US3107210A - Nuclear apparatus - Google Patents

Description

G. E. MALLINCKRODT 3,107,210

Oct. 15, 1963 NUCLEAR APPARATUS Filed June 26, 1959 2 W 3 ll w 1 a 7/ Z7 2% 27 L Q L c Q 6??? Z??? k c Z 3 R 2 w flliw 3,107,210 NUCLEAR APPARATUS George E. Mallinckrodt, 20 Kingsbury Place, St. Louis 12, M0. Filed June 26, 1959, Ser. No. 823,250 1 Claim. (Cl. 204-1032) This invention relates to nuclear apparatus, and more particularly to apparatus for inducing nuclear reactions.

Among the several objects of the invention may be noted the provision of apparatus for inducing nuclear reactions, and the provision of such apparatus which is comparatively safe in operation and economical in construction. Other objects and features will be in part apparent and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations of elements, features of construction, and arrangements of parts which will be exemplified in the structures hereinafter described, and the scope of which will be indicated in the following claim.

In the accompanying drawings, in which one of various possible embodiments of the invention is illustrated,

FIG. 1 is a schematic layout of one form of the invention;

FIG. 2 is a greatly enlarged fragmentary section of a fuel element, being taken on line -22 of FIG. 1;

FIG. 3 is a cross section of said fuel element taken on line 3-3 of FIG. 2;

FIG. 4 is a view similar to FIG. 1, showing an application of the invention; and

=F-IG. 5 is an enlarged cross section taken on line 5-5 of =F-IG. 1.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

Referring now more particularly to FIG. 1, numerals 1 and *3 indicate spaced insulating supports for a pair of one-half inch or so diameter cylindrical electrodes 5 and 7, respectively. Quartz is a suitable material for such insulating supports. Electrode 7 is faced with a disc of tungsten or tungsten carbide, as shown at 9. The parts 5 and 7 are composed of highly conductive material such as copper, silver or the like, adapted to present a very low resistance to a large flow of current. For example, the cross sections presented to current flow through electrodes 5 and (7, 9) may be on the order of three quarters of a square inch or more in area.

At numeral '11 is shown a condenser of, for example, a capacity from about one to ten farads inclusive, although this is not to be taken as limiting. One side of the condenser is connected with electrode 5 by means of a lead 13. A switch 14 may be located in this lead. The other side of the condenser '11 is connected to electrode (7, 9) by means of a lead =15. Although both leads 1 3 and =15 are shown diagrammatically by means of lines, it is to be understood these leads v13 and 15 are also composed of highly conductive material such as copper or silver and also have substantial cross sections on the order above given. The purpose of having the conductive elements 5, 7, 9, 13 and '15 of large cross sections is to present small resistance to flow of current so as to reduce the time constant of the circuit of which they form a part when the condenser 11 is discharged in the manner set forth below. The condenser 11 is adapted to be charged from a suitable high-voltage D.C. generator 17. A suitable voltage is 1,000 to 10,000 volts or so but this is not to be taken as limiting.

The electrode 5 is provided with a central small axial bore 19 which, for example, may be on the order of .060 inch in diameter for the sliding acceptance with minimum clearance of the needle-like end 21 of a cylindrical capil- 3,107,2l Patented Oct. 15, 1963 ice lary tube or shell 23. The shell may be of any suitable length but for continuous operation it is made of substantial length and wound upon a reel or drum 25. Details of this tubing are shown in FIGS. 2 and 3. Its outside wall is preferably composed of silver or copper, but this may be composed of material of low atomic number, such as beryllium. An important property of the jacket is high conductivity.

The tubing 23 is filled with a core composed of needles of nuclear fuel material 31 separated at intervals by short lengths of a quenching material 32 of high atomic number such as tungsten. The lengths are anchored by crimps 27, to form cylindrical encapsulations 29 in which are located what may be referred to as spaced sections 31 of fuel. .These needle sections 31 may be approximately inch in length. The lengths 32 may be /a inch long. This produces a inch pitch distance D. A suitable core material for the needle sections is a lithium hydride consisting of lithium deuteride with 1% to 10% inclusive by weight of lithium triteride. This form of core material is solid.

The outside diameter of the tubing 23 may be .060 inch and its inside diameter .010 inch, which corresponds to .025 inch as its wall thickness. This corresponds also to a diameter of each needle portion 3 1 of .010 inch. It is to be understood that the Wall thickness of the capillary tubing 23 may range from said .025 inch down to .010 inch, in which event its outside diameter will range from said .060 inch to .030 inch. It will therefore be understood that the range of the diameter of the passage 19 in the electrode '5 is also from .060 inch down to .030 inch, in order to accept the wire with a close sliding fit.

-It is important that the outside walls of the needle portions 3 1 and the inside and outside walls of the tubing 23 shall be highly concentric around a center line CL and that their various diameters shall be constant throughout the axial lengths of the needle portions 31 within the capsule-forming tube walls between the tcrimps or pinches 27. Thus the tolerances of the wall thickness of the tubing 23 between pinches 27 should be on the order of .0001 inch and the walls of the tubing and of the needles should be concentric within .00005 inch. It is also desirable that line CL shall be central in the cylindric forms of the electrodes 5 and (7, 9). This favors the desired condition that current flow through any portion of the tubing placed in circuit between the electrodes 5 and (7, 9) will be of even density throughout the cross section of such portion. Thus it 'will be seen that cylindr-ic symmetry throughout most of the needle portions 31 between pinches 27 is important. Symmetry is not important at the pinches. In fact, some asymmetry at the pinches is of some advantage.

The lower end of the electrode 5 is countcrbored, as shown at 33, and threaded for the acceptance of an axially slitted outlet springy collet 35 having a hole through it for Iclosely slidably fitting the capillary wire 23. A threaded thimble 30 holds the collet in place. The three conventional collet slits, being out of the paper plane, do not appear in FIG. 1, but are shown at 36 in FIG. 5. Behind the collet 35 in the counterbore 33 is a suitable fibrous packing of a highly conductive material 34, such as compacted threads of silver adapted to form a conductive brush between the electrode 5' and the contained capillary wire 23.

The reel 25 is supported above a suitable feeder mechanism 37, mounted on insulation 39 above the electrode 5. The capillary tube 23 is drawn for example by resilient grip rolls 38 of the feeder from the reel 25 and fed through the electrode 5 toward the electrode facing 9. During feed, the collet slits open slightly; otherwise they close. The feed is preferably of the intermittent va- I for circulation.

riety and may be manually controlled or, if desired, automatically controlled. Under some circumstances a continuous feed is desirable. Details of the feeder are not elaborated because various appropriate types are known in the art.

At the start of operation, the middle of a pinch 27 of the capillary tubing or 'shell 23 will be located at the outlet end 40' of the collet 35. The spacing of the tungsten electrode facing '9 from this end 40 of the tubing will be on the order of the pitch distance D between the centers of the pinches 27. .Thus an advance of the end 40 of the tubing 23 toward the tungsten electrode 9 of one pitch distance will bring one of the needle sections 31 into the gap between the electrodes ultimately contacting facing 9.

Assuming that the generator 17 has charged'the condenser 11, contact will occur between the advancing pinch 27 of tubing 23 and the tungsten electrode 9, as shown by the dotted lines at the end of 23', which will then suddenly discharge the condenser 11 through the conductive shell 23 extending in contact between the electrodes. This discharge occurs rapidly in View of the low time constant of the condenser circuit and with a flow of very heavy current through the shell andits contents 31 and 32 in the gap between electrodes. This instantly saturates and vaporizes the exposedshell between the electrodes around a needle 31. Since the initial current flow between the electrodes is in the form of a cylinder which is accurately symmetrical about axis CL, the generation of the vapor will also occur initially in a symmetrical form around the contained needle of lithium hydride. The instantaneous result will be two-foldz (a) An imploding cylindrical shock wave will convenge at once upon the center line CL of the contained lithium hydride needle. Such a shock wave is pure theory, assuming errorless cylindric symmetry about CL, should produce an infinite temperature at this center line. In practice, the temperature is of course finite but extremely high, its degree dependingupon the accuracy with which the imploding cylindrical shock wave at a given time converges all along the center line. With the symmetry brought about by tolerances on the order of those above described, the temperature rise in the present case is suificient, coupled with the high density afforded by the contained solid lithium hydride needle, to induce a nuclear reaction therein. The exact temperature that will be obtained is ditlicult to estimate or measure, but it is suificient to bring about the desired nuclear reaction.

(b) A magnetic pinch effect occurs, aiding the implosion and thus the temperature increase,

After the needle section disappears by vaporization and entry into the reaction, more of the tubing is or may be advanced from the reel .25 for subsequent cycles of operation.

The exposed extending portion (but not all) of the tungsten quench section 32 at the collet 35 will also disappear. Such a section 32 not only forms a mechanical block to progress of the reaction to the next needle or fuel element 311, but in partially vaporizing releases large quantities of Brehmsstrahlen rays having a localized quenching efiect on the reaction,

In FIG. 4 is illustrated one application of the present invention. Referring now to FIG. 4, a pressure container 41 is arranged between the insulators 1 and 3 and surrounding the electrodes and (7, 9). An atmosphere of helium may be maintained in the container 41 by use of a pump 43 which pumps helium from a helium sump 45 into the container, a return line 47 being Inlet and outlet check valves 49 and 51,

employed comes pressurized by heating and may be employed as an operating medium for a prime mover such as shown at 53, which is fed from the container 41 over a line 55 V in which is a suitable control valve 57. If desired, several units such as shown in FIG. 4 may supply one prime mover, the nuclear reactions within the respective units being timed for sequential operations so as to minimize the effects of pulsations upon the prime mover.

' Broadly considered, the invention consists in subjecting a small accurately cylindrical needle of lithium hydride to a cylindrically imploding shock wave established by application of current to a cylindrical conductive jacket which is accurately concentric around the needle, the application of the current being large and sudden enough to vaporize the needle at once, whereby a shrinking accurate cylindn'c geometry of the shock wave is established and maintained as it implodes through the needle of fuel 31 and on the center line CL.

Although the core of fuel material 31 is herein shown as being solid, it will be understood that it may be of liquid form, provided the pinches 27 are caused to close off the tubing 23 at the appropriate intervals, entrapping such liquid material in elongate cylindrical segments.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above constructions and methods without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim: 7 a Nuclear apparatus comprising a pair of spaced electrodes, one of said electrodes having an opening therethrough to receive a fuel assembly which includes cylindrical needle-like cores of solid Jithium hydnide separated by short lengths of tungsten and enclose-d by a cylindrical jacket composed of conductive material and being of cap- 1 illary dimensions, a condenser of substantial capacity, a

high-voltage generator, means for connecting said generator across said condenser to change said condenser to a high voltage, means for connecting said charged condenser across said electrodes, and means for positioning a portion of said fuel assembly including one of said lithium hydride cores between said electrodes to provide a current path therebetween, whereby said condenser is discharged through said portion of said fuel assembly, the current therethrough being sufiicient to vaporize the conductive jacket thereof and thereby implode a cylindrical shoolc wave concentrically upon the contained lithium hydride core so'that the temperature of said core is raised sufficiently to induce nuclear reactions therein.

References Cited in the file of this patent FOREIGN PATENTS 508,233 Great Britain June 28, 1939 774,052. Great Britain May 1, 1957 1,0 22,71 l Germany Jan. 11, 1958 OTHER REFERENCES Progress, October 1955, pp. 482

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