A METHOD FOR THE MANUFACTURE OF POWDER-FILLED SHAPED BODIES, SHAPED BODIES FOR INTRODUCTION INTO A COMMERCIAL NUCLEAR POWER REACTOR AND THE USE THEREOF

Abstract

To manufacture shaped bodies (10) filled with powder (22) for introduction into the reactor core of a commercial nuclear power reactor a plate made of a metal and/or metalloid is provided with one or more blind holes (14), the blind holes (14) are filled with powder (22), the blind holes (14) filled with powder (22) are reversibly sealed and shaped bodies are cut from the plate so that each blind hole (14) filled with powder (22) is surrounded by a shell made of a metal or metalloid. The powder-filled shaped bodies (10) are used in a ball measuring system for commercial nuclear power reactors and/or for the generation of radionuclides in said reactors.

Claims

1. A method for the manufacture of shaped bodies filled with a powder for introduction into a reactor core of a commercial nuclear power reactor, wherein a plate made of a metal and/or metalloid is provided with one or more blind holes, the blind holes are filled with powder, the blind holes filled with powder are reversibly sealed, shaped bodies are cut from the plate so that each blind hole filled with powder (22) is surrounded by a shell formed of a metal and/or metalloid.

2. The method according to claim 1, wherein the shaped bodies are provided with a ball-shaped outer contour.

3. The method according to claim 1, wherein the blind holes are drilled.

4. The method according to claim 1, wherein the blind holes (14) are incorporated into the plate in a hexagonal arrangement.

5. The method according to claim 1, wherein the blind holes, prior to being filled with powder, are provided with a chemically inert coating.

6. The method according to claim 1, wherein the blind holes are provided with an internal thread.

7. The method according to claim 1, wherein the blind holes are sealed with a closing element in the form of a screw.

8. The method according to claim 1, wherein the blind holes are sealed with a closing element in the form of a stopper which is clamped to a wall of the blind hole.

9. The method according to claim 8, wherein the stopper and the plate are formed of materials with different coefficients of thermal expansion.

10. The method according to claim 1, wherein the blind hole is sealed by a closing element made of a shape memory alloy which has a first state in which it can be loosened from the blind hole and a second state in which is seals the blind hole.

11. The method according to claim 10, wherein the closing element is inserted into a radial groove running along the peripheral edge of the blind hole.

12. The method according to claim 1, wherein the shaped bodies after being cut from the plate are smoothened and/or polished.

13. A shaped body for introduction into a reactor core of a commercial nuclear power reactor, obtained by a method according to claim 1, wherein the shaped body has a cavity formed by a blind hole and filled with a powder, with the blind hole reversibly sealed.

14. The shaped body according to claim 13, wherein the blind hole has a concave bottom.

15. The shaped body according to claim 13, wherein the diameter (d) of the shaped body is 1 to 10 mm.

16. The shaped body according to claim 13, wherein the diameter (dS) of the blind hole is up to 80% of the diameter (d) of the shaped body.

17. The shaped body according to claim 13, wherein the powder is a radionuclide precursor that can be converted into a radionuclide by neutron radiation, selected from the group consisting of Ac-225, Ac-227, At-211, Bi-212, Bi-213, B-10, Cd-112, C-11, C-13, Cs-131, Cs-137, Cr-51, Co-57, Co-60, Cu-67, D-1, F-18, Ga-67, Ga-68, He-3, Ho-166, In-111, I-123, I-124, I-125, I-131, Ir-192, Li-7, Lu-177, Mo-99, Mo-100, Ne-22, N-13, N-15, O-15, O-18, Pd-103, P-32, P-33, Pb-211, Pb-212, Ra-223, Ra-224, Re-186, Re-188, Rb-82, Ru-106, Sm-153, Si-28, Sn-177m, Sr-88, Sr-89, Sr-90, S-35, Tc-99, Th-227, Tl-201, Tl-203, Tm-170, Ur-235, Xe-133, Yb-169, Yb-175, Y-90, Zn-64, Zn-68.

18. The shaped body according to claim 17, wherein the powder is an oxide, phosphate, carbonate, sulfate or chloride of the radionuclide precursor.

19. The shaped body according to claim 13, wherein the plate is made of a material selected from the group consisting of high-grade steel, chrome steel, carbon steel, heat-treated carbon steel, zirconium, silicon, magnesium, aluminum, molybdenum or an alloy or mixture based on one or more of these materials with each other and/or with carbon, nitrogen, boron and phosphorus.

20-21. (canceled)

22. A method for the generation of radionuclides in a reactor core of a nuclear power reactor, the method comprising introduction of powder-filled shaped bodies according to claim 13, wherein the powder is a radionuclide precursor that can be converted into a radionuclide by neutron radiation, into a reactor core of a nuclear power reactor and exposed to neutron flux for a period of time, after which the powder-filled shaped bodies are removed from the reactor core.

23. The method according to claim 22 for measuring neutron flux density in the reactor core of a nuclear power reactor, wherein the powder-filled shaped bodies are introduced into a ball measuring system of a nuclear power reactor, and after exposure to neutron flux for a fixed period of time the powder-filled shaped bodies are removed from the reactor core and the activation level of the powder is measured.

Description

[0062] The invention is subsequently described in detail by means of several exemplary embodiments with regard to the attached drawings. In the drawings:

[0063] FIGS. 1 to 8 schematically show manufacturing steps for the manufacture of powder-filled shaped bodies according to the present invention in accordance with a first embodiment;

[0064] FIG. 9 schematically shows the use according to the present invention of the shaped bodies according to the present invention in a ball measuring system of a power reactor;

[0065] FIGS. 10 to 12 schematically show steps to remove the powder from a shaped body in accordance with the first embodiment;

[0066] FIGS. 13 to 15 schematically show steps to seal a shaped body according to the present invention in accordance with a second embodiment; and

[0067] FIGS. 16 to 18 schematically show steps to seal a shaped body according to the present invention in accordance with a third embodiment.

[0068] FIGS. 1 to 8 show the manufacture of a powder-filled shaped body 10 (see FIGS. 7 and 8) in a first embodiment.

[0069] First, a plate 12 made of a suitable metal or metalloid is provided.

[0070] In the embodiment shown here, the thickness d.sub.F of the plate 12 is selected to be slightly smaller than the desired diameter d of the subsequent shaped body 10; however, it can also be selected to be slightly larger.

[0071] The material of the plate 12 is selected so that it is as permeable as possible for neutrons, i.e. exhibits low neutron absorption. In addition, it should have a certain hardness and a good temperature and pressure stability for temperatures of up to 400 C. or more. For example, the plate 12 can be formed of high-grade steel, chrome steel, carbon steel, heat-treated carbon steel, zirconium, silicon, magnesium, aluminum, molybdenum as well as alloys or mixtures based on these materials. Carbon, nitrogen, boron or phosphorus as well as other metals such as calcium can be present as further alloying elements in common proportions.

[0072] A number of blind holes 14 spaced apart from each other are drilled into the plate 12 by means of a suitable drill 16 or by use of laser beams or water jets. Preferably, the blind holes 14 have a concave bottom.

[0073] In the embodiment shown, the blind holes 14 are arranged in a hexagonal pattern of blind holes 14, with the centers of the individual blind holes 14 spaced apart by a little more than the desired diameter d (see FIG. 2a). Preferably, the diameter d.sub.S of the blind hole 14 is approximately 70-80% of the diameter d of the finished shaped body 10.

[0074] Each of the blind holes 14 is provided with an internal thread 18 comprising one or more turns at its open end.

[0075] According to a preferred embodiment, a thin coating 20 is then applied in the region of the blind holes 14 or the entire plate completely lining the interior of the blind hole 14. The coating 20 is selected from a material that is inert towards the plate 12 and the powder material to be filled into the blind holes 14 and is pressure and temperature resistant.

[0076] Preferably, the plate 12 is formed of aluminum or an aluminum alloy. In this case, the coating 20 of the blind holes 14 is preferably generated by anodizing or hard anodizing, with a layer thickness of about 8-20 m. Anodizing is performed while the shaped bodies 10 are still linked with each other via the plate 12.

[0077] As a possible alternative to produce the coating 20, a sol-gel dispersion of silicon dioxide or water glass can be used, which is heated after application forming a glass-like, thin and chemically stable silicate layer on the surface of the blind holes.

[0078] In general, especially oxides such as silicon oxide, titanium oxide, aluminum oxide and zirconium oxide or silicates such as an alkali aluminum mixed silicate, but also similar inorganic substances showing an inert, glass-like behavior at high temperatures can be used as a material for the coating 20. For example, the coating 20 can be produced by deposition from the gas phase or by means of a PVD process or by sputtering. Layer thickness is preferably selected to be less than 20 m and is preferably in the range of approximately 5 to 20 m. Layer thicknesses of more than 20 m may lead to embrittlement and spalling off and are thus not desired.

[0079] The blind hole 14 prepared this way is filled with a pre-determined quantity of a powder 22. For example, traditional automated dosing devices with known series micropipettes 23 known from pharmaceutical technology (not described in detail herein) can be used for filling the blind holes 14.

[0080] Each of the blind holes 14 filled with the powder 22 is sealed by a closing element 24, here in the form of a screw, that is screwed in the internal thread 18. The blind hole 14 is sealed against its surrounding by the screw screwed in.

[0081] In a preferred variant the internal thread 18 is a taper thread and the screw is a taper screw.

[0082] A possible embodiment for the manufacture of a ball-shaped shaped body with an external diameter of 1.6 mm comprises the arrangement of blind holes 14 in a hexagonal pattern in the upper surface of the plate 12 by drilling, with the blind holes 14 having an internal diameter of 1.2 mm. As a result of the conical design of the drill bit the bottom of the blind holes assumes a concave shape, with the lower apex of the bottom of the blind holes being at a distance of about 0.2 mm from the lower surface of the plate. The edge of the taper at the bottom of the blind holes may have a distance of 0.2 mm to the subsequent outer edge of the ball. At the upper edge, each blind hole 14 can be provided with a fine taper thread having a slope of 0.1 mm, extending to a depth of 0.2 mm. The lower edge of the taper thread can be at a distance of 0.376 mm from the upper edge of the plate 12. The lower edge of the thread may have a diameter of 1.20 mm, the upper edge of the thread may be about 0.2 mm larger. Using such a thread, the interior of the balls formed can be safely, reversibly and tightly sealed with a taper screw using barely 4 turns. The taper screw safely seals the blind hole 14.

[0083] The inner surface of the screw can be formed as a concave curvature to increase the amount of powder 22 that can be filled into the blind hole 14.

[0084] Optionally, the bottom of the screw that comes into contact with the powder 22 can also be provided with a coating 20, thus excluding contamination of the powder 22.

[0085] The outer contour 26 of the screw head can already have the desired subsequent outer contour of the shaped body 10. However, the screw head can also be finished in the next step.

[0086] The screw head exhibits an engagement geometry 28, for example in the form of a hexagon socket, a cross recess or a simple slot where the screw can be screwed in the internal thread 18 and later be removed from it.

[0087] According to a preferred embodiment, the screw is made of a magnetic material.

[0088] In the next procedural step the plate 12 is cut, for example by means of a milling tool 30 or another suitable automated method, with the shaped bodies 10 carved out of the material, thus obtaining their desired outer contour 32. In this example, the outer contour 32 is ball-shaped, although, for example, it could also have the form of ellipsoids, lenses and discs. In this procedural step the contour 26 of the screw head can also be processed so that it fits into the desired outer contour 32 of the shaped body 10.

[0089] Subsequently, the finished powder-filled shaped bodies 10 can be smoothened and polished.

[0090] When using the shaped bodies 10 to generate radionuclides, the shaped bodies 10 are introduced into a known ball measuring system 100 of a commercial nuclear power reactor (schematically shown in FIG. 9) and exposed to the neutron flux in the core of the reactor for a pre-determined period of time.

[0091] In this case, the powder 22 filled into the blind holes 14 contains radionuclide precursors that are at least partially converted into the desired radionuclide by neutron bombardment. Examples of radionuclides obtainable by means of this method are: Ac-225, Ac-227, At-211, Bi-212, Bi-213, B-10, Cd-112, C-11, C-13, Cs-131, Cs-137, Cr-51, Co-57, Co-60, Cu-67, D-1, F-18, Ga-67, Ga-68, He-3, Ho-166, In-111, I-123, I-124, I-125, I-131, Ir-192, Li-7, Lu-177, Mo-99, Mo-100, Ne-22, N-13, N-15, O-15, O-18, Pd-103, P-32, P-33, Pb-211, Pb-212, Ra-223, Ra-224, Re-186, Re-188, Rb-82, Ru-106, Sm-153, Si-28, Sn-177m, Sr-88, Sr-89, Sr-90, S-35, Tc-99, Th-227, Tl-201, Tl-203, Tm-170, Ur-235, Xe-133, Yb-169, Yb-175, Y-90, Zn-64 or Zn-68.

[0092] Conversion of the radionuclide precursor into the desired target radionuclide is performed by neutron capture, for example by simple neutron activation based on the same element, as for example in the case of molybdenum-99:

[0093] .sup.98Mo (n, ) .sup.99Mo.

[0094] Alternatively, conversion is based on another element and the desired target nuclide is generated by any complex nuclear reaction, as for example in the case of lutetium-177:

[0095] .sup.176Yb (n, ) .sup.177Yb (-, ) .sup.177Lu.

[0096] To provide a powder 22 to be filled into the shaped bodies 10 which is easy to process, free-flowing, chemically inert towards oxygen and thermally stable, the radionuclide precursors are used, for example, as an oxide, phosphate, carbonate, sulfate of chloride of the respective elements. The radionuclide precursor can also be used in the form of the pure element if the substance used can be pulverized as a pure element.

[0097] After expiry of the specified irradiation period in the reactor core the shaped bodies 10 are removed from the ball measuring system 100 and transferred into a suitable tool to obtain the powdery radionuclide, which can be performed in a familiar way by means of compressed air or the effect of gravity.

[0098] In this embodiment, the tool used to obtain the powdery radionuclide from the shaped bodies 10 is preferably a magnetic tool 34 the head 36 of which is adjusted to the engagement geometry 28 of the screw.

[0099] The tool 34 magnetically attracts one shaped body 10 at a time, with the tool head 36 engaging into the engagement geometry 28 of the screw. Now the shaped body 10 is fixed by a suitable tool equipped with two gripper jaws 38 (see FIG. 11) and the screw is screwed out (see FIG. 12) so that the desired radionuclide, as a powder 22, is accessible in the interior of the blind hole 14 of the shaped body 10 and can be gathered in a collection device (not shown).

[0100] A second preferred embodiment for the manufacture of shaped bodies 10 is shown in FIGS. 13 to 15. In contrast to the first embodiment, here the closing element 24 sealing the blind hole 14 is a stopper. The stopper is clamped to the inner wall of the blind hole 14 and hermetically seals the blind hole 14 towards the outside.

[0101] In this example materials with different coefficients of thermal expansion are used for the stopper and the plate 12, with the material of the stopper preferably having a larger coefficient of thermal expansion than the material of the plate.

[0102] To seal the blind holes 14 the stoppers and the plate 12 are cooled, e.g. by using liquid nitrogen, reducing the diameter of the stopper to a value d.sub.K that is smaller than the diameter d.sub.S of the blind hole 14 in the cooled-down state (see FIG. 14). In this state, the stoppers are inserted into the blind holes 14.

[0103] When heated to room temperature or a higher temperature the stoppers again expand to such an extent that their diameter assumes a value d.sub.W corresponding to the diameter of the blind hole d.sub.S or are selected to be slightly larger for the stopper to brace in the blind hole 14 and tightly seal it.

[0104] Like in the first embodiment, the step of filling and closing the blind holes 14 is performed during the manufacture of the shaped bodies 10 while these are still connected by the material of the plate 12.

[0105] To remove the stopper from the blind holes 14 following exposition of the shaped bodies to neutron irradiation in the reactor core the shaped bodies 10 collected are cooled down and shaken in a drum (not shown), with the clamped connection between the stopper and the blind holes 14 coming loose again. The stoppers, together with the powder 22, are shaken out of the blind holes 14 and can be separated from the powder 22 using a screen.

[0106] The blind holes 14 can have a slightly larger diameter in the section of their upper edge than in their lower section; however, the diameter of the stoppers is adjusted to this section (not shown).

[0107] In a third preferred embodiment for the manufacture of shaped bodies 10 shown in FIGS. 16 to 18 the blind hole 14 is sealed by a closing element 24 made of a shape memory alloy with a 2-way memory effect.

[0108] The closing element 24 has a first state in which is can be loosened from the blind hole 14 and which it assumes at a first, low temperature. The first temperature, for example, can be about 10 C. or less.

[0109] In FIG. 17 the closing element 24 is shown in its first state. Preferably, the closing element 24 is a flat metal sheet with a square peripheral edge 40 and exhibits several parallel corrugations in its first state. However, the closing element can also have another shape and/or another outer contour.

[0110] The closing element 24 has a second state in which it tightly seals the blind hole 14 and which it assumes at a second, higher temperature of about 40-50 C. and exceeding temperatures as they are achieved in the reactor core. Preferably, the second temperature is about 30-40 K above the first temperature.

[0111] In its second state the closing element 24 has a larger expansion than in its first state, as can be seen in FIG. 18. In this example, the corrugations on the surface of the closing element 24 expand during transition to the second state resulting in an increased diameter or surface area of the closing element 24.

[0112] In the embodiment shown here a square, circumferential, radial groove 42 is formed in the upper section of the blind hole 14 whose axially outer edge 44 is slightly set back as compared to the axially inner edge 46.

[0113] In the first state the expansion of the closing element 24 is so small that the peripheral edge 40 of the closing element 24 can pass the outer edge 44 of the groove 42 and be placed on the inner edge 46 of the groove 42 (see FIG. 17). To seal the blind hole 14 the tailor-made closing element 24 is thus cooled down to such an extent that it again assumes its first state and is supported by the edge 46 of the groove 42.

[0114] When heated to the second temperature the peripheral edge 40 of the closing element 24 slides into the groove 42 and thus fixes the closing element 24 at the body of the shaped body 10, tightly sealing the blind hole 14 (see FIG. 18).

[0115] To remove the powder 22 from the shaped bodies 10 following irradiation in the reactor core the shaped bodies are cooled down to the first temperature at which the closing elements 24 again assume their first state and can be loosened from the blind holes 14.

[0116] As described above, the powder 22 can be separated from the shaped bodies 10 and the detached closing elements 24 in a drum.

[0117] Apart from the kind of closing element 24, 24, the shaped bodies 10, 10 used for the second and third embodiment correspond to the shaped bodies 10 described in the first embodiment. The other steps of the manufacturing process are also identical. As in the first embodiment it is, for example, possible to provide the side of the closing element 24, 24 directed to the blind hole 14 with a coating 20.

[0118] The radionuclides obtained this way are preferably used in medical, scientific or industrial applications generally known to those skilled in the art.

[0119] Alternatively, it is also conceivable to use the generated radionuclides to determine a very precise position-dependent neutron density in the reactor core by means of the ball measuring system 100. To this end, the shaped bodies employed as measuring probes and/or the individual powder lots are fed into a basically known detector device where the activity of the powder lots is determined.