Patent Number: 
Section: claims

1. A method of generating a medical isotope comprising:providing an annular reaction vessel holding an aqueous fissile solution, the annular reaction vessel having an inner cylindrical wall and an outer cylindrical wall, and a particle emitter positioned inside a cylindrical space defined by the inner cylindrical wall;directing a beam of charged particles along a central axis of the annular reaction vessel into the particle emitter positioned concentrically along the central axis within the annular reaction vessel to produce a beam of neutrons passing radially outward from the particle emitter through the annular reaction vessel into the aqueous fissile solution to produce a nuclear fission reaction dominated by neutrons bombarding the aqueous fissile solution and producing with the neutrons a fission reaction in the aqueous fissile solution to produce additional neutrons in the annular reaction vessel; andcooling the inner and outer cylindrical walls of the annular reaction vessel to provide cooling of the aqueous fissile solution during the nuclear fission reaction within the annular reaction vessel by a cooling fluid. 2. The method of claim 1 wherein the medical isotope is 99Mo and the method further comprises extracting the 99Mo from the aqueous fissile solution. 3. The method of claim 1 wherein cooling of the inner and outer cylindrical walls of the annular reaction vessel is by circulating the cooling fluid through the first and second annular cooling jackets, the first annular cooling jacket abutting and surrounding the outer cylindrical wall of the annular reaction vessel and the second annular cooling jacket abutting the inner cylindrical wall of the annular reaction vessel. 4. The method of claim 3 further comprising providing a feedback controller comprising at least one temperature probe in thermal communication with at least one of the first and second annular cooling jackets and a valve in fluid communication with the aqueous fissile solution and actuating the valve to adjust a level of the aqueous fissile solution based on a temperature sensed by the temperature probes. 5. The method of claim 1 wherein the aqueous fissile solution contains low enriched uranium. 6. The method of claim 5 wherein the low enriched uranium has a concentration between 10 and 450 grams of low enriched uranium per liter solution. 7. The method of claim 5 wherein the aqueous fissile solution contains a mixture of water and at least one of uranyl nitrate, uranyl sulfate, uranyl fluoride or uranyl phosphate. 8. The method of claim 1 further comprising a neutron multiplier absorbing neutrons from the particle emitter traveling outward and releasing more neutrons than the neutron multiplier absorbs. 9. The method of claim 8 wherein the neutron multiplier is selected from a group consisting of beryllium, depleted uranium, and natural uranium. 10. The method of claim 9 wherein the neutron multiplier provides for a neutron multiplication of 1.5-3.0. 11. The method of claim 1 further comprising a neutron moderator absorbing neutrons traveling inward toward the particle emitter and reducing a speed of the neutrons that the neutron moderator absorbs. 12. The method of claim 1 further comprising producing the beam of charged particles by ionizing a gas by at least one of a microwave emission, ion impact ionization, and laser ionization. 13. The method of claim 12 wherein the beam of charged particles directed into the particle emitter are deuterium ions (D+). 14. The method of claim 1 further comprising an accelerator receiving the beam of charged particles and accelerating the beam of charged particles toward the particle emitter. 15. The method of claim 1 further comprising reflecting neutrons back into the annular reaction vessel. 16. The method of claim 1 wherein the cooling fluid is chilled water. 17. The method of claim 1 wherein the particle emitter is a target material receiving the beam of charged particles from a particle source. 18. The method of claim 1 wherein an aspect ratio defined by a radial thickness of the annular reaction vessel perpendicular to the axis to a height of the annular reaction vessel along the axis is greater than 0.1. 19. The method of claim 18 wherein the aspect ratio is between 0.1 and 0.3. 20. The method of claim 19 wherein the aspect ratio is between 0.12 and 0.25.