JP2003207598A - Method of manufacturing calibrating volumetric radiation source by solidifying alumina powder by resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To supply long-term soundness and safety in use in a calibrating volumetric radiation source since a conventional alumina powder-made calibrating volumetric radiation source used for measuring environmental radioactivity causes a crack in a plastic vessel, and causes pollution by scattering powder at damaged time. <P>SOLUTION: A problem solving means is provided by a method for preparing the calibrating volumetric radiation source by hardening alumina powder of adsorbing a radioactive isotope in the plastic vessel by a resin solution and a hardening agent. Actually, the method solidifies the alumina powder of adsorbing the radioactive isotope by the hardening agent by using an unsaturated polyester resin and a vinyl ester resin. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an industry dealing with radioactive materials, such as a nuclear power plant, and belongs to the field of analyzing and measuring radioactivity in the environment. 2. Description of the Related Art In the measurement of radioactivity, a standard source having a known radioactivity is required for confirming and calibrating the performance of a measuring instrument. G
In the measurement of a large-volume environmental sample or the like using a high-resolution spectrometer such as an e-semiconductor detector, a large-volume calibration volume source is used as a standard source.
Generally, in order to ensure safety during use, a sealed source is required to guarantee sealing, not to be opened or damaged, and to be free of radioisotope due to leakage or penetration. The volume source for calibration must be airtight and watertight to ensure long-term safety and soundness. In the measurement of low-level radioactivity of an environmental sample such as soil, plastic is used for a sample container to reduce the effect of self-absorption due to the material of the container. For this reason, in the production of a calibration volume radiation source used for measurement of environmental radioactivity, etc., no error is given to the measured value, so that a container of the same shape and the same quality must be used. A domestically produced volume source for calibration corresponding to a soil sample for environmental radioactivity measurement is obtained by placing alumina powder adsorbed with various radioisotopes simulating soil in a plastic container and sealing it with an airtight lid. The volume powder source for calibration made of alumina powder has a problem that when a plastic container is cracked or damaged, it is scattered and causes contamination. The present application proposes a manufacturing method that uses a resin solution having curability to solidify and solidify alumina powder adsorbing a radioactive isotope in a plastic container and guarantees long-term soundness and safety in use. It is. [0004] A plastic container having the same self-absorption as the environmental sample container must be used for the container of the calibration volume radiation source used for the measurement of environmental radioactivity and the like. . In a conventional alumina powder volume source for calibration, when a plastic container is cracked or damaged, the powder is scattered and contamination occurs. This calibration volume source has a problem as a source in which a radioactive substance that requires long-term soundness and safety in use is sealed. [0005] Vinyl ester resins and unsaturated polyester resins are used in FRP flues, corrosion-resistant FRP ducts, etc., as well as in hulls and pools. Thus, both resins are robust and can be used for a long time. Both resins generate heat and are cured by the oxidizing agent, but can be cured at a low temperature depending on the curing agent. Therefore, a method was developed to solidify alumina powder adsorbed with radioisotopes in a plastic container using both curable resin solutions to produce a volume source for calibration. Specifically, it is a method of solidifying together with alumina powder with a curing agent using Rigolac 2004WMB, a kind of unsaturated polyester resin, or Lipoxy R806B, a kind of vinyl ester resin. This solidified body prevents the occurrence of contamination even if the plastic container is broken due to cracks or the like, and can secure long-term soundness and safety in use. DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples Rigorac 2004 WMB (specific gravity 1.23) is a trade name of unsaturated polyester resin and Lipoxy R806B (specific gravity 1.03) which are commercially available from Showa Kogyo Co., Ltd. Vinyl ester resins commercially available from Showa Polymer Co., Ltd. include Nyper NS (benzoyl peroxide, Nippon Oil & Fat Co., Ltd.), N, N-dimethylaniline, and Permec N (methyl ethyl ketone peroxide, Nippon Oil & Fat Co., Ltd.). It is cured by uniformly mixing the curing agent. Therefore, using this resin solution and a curing agent, alumina powder having a particle size of 45 to 150 μm to which a radioactive isotope was adsorbed was solidified in a plastic container. The solidification shown in the following examples shows a state in which the glass rod is not embedded and the solidified body is not deformed when pressed with a glass rod. When a stock solution of a highly viscous resin solution is directly used for solidifying alumina powder, the volume of the solidified body becomes larger than the volume of alumina powder, which is not suitable for a calibration volume source. Both resin solutions were diluted with ethyl alcohol for solidification in the same volume as the alumina powder. In addition, a centrifugal mixing and stirring machine HM-500 manufactured by Keyence Corporation was used for mixing the resin solution with the alumina powder and defoaming the mixture. The calibration volume source is used for correcting the counting efficiency of a γ-ray spectrometer. When the calibration volume source used for this purpose is manufactured from a resin, the specific gravity increases, and self-absorption of γ-rays emitted from the radioisotope becomes a problem. Therefore, the necessity of correction was confirmed for a low energy gamma ray having a high self-absorption rate using ¹⁷⁰ Tm of a radioisotope. Example 1-1 Curing of Rigolac 2004WMB Diluent with Permec N The Rigolac 2004WMB was diluted with ethyl alcohol at a different dilution ratio, and 0.2 ml of Permec N was uniformly mixed with the diluted solution. Shown in [Table 1] In this example, when the dilution ratio with ethyl alcohol was increased to 2: 1 or more, no curing was performed. Here, the No. 1 solution having a dilution ratio of 2: 1 gels from the lower part of the resin in the container after about 3 hours, and requires about 23 hours to cure to about 50% of the total volume, and to cure to 90%. It took 47 hours. From the dilution ratio and the cured state, it is practical to use a dilution ratio of 2: 1 in which the onset of gelation is 3 hours or more and the time available for use as a liquid (pot life) is long. Example 1-2 Amount of Permec N Required for Curing 2: 1 Diluent 20 g of Rigolac 2004WMB and 10 g of ethyl alcohol
An experiment was performed in which the amount of Permec N added to the diluted solution of ml was changed, and the amount of Permec N required for curing was determined. Table 2 shows the results of this example. [Table 2] Here, each of the 2: 1 diluents gradually gelled from below the resin in the container, and gelled early according to the concentration of Permec N. In this process, no heat was generated, and no generation of bubbles was observed. The practical application of solidification of alumina powder requires the production of a large number of homogeneous sources. For this, it is necessary to aliquot the diluted Rigolac 2004WMB containing Permec N and to maintain the liquid state until the mixing operation with the alumina powder is completed. If the pot life required for this operation is 2 hours or more, the conditions of No. 2 or No. 3 are suitable. Example 1-3 Rigorac 2004WMB 2:
3.5 g of Permec N per 100 g of solidified alumina powder of 100 g of alumina powder with 1 diluent and Permec N
The alumina powder was solidified by making the total amount of the 2: 1 diluent containing the mixture 67 ml. The mixing of the alumina powder with the 2: 1 diluent was not performed at one time, and was therefore performed twice. The mixture by this mixing became mud-like containing air, and thus was defoamed. Then, the mixture was sedimented by a centrifugal separator to produce a few ml of supernatant. Then, after leaving still for about 20 hours, it heated at 60 degreeC with a dryer for 4 hours, and the unsolidified part was solidified. The styrene gas generated here was exhausted by a vacuum pump. The difference in weight before and after the drying is about 5 g. [0015] The solidified product produced in the above-mentioned process was hard without generating bubbles. The height of the solidified body is about 41 mm, which is the same as that of the alumina powder alone, and is equal in volume. FIG. 1 shows the established manufacturing process. still,
Solidification of alumina powder with 2: 1 Rigolac 2004WMB diluent and Niper NS and N, N-dimethylaniline has a pot life of about 0.5 hours and is not practical. Example 2-1 Hardening of Lipoxy R806B Diluent with Niper NS and N, N-Dimethylaniline 20 g of Lipoxy R806B was diluted with ethyl alcohol, and about 0.25 g of Niper NS and 0.1 ml of N, N-dimethylaniline were diluted. Table 3 shows examples cured by the method described above. [Table 3] Here, each diluting liquid gelled or hardened within one hour. In all samples, no heat was generated at 30 ° C. or higher, and no bubbles were observed. This Nipper N
Curing with S and N, N-dimethylaniline has a wide range of applications. Since the higher the resin concentration becomes, the more solidified the alumina powder becomes, the condition of the No. 1 dilution ratio of 2: 1 is optimal. Example 2-2 Solidification of Alumina Powder with Lipoxy R806B Diluent, Niper NS and N, N-Dimethylaniline 2: 1 Lipoxy R8 necessary for solidification of 100 g of alumina powder
06B Make the total volume of the diluent 67 ml and add Nyper NS
0.6 g and 0.1 ml of N, N-dimethylaniline were added, and the mixture was solidified in the same manner as in Example 1-3. Here, the mixed sample after sedimentation by centrifugation became about 25 ° C., solidified after about 1.5 hours, and the pot life was extended. The supernatant liquid also self-cured at the same time. In the case of Rigolac 2004WMB diluent, it was necessary to heat and cure the supernatant,
With the 2: 1 Lipoxy R806B diluent, self-curing is possible. FIG. 2 shows the established manufacturing process. The solidified body produced in this step is hard and cannot be easily broken. Also, the height of the solidified body of the alumina powder portion is about 41 mm, which is the same as the alumina powder alone,
They are also equal in volume. Solidification with a 2: 1 lipoxy R806B diluent, Niper NS and N, N-dimethylaniline has a short pot life of about 1.5 hours, but is practical for the production of a small number of calibration volume sources. is there. still,
Solidification of the alumina powder with the 2: 1 Lipoxy R806B diluent and Permec N requires a heat-solidification step as in the case of the Rigolac 2004WMB diluent, and in this case, there is no practicality because bubbles are generated inside. Example 3 Self-Absorption of Alumina Solidification Calibration Volume Source In the production of a calibration volume source by solidifying alumina powder,
The resin is filled into the air space between the powders and solidified. In this case, since the specific gravity is higher than that of the calibration volume radiation source using only powder, self-absorption of radiation becomes a problem. So Rigolac 2004WMB
Using a 2: 1 diluent of (specific gravity 1.23) and Lipoxy R806B (specific gravity 1.03), the self-absorption of the solidified product was measured. In confirming the self absorption, ¹⁷⁰ Tm having a low γ-ray energy of 84.32 keV was used. (1) Preparation of alumina powder adsorbing ¹⁷⁰ Tm 450 g of alumina powder and ¹⁷⁰ Tm adjusted to about pH 5
The solution was prepared by forcibly stirring 400 ml of the solution with an impeller stirrer for about 1 hour, removing the supernatant, and drying with an infrared lamp and a heater. (2) Preparation and measurement of self-absorption measurement sample 2: 1 diluent of Rigolac 2004WMB and Lipoxy R806B 6
7 g, 0.5 g to 0.6 g of Niper NS, and 0.1 ml of N, N-dimethylaniline solidify 100 g of alumina powder adsorbing ¹⁷⁰ Tm under the same conditions, and 100 g of alumina powder adsorbing ¹⁷⁰ Tm as a reference. Was measured. Table 4 shows the results of this example. [Table 4] 84.32 keV γ of both solidified alumina
The self-absorption rate of the radiation is 0.15 to 0.16, and when actually used as a calibration volume radiation source, it needs to be corrected in accordance with the γ-ray energy emitted by the radioisotope used. According to the present invention, since a plastic container is used, the alumina powder is solidified with a resin and a curing agent instead of a calibration volume source using only the alumina powder, which has a high possibility of radioactive contamination. It is intended to provide a method for manufacturing a solid-state calibration volume radiation source. This method is based on Rigolac 2004WMB of unsaturated polyester resin and lipoxy resin of vinyl ester resin.
Using a diluent of R806B and a combination of a curing agent such as Permec N or Nyper NS and N, N-dimethylamine, alumina powder having various radioisotopes adsorbed therein is stirred and mixed in a radiation source container. It is a method of solidifying. The calibration volume source manufactured by this method is harder and stiffer than a commercially available volume source for calibration using only alumina powder, and even if the outer container of plastic is damaged, the alumina powder does not leak and radioactive contamination does not occur. Does not occur. As described above, the calibration volume source according to the present invention is excellent in long-term soundness and safety in use. In addition, Rigo rack 2004WMB
Do not use lipoxy R806B in containers because it has the solubility of styrene resin.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a solidification process of alumina powder using a 2: 1 Rigolac WMB diluent and permelic N. FIG. 2: 2: 1 Lipoxy R806B diluent and Niper N
It is a figure showing the solidification process of the alumina powder with S and N, N-dimethylaniline.

Claims (1)

Claims: 1. A method for preparing a calibration volume radiation source by curing an alumina powder to which a radioisotope is adsorbed with a resin solution and a curing agent in a plastic container.