Note: Descriptions are shown in the official language in which they were submitted.
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APART FOR TIE Royalty IOCALIZATIO~ OF Redirect SATIRIC
BAC~GROU~TD OF THE INTENTION
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The present invention relates to an apparatus for the remote
localization or location of radioactive sources.
In an area with radioactive risks, it is sometimes necessary
to seek and locate the radioactive sources. An attempt is
theft made to prepare a myopia" of the gamma activity of the
zone to be monitored by attempting to operate remotely and
consequently reducing the rislcs of contamination for operators.
At present, an apparatus for the remote localization of gamma
emitting radioactive sources comprises a gamma ray detector,
a distance sensor and a video camera. This apparatus
travels on rails and can be moved in accordance with limited
angles towards the sources to be located. converter converts
the signals transmitted by the gamma ray detector and
distance sensor into colored zones on a control screen. A
first image showing -the intensity and distribution of` the
gamma rays emitted by the radioactive sources is therefore
formed point-by-point. On said first image is superimposed
a second image from the video camera, in order to permit the
location of the sources as a function O-r their intensity in
the zone to be monitored.
Such an apparatus is difficult to transport and realize as a
result of its weight complexity and fragile nature, so that
the detector and camera have to be manipulated carefully. It
is therefore not very suitable for use as an apparatus for
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monitoring nuclear installations, where radioactive sources
can appear at random locations. The time for obtaining the
first image is very long and it is consequently difficult
to ra~idlv obtain several photograph. As a result of its
complexity, the apparatus is very costly, which makes it
impossible to install such an apparatus permanently in each
zone to be monitored.
U.S. Patent 3107 276 describes an apparatus for the localize
anion of radioactive sources designed to be airborne and
having a pinhole camera made from a shielding material. This
camera is provided with a scintillation converter associated
with a cathode ray tube, which converts the image focused by
the pinhole into electronic signals with a view to their
teletransmission. An independent video camera makes it
possible to display the space to be monitored. In such an
apparatus, the superimposing of the video image and the image
of the radioactive sources is very difficult to bring about
on an accurate basis. Moreover, the apparatus has large
dimensions, is costly to manufacture and use and is not very
suitable for use within a building.
SUMMARY OF THE INVENTION
The present invention relates to an apparatus for the remote
localization of radioactive sources making it possible to
obviate the afor~mclltiolled disadvantages.
More specifically, the Present invention comprises a pinhole
camera, whose walls constitute a shielding for the radioactive
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rays. this pinhole camera has an elan making it possible
to introduce a first film able to detect the radioactive
radiation emitted by said sources and positioned in front of
the pinhole. Preferably the pinhole camera also has a plug
constituting a shield for the radioactive radiation possibly
coming from the rear and used for closing said opening during
the operation of the apparatus.
Advantageously, a second light-sensitive film is placed in
the pinhole camera substantially at the same location as the
first film, so as to be exposed by the light penetrating via
the pinhole.
Preferably the pinhole camera is provided by a collimator
defined by a cone, whose narrowest part constitutes the
pinhole and whose opening defines the photographing or shooting
field. It is preferable to place the narrowest opening on
the side of the entrance for the radiation, so that it is
possible to move the radioactive radiation-sensitive film
as close as possible to said entrance, which leads to a
reduction of the -total volume. In an optimized construction,
the pinhole camera is defined by a double cone (two cones
with -the same aperture opposed by the apex), which leads to
a reduction in the total volume of the shielding material.
Preferably, said pinhole camera constitutes a double
clial]lram~ a smear diaDllragm r1ermitting the nascage of
radioactive radiation and light and a large diaphragm only
parenting the passage of radioactive radiation. The small
diaphragm is formed by a small diameter hole made in a
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material which is permeable to radioactive radiation and
light-proof, said material being placed in a larger diameter
hole made in the Allis of said chamfer, said hole forming
the said large diaphragm.
Advantageously, a third film able to detect the radioactive
radiation is disposed in the pinhole camera, so as to be
exposed by the radioactive radiation entering by the pinhole,
said third film being separated from the first film by an
absorbent screen.
Advantageously, an image converter able to transform radio-
active radiation into a photon emission making it possible to
expose a photographic film, is positioned adjacent to the
first film, said converter having a bundle of scintillating
optical fires, which are adjacent to one another and converge
towards the pinhole of the pinhole camera.
In practice, a film sensitive -to visible light, the film able
to detect the radioactive radiation, the converter and a
reflector are successively placed in the pinhole camera from
the pinhole to the opening.
Advantageously, a film which is both sensitive to visible
light and lo, photon emission corresponding to -the radioactive
radiation converted by the converter, the converter aloud a
reflector are successively- positioned in -the pinhole camera
from the pinhole to the opening.
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BRIEF DESCRIPTION OF THE DRAWINGS
The invention is described in greater detail hereinafter
relative to non-limitative embodiments and the attached
drawings, wherein show:
Fig. 1 in longitudinal section, the vocalization apparatus
according to a preferred embodiment of the invention.
Fig. 2 in section, a larger scale view of the pinhole camera.
Fig. 3 in section, a larger scale view of the film chamber
and the film magazine.
Fig. 4 in section, the film magazine according to a variant
of the apparatus according to the invention.
Fig. 5 in perspective, a diagrammatic view of an image
converter according to the invention.
Fig. 6 in perspective, a diagrammatic vie- of a configuration
of the pinhole camera including the converter.
Fig. 7 diagrammatically, another configuration of the pinhole
camera provided with the converter.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The apparatus -for the remote localization or location of
radioactive surcease is shown in fig. 1 in accordance with a
preferred embodiment of the invention.
In the area to be monitored, a frame 2 is placed at the
desired location for producing the photographs and said frame
is e.g. molehill. A base I is fixed to frame 2 and is used -for
supporting a body 6 via two horizontal spindles 8. The latter
permit the rotation of howdy 6 about a horizontal geometrical
axis 9. Body 6 has a symmetry of revolution about an axis 10.
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Axis lo and rotation axis 9 are preferably perpendicular.
In its upper -part, body 6 is provided with a handle 12 making
it possible to easily orient the Buick 6 about axis 9. A
vertical graduated disc 14 is fixed to base Lo level with one
of the sides of body 6. The revolution axis of graduated
disc 14 coincides with axis 9. Body 6 is provided with a
pointer 16 making it possible to indicate the orientation of
body 6 on graduated disc 14. Not Sheehan locking means are
arranged on either side of the body level with the two spindles
8, in order to ensure the locking of the body in rotation
about said axis 9. It is thus possible to orient body 6 and
sight the radioactive sources 18, indicate the orientation
of body 6 by pointer 16 on graduated disc Eli and find the
same position again if e.g. the apparatus has been moved.
According to a variant, body 6 is not integral with a frame
and con be introduced into the zone to be monitored at the
end of a support rod, passing through an opening, e.g. into
a duct or shaft. Body 6 has a front face 17 to be positioned
facing the sources to be photographed and an opposite or
rear face 19.
The apparatus according to the invention has a pinhole camera
20, whereof body 6 constitutes part of its constituent walls.
The camera comprises a collimator 21, the litter being
defiled by a circular cone 22, whose base is located on front
face 17. Collimator 21 is centered on axis lo of body 6 and
the apex of cone 22 constitutes the pinhole 24. Behind the
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latter is provided a second circular cone 25 in accordance it
an angular aperture eel to that of the cone 22. In its
widest nary, the second cone 25 issues in to a circular film
chamber 26 which, like said cone, is centered on axis 10.
film chamfer 26 is extended up to rear face lo ho a cylindrical
opening 27, which is normally closed by a cylindrical plug 28.
A handle 29 and locking means 30 make it possible to insert
and then lock plug 28. The apparatus is loaded by placing a
film magazine 32 in said film chamber 26. A spring 34 fixed
on the inner face of plug 28 makes it possible to engage the
magazine 32 against a shoulder formed in chamber 26.
The thicknesses of body 6 and plug 28 are such that -they
constitute a shield against radioactive radiation. Body
and plug 28 are made from a material which greatly attenuates
gamma radiation. The alloy Dental has been chosen in preference
to lead in order to obtain a smaller volume and consequently
a lower weight. The resulting apparatus can easily be
carried by a man and can be brought to any place where
monitoring is required.
In order to produce a standard photograph of the area to be
monitored, Kit is necessary to bring about an optimum
distinction of the details of the installations. However, the
smaller the hole or pinhole 24 the greater the sharpness.
Thwack the diameter of Pinhole I is r~referclhlv smell, rug
approximately 1/10 mm. It is always possible to adapt the
brightness of the zone to be monitored as a function of this
diameter and as a function of the sensitivity of the film used.
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Louvre, an inadequacy of the gamma intensity of the radio-
active sources to be located cannot be artificially increased,
as for light.
In order to solve this problem, the pinhole 24 is formed in
the manner shown in fig. 2. In body 6 is firstly formed a
hole, whose diameter 38 corresponds to the optimization on
the corresponding photograph of the spot representing a
radioactive source, no matter what the energy of the radiation,
(e.g. approximately 0.5 mm). This hole is then collimated
with a lightweight material 39 of the polyester resin type
and which is permeable to radioactive radiation and light-
proof. Finally, a small diameter hole 36 is made in this
material. In this way a double diaphragm pinhole is obtained,
the small diaphragm corresponding to the pinhole for obtaining
satisfactory photographs of the installations present in the
zone to be monitored and the large diaphragm to the pinhole
for obtaining an adequate spot for locating the radioactive
sources.
The film magazine 32 can contain between l and 3 superimposed
films. As a function of the photographs required, the films
are arranged in the following way. firstly, in order to
localize radioactive sources in the zone to be monitored, e.g.
two photographs are produced with a film magazine containing
a single film for each ~hotoraph. The first ~)hotogral-h is
obtained it a first film /12 able -to detect the radioactive
radiation of the radioactive sources to be located. The
second photograph is obtained with the second film 40 sensitive
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to visible light and intended to photograph the zone in a
convf~ntiollal manner. The second lily JO is placed in the
magazine substantially at the same location as the first film
1l2. Three lugs, such as 41 make it newsboy to determine,
without any possible error, the placing of the films in the
film magazine 32, thus permitting a subsequent strict
superimposing of the two photographs.
In this case, the attempt is made to take two photographs
using the same observation point and the same viewing angle
corresponding to the position of pointer 16 on graduated
disc I Obviously the manipulation time is relatively long,
positioning errors are possible and the operator is obliged
to manipulate in a radioactive zone for reloading the
apparatus, which leads to hazards.
Thus, according to a preferred embodiment of the invention,
partly shown in -fig. 3, the two photographs are simultaneously
produced with a film magazine containing two superimposed
films ~10, l12, the gamma radiation-transparent film 40 and
which is insensitive to said radiation being positioned in
front of film To This ensures a good positioning cores-
pondence of -the two films and easy, fast manipulation.
Once the films ~10, 1~2 have been processed, their superimposing
males Kit r)ossib1e to distinguish spots corresnollding to
radioactive sources in the photographed installation. In
this way the elements forming the object of a radioactive
activity are locate. The optical density and size of the
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spots make it possible to determine the value of the intensity
of the radioactive activity.
Informatics processing of the two images mazes it possible to
superimpose the two photographs to give a single photograph,
directly identifying the radioactive sources. By means of a
calibration, another informatics processing of the image of
the radioactive sources makes it possible to obtain
approximate dissymmetry. The results obtained are preferably
in the form of colored zones, using standard known procedure.
It may also be of interest to determine, by their energy, the
nature of` the materials forming the radioactive sources.
For this purpose, use is jade of a magazine with three films
shown in fig, 4. These three films comprise films Lo and 42,
as well as a third film 44 able to detect the radioactive
radiation and separate from the first film 42 by an absorbent
screen 46, the second film 40 still being positioned in front
of the first film 42. By comparison of the optical densities
of these spots corresponding -to the radioactive sources and
received respectively by the two films 42 and 44, it is
possible to identify the nature of certain of the radioactive
sources. For a given absorbent and a given screen thickness,
a curve directly gives the energy corresponding to a given
ratio of the intensities, measured by the optical densities.
In certain cases, it can be advantageous to place an image
converter in the pinhole camera. The converter is e.g.
positioned adjacent -to the firs-t film axle to detect the
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radioactive radiation. It makes it possible to convert the
radioactive radiation into a photon emission axle to expose
the first film.
An image converter according to the invention is shown in
fig. 5. This converter 50 makes i-t possible to convert a
special distribution of an ionizing radiation, e.g. a gamma
radiatiort, whose path is indicated by arrows F, into a
visible image, as well as to transmit this image. For example,
this gamma radiation comes from a point source 52 constituted
by -the virtual image of the radioactive sources 18 produced
by pinhole I
Image converter 2 is constituted by a boldly ELI of scintilla
cling, adjacent optical fires 56 and which can either be made
from glass, or a plastics material. These optical fires 56
are all oriented in a direction geometrically coinciding with
the path, indicated by arrows F, of the gamma radiation from
source 52. Thus, they converge towards the same point
constituted by the point source 52.
As show in fig. 6, the image of the gamma radiation to be
detected entering by the pinhole 24 of camera 20 can be
obtained on a photographic film 58 located on the extreme
face 60 of the bundle ELI of optical fires 56 positioned
racing thy pinhole I Film I is hot sensitive to visible
light and to the photon emission corresponding to the
radioactive radiation of` the radioactive sources to be
detected and converted by the converter. The other extreme
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face 62 of the bundle is provided with a reflector 64 (e.g.
constituted by an aluminum deposit) used for reflecti3lg the
image supplied by the converter towards the nhotogra~hic
film 58.
The front position of film 58 makes it possible to
simultaneously use the pinhole camera for obtaining a
conventional image in visible light of the space to be
monitored. The image of the space to be monitored and the
image of the radiation are superimposed on the film, so
that it is possible to easily define the radioactive sources
If it is wished to retain the two images on -two separate
films, whilst using the image converter 50~ it is possible
to e.g. adroit the configuration shown in fig. 7.
Image converter 50 is once again located facing the pinhole
24 of camera 20. From pinhole 24 towards converter 50 are
successively arranged the visible light-sensitive film 40,
a black plastic screen 68, a polished aluminum reflector
70 and -the film 42 able to detect gamma radiation. Screen
f,8 and reflector 70 make it possible to separate the images
by absorbillg the back scattered radiation. Face 62 of
converter 50 is provided with reflector 64.
Obviously the above description has only been given in
exemplified manner, all modifications to be embodiments given
beillg possible without changing the basic Principle of the
invention.
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For example, the angular aperture of collimator 22 -is given
in exem~lififd manner in fix. l. It I ~ossiblf- to f-it a
rink at the entrance of said collimator level with thy front
face 17 of body 6, if it is wished in reduce said angular
aperture. The shape of body is such that the thicknesses
of the walls are adequate for forming a shield with respect
to the radioactive radiation This shape is optimized to
make the apparatus light and portable.
Moreover, plug 28 is not strictly indispensable in the case
where the user is certain that no radioactive radiation from
the rear is able to expose the sensitive film 42. Moreover,
the introduction of the film can optionally take -place by
a lateral slot, which is preferably closed by an appropriately
shaped plug.
The collimator can be de-fined by a simple cone, whose
narrowest orifice is then preferably located on the side of
the radiation entrance. Thus, the film sensitive to the
radioactive radiation can be moved as close as possible to the
entrance, which makes it possible to reduce the volume and
therefore -the weight.
Finally, the arrangement of the films can be modified as a
function of the intended uses and the characteristics of the
films used. For example, it is risibly to us thy
configuration of fig. 7 by adding another film for the
gamma radiation between converter 50 and reflector I This
film will be the equivalent of the third film permittin~fr a
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comparison I the optical densities.
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