US PATENT 2,206,634 (Process for the Production of Radioactive Substances); E. Fermi, E. Amaldi, F. Rasetti, E. Segre, B. Pontecorvo; July 2, 1940. The process, for production of isotopes including transuranic elements by reaction of neutrons, employs means for generating neutrons having a high average energy, slowing down and scattering the neutrons by projecting them through a medium of an element of a class including H, He, Be, C, Si, and Pb, and then passing the neutrons into a mass of material containing an element capable of forming a radioactive isotope by neutron capture, including radioactive isotopes capable of emitting beta rays.

US PATENT 2,524,379 (Neutron Velocity Selector), Enrico Fermi, Oct 3, 1950. The present invention relates to neutron velocity selector apparatus and particularly to apparatus of this type which utilizes a rotating shutter. Full text courtesy of Los Alamos National Laboratory (LANL) Research Library, PDF (798KB)

US PATENT 2,708,656 (Neutronic Reactor), Enrico Fermi and Leo Szilard, May 17, 1955. The present invention relates to the general subject of nuclear fission and particularly to the establishment of self-sustaining neutron chain fission reactions in systems embodying uranium having a natural isotopic content. Full text courtesy of LANL Research Library, PDF (5497KB). Additional Information.

US PATENT 2,714,577 (Neutronic Reactor); E. Fermi, W.H. Zinn; August 2, 1955. A heavy water moderated neutron reactor has been designed to employ as fuel uranium metal of natural isotopic composition. The composite fuel rods are suspended from the cover so as to extend well into the reactor tank. Each rod is composed of an aluminum portion extending vertically into the tank from the cover and a thermal neutron fissionable portion secured to the lower end of the aluminum portion. Heavy water fills the tank to a level above the juncture of the aluminum portion with the fissionable portion of each composite rod so as to cause the fissionable portion to be wholly immersed.

US PATENT 2,768,134 (Testing Material in a Neutronic Reactor); E. Fermi et al.; October 23, 1956. A means of testing the nuclear properties of materials to be used in a nuclear reactor is given. This is accomplished by placing in an operating reactor the materials loaded on a transverse stringer or tray-type device of sufficient length that upon withdrawing the portion containing the materials tested a portion containing the customary reactor components is drawn into place, thereby completing the reactor core integrity. A cadmium control rod suitably indexed is used to maintain constant flux density in the reactor, thus, by comparing the two readings of the control rod positions, a relationship may be established between the nuclear properties of the tested material and the normal reactor components. Such information is an important aid in atomic research.

US PATENT 2,780,595 (Test Exponential Pile); E. Fermi; February 5, 1957. A nuclear fission test pile is described which is designed to measure the fissioning chain reaction induced in a sub-critical mass of natural U by a neutron source. The pile comprises a number of cells containing natural U, disposed in a graphite moderator, and adjacent to an independent source of neutrons for the purpose of causing in the test pile a chain reaction that cannot be self-sustaining. Measurements are made of the radioactivity induced in strips of indium foil which are inserted in appropriate slots or channels in the core. This pile permits the taking of such measurements from a reactor requiring a reduced amount of valuable material, and eliminates the possibility of a dangerous buildup of reactivity.

US PATENT 2,798,847 (Method of Operating a Neutronic Reactor); E. Fermi et al.; July 9, 1957. A method of operating a reactor and particularly the operation of the shim and control rods to maintain an operational reactivity factor of unity is described. The shim rods of a highly neutron absorbent material are gradually withdrawn to compensate for the build up of fission product poisons, which would otherwise decrease the innate reactivity factor, whereas the control rods compensate for the normal fluctuations of the power level and for the power demand of varying loads or start up procedure.

US PATENT 2,807,581 (Neutronic Reactor); E. Fermi, L. Szilard; September 24, 1957. Reactors of the type employing plates of natural uranium in a moderator are discussed wherein the plates are uniformly disposed in parallel relationship to each other thereby separating the moderator material into distinct and individual layers. Each plate has an uninterrupted surface area substantially equal to the cross-sectional area of the active portion of the reactor, the particular size of the plates and the volume ratio of moderator to uranium required to sustain a chain reaction being determinable from the known purity of these materials and other characteristics such as the predictable neutron losses due to the formation of radioactive elements of extremely high neutron capture cross section.

US PATENT 2,807,727 (Neutronic Reactor Shield); E. Fermi, W.H. Zinn; September 24, 1957. The reactor radiation shield material is comprised of alternate layers of iron-containing material and compressed cellulosic material, such as masonite. The shielding material may be prefabricated in the form of blocks, which can be stacked together in any desired fashion to form an effective shield.

US PATENT 2,813,070 (Method of Sustaining a Neutronic Chain Reacting System); E. Fermi, M.C. Leverett; November 12, 1957. This patent relates to neutronic reactors and a method of sustaining a chain reaction. The reactor shown in the patent for carrying out the method is the gas-cooled type comprised of a solid moderator having a plurality of passages therethrough for receiving bodies of fissionable material. In carrying out the method, the reactor is loaded by inserting in the passages fuel elements and moderator material in a proportion to sustain a chain reaction. As the reproduction ratio decreases below the desired figure due to impurities formed during operation of the reactor, the moderator material is gradually replaced with additional fuel material to maintain the reproduction ratio above unity.

US PATENT 2,836,554 (Air Cooled Neutronic Reactor); E. Fermi, L. Szilard; May 27, 1958. A nuclear reactor of the air-cooled, graphite moderated type is described. The active core consists of a cubical mass of graphite, approximately 25 feet in each dimension, having horizontal channels of square cross section extending between two of the opposite faces, a plurality of cylindrical uranium slugs disposed in end to end abutting relationship within said channels providing a space in the channels through which air may be circulated, and a cadmium control rod extending within a channel provided in the moderator. Suitable shielding is provided around the core, as are also provided a fuel element loading and discharge means, and a means to circulate air through the coolant channels through the fuel channels to cool the reactor.

US PATENT 2,837,477 (Chain Reacting System); E. Fermi, M.C. Leverett; June 3, 1958. A nuclear reactor of the gas-cooled, graphite-moderated type is described. In this design, graphite blocks are arranged in a substantially cylindrical lattice having vertically oriented coolant channels in which uranium fuel elements having through passages are disposed. The active lattice is contained within a hollow body, such as a steel shell, which, in turn, is surrounded by water and concrete shields. Helium is used as the primary coolant and is circulated under pressure through the coolant channels and fuel elements. The helium is then conveyed to heat exchangers, where its heat is used to produce steam for driving a prime mover, thence to filtering means where radioactive impurities are removed. From the filtering means the helium passes to a compressor and an after cooler and is ultimately returned to the reactor for recirculation. Control and safety rods are provided to stabilize or stop the reaction. A space is provided between the graphite lattice and the internal walls of the shell to allow for thermal expansion of the lattice during operation. This space is filled with a resilient packing, such as asbestos, to prevent the passage of helium.

US PATENT 2,852,461 (Neutronic Reactor); E. Fermi, W.H. Zinn, H.L. Anderson; September 16, 1958. Means are presented for increasing the reproduction ratio of a graphite-moderated neutronic reactor by diminishing the neutron loss due to absorption or capture by gaseous impurities within the reactor. This means comprised of a fluid-tight casing or envelope completely enclosing the reactor and provided with a valve through which the casing, and thereby the reactor, may be evacuated of atmospheric air.

US PATENT 2,931,762 (Neutronic Reactor); E. Fermi; April 5, 1960. A nuclear reactor is described consisting of blocks of graphite arranged in layers, natural uranium bodies disposed in holes in alternate layers of graphite blocks, and coolant tubes disposed in the layers of graphite blocks which do not contain uranium.

US PATENT 2,969,307 (Method of Testing Thermal Neutron Fissionable Material for Purity); E. Fermi, H.L. Anderson; January 24, 1961. A process is given for determining the neutronic purity of fissionable material by the so-called shotgun test. The effect of a standard neutron absorber of known characteristics and amounts on a neutronic field also of known characteristics is measured and compared with the effect which the impurities derived from a known quantity of fissionable material has on the same neutronic field. The two readings are then made the basis of calculation from which the amount of impurities can be computed.