KR20000066664A - Disk type thermoluminescent detectors by sintering LiF phosphor activated with Mg, Cu, Na and Si and its manufacturing method - Google Patents

Abstract

PURPOSE: A disk type radiation detector in which thermoluminescent material having Mg, Cu, Na, Si as impurities added in LiF is sintered, and a manufacturing method thereof are provided to solidify power type LiF:Mg,Cu,Na,Si phosphor for improving treatment, usage and sensitivity while realizing the inherent characteristics of the powder with relation to the radiation without mixing any other substances. CONSTITUTION: A method form manufacturing a disk type radiation detector in which thermoluminescent material having Mg, Cu, Na, Si as impurities added in LiF is sintered, includes the steps of forming a disk type metal mold set and pressing powder type LiF:Mg,Cu,Na,Si phosphor by a pressure of approximately 10±3 ton for molding the powder in the shape of a disk having a diameter of 5mm and a thickness of 0.8mm, and carrying out heat treatment for the disk type element in an electric furnace at 820±10°C for 60±30 minutes under nitrogen atmosphere.

Description

Disk-type radiation detection device sintered thermoluminescent material in which Mg, Cu, Na and Si are added as impurities in a LIF and a method for manufacturing the same method}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk-type radiation detection device obtained by sintering a thermoluminescent (TL) material in which Mg, Cu, Na and Si are added as impurities to LiF, and a method of manufacturing the same. Particularly, a powder form of LiF: Mg, Cu To develop a solidified device that reproduces the intrinsic characteristics of radiation possessed by, Na, Si materials, and to provide a disk-type radiation detection device and a method for manufacturing the same each device acts as an independent detection device. These detection elements are easier to handle than powders, can be used in a variety of radiation measurements, and in particular can be used as elements constituting a personal dose dosimeter badge.

Thermoluminescent detectors (TLDs) use thermal fluorescence to detect radiation with the light emitted from heating when the radiation is applied to the thermal fluorescence material.

Currently, several countries, including the United States, China, Poland, and France, have commercialized various types of thermoluminescent materials as solidified devices, and have been widely used in measuring individual exposure doses, environmental radiation doses, and absorbed doses in patient diagnosis and treatment. I use it. In particular, the LiF-based thermofluorescent material has an effective atomic number (Z _eff = 8.14) similar to that of human tissue (Z _eff = 7.42), so the energy response to photons is similar, which is advantageous when evaluating the radiation dose to the human body. Therefore, it is widely used for individual dose and medical use.

LiF: Mg, Ti, the first material developed among LiF-based TLDs, has been commercialized as TLD-100 and has been used continuously to date despite low thermal fluorescence sensitivity. The more sensitive the thermofluorescent material is, the more advantageous it is to accurately evaluate the low dose. Therefore, the research on the development of the new high-sensitivity thermofluorescent material has been actively conducted. By adding a new impurity, LiF: Mg, Cu, P, which has about 20-30 times better thermal fluorescence sensitivity than TLD-100, was developed and commercialized under the name GR-200 (China) or MCP-N (Poland). It is the most widely used products that have been found to be a device in the form of powder to find the proper solidification conditions. In Korea, new LiF: Mg, Cu, Na, Si materials, which have twice the sensitivity compared to LiF: Mg, Cu, P, have been developed in powder form (Refs. 1 and 2). It was limited.

Development of a solidified device is required for various uses. The method of device formation is largely divided into a 100% thermophosphor powder without an adhesive and a method of mixing a suitable adhesive material with the thermophosphor powder. The former methods include sintering, extrusion, hot pressing, single crystal growth, and the latter 30% to 90% of Teflon (polytetrafluoroethylene) or silicone resin. Or a degree of mixing. LiF: Mg, Ti materials were commercialized by solidification by extrusion molding (Ref. 3), sintering method (Ref. 4), and Teflon mixed with adhesive materials (Ref. 5).

Demagnetization of LiF: Mg, Cu, Na, Si materials can be accomplished through a process similar to the solidification method of LiF: Mg, Ti materials. However, different impurities may vary the shape of the glow curve, the thermal fluorescence sensitivity, the temperature of the main peak, and the fading characteristics. Therefore, the solidification conditions for maintaining the thermal fluorescence characteristics of the powdery materials depend on the characteristics of the materials. Differ Therefore, in order to elementize LiF: Mg, Cu, Na, Si materials, it is necessary to find the optimum conditions for proper solidification. Although the research on the characteristics of devices and the characteristics of devices that incorporate Teflon in LiF: Mg, Cu, Na, Si materials has been conducted (Ref. 6), the mixing of Teflon lowers the thermal fluorescence sensitivity and the device has a weak heat. .

An object of the present invention for solving the above problems is to reproduce the intrinsic properties of the radiation of the LiF: Mg, Cu, Na, Si material in the form of powder, while being easier to handle than the powder, various uses for radiation measurement In order to improve the sensitivity and to facilitate reuse by heat treatment, it has been developed as a solidified device that can be used as a component of the individual exposure dosimeter badge, which solidifies the powder itself without mixing other materials in the powder. Another object of the present invention is to provide a disk-type radiation detection device in which each device functions as an independent detection device, and a method of manufacturing the same.

1 is a manufacturing process of a disk-type LiF: Mg, Cu, Na, Si detection device of the present invention,

2 is the shape of the LiF: Mg, Cu, Na, Si material and the disk-type LiF: Mg, Cu, Na, Si detection element of the present invention,

Figure 3 is a comparison of the measured thermofluorescence sensitivity of the TL material compatible with the powder type LiF: Mg, Cu, Na, Si material,

4 is a measurement thermal fluorescence sensitivity comparison of a powder type LiF: Mg, Cu, Na, Si material and a disk type LiF: Mg, Cu, Na, Si detection element.

The present invention relates to a disk-type radiation detection device and a method for manufacturing the same, which are used for radiation measurement. After press molding into a mold and heat treatment, they have the characteristic of reproducing the intrinsic properties of the radiation of LiF: Mg, Cu, Na, Si powder.

The thermofluorescence detection device of the present invention is LiF: Mg, Cu, Na, Si (LiF: 74.5 ± 15.0 wt%, Mg: 4.4 ± 0.9 wt%, Cu: 5.9 ± 1.2 wt%, NaSi: 15.2 ± 3.0) wt%) powder is press-molded using a press and characterized in that the element is formed into a disk shape through a heat treatment.

Thus, the molding method of the present invention thermofluorescent material is as follows.

MgSO _{4 ·} 7H ₂ O (0.6 ± 0.2 mol%), CuSO _{4 ·} 5H ₂ O (0.8 ± 0.2 mol%), and Na ₂ SiO _{3 ·} 9H ₂ O (1.8 ± 0.4 mol%) added as impurities to LiF After quantification, ion-exchanged water was added and mixed well at 80 ° C., and then the mixed solution was dried, placed in a platinum crucible and sintered at a temperature of 820 ± 10 ° C. in an electric furnace in a nitrogen atmosphere, and then quenched in air and a hard mass. The sample was ground, washed with 1N HCl solution and dried to form LiF: Mg, Cu, Na, Si powdered powder of LiF: Mg, Cu, Na having a grain size of 80 μm or less. , Si thermal phosphor manufacturing step (a);

After forming a mold set (5 mm diameter disk type) for molding the powdered LiF: Mg, Cu, Na, Si material, the LiF: Mg, Cu, Na, Si material was cooled to room temperature at a pressure of about 10 ± 3 ton. Press-molding step (b) to produce a disk (diameter 5 mm, thickness 0.8 mm) by applying pressure with a press in the;

The press-formed disk-shaped elements were heat-treated in an electric furnace in a nitrogen atmosphere for 60 ± 30 minutes at a temperature of 820 ± 10 ° C to reproduce the inherent characteristics of the thermoluminescent dosimeter of the powdered LiF: Mg, Cu, Na, Si material. It characterized in that it is manufactured through a heat treatment step (c).

Hereinafter, the present invention as a preferred embodiment of the present invention is not limited to the following examples.

<Example 1>

1 shows a method of manufacturing a disk-type radiation detection device composed of LiF: Mg, Na, Cu, Si materials. The method is as follows.

a) preparation of powdered LiF: Mg, Cu, Na, Si thermophosphor;

MgSO _{4 ·} 7H ₂ O (0.6 mol%), CuSO _{4 ·} 5H ₂ O (0.8 mol%), and Na ₂ SiO _{3 ·} 9H ₂ O (1.8 mol%) added as impurities to LiF were ion-exchanged. Water was added and mixed uniformly at 80 ° C. Then, the mixed solution was dried, sintered in a platinum crucible and sintered at a temperature of 820 ± 10 ° C. in an electric furnace in a nitrogen atmosphere, and then quenched in air. The solid lumped sample was ground, washed with 1 N HCl solution and dried to prepare a LiF: Mg, Cu, Na, Si thermophosphor having a grain size of 80 μm or less.

b) a press forming step;

Pressing the powder-type LiF: Mg, Cu, Na, Si thermophosphor by pressing at room temperature into a press form to form a mold set (5 mm diameter disk type) for molding. The LiF: Mg, Cu, Na, Si material is then pressed at room temperature to a pressure of about 10 ± 3 ton to form a disk (5 mm in diameter, 0.8 mm in thickness).

c) a heat treatment step;

Pressurized disk-shaped devices have a weak bonding force, so they break well and the crystal structure is deformed so that they do not exhibit the original thermoluminescent properties. In order to solidify these disk-like elements and to restore the thermal fluorescence characteristics which were in the powder state, heat treatment is performed.

When the pressurized disk-type elements were heat-treated in an electric furnace in a nitrogen atmosphere for 60 ± 30 minutes at a temperature of 820 ± 10 ° C, the inherent characteristics of the thermoluminescent dosimeter of the powdered LiF: Mg, Cu, Na, Si material were reproduced. It is made of a disk-like element.

<Example 2>

The present invention manufactured by the above method finds the proper condition of sintering to solidify the powder type LiF: Mg, Cu, Na, Si material into the disk type radiation detection element, Not only the disk shape but also any shape that can reproduce the characteristics of the powder material can be produced. Therefore, it is possible to manufacture a variety of sizes and shapes according to the use of a rod type or a square chip type commonly used.

Examples of medically applicable methods for radiological diagnosis or treatment include: By attaching detection elements to the inside or outside of the phantom (phantom) and irradiating them with radiation, measuring the TL sensitivity of these elements can directly assess the absorbed dose received by the human body at the point of attachment. As the size of the TLD device is smaller, the dose at the local irradiation site can be assessed, and if several devices are placed in one plane, the dose distribution of the plane can be seen. At this time, the shape of the TLD device is variously selected depending on the intended use.

In addition, these detection elements can be used in environmental monitoring to evaluate environmental radiation doses by periodically measuring thermal fluorescence intensity by placing them near a nuclear power plant or a radiation zone.

<Example 3>

Using a combination of disk-type LiF: Mg, Cu, Na, Si detection elements as a basic element, a combination of several can be used to produce a personal exposure dose meter badge that monitors an individual's radiation dose.

In FIG. 2, the light blue powder of a) is a LiF: Mg, Cu, Na, Si material, and b) is a material made of a disk type radiation detection device. And c) of FIG. 2 shows any commercially available personal dose dosimeter badges and cases. If the device of b) developed in the present invention is composed as a basic element similar to the shape of the individual dose dosimetry badge of c), and a dose evaluation algorithm is made, it is possible to develop a new personal exposure dosimeter badge for the evaluation of the exposure of the individual.

The present invention as described above is excellent in the thermal fluorescence sensitivity of LiF: Mg, Cu, Na, Si material used in the present invention as shown in Table 1 below about 2 times the commercialized TLD powder (see Fig. 3) ), When the material is manufactured as a disk-like device, the thermal fluorescence sensitivity is reproduced as shown in FIG. 4, and thus, it can be used as a detection device for measuring radiation better than commercially available products in other countries.

If a domestic individual dose dosimeter badge manufactured by the detection device of the present invention is used by about 30,000 radiation workers in Korea, the foreign exposure reduction effect expected by replacing the individual exposure dose badge of about 30 dollars per foreign country Is about 2 billion won a year.

Thermofluorescent TL sensitivity Peak height Area MCP-N (Poland: LiF: Mg, Cu, P) One One GR-200P (China: LiF: Mg, Cu, P) 1.1 1.1 KAERI-LiF (Korea: LiF: Mg, Cu, Na, Si) 1.8 2.0

Table 1. Glow curve measured at a heating rate of 5 ° C / sec by irradiation of ¹³⁷ Cs 0.1mGy of the relative thermal fluorescence of several thermophosphor powders per 10 mg

<References>

(1) S. H. Doh, M. C. Chu, W. H. Chung, H. J. Kim, D. S. Kim and Y. H. Kang, Preparation of LiF (Mg, Cu, Na, Si) Phosphor and Its Thermoluminescent Characteristics, Korean Appl. Phys. 2 425-431 (1989)

(2) Y. M. Nam, J. L. Kim, S. Y. Chang and G. D. Kim, The Study of Glow Curves for LiF: Mg, Cu, Na, Si Phosphor with Different Dopant Concentrations, Korean Appl. Phys. 11 578-583 (1998)

(3) US patent 1,186,899 (1970)

(4) T. Niewiadomski, Pressure Deformation and Recovery of Thermolumine scence in Lithium Fluoride, Health Physics, Vol. 31 pp. 373-376 (1976)

(5) US patent 1,140,028 (1969)

(6) Nam Young-mi, Ph.D. Thesis, A Study on the Characteristics and Applications of LiF: Mg, Cu, Na, Si Teflon TLD, Pusan National University (1997)

Claims (2)

In the thermal fluorescence detection element, Powder composed of LiF: Mg, Cu, Na, Si (LiF: 74.5 ± 15.0 wt%, Mg: 4.4 ± 0.9 wt%, Cu: 5.9 ± 1.2 wt%, NaSi: 15.2 ± 3.0 wt%) Disk-type radiation detection device sintering a thermophosphor containing Mg, Cu, Na, and Si as impurities in LiF, which is formed into a disk shape by sintering (ie, press molding and heat treatment) using a press . In the manufacturing method of solidifying LiF: Mg, Cu, Na, Si thermophosphor powder, After forming a mold set (5 mm diameter disk type) for forming the powder-type LiF: Mg, Cu, Na, Si thermophosphor, the LiF: Mg, Cu, Na, Si material was heated at a pressure of about 10 ± 3 ton. Press molding step to press the press to produce a disk shape (diameter 5mm, thickness 0.8mm); The press-formed disk-shaped elements were heat-treated in an electric furnace in a nitrogen atmosphere for 60 ± 30 minutes at a temperature of 820 ± 10 ° C to reproduce the inherent characteristics of the thermoluminescent dosimeter of the powdered LiF: Mg, Cu, Na, Si material. A method of manufacturing a disk-type radiation detection device comprising sintering a thermoluminescent material in which Mg, Cu, Na, and Si are added as impurities to LiF.