This invention is designed to enhance the production of rare radioactive materials that have significant value for national defense, industrial research, and medical care.
Some radioactive materials — such as tritium, helium-3, and various radioisotopes derived from nuclear-fission byproducts — are scarce in nature and difficult to produce; yet they have important roles in advanced national-security applications, ongoing scientific/industrial research, modern medical diagnosis/treatment, and future fusion-energy production.
A lithium-liquid-cooled fission reactor (liquid-metal reactor — LMR), fueled by uranium and/or thorium, has tangible attributes that can be tailored to enhance the production of scarce radioactive materials. The liquid lithium in this invention has a multipurpose role: as a neutronic moderator, as a circulating reactor coolant, and as a medium for transporting radioactive substances to various extraction devices.
Compared with other nuclear reactors that have been adapted for radioactive-material production, the proposed LMR disclosed in this invention would provide higher production rates specifically for weapons-grade tritium, as well as valuable commercial fission-product radioisotopes. Also, the LMR would have greater production flexibility to meet uncertain and potentially changing national and international requirements in a multi-decade planning horizon.
An attribute of this invention is a designed capability such that such a specialized lithium-cooled reactor would be functionally licensable and economically viable, while meeting prioritized goals of national importance. It would be based on prior well-developed and tested technology that has used liquid-metal coolants containing lithium. Its combined capability of simultaneously producing national-defense tritium, medical radioisotopes, and marketable heat provides a commercially feasible concept.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
There are four embodiments of this Lithium-Metal-Cooled Fission Reactor for Producing Radioactive Materials (Liquid-Metal Reactor — LMR) invention . In each embodiment, radioactive products produced inside the reactor vessel, within or in conjunction with the lithium coolant, would be transported — by a liquid-transport continuously circulating pipage loop — to a designated location outside the reactor vessel where an extraction system is attached to chemically process the continuously recirculating fluid and to where a separate heat-transfer system is located to reduce the temperature of the liquid coolant, thus generating usable or marketable steam, heat, or electricity.
1. The first embodiment (LMR-cladded solid fuel) is a nuclear reactor with traditional cladded solid-fuel elements in the reactor core zone, with the core permeated and cooled by a lithium-based liquid metal, and with the core surrounded by the same coolant circulating in an external neutron moderator and reflector zone inside the reactor containment vessel. In this first embodiment, the primary radioactive material produced is tritium, while radioactive fission products might or might not be recovered after the core fuel elements are removed from the reactor and undergo a deliberate fission-product removal process. The tritium product is recovered from the circulating coolant by continuous on-line separation processes that are accomplished outside the reactor containment vessel.
2. The second embodiment (LMR-porous solid fuel) is a nuclear reactor with porous solid-fuel elements in the reactor core zone, with the core permeated and cooled by a lithium-based liquid metal, and with the core surrounded by the same coolant circulating in an external neutron moderator and reflector zone inside the reactor containment vessel. In this second embodiment, tritium is the primary radioactive material produced; however, fission products would also migrate or be expelled continuously from the fuel into the coolant and be transported by said coolant. Both the tritium and the fission products would be separated and recovered from the circulating coolant by continuous on-line processes that are accomplished outside the reactor containment vessel.
3. The third embodiment (LMR-liquid fuel) is a liquid-metal cooled nuclear reactor in which the fissionable fuel is chemically and physically mixed with the lithium-based liquid coolant, and the circulating mixture is surrounded by an external neutron reflector at the inside wall of the reactor containment vessel. In this third embodiment, tritium is produced and transported in the coolant; however, fission products would also accumulate and be transported within the circulating fuel-coolant mixture. Both the tritium and the fission products would be recovered from the circulating coolant by continuous on-line separation processes that are accomplished outside the reactor containment vessel.
4. The fourth embodiment (LMR-breeder) is a variation of each of the previous three embodiments of a liquid-metal cooled nuclear reactor operated in such a way as to remove and recycle the fissionable content of the fuel, whether the reactor is operated with solid or liquid fuel mixtures, whether or not the fissionable fuel is chemically and physically mixed with the lithium-based liquid coolant.
In this fourth embodiment, tritium, fission products, and reactor fuel are subject to chemical reprocessing so as to recycle the fissile component. The physical plant would be essentially the same as each of the first three embodiments, but with the addition of reactor-core materials chemically removed and reprocessed from either the liquid or solid fuel so as to implement any of the three previous embodiments, with the aim of recovering unconsumed fuel and recycling it for extended operation of the reactor.
Reactor criticality for the fourth embodiment would be sustained and balanced by reconstituting and replacing the solid or liquid fuel that constitutes the reactor core with the necessary fissile and fertile fuel composition, by such means as to reconstitute and resupply the fuel cycle in a manner the effectively sustains, converts, or breeds new fissile nuclear fuel from fertile nuclear components, such as U-238 or Th-232.
Here’s the Table of Contents for the provisional patent, dated 16 Feb. 2012, as filed:
BACKGROUND OF THE INVENTION 1
RADIOACTIVE-MATERIAL PRODUCTION IN NUCLEAR REACTORS 1 Reactor Design Considerations for Radioactive-Material Production 3 SCENARIOS THAT DRIVE RADIOISOTOPE PRODUCTION REQUIREMENTS 4 Nuclear Arms-control Reductions 4 Tritium Requirements 4 Medical and Industrial Radioisotopes 5 Radioisotopes 6 MOLTEN-SALT LIQUID-FUELED REACTORS 6 MOLTEN-SALT CONVERTER REACTORS 8 AQUEOUS SOLUTION REACTORS 10 SOLUTION REACTORS FOR MEDICAL-ISOTOPE PRODUCTION 12
BRIEF DESCRIPTION OF THE DRAWINGS 13 DETAILED DESCRIPTION OF DRAWINGS 13 BRIEF DESCRIPTION OF THE INVENTION 15
DETAILED DESCRIPTION OF THE INVENTION 15 LITHIUM-COOLED LMR DESIGN AND OPERATION FLEXIBILITY 15 TECHNICAL ASPECTS OF THE LMR-LIQUID FUEL INVENTION 16 TECHNICAL ASPECTS OF THE LMR-SOLID FUEL INVENTION 18 ESTIMATED FISSION-PRODUCT PRODUCTION RATES 19 Molybdenum-99 Production Example 19 EXTRACTION OF TRITIUM FROM THE LMR COOLANT 20 OPTIMIZING TRITIUM PRODUCTION 20 ELECTRICAL OR PROCESS-STEAM PRODUCTION IN LMR 21 TRITIUM PRODUCTION RATES 21 Moderator Blanket 22 Some Relevant Parameters Involving Lithium and Tritium 24 ESTIMATED FINANCIAL COST AND VALUE 25 U.S. GOVERNMENT TRITIUM-PRODUCTION COSTS 26 LITHIUM AVAILABILITY 27 COST OPTIMIZATION 28
SUMMARY OF THE INVENTION 28 BRIEF DESCRIPTION OF THE DRAWINGS 29 DETAILED DESCRIPTION OF DRAWINGS 29 DESCRIPTION OF THE PREFERRED EMBODIMENTS 31 LMR-cladded solid fuel 32 LMR-porous solid fuel 32 LMR-liquid fuel 32 LMR-breeder 32 ABSTRACT 33 DRAWINGS 34