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.
