USH558H - Radation shielding pellets - Google Patents
Radation shielding pellets Download PDFInfo
- Publication number
- USH558H USH558H US07/020,070 US2007087A USH558H US H558 H USH558 H US H558H US 2007087 A US2007087 A US 2007087A US H558 H USH558 H US H558H
- Authority
- US
- United States
- Prior art keywords
- pellets
- shielding
- outer shell
- melting point
- radiation
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 239000008188 pellet Substances 0.000 title claims abstract description 37
- 239000000463 material Substances 0.000 claims abstract description 31
- 229910000103 lithium hydride Inorganic materials 0.000 claims abstract description 16
- 230000005855 radiation Effects 0.000 claims abstract description 16
- 238000002844 melting Methods 0.000 claims abstract description 10
- 230000008018 melting Effects 0.000 claims abstract description 10
- 229910052721 tungsten Inorganic materials 0.000 claims abstract description 9
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract 3
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract 3
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 8
- 239000010937 tungsten Substances 0.000 claims description 8
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 6
- 239000012809 cooling fluid Substances 0.000 claims description 4
- 229910052751 metal Inorganic materials 0.000 claims description 4
- 239000002184 metal Substances 0.000 claims description 4
- 229910052742 iron Inorganic materials 0.000 claims description 3
- JFALSRSLKYAFGM-UHFFFAOYSA-N uranium(0) Chemical compound [U] JFALSRSLKYAFGM-UHFFFAOYSA-N 0.000 claims description 3
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims 2
- 229910045601 alloy Inorganic materials 0.000 claims 2
- 239000000956 alloy Substances 0.000 claims 2
- 230000014759 maintenance of location Effects 0.000 claims 2
- 239000011733 molybdenum Substances 0.000 claims 2
- 239000011257 shell material Substances 0.000 abstract description 10
- SIAPCJWMELPYOE-UHFFFAOYSA-N lithium hydride Chemical compound [LiH] SIAPCJWMELPYOE-UHFFFAOYSA-N 0.000 description 13
- 238000010586 diagram Methods 0.000 description 8
- 229910000831 Steel Inorganic materials 0.000 description 5
- 239000010959 steel Substances 0.000 description 5
- 241000264877 Hippospongia communis Species 0.000 description 4
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 4
- 229910052739 hydrogen Inorganic materials 0.000 description 4
- 239000001257 hydrogen Substances 0.000 description 4
- 238000001816 cooling Methods 0.000 description 3
- 230000005251 gamma ray Effects 0.000 description 2
- 229910001385 heavy metal Inorganic materials 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- 239000011358 absorbing material Substances 0.000 description 1
- 239000002775 capsule Substances 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000002788 crimping Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- -1 molybdenumn Chemical compound 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Images
Classifications
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
- G21F3/00—Shielding characterised by its physical form, e.g. granules, or shape of the material
- G21F3/04—Bricks; Shields made up therefrom
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
- G21F1/00—Shielding characterised by the composition of the materials
- G21F1/02—Selection of uniform shielding materials
Definitions
- This invention relates in general to radiation shielding means, and more particularly to radiation shielding pellets containing at least two shielding materials within individual pellets.
- Radiation shields often contain more than one type of material in order to provide attentuation over the entire spectrum of incident radiation.
- One common type of shielding application requires a gamma ray shielding metal such as tungsten or steel in combination with a hydrogen-rich neutron shielding material such as lithium hydride.
- the radiation shield Since the radiation shield must provide uniform attenuation over a large surface area, the two required materials must be prevented from separating within the shield. This means that lithium hydride in a shield must be trapped in place. If it is allowed to liquify or form vapor bubbles, portions of the shield volume will come to have an incorrect ratio of LiH versus metal, and shielding will not be uniform.
- Prior art shielding systems have dealt with this problem by attempting to maintain all portions of the shield below the melting point of LiH.
- the interior of the shield was filled with a honeycomb-like structure of tungsten or steel with LiH placed in the cells of the honeycomb.
- the metallic honeycomb conducted heat away from the LiH and to the outer surface of the shield.
- honeycomb structures are difficult to fabricate, particularly if an active cooling means, such as a fluid flow heat removal system, is required.
- honeycombs and cooling pipes required to maintain LiH in solid form tend to be heavy. This makes them undesirable for use in systems requiring active cooling which must be launched into space.
- shielding materials into pellets, wherein the exterior of each capsule is formed of a high melting point gamma ray shielding material, such as steel or tungsten, and the interior is formed of a lower melting point neutron shielding substance, such as lithium hydride.
- FIG. 1 is a diagram of a shield containing pelletized shielding material.
- FIG. 2 is a diagram of an individual pellet.
- FIG. 3 is a diagram illustrating one method of manufacture 8 for pellets of shielding material.
- FIG. 4 is a diagram of an actively cooled shield constructed using pellets of shielding material.
- FIG. 1 is a diagram of a shield containing pelletized shielding material.
- Shield retaining wall 10 may be of any convenient shape or material consistent with structural requirements.
- Pellets of shielding material 20 are used as fill within the shield.
- Pellets 20 may be of any convenient size. However, pellets of about one-quarter inch length are conveniently handled and placed into shields of odd shapes.
- FIG. 2 is a diagram of an individual pellet.
- the outer shell of the pellet 21 is composed of a high melting point material, for example tungsten, molybdenumn, depleted uranium, or iron. This material will inhibit the passage of particular types of radiation and not inhibit to the same extent other types of radiation.
- Filling 22 comprises another type of shielding material. Ideally, this material will have shielding properties complementary to those of the outer shell. Thus, the radiation which the material in the outer shell does not shield against tends to be absorbed by materials inside the pellets.
- Lithium hydride is a typical material that can be used for filling of pellets.
- the filling material may be any substance which is rich in hydrogen. Thus, paraffins, plastics, and other hydrocarbon-rich materials could be used. If a thick outer shell is employed, water would also be a suitable filling material.
- the outer shell material will be a heavy metal with a higher melting point than the filling. Typically, a hydrogen-rich pellet filling will retard neutrons, and a heavy metal shell will act against gamma rays.
- outer shell 21 should be chosen to be of sufficient thickness so as to resist internal pressures exerted when filling 22 is heated. Adequate thickness may be determined by constructing pellets with shells of varying thickness and then heating them to the maximum rated temperature of the shield. For quarter inch pellets of steel or tungsten, filled with lithium hydride, a shell of one-sixteenth inch thickness will be adequate for temperatures of 500 degrees
- FIG. 3 is a diagram illustrating one method of manufacture for pellets of shielding material.
- Lengths of steel or tungsten tubing 100 are filled with liquid lithium hydride, which is then allowed to solidify.
- Crimping tool 110 is then used to crimp the tubing at quarter-inch intervals in order to form crimped sections of tubing 115.
- Arc welder 120 is then applied to the tubing in order to seal the ends of individual crimped sections.
- saw 130 is used to cut crimped sections of the tubing into individual pellets.
- FIG. 4 is a diagram of a shield constructed using shielding pellets.
- Container 400 is filled with a bed of shielding pellets, 410.
- Container 400 may be made in any convenient shape. It functions merely to physically restrain pellet bed 410 and to provide a containier for cooling fluid 420, which flows through the pellet bed. Cooling fluid 420 enters container 400 via inlet port 430, picks up heat from shielding pellet bed 410, and exits via outlet port 431. Thus, heat is conveyed from the shield.
Landscapes
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- High Energy & Nuclear Physics (AREA)
- Powder Metallurgy (AREA)
Abstract
Radiation pellets having an outer shell, preferably, of Mo, W or depleted Und an inner filling of lithium hydride wherein the outer shell material has a greater melting point than does the inner filling material.
Description
This invention was made or conceived in the course of or under a contract with the U.S. Department of Energy.
This invention relates in general to radiation shielding means, and more particularly to radiation shielding pellets containing at least two shielding materials within individual pellets.
Radiation shields often contain more than one type of material in order to provide attentuation over the entire spectrum of incident radiation. One common type of shielding application requires a gamma ray shielding metal such as tungsten or steel in combination with a hydrogen-rich neutron shielding material such as lithium hydride.
Since the radiation shield must provide uniform attenuation over a large surface area, the two required materials must be prevented from separating within the shield. This means that lithium hydride in a shield must be trapped in place. If it is allowed to liquify or form vapor bubbles, portions of the shield volume will come to have an incorrect ratio of LiH versus metal, and shielding will not be uniform.
Prior art shielding systems have dealt with this problem by attempting to maintain all portions of the shield below the melting point of LiH. The interior of the shield was filled with a honeycomb-like structure of tungsten or steel with LiH placed in the cells of the honeycomb. The metallic honeycomb conducted heat away from the LiH and to the outer surface of the shield.
However, honeycomb structures are difficult to fabricate, particularly if an active cooling means, such as a fluid flow heat removal system, is required. Moreover, honeycombs and cooling pipes required to maintain LiH in solid form tend to be heavy. This makes them undesirable for use in systems requiring active cooling which must be launched into space.
In addition, in shields wherein lithium hydride is cast and allowed to solidify, cracks often develop in the solid lithium hydride. These permit radiation to stream through.
Thus, it is one object of this invention to provide a radiation shield, incorporating more than one type of material, which is easy to fabricate.
It is a further object to provide a pelletized radiation shielding material which can operate at elevated temperatures without failure, despite liquifaction or cracking of the hydrogen-rich neutron absorbing material.
It is a further object to provide a shield which is light weight and therefore particularly suitable for space applications.
These and other objects are obtained by forming shielding materials into pellets, wherein the exterior of each capsule is formed of a high melting point gamma ray shielding material, such as steel or tungsten, and the interior is formed of a lower melting point neutron shielding substance, such as lithium hydride.
FIG. 1 is a diagram of a shield containing pelletized shielding material.
FIG. 2 is a diagram of an individual pellet.
FIG. 3 is a diagram illustrating one method of manufacture 8 for pellets of shielding material.
FIG. 4 is a diagram of an actively cooled shield constructed using pellets of shielding material.
FIG. 1 is a diagram of a shield containing pelletized shielding material. Shield retaining wall 10 may be of any convenient shape or material consistent with structural requirements. Pellets of shielding material 20 are used as fill within the shield. Pellets 20 may be of any convenient size. However, pellets of about one-quarter inch length are conveniently handled and placed into shields of odd shapes.
FIG. 2 is a diagram of an individual pellet. The outer shell of the pellet 21 is composed of a high melting point material, for example tungsten, molybdenumn, depleted uranium, or iron. This material will inhibit the passage of particular types of radiation and not inhibit to the same extent other types of radiation.
Filling 22 comprises another type of shielding material. Ideally, this material will have shielding properties complementary to those of the outer shell. Thus, the radiation which the material in the outer shell does not shield against tends to be absorbed by materials inside the pellets. Lithium hydride is a typical material that can be used for filling of pellets. Typically, the filling material may be any substance which is rich in hydrogen. Thus, paraffins, plastics, and other hydrocarbon-rich materials could be used. If a thick outer shell is employed, water would also be a suitable filling material. Typically, the outer shell material will be a heavy metal with a higher melting point than the filling. Typically, a hydrogen-rich pellet filling will retard neutrons, and a heavy metal shell will act against gamma rays.
As pellet 20 heats during use of the shield, filling 22 will eventually crack, melt, and perhaps, vaporize. Thus, outer shell 21 should be chosen to be of sufficient thickness so as to resist internal pressures exerted when filling 22 is heated. Adequate thickness may be determined by constructing pellets with shells of varying thickness and then heating them to the maximum rated temperature of the shield. For quarter inch pellets of steel or tungsten, filled with lithium hydride, a shell of one-sixteenth inch thickness will be adequate for temperatures of 500 degrees
FIG. 3 is a diagram illustrating one method of manufacture for pellets of shielding material. Lengths of steel or tungsten tubing 100 are filled with liquid lithium hydride, which is then allowed to solidify. Crimping tool 110 is then used to crimp the tubing at quarter-inch intervals in order to form crimped sections of tubing 115. Arc welder 120 is then applied to the tubing in order to seal the ends of individual crimped sections. Finally, saw 130 is used to cut crimped sections of the tubing into individual pellets.
FIG. 4 is a diagram of a shield constructed using shielding pellets. Container 400 is filled with a bed of shielding pellets, 410. Container 400 may be made in any convenient shape. It functions merely to physically restrain pellet bed 410 and to provide a containier for cooling fluid 420, which flows through the pellet bed. Cooling fluid 420 enters container 400 via inlet port 430, picks up heat from shielding pellet bed 410, and exits via outlet port 431. Thus, heat is conveyed from the shield.
The foregoing is a description of a preferred embodiment of this invention. However, the invention need not be limited to particular types of shielding materials or pellet sizes.
Claims (6)
1. Radiation sheilding pellets comprising:
an outer shell of radiation shielding material having a first melting point; and
an inner filling of radiation shielding material having a second melting point,
wherein said first melting point is greater than said second melting point.
2. The pellets of claim 1 wherein said outer shell comprises a metal effective for shielding against gamma rays.
3. The pellets of claim 2 wherein said metal is selected from the group containing: iron, molybdenum, tungsten, depleted uranium, and alloys thereof.
4. The pellets of claim 1 wherein said inner filling comprises lithium hydride.
5. The pellets of claim 2 wherein said inner filling comprises lithium hydride and said outer shell is selected from the group containing tungsten, iron, molybdenum, depleted uranium, and alloys thereof.
6. A bed of radiation shielding pellets comprising pellets and retention means effective for maintaining a plurality of said pellets in position with repect to one another and also effective for containment of a cooling fluid in contact with said pellets,
wherein said pellets comprise an outer shell of a first shielding material and an inner filling of a second shielding material; and
wherein said retention means further comprises means for admission and exit of said cooling fluid.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/020,070 USH558H (en) | 1987-02-27 | 1987-02-27 | Radation shielding pellets |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/020,070 USH558H (en) | 1987-02-27 | 1987-02-27 | Radation shielding pellets |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| USH558H true USH558H (en) | 1988-12-06 |
Family
ID=21796577
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US07/020,070 Abandoned USH558H (en) | 1987-02-27 | 1987-02-27 | Radation shielding pellets |
Country Status (1)
| Country | Link |
|---|---|
| US (1) | USH558H (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4997619A (en) * | 1989-10-13 | 1991-03-05 | The Babcock & Wilcox Company | Shield for a nuclear reactor |
| US5015863A (en) * | 1989-05-31 | 1991-05-14 | Sumitomo Heavy Industries, Ltd. | Radiation shield and shielding material with excellent heat-transferring property |
| US20080198960A1 (en) * | 2007-02-20 | 2008-08-21 | Keegan C Patrick | Nuclear reactor vessel fuel thermal insulating barrier |
| US9193105B1 (en) | 2011-08-31 | 2015-11-24 | Consolidated Nuclear Security, LLC | Casting fine grained, fully dense, strong inorganic materials |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4130459A (en) | 1976-03-29 | 1978-12-19 | Westinghouse Electric Corp. | Poison and diluent system for nuclear power plants |
| US4507359A (en) | 1980-12-22 | 1985-03-26 | Chomerics, Inc. | Electromagnetic shielding |
| US4657784A (en) | 1986-03-10 | 1987-04-14 | Ecolab Inc. | Process for encapsulating particles with at least two coating layers having different melting points |
-
1987
- 1987-02-27 US US07/020,070 patent/USH558H/en not_active Abandoned
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4130459A (en) | 1976-03-29 | 1978-12-19 | Westinghouse Electric Corp. | Poison and diluent system for nuclear power plants |
| US4507359A (en) | 1980-12-22 | 1985-03-26 | Chomerics, Inc. | Electromagnetic shielding |
| US4657784A (en) | 1986-03-10 | 1987-04-14 | Ecolab Inc. | Process for encapsulating particles with at least two coating layers having different melting points |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5015863A (en) * | 1989-05-31 | 1991-05-14 | Sumitomo Heavy Industries, Ltd. | Radiation shield and shielding material with excellent heat-transferring property |
| US4997619A (en) * | 1989-10-13 | 1991-03-05 | The Babcock & Wilcox Company | Shield for a nuclear reactor |
| US20080198960A1 (en) * | 2007-02-20 | 2008-08-21 | Keegan C Patrick | Nuclear reactor vessel fuel thermal insulating barrier |
| US8401142B2 (en) * | 2007-02-20 | 2013-03-19 | Westinghouse Electric Company Llc | Nuclear reactor vessel fuel thermal insulating barrier |
| US9193105B1 (en) | 2011-08-31 | 2015-11-24 | Consolidated Nuclear Security, LLC | Casting fine grained, fully dense, strong inorganic materials |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| STCF | Information on status: patent grant |
Free format text: PATENTED CASE |