DE1913100A1 - Paint for the absorption of backscattered and transmitted, low-energy X-ray and gamma rays - Google Patents

Description

1913100 Patent attorney Dipl.-Phys. Gerhard Liedl 8 Munich 22 Steinsdorfstr. 21-22 Tel, 29 84 62

B 4079

Giken Kogyo Kabushiki Kaisha No. 3, Kioicho, Chiyoda-ku, Tokyo / JAPAN

Paint for the absorption of backscattered and transmitted, low-energy X-rays and gamma rays.

The invention relates to a paint for the absorption of backscattered and transmitted, low energy X-rays and gamma rays.

Dr. D / K

009 837/1827

With the increasing use of X-rays and gamma rays in the broadest areas of application, for example in the clinical and industrial sector, the risk has also increased that X-rays or gamma rays hitting people will cause damage to health and genetic makeup. For this reason, various measures have been taken to prevent X-rays or gamma rays from being radiated outside. The room in which X-rays or gamma rays are used is therefore shielded to prevent harm to third parties. If, however, the ceiling, floor and walls are provided with a shielding device (in the following this should always be referred to as "shielding walls and the like"), the X-rays and gamma rays are partially reflected back into the room in which they are used. There is therefore a danger that will hit the operator of the installation of more X- or gamma rays, as would be the case if no shielding walls or similar * would royal present.

According to the present invention, a paint is now to be produced, the backscattered and transmitted, low-energy X-ray and gamma rays are absorbed in order to also for the individuals within this Shielding to achieve effective radiation protection.

This problem was solved by using this paint lead and at least contains a substance which absorbs the secondary emission of lead

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It preferably contains a mixture of 70 to 90% by weight as filler a lead compound, 5 to 25% by weight of iron or an iron compound and 5 to 10% by weight ■ of a calcium compound which is mixed with a binder is that relative to the above mixture of 25 to 50% by weight of a one Film-forming agent, 10 to 20% by weight of a thickening agent and 2 to 10% by weight of a dispersing and wetting agent.

If X-rays or gamma rays with a frequency ν strike an atom of a substance whose electrons in the K-shell have a binding energy A, then if the energy h ··ν (h = Planck's constant) becomes the X-ray - or gamma quanta is greater than this binding energy A, an electron or electrons are knocked out of the K shell and the corresponding amount of energy is absorbed (K absorption edge). Then the electrons of the L-shell, M-shell, N-shell etc. fall into the empty orbital of the K-shell, resulting in a line emission with the energies α., Α §> ft _ etc. The intensities of these emitted lines ocj, c ^, P ₁ , βg etc. depend on the ratio of the statistical weights determined by the inner quantum numbers. In this way, the incident x-rays or gamma rays - depending on their energy - are absorbed by any of the K, L or M shells of the substance atoms.

For example, X-rays or gamma rays deliver with an energy that

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is greater than 83.95 KeV, absorptions in the K-edge emerge, leading to the Emission of characteristic X-ray radiation of 74.95 KeV (greatest statistical weight) leads. This radiation leads to another Absorption in the L-edge and this in turn leads to the emission of characteristic X-rays at 14.76 KeV.

Iron, on the other hand, absorbs X-rays or gamma rays with a larger one Energy than 7.11 KeV and emits a characteristic X-ray radiation with an energy of 6.40 KeV.

Finally, calcium absorbs x-ray or gamma rays with a higher energy than 4.03 KeV, and emits characteristic X-rays from 3.69 KeV.

In addition to the photoelectric effects described above, the Compton effect occur. However, its relative proportion becomes very small when the energy of the primary X-rays or gamma rays decreases.

As the filler for paint according to the present invention preferably from 70 to 90% by weight of a lead compound, 5 to 25% by weight of iron or an iron compound and 5 to 10% by weight of one If there is a calcium compound, experience the X-rays or gamma rays an absorption in the K or L edge of the lead and are converted into characteristic X-rays of 14.76 KeV. This will by absorption in the K-edge of the iron into a characteristic

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X-rays of 6.4 ° KeV converted, and the latter into the characteristic X-rays of calcium at 3.69 KeV through absorption in its K-edge. Finally, the characteristic X-ray or gamma rays, the energy of which is equal to or less than 3.69 KeV, by absorption in the M-edge of the binder as well as the Lead, iron and calcium self-absorbed.

Also the Compton scatter, which is caused by the impact on the inventive absorbent paint is absorbed by the lead.

In addition, you can use a paint according to the present Invention, even after a long time, carry out the painting process easily if you stir and mix them. The paint layer leaves then apply evenly.

Therefore, when looking at one made in accordance with the present invention Paint on the surface of a z. B. from mortar or similar existing shielding wall applies in a certain thickness, the backscattered x-rays or gamma rays from the mortar wall or the like are strongly absorbed. The risk that that Operating personnel located within the shielding walls is exposed to radiation damage, is thereby greatly reduced. the Layer of absorbent paint can also be applied firmly to the mortar base or the like in such a way that it lasts for a long time Time does not crack or peel.

00983 7/1827

The following examples and the accompanying drawings serve as further information Explanation of the invention.

Show it;

Fig. 1 in the diagram shows a comparison between the energy spectrum

W giespektrum, the supply of back-scattered radiation of aluminum, and the energy backscattered rays when

paint according to one embodiment of the present invention Invention applied to aluminum;

Fig. 2 in a diagram, the ratio of the mass occupancy per Unit area of filler to scatter rate using the same embodiment;

) Fig. 3 in a diagram the ratio of the mass occupancy per

Unit area of the filler to the lead equivalent thickness using the same embodiment.

In the following, the invention will be based on preferred embodiments to be discribed.

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example Ίι

PbO 2.45 kg 80% by weight

. Fe ₂ O ₃ 0.45 kg 15% by weight

CaCO ₃ 0.15 kg 5% by weight

A filler with the above composition of lead, iron and calcium compounds is evenly mixed with a binder containing the following ingredients:

V lylacetat 0.90 kg 30%

(a film forming

Middle)

aqueous solution of methyl 0.30 kg (water 0.29 kg 10% cellulose (a thickening methyl cellulose

Medium) '0.01 kg)

aqueous solution of 0.09 kg (water 0.0675 kg 3% Ammonium salt of vinyl ammonium salt

acetate copolymers (a dis- 0.0225 kg)

pergating and wetting agents)

Because the lead oxide in the filler and the methyl cellulose gelatinize cause, the emulsion of filler and vinyl acetate is mixed together and kneaded and the methyl cellulose to this mixture and the ammonium salt of the vinyl acetate copolymer is added. Then everything is mixed together uniformly to make the paint to manufacture.

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An energy spectrum of the backscattered X-rays was determined as follows. The surface of a normal aluminum plate (350 mm × 350 mm × 15 mm, purity 99.99 %) was perpendicularly irradiated in an area of 5 × 5 cm with X-rays with a peak voltage of 70 KV, 0.1 mA. The energy spectrum was measured at a scattering angle of 45 with a scintillation counter made of NaJ (Tl) crystals and a 100-channel amplitude discriminator (TMC, Gammascope II Model-102). Curve A in Fig. 1 shows the result. The energy of the backscattered x-ray radiation (in KeV) is plotted on the abscissa, and the count rate of the backscattered x-ray quanta (in cpm = counts per minute) is plotted on the ordinate. If, on the other hand, the normal aluminum plate is coated with a paint produced by the method described above so that 3 kg hit the square meter, and if this layer is irradiated by the X-ray source after drying and curing as above, the energy spectrum of is obtained under the same measurement conditions Curve B. A comparison of these curves shows that, with the exception of the vicinity of 15 KeV (the characteristic X-ray radiation of lead), the backscattered X-rays are strongly absorbed.

If you carry one of the above example onto the surface of a The layer of paint applied to the mortar wall counteracts the measured scatter rate shows the mass coverage per unit area, then one obtains Fig. 2. Here is the mass coverage per unit area (mg / cm) of the

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layer contained filler on the abscissa and the scattering rate (%) plotted on the ordinate. If the mass occupancy per area

the amount of filler contained in the paint layer is greater than 300 mg / cni the dose of backscattered rays remains essentially constant.

The mentioned "spreading rate" is defined as follows?

Count rate of the X-ray backscattered from a test plate

quantum

Counting rate of the X-ray quanta backscattered from a normal aluminum plate (minus the TL & uec ¹ background)

Since the paint contains lead, an excellent shielding agent against radiation, X-rays or gamma rays are greatly weakened when they penetrate the foil. If, therefore, X-rays with a peak voltage of 140 KV, 0.18 mA, are incident vertically on the surface of a normal lead plate (0.1 to 0.3 mm thickness, purity 93.99%), a field of 5 × 5 cm is irradiated on this lead plate The attenuation of the x-rays was measured with a dosimeter of the ionization chamber type and an attenuation curve for x-rays was established with it. The paint layer is then exposed to the X-rays, and the corresponding lead equivalent thickness is obtained by interpolation from the attenuation curve for X-rays determined on the normal lead plate. In Fig. 3 the lead equivalent is -

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thickness (in mm Pb) is plotted on the ordinate and the mass coverage per unit area (in mg / cm ² ) of the filler is plotted on the abscissa. The diagram shows that the lead equivalent thickness and the mass coverage

per unit area of the filler are proportional to one another.

Since the composition of the binding agent is suitably selected to obtain a paint, in the case of the present embodiment, the w also in terms of both in economic point of view as their specific

Paint properties are satisfactory. The color can therefore be dispersed evenly and it can also be easily processed with a roller, a brush, or a spray gun provided with a sufficiently large nozzle. After application and drying, the paint layer obtained in this way has a high level of water resistance and is excellent in its mechanical properties Properties, shockproof and difficult to remove.

Even if the composition of the filler contained in the mixture varies within the limits specified in the claim, the absorption capacity for backscattered X-rays or gamma rays remains essentially the same as the previous example.

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Example Π

Vinyl acetate 0.75 kg 25%

(a film forming

Middle)

aqueous solution of methyl 0.60 kg (water 0.576 kg 20%

cellulose (a thickening methyl cellulose 0.024 kg)

Middle)

aqueous solution of 0.30 kg (water 0.225 kg 10%

Ammonium salt of vinyl ammonium salt 0.075 kg)

acetate copolymers (a dispersing and wetting agent)

In example Π, a binder with the above composition is used instead those listed in Example I used. The proportion of being a fuming Agent used vinyl acetate is relatively small in relation to the filler, while the proportion of as a thickening agent serving methyl cellulose and the ammonium salt of vinyl acetate copolymer used as a dispersing and wetting agent is relatively large, so that separation by failure is possible. Even so, this material can easily be made into a paint by mixing and stirring will.

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Example ΠΙ

Vinyl acetate 1.50 kg 50%

(a film forming

Middle)

aqueous solution of methyl 0.30 kg (water 0.29 kg 10%

cellulose (a thickening methy! cellulose 0.01 kg)

Middle)

aqueous solution of 0.06 kg (water 0.048 kg 2%

^ Ammonium salt of vinyl ammonium salt 0.012 kg)

w acetate copolymers (a dispersing and wetting agent)

This third example uses the composition listed above of the binder instead of those listed in Example I. Here, too, the specific paint properties are satisfactory. Disadvantageous is, however, that the time for the painting process to achieve a certain absorption capacity increases and thus of course also the Costs because the proportion of filler per unit area of the color layer, measured on the other examples, is low.

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Claims (6)

■ - 13 - claims 1.Paint for the absorption of back-scattered and transmitted, low-energy X-rays and gamma rays, characterized in that it contains lead and at least one substance which causes the secondary emission absorbed by the lead. 2. paint for absorbing backscattered and transmitted, low-energy X-rays and gamma rays, characterized in that this paint as a filler a mixture of 70 to 90 wt -.% Of a lead compound, 5 to 25 wt ..-% of iron or an iron compound and contains% of a calcium compound which is mixed with a binder relative to the above mixture of 25 to 50 wt - - 5 to 10 wt..% of a film-forming agent, 10 to 20 wt -.% of a thickening agent and 2 to 10% by weight of a dispersing and wetting agent. 3. paint for absorbing backscattered and transmitted, low-energy X-rays and gamma rays according to claim 2, characterized in that the mixture of 80 wt -.% Lead oxide, 15 wt -.% Iron oxide and 5 wt -.% Calcium carbonate is made. 00 9837/1827 4. paint for the absorption of backscattered and transmitted, low-energy X-rays and gamma rays according to claim 2 or 3, characterized in that the binder relative to the mixture of the filler 30 wt. % Vinyl acetate as a film-forming agent, 10 wt. % a 3.3% aqueous solution of methyl cellulose as a thickening agent, and 3% by weight of a 25% aqueous solution of an ammonium salt of vinyl acetate copolymers as a dispersing and wetting agent. 5. paint for absorbing backscattered and transmitted, low-energy X-rays and gamma rays according to claim 2 or 3, characterized in that the binder relative to the mixture of the filler 25 wt -.% Forming of vinyl acetate as a film-agent, 20 wt. - % of a 4% aqueous solution of methyl cellulose as eindickendes agent and 10 wt -.% of a 25% aqueous solution of a V ammonium salt of vinyl acetate copolymers as a dispersing and wetting agent. 6. paint for absorbing backscattered and transmitted, low-energy X-rays and gamma rays according to claim 2 or 3, characterized in that the binder relative to the mixture of the filler 50 wt -.% Vinyl acetate as a film-forming agent, 10 wt -.% a 3, 3% aqueous solution of methyl cellulose as eindickendes agent and 2 wt -.% of a 20% aqueous solution of a 4079 009837/1827 Ammonium salt of vinyl acetate copolymers as a dispersing and wetting agent contains. 009837/1827