JPH02201440A - Composition for display by radiation exposure - Google Patents

Abstract

PURPOSE:To clearly color a compsn. by irradiation with a medium dose of radiation and to keep the colored state for ordinary handling time by using a compsn. consisting of a single crystal or polycrystal of KCl or NaCl doped with a divalent metallic element, especially Ca. CONSTITUTION:The dependency of the coloring life of a compsn. for display by radiation exposure on doping weight is largely varied in accordance with the kind of alkali halide and the kind of doping element used in combination. A compsn. consisting of a single crystal or polycrystal of KCl or NaCl blended with 1X10<-2>-1mol% Ca as a doping element is used as the compsn. for display. This compsn. is colored by irradiation with a medium dose of radiation to such a degree that the colored state can be recognized at first glance without requiring special post-treatment such as development and the colored state can be kept for ordinary handling time.

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a display composition that indicates that an irradiated object has been irradiated with radiation such as X-rays or electron beams, and particularly relates to a display composition that changes from colorless to colored. The present invention relates to a radiation irradiation display composition that can be colored by irradiation and can maintain its colored state for a long period of time. [Conventional technology] In recent years, X has been used in a wide range of industrial fields, including sterilization of medical instruments, sterilization of foods, suppression of germination of onions and potatoes, crosslinking of polymeric compounds, surface treatment, diagnosis of the inside of the human body, and non-destructive testing of the inside of materials. The use of rays and electron beams is progressing, and when using these, whether it is to intentionally irradiate an irradiated object or to detect leakage due to some reason from X-ray or electron beam application equipment. However, from the viewpoint of work efficiency and safety, a simple means is desired that allows one to recognize at a glance that the irradiation process with irradiation has been completed or that a leak has occurred. Up until now, silver halide photography has been used, such as the film badges worn by X-ray and electron beam handlers, for small doses of radiation on the order of 10-3 rad-10-" rad. However, This method is a method that detects color changes that become apparent only after the development process, and it is not possible to detect color changes immediately after irradiation.In addition, in cases such as sterilizing medical instruments or suppressing the germination of potatoes, A large amount of X-rays and electron beams of around 10'rad are irradiated, and many compositions are known that cause color changes when the irradiation dose is large.For example, halogenated organic compounds and A composition whose main component is an acid-sensitive dye, in which the halogenated organic compound undergoes dehydrohalogenation by irradiation with X-rays or electron beams, and the generated hydrogen halide acts on the acid-sensitive dye, causing the dye to undergo dehydrohalination. There are some compositions that utilize color change.However, compositions made of such organic compounds that utilize color change are
It has extremely low sensitivity to radiation doses below 1.
In the case of an irradiation dose of about 0.03 to IO'rad, no color change can be expected for practical use. Typical materials that exhibit coloration that can be recognized at a glance with a moderate radiation dose of 103 to 1 O'rad include sodium chloride (NaCIl) and potassium bromide (KB).
Examples include alkali halides such as r). These materials have 10
``It shows a change in color from colorless and transparent to orange or blue at a radiation dose of about 103 to 10'rad.
When left at room temperature, normal pressure, and exposed to natural light,
The color fades in about 4 minutes and returns to a colorless and transparent state. [Problem to be solved by the invention] As described above, in the prior art. Materials that exhibit an effective color change at an intermediate irradiation dose of about 10' to 10' rad and that can maintain the colored state for a sufficient period of time (at least 1 hour) to withstand normal handling are available. It wasn't. An object of the present invention is to solve the problems of the above-mentioned prior art, and to achieve visual recognition at the above-mentioned medium dose of radiation without requiring any special post-processing such as development. It is an object of the present invention to provide a radiation exposure display composition that can exhibit coloration that can be applied to the radiation exposure display and that can maintain the coloring state for a time that can withstand normal handling. [Means for solving problem a] The above purpose is to use calcium (Ca) as a doping element.
A composition consisting of a single crystal or polycrystal of potassium chloride (K(J)) or sodium chloride (NaCα) containing 1×10'''1 mo 1% to 1 mo 0% is used as a composition for radiation irradiation display. Alternatively, in a formulation using a combination of Ca and other divalent metal elements as a doping component, the total amount of the doping component is l
X 10””mo (in the range of 1% to 1moQ%,
This can also be achieved by using a composition for radiation irradiation display comprising a single crystal or polycrystal of KCQ or NaCl blended to contain at least 1 x 10-''no Q% of Ca. [Function] The inventors have discovered that the color density after radiation irradiation is improved by doping a small amount of a different element into a NaCl single crystal (“Co1or Center Formati
onin sodium chloride”: H
, V, Etzal & J, G, A11ard; Phy
s, Rev, Lett, 2 pp, 452-45
4 (1959)), we experimentally investigated combinations of various alkali halides and various doping elements with the aim of maintaining the colored state for a long time by optimizing the doping amount. First, regarding the types of alkali halides, Li, Na, and K are used as alkali metals for the purpose of obtaining materials with various hues by radiation irradiation. Cs, and F, Cjl, Br as halogen elements
The target was alkali halides obtained in combination with the four types listed below. On the other hand, as for the type of doping element, there are relatively few restrictions on the amount of doping, that is, it is relatively easy to replace monovalent alkali metal ions in the crystal structure, and forms divalent ions. We decided to select the metal elements that will
a, Ba and pb were selected. In addition to the types of alkali halides and doping elements mentioned above, factors governing the maintenance of the colored state after radiation irradiation (hereinafter referred to as coloring life) include whether the resulting composition is single crystal or polycrystalline. After adding and melting the doping element halide to the alkali halide, there may be a difference in the phase state, such as whether it is solid or powdery. A comparison was made of a single crystal obtained by slow cooling over a long period of time, a polycrystal obtained by rapid cooling after melting, and a sample obtained by crushing the single crystal or polycrystal and then tableting it with a tablet machine. We conducted an evaluation. (In addition, discrimination between single crystal and polycrystal was performed by microscopic observation of the sheared plane). As a result, for example, Ca is 5XIO
Regarding KCLL doped with OQ%, there was almost no difference in the lifespan of purple coloration after radiation irradiation between single crystal and polycrystal.
) using a tube-type X-ray generator as a target material,
When irradiated with 3000 rad of X-rays at a tube voltage of 150 kV and a tube current of 20 mA, it took about 45 hours for both to completely fade when left indoors under natural light. On the other hand, in the case of a crushed sample tableted under a pressure of 150 kg/c2, when irradiated at x1 m and left under natural light under the same conditions as above. The color completely faded in just 2 minutes. From this, it has been found that the coloring life is significantly different between the crystalline state and the pulverized powder state, and that the coloring lifespan is longer in the crystalline state. This relationship was similarly observed for various combinations of alkali halides and doping elements. The relationship between the type of doping element and the amount of doping and the coloring life will be described in detail in the Examples below, but for example, in the case of KCA doped with Ca element, the one coloring life largely depends on the amount of doping. Moreover, there is an optimum doping amount. In addition, in the case of Na (J) doped with Ca element, doping has the effect of improving the coloring life, but the dependence on the doping amount is extremely small. It can be seen that the dependence of the coloring life on the doping amount is significantly different.It should be noted that if the colored sample is wrapped in, for example, Aa foil after irradiation and left at room temperature and pressure in a light-shielded state, it will not be exposed directly to natural light. The lifespan of coloring could be further extended compared to the case where

[Examples] The content of the present invention will be explained in more detail below using Examples. Here, in the following explanation, mo indicating the doping amount is
The number Q% indicates the ratio of the 1oQe number of the doping element to the total v*oQ,e number of the alkali halide and doping element in percentage (%). The single crystals or polycrystals used in the Examples were obtained by first melting each composition at a high temperature, then slowly cooling it to room temperature over a period of 7 days, or rapidly cooling one product overnight. Regarding X-ray irradiation, a tube-type X-ray generator with W as the target material is used as the X-ray source, and a tube voltage of 1
Generate X-rays under the conditions of 50kV and tube current of 201IA,
For the purpose of cutting long wavelength components, a 1-thick aluminum plate was inserted between the source and the irradiated sample, and the dose was 3000 r.
Irradiation was continued until ad. Hereinafter, the case where X-ray irradiation is performed under the above conditions will be referred to as tube X-ray irradiation. Note that to measure the irradiation dose, an air ionization-type generated ion amount measuring instrument was used that had been calibrated in advance for the relationship between the irradiation dose and the amount of generated ions. Table 1 shows the lifespan of coloring when various crystal samples were exposed to natural light after being irradiated with tube X-rays, and the lifespan of coloring was measured as follows. In other words, the irradiated sample was placed in a room with natural light from 8:00 am until 1:00 pm.
The sample was left until 6 o'clock, after which the sample was wrapped in M foil and stored to protect it from light.The next day, the sample was unwrapped again and exposed to natural light.The operation was repeated until the color completely faded.The total time of exposure to natural light was repeated. This is shown below. Example I First, the results of the coloring life after tube X-ray irradiation for crystal samples of KCa and KCQ doped with divalent metal elements are shown.
Samples Nα] to 11 in the table are shown. These results show that the color life can be improved by doping KCfi with divalent metal elements, especially Ca
In the case of elemental doping, there is a remarkable dependence on the doping amount, especially when the Ca element doping amount is I
It is known that it has a long life of 14,400 minutes (10 days) when it is closed at 9%. In addition, when the sample was stored under light-shielding conditions, it was found that the color did not completely fade even after 120 days. Note that when the doping amount of Ca element was 5 mo12%, uniform dispersion of the doping agent was not obtained, resulting in cloudy crystals. From this result, the preferred range for Ca element doping is 1 x 10-
”~1vroQ%. On the other hand, the combination doping of Ca element and Mg element KCa
For each sample, I x 10""so 9%
, 9 x 10-"no 9%, the coloring life was equivalent to that of sample Ha 3. In addition, in the above combination doping, Ca
element and Mg element each in 5 x 10-”ago
When 9% each was added, the coloring life was almost the same as that of sample Nα5. This result shows that in the case of doping with a combination of divalent metals, the effect of the component elements effective in prolonging the lifespan among the doping elements is more dominant on the coloring life, and the addition of other divalent metal elements is more dominant. This indicates that there is almost no disturbing influence. In addition, the above-mentioned Ca element doping amount I
When a 9% KCa sample was irradiated with an electron beam of 3000 rad at an acceleration voltage of 2 MV and a beam current of 5 mA, the coloring life when left indoors under light shielding was the same as that of the X-ray irradiated sample, and the result was 120 days or more. . Example 2 Samples Nα12 to Nα21 in Table 1 show the results of coloring life after irradiation with xg tube for crystal samples in which NaCQ and NaCn were doped with a divalent metal element. From this result, as in the case of KCII shown in Example 1, the effect of improving the coloring life by doping with a divalent metal element is recognized. However, as seen in the results of samples Nα13 to Nα17, when doping with Ca element, the dependence on the doping amount is small, and the life time is limited to about 4 hours at maximum. The preferred range for Ca element doping is judged to be in the range of 1X10-'' to I1109%, as in Example 1. Regarding the combined doping of divalent metals, the preferred range in Example 1 is as follows. The same results as in Example 1 were obtained.Example 3 Coloring of NaBr and crystal samples of NaBr doped with divalent metal elements after tube X-ray irradiation The life results are shown in samples &22 to 26 in Table 1. From these results, in the case of NaBr, the effect of improving the coloring life by doping with divalent metal elements is generally small;
Only a slight improvement is observed when doping I X 10-"so 0%. Comparative Example I X 10""vao 0% doped KCfl single crystal with ICa element is about 10 'X of double strength
When irradiated with synchrotron radiation, which generates radiation, for about 1 minute, only the surface of the sample was colored purple (in the case of tube X-rays, the inside of the sample was also colored), but this coloring could be removed by leaving it exposed to natural light. However, no discoloration was observed for more than 6 months. Comparative Example 2 When single crystals of LiF and LiC11 were irradiated with tube X-rays, the results were as shown in Table 1 Sample &27.28.
No coloration was observed. This is thought to be due to the small sensitivity of the sample to the X-ray wavelength range generated by the tube X-ray source. Incidentally, when a LiF single crystal was irradiated with synchrotron radiation for 2 minutes, the inside of the crystal was colored yellow, and this coloring remained unchanged even after 6 months of exposure under natural light. This means that the wavelength range and intensity of the irradiated X-rays are
This is thought to be due to the difference between the radiation source and the synchrotron radiation. Comparative Example 3 When a single crystal of KBr was irradiated with tube X-rays, the results were as shown in Table 1, Sample-29. Although the irradiation showed deep blue coloring, the coloring life was extremely short, and No improvement in coloring life was observed even by doping with divalent metal elements. Comparative Example 4 When tube X-ray irradiation is applied to a single crystal of KI (sample & 3G
), pale green coloration was observed. This coloring faded in about 4 minutes, but a light brown color remained behind. This color did not fade even after being exposed to natural light for 3 months. This coloring is thought to be due to free iodine generated by decomposition of Kl by X-ray irradiation. Comparative Example 5 When CsBr single crystal was subjected to tube X-ray irradiation (sample #31), freshwater coloration was observed, but this coloration was pale and the coloring life was extremely short. The following is a blank table [Effects of the Invention] As described above, the composition for radiation irradiation display is made into a composition of the present invention, that is, it is doped with a divalent metal element, particularly Ca, in an amount within an appropriate range. By creating a composition consisting of a single crystal or polycrystal of KCfi or NaC1, it is clearly colored by irradiation with a moderate radiation dose of 10' to 10' rad, and has a coloring life that can withstand normal handling time. It was possible to provide a radiation irradiation display composition exhibiting excellent performance. By using the composition, it is possible to easily recognize at a glance that a radiation irradiated object has been irradiated with radiation. Note that by storing the sample in a light-shielded state after irradiation, the colored state can be maintained for a longer period of time, so the composition can be expected to be applied in a wide range of fields. Representative Patent Attorney Junnosuke Nakamura

Claims (1)

[Claims] 1. Calcium (Ca) as a doping element 1×1
A radiation irradiation display composition characterized by comprising a single crystal or polycrystal of potassium chloride (KCl) blended in a range of 0^-^2 mol% to 1 mol%. 2. 1×10^-^2mo of Ca as a doping element
Sodium chloride blended in the range of 1% to 1mol% (
1. A radiation irradiation display composition comprising a single crystal or polycrystal of NaCl. 3. In a formulation using a combination of Ca and other divalent metal elements as a doping component, the total blending amount of the doping component is in the range of 1×10^-^2 mol% to 1 mol%, and Ca is at least 1× 1. A radiation irradiation display composition comprising a single crystal or polycrystalline KCl containing 10^-^2% or more. 4. In a formulation using a combination of Ca and other divalent metal elements as a doping component, the total blending amount of the doping component is in the range of 1×10^-^2 mol% to 1 mol%, and Ca is at least 1× A radiation irradiation display composition comprising a single crystal or polycrystal of NaCl blended to contain 10^-^2 mol% or more.