when fully exploited, could even match that provided with the vast coal reserves in this country, and provide all its clean energy demand for thousand of years.
Thorium does not contain fissile material itself. When it absorb neutrons, an artificial fissile element, U-233, is formed. The latter, when irradiated with neutron flux, gives more secondary neutrons (>2.3) is a better nuclear fuel as compared with the natural fissile material U-235, In a thermal breeder comprising of thorium and U-233, more U-233 could be produced than consumed.
The world has been interested in thorium breeders since the earliest time of 1960s. The US ORNL designed, built, and operated the research a 7.4 MWt MSBR through the 1960s; constructed by 1964, it went critical in 1965 and was operated until 1969. A 1000 MWe full-scale MSBR was studied afterward. Holden, Charles S. et al. U.S. Pat. No. 20080144762, disclosed a set of alloy formulations with thorium based nuclear fuels in existing fast and thermal spectrum power reactors; for medical isotope production in the epithermal, the fast, the fission spectrum and the thermal spectra; and to use as fuel in test and experimental reactors.
D'Auvergne, Hector A, U.S. Pat. No. 20100067644, Thorium-based nuclear reactor and method, shows A nuclear reactor and method for generating energy from fertile and fissile nuclear fuel material.
Boubcher, Mustapha, et al. U.S. Pat. No. 20130202076 shows three kinds of fuel bundles for a nuclear reactor, one with thorium, and the others with two different types of fissile fuel.
Kim, Dae-Ho, et al. U.S. Pat. No. 20110299645, shows a breeding nuclear fuel mixture including metallic thorium useable in a nuclear power plant, prepared by mixing uranium dioxide (UO.sub.2) or plutonium dioxide (PuO.sub.2).
It is noted that no big technology break-through in the area of thorium breeder has been addressed in these previous foreign patents. During the past decade, the INET (Institute of Nuclear Energy) in PRC has carried out a series of studies in this area and made substantial progress. The inventor has prepared the following relevant patents to the Chinese Patent Office: (1) Lv, Y, The method to accelerate the breeding of nuclear fuel and the breeders, Chinese Pat. No. ZL200810105349.6, 2008; (2) Lv, Y.A full power, natural circulation, inherently-safe reactor for producing high-temperature nuclear energy, Chinese Pat. No. ZL201010145086.9; and (3) Lv, Y., A comprehensive uranium-thorium converter-breeder and a process for producing U233, Chinese Pat. No. 201310011868.7.
An advanced Th232/U233 thermal breeder with both high specific fuel power and breeding yield is presented. Said breeder is designed as a high specific power, unique hybrid reactor, comprising of a reactor core of solid coated particles of uranium kernel and a separated thorium fluoride liquid annular blanket. The contamination of the first loop is thus greatly reduced. Such a design is based on the existing experience of molten-salt cooling fixed-bed power reactors and HTGR, and, at the same time, eliminates the fatal high contamination resulted from the fission products in traditional liquid fuel thorium breeders. The strong contamination jeopardized the commercialization of the traditional liquid fuel thorium breeders. The high specific power of fuel increases the breeding yield of new fuel. Said low contaminated, high breeding-yield thorium breeder is, therefore, most likely selected as one of the candidates in the Second Nuclear Era.
Included among the objects and advantages of the invention is to provide an advanced Th232/U233 thermal breeder with both high specific fuel power and breeding yield.
Another object of the invention is to provide a system to reduce the fission product contamination of the fluid thorium fluoride breeding blanket of said breeder.
Yet another object of the invention is to provide a liquid Bi-Li metal extractor to carry the long-half lived Pa-233 to a storage-decay tank outside the breeder.
Still another object of the invention is to provide a fuel preparation chamber to manufacture new fuel elements and fluid thorium fluoride salts for the breeding blanket.
An additional object of the invention is to propose a detailed structure of the low- contamination, high specific fuel power and breeding yield breeder
These and other object and advantages of the invention may be ascertained by the following description and appended drawings.
A sketch of the complete system of the breeder and associated facilities is illustrated in
The two sides of the broken way elevational view of the breeder are taken from different angles of the separate van-shape breeder core and fertile thorium fluoride blanket, respectively. The right-hand view belongs to annular breeder core 11, which comprises of a pebble bed of spherical graphite balls containing coated particles with fissile uranium fuel kernels. Said core is surrounded with graphite reflector 12 on upper, lower and inner sides. The outside is occupied with liquid thorium fluoride blanket 13. A central coolant flow channel 14 is also illustrated.
The left hand elevational view illustrates the fluid thorium fluoride blanket 15, A Bi-Li liquid-metal extractor 16 is located at the outer rim of the breeder section.
The Bi-Li liquid metal with Pa-233 then flows into the storage-decay tank 17. The U-233 produced therein is converted into UF6 vapor, and finally fabricated into new fuel element in facility 18 for refueling the breeders.
After the cooled primary coolant enters the lower plenum 310, the coolant down-flow alone the down-comer channels 313 into a annular plenum 314, wherein it eventually turns inward, passing through the pebble-bed breeder core 311. The coolant is heated in the pebble-bed with fission energy. Then it is collected and flows upward alone the central high-temperature coolant pipe 315. The up-flowing coolant then enters a diffuser 316, and flows upward alone the riser 317. The high-temperature coolant is pushed upward with the buoyancy force created by the density difference between low-temperature and high-temperature coolants. Natural circulation of the entire primary system is thus realized.
The left half of the elevational view of the breeder is taken through the fertile thorium fluoride blanket section 318. The attached Bi-Li extractor is illustrated as 319. A pipeline 320 connecting the extractor to the outside Pa233 storage-decay tank is also illustrated.
