KR-20260063685-A - METHOD FOR DERIVING THE GROSS ALPHA COCENTRATION OF RADIOACTIVE WASTE

KR20260063685AKR 20260063685 AKR20260063685 AKR 20260063685AKR-20260063685-A

Abstract

A method for deriving the total alpha concentration of radioactive waste is provided, comprising the steps of: measuring the concentrations of uranium ( 235 U) and americium ( 241 Am) in the radioactive waste by applying gamma spectroscopy to accurately derive the total alpha concentration, reduce the deviation between the total alpha concentration of the selected radioactive waste and the sum of individual alpha particle concentrations, and safely dispose of radioactive waste that meets the acceptance criteria for a cavern disposal facility for intermediate and low-level radioactive waste; classifying the radioactive waste into either a first group or a second group based on the results of the measurement step; and measuring the total alpha concentration of the radioactive waste using a calibration formula determined based on the classification results of the classification step.

Inventors

박태홍
정경훈
유강현
유정보
박재일

Assignees

한국원자력연구원

Dates

Publication Date: 20260507
Application Date: 20241031

Claims (11)

A step of measuring the concentrations of uranium ( 235 U) and americium ( 241 Am) in radioactive waste by applying gamma spectroscopy; A step of classifying the radioactive waste into either a first group or a second group based on the result of the above-mentioned measuring step; and A step comprising measuring the total alpha concentration of the radioactive waste using a calibration formula determined based on the classification result in the above classification step, Method for deriving total alpha concentration of radioactive waste.
In paragraph 1, In the step of measuring the concentrations of the above uranium and americium, if uranium ( 235 U) and americium ( 241 Am) are not detected, or if the concentration of uranium ( 238 U) is measured to be higher than or equal to the concentration of americium ( 241 Am), In the above classification step, the radioactive waste is classified into a uranium main component group corresponding to the first group, Method for deriving total alpha concentration of radioactive waste.
In paragraph 2, When the radioactive waste is classified into the first group in the above classification step, the total alpha concentration of the radioactive waste in the step of measuring the total alpha concentration is measured by applying a uranium calibration formula, Method for deriving total alpha concentration of radioactive waste.
In paragraph 1. In the step of measuring the concentrations of the above uranium and americium, if the concentration of americium ( 241 Am) is measured to be higher than the concentration of uranium ( 238 U), In the above classification step, the radioactive waste is classified into other groups corresponding to the second group, Method for deriving total alpha concentration of radioactive waste.
In paragraph 4, If the radioactive waste is classified into the second group in the above classification step, the total alpha concentration of the radioactive waste in the step of measuring the total alpha concentration is measured by applying an americium calibration formula, Method for deriving total alpha concentration of radioactive waste.
A step of measuring the concentration of daughter nuclides of uranium ( 238 U) and americium ( 241 Am) in radioactive waste by applying gamma spectroscopy; A step of estimating the concentration of uranium ( 238 U) from the daughter nuclides of the above uranium ( 238 U); A step of classifying radioactive waste into either a first group or a second group based on the results of the above-mentioned measuring and estimating steps; and It includes a step of measuring the total alpha concentration of radioactive waste using a calibration formula determined based on the classification results in the above-mentioned classification step, and Daughter nuclides of uranium ( 238 U) include one or more of thorium ( 234 Th) or protactinium ( 234 m Pa), Method for deriving total alpha concentration of radioactive waste.
In paragraph 6, In the step of measuring the concentrations of the daughter nuclides of the above uranium and americium, if the daughter nuclides of uranium ( 238 U) and americium ( 241 Am) are not detected, In the above classification step, the radioactive waste is classified into a uranium main component group corresponding to the first group, Method for deriving total alpha concentration of radioactive waste.
In paragraph 6, When comparing the concentration of americium ( 241 Am) measured in the step of measuring the concentrations of the daughter nuclides of the uranium and americium with the concentration of uranium ( 238 U) estimated in the step of estimating the concentration of the uranium, if the concentration of uranium ( 238 U) is measured to be higher than or equal to the concentration of americium ( 241 Am), In the above classification step, the radioactive waste is classified into a uranium main component group corresponding to the first group, Total alpha screening method for radioactive waste.
In Article 7 or Article 8, When the radioactive waste is classified into the first group in the above classification step, the total alpha concentration of the radioactive waste in the step of measuring the total alpha concentration is measured by applying a uranium calibration formula, Method for deriving total alpha concentration of radioactive waste.
In paragraph 6, When comparing the concentration of americium ( 241 Am) measured in the step of measuring the concentrations of the daughter nuclides of the uranium and americium with the concentration of uranium ( 238 U) estimated in the step of estimating the concentration of the uranium, if the concentration of americium ( 241 Am) is measured to be higher than the concentration of uranium ( 238 U), In the above classification step, the radioactive waste is classified into other groups corresponding to the second group, Method for deriving total alpha concentration of radioactive waste.
In Paragraph 10, If the radioactive waste is classified into the second group in the above classification step, the total alpha concentration of the radioactive waste in the step of measuring the total alpha concentration is measured by applying an americium calibration formula, Method for deriving total alpha concentration of radioactive waste.

Description

Method for Deriving the Gross Alpha Concentration of Radioactive Waste The present invention relates to a method for determining the total alpha concentration of radioactive waste. Radioactive waste refers to materials subject to disposal because they contain radionuclides at concentrations exceeding the self-disposal allowable concentration set by regulatory authorities, or are contaminated with radionuclides and are no longer expected to be used. Radioactive waste can be classified by level based on the concentration and half-life of the contained radionuclides, as well as the heat generated. Fuel used in nuclear power plants is classified as High Level Waste. Conversely, items such as work clothes, gloves, equipment parts, spent resins, and spent filters generated at nuclear facilities and radiation controlled areas are classified as Low and Intermediate Level Waste (LILW) if their radioactivity exceeds the self-disposal allowable concentration. For the safe management and disposal of radioactive waste, the assessment of its physicochemical and radiological characteristics is essential. In particular, in order to entrust intermediate- and low-level radioactive waste to a disposal facility, the radionuclides contained in the waste and their concentrations must be identified in accordance with Article 8 of Nuclear Safety and Security Commission Notice No. 2023-8. Among these, the concentration of alpha nuclides contained in the radioactive waste is evaluated as gross alpha, which refers to the total value of all alpha radiation emitted from the sample. Gross alpha is suitable for determining the total concentration of various alpha nuclides because it measures the overall radiation dose of alpha particles emitted during the radioactive decay of uranium, radium, polonium, etc., without distinguishing the energy of the alpha particles. However, to quantify the concentration of individual isotopes undergoing alpha decay, alpha spectroscopic analysis following additional chemical separation is required. Meanwhile, according to the Korea Atomic Energy Environmental Corporation's acceptance criteria for intermediate- and low-level radioactive waste cavern disposal facilities, if the gross alpha concentration is 10 Bq/g or higher, the concentration of individual alpha particles must be analyzed. The total alpha concentration of radioactive waste can be measured by using a gas-flow proportional counter to detect the alpha signal of the remaining dry matter after evaporating the pretreatment solution obtained by dissolving or leaching the radioactive waste sample. At this time, since self-absorption of alpha particles occurs depending on the thickness of the dry matter, calibration that considers the change in measurement efficiency according to the thickness of the dry matter is necessary to accurately measure the total alpha concentration. In total alpha measurement, since the thickness of the dry matter is proportional to its weight, the weight of the dry matter, which is easy to measure, is generally used for calibration of measurement efficiency. In this context, americium ( 241 Am) is widely used as a standard material for calibrating gas-flow proportional counters for the total alpha measurement of radioactive waste. The alpha emission characteristics of americium are well known, and because americium ( 241 Am) has a relatively long half-life, it is widely used as a standard material for total alpha measurements. However, there are problems with calibration methods utilizing americium ( 241 Am). First, energy differences among various alpha nuclides contained in a sample can cause differences in measurement efficiency. While americium ( 241 Am) emits alpha particles with an energy of approximately 5.5 MeV, other alpha nuclides emit alpha particles with different energies. In particular, uranium isotopes emit alpha particles between 4.2 MeV and 4.8 MeV, and errors may occur due to the difference in energy compared to americium ( 241 Am). Therefore, when measuring the total alpha concentration of uranium-containing radioactive waste using measurement efficiency calibrated with americium ( 241 Am), total alpha analysis results may be obtained that are lower than the concentration of alpha nuclides in the sample, resulting in errors in the concentration of the radioactive waste transported to the disposal facility. In addition, due to errors that occur in this way, there may be cases where the concentration of total alpha is measured as lower than the acceptance standard of 10 Bq/g for intermediate- and low-level radioactive waste cave disposal facilities, and thus the analysis of the concentration of individual alpha particles is omitted. Prior art KR 2159037 B1 discloses measuring total alpha and deriving the radiation dose of total alpha emitted from a target sample using the measurement efficiency determined therefrom, but does not disclose a method for accurately deriving the concentration of total alpha. A