US 2707555 A
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W 3,. 1955 A. M. GAUDIN 2,767,555
BERYL oar: SELECTOR Filed June 8, 1950 3 Sheets-Sheet l INVENTOR. momz M. Muom fi flm A. M. GAUDIN BERYL ORE SELECTOR Filed June 8, 1950 FIG.4.
COUNTER 8; PREAMPLIFIERS 3 Sheets-Sheet 3 POWER SUPPLY LINEAR AMPLIFIER SOLENOID VIBRATORY FEEDER RADIATION SHIELD SGALER WITH DISORIMINATOR ELECTRONIO CONTROL RELAY VARIAO INVENTOR.
ANTOINE M. BAUDIIW BERYL ORE SELECTOR Antoine M. Gaudin, Newtonville, Mass, assignor to the United States of America as represented by the United States Atomic Energy Commission Application June 8, 1950, Serial No. 166,964
4 Claims. (Cl. 209-72) The present invention relates to a method and apparatus for concentrating portions of beryllium ore and beryllium-containing minerals having a relatively high beryllium content. When beryllium ore is crushed to particles in the order of an inch or fraction of an inch some are found to contain a high percentage of beryllium and other little or no beryllium.
It is an object of the present invention to provide an apparatus which may be used in concentrating ores and minerals containing beryllium.
it is another object of the present invention to provide a method of discriminating between particles of ore containing a certain minimum percentage of beryllium and ore particles which contain less than this percentage of beryllium.
It is likewise an object'of the invention to provide a method and apparatus for automatically selecting berylhum-containing minerals, such as emeralds, from feed material. I 1
Other objects will be in part obvious and in part pointed out hereinafter.
When beryllium is bombarded with gamma rays a nuclear reaction results which proceeds according to the equation,
It has been discovered that a range of gamma ray energies exists which will cause a neutron producing reaction with beryllium only.
in one of its broader aspects the method of the present invention comprises subjecting-particles of ore to the action of high energy gamma rays, detecting the amount of neutron radiation emitted from the piece of ore as a result of the bombardment with gamma rays, and separating those pieces which result in a production of a larger number of neutrons from those which result in the production of a smaller number of or no neutrons. An apparatus which is suitable for carrying out this purpose is illustrated in the drawings. Reference is made to the drawings in describing the construction and operation of this apparatus.
Figure 1 is a perspective and schematic view, in part broken away, of the entire apparatus.
Figure 2 is a view of the arrangement of the ports in a neutron moderating block.
Figure 3 is a horizontal section of the neutron modcrating block of Figure 2.
Figure 4 is a block diagram of a circuit suitable for use in conjunction with the ore selector.
Referring now particularly to Figure l the pieces of ore to be separated according to their beryllium content are initially placed in the vibrator feeder 100. This feeder is'a hopper-like funnel which allows particles of ore to pass through the channel 102 to a conveyor belt 104. Particles are carried along the belt through a semi-circular channel 140 in a block 106 of a neutron moderating material. This block may consist, for example, of wax, paraffin or some other material having a high content of hydrogen. The pieces of ore are carried on the belt past the bottom of a vertical shaft 108 where they are subjected to the bombardment of a beam of high energy gamma rays. The gamma rays are produced in an apparatus 10 of the Van de Graaff type situated directly above the shaft. Neutrons are produced when the gamma rays strike beryllium containing ore particles passing beneath the shaft 108. In order to detect the neutrons produced a number of neutron detector tubes 113 (shown in phantom) are disposed in the moderating block 106. The neutrons emitted from the beryllium in the ore by interaction with gamma rays are relatively high energy neutrons. The neutron detector tubes are positioned in the moderator block 106 so that the high energy neutrons which leave the beryllium will be moderated to thermal energies before entering the detector tubes 113.
In order to sep'aratethe berylium containing pieces of ore from those which do not contain beryllium, a mechanism 151 is incorporated in the geometry of the moderator block at the point where the pieces of ore pass into the beam of gamma rays to separate them according to their neutron producing ability. Reference is made'particw larly to Figure 5, which is a horizontal section of the block 106, in describing the operation of this kicker mechanism. The mechanism is preferably activated by passing a current through a solenoid 153 responsive to the arrival I of neutrons in one of the detector tubes. Thesolenoid operates a kicker arm 152 to displace the particle from the conveyor belt. The arm 152 is returned to its rest position by the action of spring 155. The passage of a current through the solenoid is triggered by circuit units indicated in Figure l and described below with reference to Figures 1 and 4.
Referring now to Figure 2 the geometry of the ports is shown as they would appear in a phantom moderator block. The path of the belt is through the semi-circular longitudinally extending port 140. A 'y ray beam passes into the moderator block from the top through the shaft 108 generally centrally located with respect to the top of the block. The pieces of ore which are kicked off the belt in its passage through the block leave the block through the port 144 at one side. The lower side of this port is sloped downward to permit the easy exit of the particles from the block. Four neutron detector tube shafts 146 are positioned around the shaft 108 generally parallel thereto so that a substantial amount of the moderating material is located between the particle of ore being bombarded and the counter tubes contained in the shafts 146. A graphite plug 148 is positioned beneath the shaft 108 to minimize the production of background neutrons from a reaction between deuterium and gamma-rays when the gamma-ray energy exceeds 2.2 million electron volts.
Referring now to Figure 3 the passage of the ore particles through the port may be seen best in this horizontal sectional view of the moderator block. The ore passes from right to left through the port 140. As it enters the port at the right a set of guides 150 moves the particles to one side of the conveyor belt. Other means integral with the vibrator feeder are used to space the.
particles so that only one particle will be subjected to the bombardment of the X-rays at one time. The plunger arm or kicker 152 is activated by the solenoid kicker unit 151 located in the port opposite the exit port 144. The plunger arm is shown in its recessed or rest position and it is shown in phantom in its extended position. By this movement of the arm particles on the belt passing beneath the source of 'y rays are knocked from the belt through the exit port.
It has been found that the neutrons are produced solely in beryllium from a gamma-neutron reaction when the energy of the gammas is sufficiently high. The approximate minimum activation energy for the gamma neutron reaction in beryllium is approximately 1.63 million electron volts. If the energy of the gammas is of this value or greater, the neutrons will be produced by reaction with beryllium. It has also been discovered that between the gamma energies of 1.63 and 2.2 million electron volts a gamma neutron reaction occurs for beryllium only. That is, no neutrons will result from the interaction of gammas having energies in this range for any substance other than beryllium. Above the gamma energy of 2.2 million electron volts a gamma neutron reaction proceeds with deuterium. It is therefore preferred in carrying out the method of the present invention to subject the ore particles to gammas having energies between 1.63 and 2.2 million electron volts. However, if it is known that no other sub stance is present in the ore which will produce neutrons on reaction with high energy gammas. gammas having energies in excess of 2.2 million electron volts may be employed.
An arrangement of the moderator 106 and shafts, wherein the detector containing shafts 146 are four inches from the center of the block. and a gamma ray beam having a cross section of four square inches and an intensity of about 80 roentgcns per minute is employed, is satisfactory for use with particles of a fraction of an inch. In one specific operation of the process with the apparatus described above, one to two percent of the gamma rays exceeded 1.63 million electron volts in energy.
Referring now to Figures 1 and 4 the operation of the standard electronic components will be described. High voltage for operation of the neutron detector tubes 113 is supplied from a high voltage power supply 111. Neutrons passing through detector tubes 113 cause ionization therein resulting in a pulse being applied to preamplifier 112. This pulse is amplified in preamplifier 112, further amplified in linear amplifier 115 and applied to the discriminator portion of the sealer and discriminator circuit 130. The discriminator output operates the sealer. The output of sealer 130 actuates an electronic control relay 131 which energizes solenoid 153 to operate the kicker mechanism previously described. After the output pulse of sealer 130 the electronic control relay 131 returns to its normal operating position and solenoid 153 is deenergized.
The discriminator used in conjunction with sealer 130 is a standard amplitude discriminator. The characteristic of this type of circuit is that it emits a constant amplitude output pulse for any input pulse in excess of a certain fixed amplitude. Input pulses below the fixed amplitude do not pass through the discriminator. In this manner pulses from beta and gamma radiation do not actuate the kicking mechanism as these pulses are too small to pass through the discriminator.
it is apparent from the foregoing that an efiicient means for concentrating the coarsely particulate ores of beryllium is provided according to the present invention. It is to be understood however that the foregoing description is given as illustrative and is not to be interpreted as limiting the scope of the present invention. Other gamma ray sources may be used instead of the disclosed Van de Graaff type source, for example pure radium sources or sources made of cerium antimony cobalt, and others, may be used as gamma ray sources. Further, the particular geometry of the neutron block and gamma source may be adapted or changed without departing from the scope of the present invention. The circuit is composed of conventional units and substantially the same results may be obtained by the substitution of other similar units.
Since many embodiments might be made of the present invention and since many changes might be made in the embodiment described, it is to be understood that the foregoing description is to-be interpreted as illustrative only and not in a limiting sense.
1. Apparatus for automatically sorting beryllium ore particles according to their beryllium content which comprises a source of gamma radiation in excess of 1.63 million electron volts adapted to produce a beam of gamma rays, means for passing ore particles singly through said beam, means for neutron detection disposed proximately to the point at which the particles pass through the beam, a neutron moderating medium positioned between said point and said detector and means for changing the path of passage of said particles through said beam responsive to the detection of neutrons emitted from said particles.
2. Apparatus for automatically sorting beryllium ore particles according to their beryllium content which comprises a conveyor, means for positioning said particles in linear spaced relation on said conveyor, a source of high energy gamma radiation in excess of 1.63 million electron volts, said source being positioned to emit a beam of gamma rays into the path of the particles on said conveyor, neutron detector tubes disposed about the point at which said beam is incident on said conveyor, a neutron moderating substance disposed between said point and said detector tubes to moderate at least some of the neutrons emitted from the beryllium in the ore to thermal energies before they enter the neutron detector tubes, and means activated by neutron induced ionization in said detector tubes for removing said particles from said conveyor responsive to the emission of neutrons from said particles.
3. The method of concentrating the ores of beryllium which comprises providing a beam of gamma rays having energies in excess of 1.63 million electron volts, passing ore particles singly through said beam, moderating at least some of the neutrons emitted from said ore particles to thermal energies, detecting at least some of the moderated neutrons, and sorting said particles according to the number of neutrons detected.
4. The method of concentrating the ores of beryllium which comprises providing a beam of gamma rays having energies between 1.63 and 2.2 million electron volts, passing ore particles singly through said beam, moderating at least some of the neutrons emitted from said ore particles to thermal energies, detecting at least some of the moderated neutrons and sorting said particles according to the number of neutrons detected.
References Cited in the file of this patent UNITED STATES PATENTS 1,678,884 Sweet July 31, 1928 2,179,859 Page Nov. 14, 1939 2,220,509 Brons Nov. 5, 1940 2,280,948 Gulliksen Apr. 28, 1942 2,390,433 Fearon Dec. 4, 1948 2,508,772 Pontecorvo May 23, 1950 2,575,769 Rajchman Nov. 20, 1951 OTHER REFERENCES Nature," vol. 134, page 880, December 8, 1934, article entitled Liberation of Neutrons from Beryllium by X-Rays; Radioactivity Induced by Means of Electron Tubes.
Atomic Energy Commission declassified document Neutrons Emitted by a Radium-Beryllium Photosource by B. Feld and E. Fermi.