GB2142183A - A shield for protecting an object against neutron radiation - Google Patents
A shield for protecting an object against neutron radiation Download PDFInfo
- Publication number
- GB2142183A GB2142183A GB08312700A GB8312700A GB2142183A GB 2142183 A GB2142183 A GB 2142183A GB 08312700 A GB08312700 A GB 08312700A GB 8312700 A GB8312700 A GB 8312700A GB 2142183 A GB2142183 A GB 2142183A
- Authority
- GB
- United Kingdom
- Prior art keywords
- cavity
- shield
- shield according
- liquid
- hydrogenous
- 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.)
- Withdrawn
Links
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
-
- 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
- G21F1/023—Liquids
Abstract
In shielding objects, especially vehicles, against neutrons emitted from a source which is above the ground, a shield is used which comprises a cavity containing a hydrogenous liquid, e.g. water, which can be introduced into and discharged from the cavity when desired. The cavity extends around the top and sides of the object.
Description
SPECIFICATION
A shield for protecting an object against neutron radiation
This invention relates to a shield for objects, especially vehicles, against a neutron flux emitted from a source lying above the horizon line. According to the modern view of weapon technique it is supposed that such radiation will be produced by a neutron weapon detonating in the air. A detonation on the ground cannot be assumed because in this case the major part of the radiation would be absorbed in the soil or in the atmosphere without having had the opportunity to reach men.
It is characteristic of neutron radiation that this uncharged radiation of particles reacts in material only by the nucleon-nucleon interaction. This results in a high possibility of penetration through material. The
definition of interaction of fast neutrons with material is described by the reaction and scattering cross
sections. With regard to the qualities of absorption of materials for fast neutrons, the so-called removal cross
section is important. This depends on the sort of material and on the energy of the neutrons.Thus, the
intensity of a neutron flux behind a shield is usually given in the relation:
12 = la -exp(-X-x) 12 : Intensity of the neutron flux behind the shield
In : Intensity of the neutron flux in front of the shield s : the removal cross section, depending on the sort of material and on the neutron energy
x : thickness of the shielding
Experiments in nuclear physics have determined these data for all usual materials and for an energy range
for neutrons between about 0 - 15 MeV. These analyses have the result that, besides the expensive elements
tungsten and copper, iron, boron, water and all hydrogenous compounds (e.g. paraffin) give good
absorption characteristics (e.g. ref.DE-Asen 1052587, 1167459, 1230933 and 1453899 as also the paper
"Shielding for fast neutron scattering experiments of high sensitivity", Nuclear instruments and methods
114(1974) 521.534, North Holland Publishing Co.). According to the removal cross section of a given material
one can derive an effective shield which however is of very thick dimensions. Here is an example.
A lethal 10 MeV-neutron dose of 100 rem is reduced only insignificantly by the usual armament of a tank
(8- 20mm); the number of victims of the radiation will not be diminished. The task of reducing the
aforementioned neutron dose to a humanly tolerable size of 10 rem by strengthening such armament would
only be fulfilled by a thickness of 200 mm of iron. Bearing in mind that the radiation is normally emitted from
above as previously stated, it would be necessary to take into account a 200 mm thick top and side armament
which would represent a fixed ballast or weight of unacceptable size. Such a vehicle would therefore be
useless to carry out its real task.
The present invention is based on the requirement to produce a special shield for an object, especially a
mobile object, against a neutron radiation emitted from a source lying above the horizon line, said shield
being such that it does not unacceptably limit the mobility of the object during a usual operation. In
accordance with the invention, there is provided a shield for an object, especially a vehicle, against neutrons
which are emitted from a source above the ground, wherein said shield comprises a cavity which extends
around the top and sides of the object and which contains a hydrogenous liquid, said cavity having means
whereby said liquid can be introduced into or discharged from the cavity when desired.
The above defined arrangement involves fundamental advantages. The most essential advantage is given
by the fact that the shield and therefore its weight can be brought into use only in standby or emergency
conditions - contrary to a fixed shield of solid form. As soon as such a situation has passed, the liquid can be
drained out of the cavity and the mobile object (e.g. tank or truck or the like) will resume its normal state and
can be used in the usual way. A further advantage lies in the fact that even in the case of standby or
emergency the mobile object will still be manoeuvrable because the weight of the shield (consisting for
example of water) is about 5.2 times smaller than that of a comparable shield made out of iron.Finally, there
is an advantage which should not be underestimated in that the shield formed by water can be produced
almost everywhere, in a very short time and at a low cost- and above all the shield can quickly be evacuated
in order to restore the mobile object to its normal condition.
In a further development of the invention the aforesaid cavity is preferably arranged to provide a thickness of the hydrogenous liquid given by the following formula, x = X =}.in.(N.sin2 where
x : thickness of the hydrogenous liquid, r : removal cross section
N : a factor of extinction of the primary neutron flux angle of incidence
It should be appreciated that the invention is based on the assumption that, in order to obtain the optimum efficiency of a neutron weapon, said weapon would detonate at a definite height above the surface of the ground according to the strength of the weapon in question. Since the strength of the weapon would be known, the normal height of detonation is calculable.Under this condition the optimum thickness of the required shield can be calculated in consequence of the geometrical law of radiation. At first, it should be borne in mind that the intensity Ii of radiation is inversely proportional to the square of the distance r of the radiation from its source, i.e.
17 = lo 12 where lo = the primary intensity of radiation
This means that for the most adverse case for a perpendicular incidence of rays from a height H: Ii = lo H2 Also, the distance of a side-shifted object from a source of radiation can be written as: H
r=
sin#, where e is the angle of incidence in relation to a horizontal line.So the remaining intensity in front of a shield of a side-shifted object can be written as
Behind the shield, the real intensity 12 will be given as a function of the removal cross section:
The requirement now is as follows: The intensity 12 behind the shield should be reduced to a constant proportion 1/N of the maximum intensity 1 in front of the shield; that is the intensity of perpendicular incidence. This demand can be written as:
The thickness x of the hydrogenous liquid is thus given by the following formula: in. 1n. (N sin26).
It is obvious that under the requirement for a constant efficiency of shielding the sides of the shield can be thinner than the upper parts, wherein only the aforementioned removal cross section Z (depending on the material used) is to be considered for the exact definition of the thickness of shielding. This possibility to optimize the shape of the cavity creates a further reducing of the overall weight of the shield in case of a standby or emergency.
In consequence of such optimizing of the shape of the cavity it is convenient that the cavity should be formed so that it is of generally sickle-shaped configuration in cross-section, the thickness of the cavity diminishing at the sides.
According to a further feature of the invention, the wall separating the cavity from the interior of the mobile object is coated with a layer of cadmium or a cadmium compound or tin. This layer has to absorb thermalized neutrons which are produced in penetrating the shield.
In order to prevent leakage of the hydrogenous liquid in case of damage of the exterior wall of the cavity caused by a projectile, it is recommended to coat the interior of the external wall of the cavity with a durably elastic material. In the case of a leak such an elastic layer will stop this leak automatically.
In a further advantageous development of the invention, the cavity is formed of separate chambers. Apart from the fact that with such a construction less material is necessary than for a single cavity for a comparable protection against damage caused by projectiles (that means less weight), it is possible to prevent or substantially reduce in this arrangement complete discharge of the liquid from the cavity.
In this context it has proved appropriate that the upper part of the cavity of the mobile object should comprise a separate chamber which is not connected with the side parts of the cavity. The effect of this is that an impact of a projectile or other damage on the sides of the cavity does not necessarily result in the draining off the hydrogenous liquid from the upper part of the cavity so that the shield will remain in this especially important part of the mobile object.
In order to limit the breakdown of the shield in the side parts of the cavity to a minimum, these side parts of the cavity may consist of several chambers arranged side by side. These chambers are connected during the filling or evacuating of the hydrogenous liquid but at other times they are perfectly separated. This arrangement of the chambers leads to a breakdown of the shield only in a damaged chamber, while the separate chambers not being connected in a case of standby or emergency; however, such connections will exist during the filling or evacuating of the cavity in order that these operations can be carried out quickly and perfectly, without the possibility of an erroneous omission of one or more chambers.
On the other hand, the procedure of filling or evacuating the cavity may be carried out faster when the cavity is given several entrance and exit valves.
According to a further feature of the invention, the mobile object may be equipped with a fountainhead arrangement which can be used to spray the whole surface of the mobile object by evacuation of the cavity containing the hydrogenous liquid. Thus, after an emergency the mobile object may be decontaminted by draining off the hydrogenous liquid, without the help of a special and separate unit.
It may be useful in some cases to form the cavity either in its entirety or in some of its chambers - as a reserve fuel tank, providing a shield at least partially consisting of fuel without producing additional ballast.
In a further development of this idea it would be possible at least to connect some chambers of the cavity with the fuel tank in order to pump fuel from there into the shield cavity in the case of a standby or emergency.
Finally it may be useful to form the cavity by a removable element like waterbags or plastic shields fillable with liquid or comparable things. Similarly, tilts, tents or such things may be used.
It is self-evident that the conception of invention may also be applied to stationary objects.
Claims (13)
1. A shield for an object, especially for a vehicle, against neutrons emitted from a source above the ground, wherein such shield comprises a cavity which extends around the top and sides of the object and which contains a hydrogenous liquid, said cavity having means whereby said liquid can be introduced into or discharged from the cavity when desired.
2. A shield according to Claim 1, wherein the cavity is arranged to provide a thickness of the hydrogenous liquid given by the following formula: x =ln. (Nsin2 where
x : thickness of the hydrogenous liquid, X : the removal cross section
N : the factor of extinction of the primary neutron flux angle of incidence.
3. A shield according to Claim 2, wherein the cavity is formed so that it is of generally sickle-shaped configuration in cross-section, the thickness of the cavity diminishing at the sides.
4. A shield according to any one of Claims 1 -3, wherein the wall separating the cavity of the interior of the mobile object is coated with cadmium or a cadmium compound or tin.
5. A shield according to any one of Claims 1-4, wherein the interior of the external wall of the cavity is coated with a durably elastic material.
6. A shield according to any one of Claims 1-5, wherein the cavity comprises a plurality of separate chambers.
7. A shield according to Claim 6, wherein the upper part of the cavity comprises a separate chamber, which is not connected with the sides of the cavity.
8. A shield according to Claim 6 or Claim 7, wherein the sides of the cavity comprise a plurality of chambers arranged side by side.
9. A shield according to Claim 8, wherein the interiors of the side chambers of the cavity are connected only during the filling or discharging of the hydrogenous liquid.
10. A shield according to any one of Claims 6-7, wherein the cavity is provided with several entrance and exit valves.
11. A shield according to any one of the preceding claims wherein the object is provided with a fountainhead arrangement which can be used to spray the whole surface of the object by evacuation of the hydrogenous liquid from the cavity.
12. A shield according to any one of the preceding claims wherein the object for which the shield is provided is a vehicle and wherein said cavity forms at least in part a fuel tank for the vehicle.
13. A shield for an object against neutrons emitted from a source above the ground wherein said shield comprises a cavity containing a hydrogenous liquid substantially as hereinbefore described.
13. A shield according to Claim 1 or Claim 2, wherein the shield is provided by movable elements like waterbags or plastics containers filled with the hydrogenous liquid.
14. A shield for an object against neutrons emitted from a source above the ground wherein said shield comprises a cavity containing a hydrogenous liquid substantially as hereinbefore described.
New claims or amendments to claims filed on 12 March 1984
Superseded claims All
New or amended claims:
1. A shield for an object, especially for a vehicle, against neutrons emitted from a source above the ground, wherein such shield comprises a cavity which extends around the top and sides of the object and which contains a hydrogenous liquid, said cavity having means whereby said liquid can be introduced into or discharged from the cavity when desired, wherein the cavity is arranged when filled to provide a thickness of the hydrogenous liquid given by the following formula:
x =}1n.(N.sin2) where
x : thickness of the hydrogenous liquid, r : the removal cross section
N : the factor of extinction of the primary neutron flux angle of incidence
2.A shield according to claim 1, wherein the cavity is formed so that it is of generally sickle-shaped configuration in cross-section, the thickness of the cavity diminishing at the sides.
3. A shield according to claim 1 or claim 2, wherein the wall separating the cavity of the interior of the mobile object is coated with cadmium or a cadmium compound or tin.
4. A shield according to any one of claims 1-3, wherein the interior of the external wall of the cavity is coated with a durably elastic material.
5. A shield according to any one of claims 1-4, wherein the cavity comprises a plurality of separate chambers.
6. A shield according to claim 5, wherein the upper part of the cavity comprises a separate chamber, which is not connected with the sides of the cavity.
7. A shield according to claim 5 or claim 6, wherein the sides of the cavity comprise a plurality of chambers arranged side by side.
8. A shield according to claim 7, wherein the interiors of the side chambers of the cavity are connected only during the filling or discharging ofthe hydrogenous liquid.
9. A shield according to claim 5 or claim 6, wherein the cavity is provided with several entrance and exit valves.
10. A shield according to any one of the preceding claims wherein the object is provided with a fountainhead arrangement which can be used to spray the whole surface of the object by evacuation of the hydrogenous liquid from the cavity.
11. A shield according to any one of the preceding claims wherein the objectforwhich the shield is provided is a vehicle and wherein said cavity forms at least in part a fuel tank for the vehicle.
12. A shield according to claim 1, wherein the shield is provided by movable elements like waterbags or plastics containers filled with the hydrogenous liquid.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08312700A GB2142183A (en) | 1983-05-09 | 1983-05-09 | A shield for protecting an object against neutron radiation |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08312700A GB2142183A (en) | 1983-05-09 | 1983-05-09 | A shield for protecting an object against neutron radiation |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2142183A true GB2142183A (en) | 1985-01-09 |
Family
ID=10542406
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08312700A Withdrawn GB2142183A (en) | 1983-05-09 | 1983-05-09 | A shield for protecting an object against neutron radiation |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2142183A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3923978A1 (en) * | 1989-07-20 | 1991-01-31 | Blohm Voss Ag | Radiation shielding for armoured vehicle crew room and electronics - uses shielding material plates adhered to inside and system of measurements to tailor thickness to position |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1225111A (en) * | 1966-03-30 | 1971-03-17 | ||
| GB1420940A (en) * | 1971-12-30 | 1976-01-14 | Dow Chemical Co | Aqueous radiation shield |
| GB1573065A (en) * | 1976-09-08 | 1980-08-13 | Weissenfluh J | Radiation shield for nuclear racotrs |
| GB2088431A (en) * | 1980-11-12 | 1982-06-09 | Crookes Thomas Anderson | Radiation shelter |
-
1983
- 1983-05-09 GB GB08312700A patent/GB2142183A/en not_active Withdrawn
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1225111A (en) * | 1966-03-30 | 1971-03-17 | ||
| GB1420940A (en) * | 1971-12-30 | 1976-01-14 | Dow Chemical Co | Aqueous radiation shield |
| GB1573065A (en) * | 1976-09-08 | 1980-08-13 | Weissenfluh J | Radiation shield for nuclear racotrs |
| GB2088431A (en) * | 1980-11-12 | 1982-06-09 | Crookes Thomas Anderson | Radiation shelter |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3923978A1 (en) * | 1989-07-20 | 1991-01-31 | Blohm Voss Ag | Radiation shielding for armoured vehicle crew room and electronics - uses shielding material plates adhered to inside and system of measurements to tailor thickness to position |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |