• Nuclear Engineering and Technology
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• 제55권10호
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• pp.3617-3627
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• 2023

This study presents a method to solidify spent ion-exchange resin (IER) in a metakaolin-based geopolymer and shows results of mechanical strength, immersion, leaching, irradiation, and thermal cycling tests for waste acceptance criteria (WAC) to repository. The geopolymer waste form with 20 wt% of simulated spent IER met the WAC in South Korea (ROK), and the leaching tests of various sized-waste forms up to 15.0 × 30.0 cm and waste loadings up to 20 wt% for 1-5 d and 1-90 d achieved a leachability index, L_i > 6. In a leaching test for 5 d, the cumulative fraction leached (CFL) for Cs, which leached the most, was linearly correlated with the square root of leaching time for all waste forms, and L_i increased as the size of the waste form increased. The CFL was also correlated with elapsed time in the 90 d leaching test. The correlations among CFL, time, and volume-to-surface area ratio of waste forms used to estimate the L_i of Cs of a 200-L sized geopolymer with 15 wt% IER showed the L_i values as 14.73 (5 d) and 17.71 (90 d), respectively, indicating that the large-sized geopolymer waste form met the WAC.

• 방사선산업학회지
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• 제17권4호
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• pp.501-508
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• 2023

There are various factors that have a negative impact on safety over a long period of time after the closure of a radioactive waste disposal facility. In particular, it is important to limit substances that accelerate radionuclide migration while inhibiting adsorption between radionuclides and the subsurface medium. Through this study, a method for deriving a quantitative criteria evaluation method is proposed for cellulose among materials that accelerate the movement of these radionuclides after closure of the disposal facility. Since Sweden's SKB is representative worldwide for preparing criteria for cellulose in disposal facilities, it analyzed Sweden's acceptance criteria method and presented a method that can be applied domestically. The decomposition characteristics of cellulose and the adsorption and dissolution characteristics of ISA among degradation products were reviewed, and quantitative analysis of cement materials that create a high pH environment favorable for cellulose decomposition was also included. In addition, the total amount of the finally disposable cellulose material can be derived by using the volume information of the waste containing the cellulose material. Through this methodology for calculating the total amount of cellulose, it is expected that subsequent studies will be conducted to secure data reflecting the environmental conditions of radioactive waste disposal facilities in Korea. In addition, it is expected to be utilized as a good method to evaluate the impact of other complexing agents other than cellulose and to suggest the amount of disposal.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2005년도 추계 학술대회 논문집
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• pp.143-152
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• 2005

중저준위 방사성폐기물 중 장반감기핵종의 농도가 처분시설의 인수기준을 초과하는 경우에 대비한 처분방안이 필요하다. 본 논문에서는 장반감기 중저준위폐기물의 처분을 수행하고 있거나 계획하고 있는 대표적인 국가들의 사례를 정리하였으며, 각 국의 사례를 중심으로 장반감기 중저준위 방사성폐기물의 처분방안 설정을 위한 기본절차를 도출하였다. 국내에서도 장반감기 중저준위 방사성폐기물의 처분을 위한 활발한 논의가 필요하다고 하겠다.

• Nuclear Engineering and Technology
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• 제55권3호
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• pp.876-883
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• 2023

Radioactive waste should be solidified before being disposed of in the repository to eliminate liquidity or dispersibility. Cement is a widely used solidifying media for radioactive waste, and cement solidified waste should satisfy the minimum compressive strength of the waste acceptance criteria of a radioactive repository. Although the compressive strength of waste should be measured by the test method provided by the waste acceptance criteria, the method differs depending on the operating repository of different countries. Considering the measured compressive strength changes depending on test conditions, the effect of test conditions should be analyzed to avoid overestimation or underestimation of the compressive strength during disposal. We selected test conditions such as the height-to-diameter ratio, loading rate, and porosity as the main factors affecting the compressive strength of cement solidified radioactive waste. Owing to the large variance in measured compressive strength, the effects of the test conditions were analyzed via statistical analyses using parametric and nonparametric methods. The results showed that the test condition of the lower loading rate, with a height-to-diameter ratio of two, reflected the actual cement content well, while the porosity showed no correlation. The compressive strength assessment method that reflects the large variance of strengths was suggested.

• 방사성폐기물학회지
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• 제16권1호
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• pp.65-82
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• 2018

With the significant increase in spent ion-exchange resin generation, to meet the requirements of Waste Acceptance Criteria (WAC) of the Wolsong disposal facility in Korea, blending is considered as a method for enhancing disposal options for intermediate level waste from nuclear reactors. A mass balance formula approach was used to enable blending process with an appropriate mixing ratio. As a result, it is estimated around 44.3% of high activity spent resins can be blended with the overall volume of low activity spent resins at a 1:7.18 conservative blending ratio. In contrast, the reduction of high activity spent resins is considered a positive solution in reducing the amount of spent resins stored. In an economic study, the blending process has been proven to lower the disposal cost by 10% compared to current APR1400 treatment. Prior to commencing use of this blending method in Korea, coordinated discussion, and safety and health assessment should be undertaken to investigate the feasibility of fitting this blending method to national policy as a means of waste predisposal processing and management in the future.

• 방사성폐기물학회지
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• 제19권3호
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• pp.323-330
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• 2021

Silver tellurite glasses with melting temperature of approximately 700℃ were developed to immobilize ¹²⁹I wastes. Long-term dissolution tests in 0.1 M acetic acid and disposability assessment were conducted to evaluate sustainability of the glasses. Leaching rate of Te, Bi and I from the glasses decreased for up to 16 d, then remained stable afterwards. On the contrary, tens to tens of thousands of times more of Ag was leached in comparison to the other elements; additionally, Ag leached continuously for all 128 d of the test owing to the exchange of Ag⁺ and H⁺ ions between the glasses and solution. The I leached much lower than those of other elements even though it leached ~10 times more in 0.1 M acetic acid than in deionized water. Some TeO₄ units in the glass network were transformed to TeO₃ by ion exchange and hydrolysis. These silver tellurite glasses met all waste acceptance criteria for disposal in Korea.

• Nuclear Engineering and Technology
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• 제53권7호
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• pp.2261-2267
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• 2021

This paper evaluates the efficacy of magnesium potassium phosphate cements (MKPCs) as waste forms for the solidification of radioactive concrete powder wastes produced by the decommissioning of nuclear power plants. MKPC specimens that contained up to 50 wt% of simulated concrete powder wastes (SCPWs) were evaluated. We measured the porosity and compressive strength of the MKPC specimens, observing them using scanning electron microscopy and X-ray diffraction. The addition of SCPWs reduced the porosity and increased the compressive strength of the MKPC specimens. Struvite-K crystals were well-synthesized, and no additional crystal phase was formed. After thermal cycling and after immersion, MKPC specimens with 50 wt% SCPWs satisfied the waste-acceptance criteria (WAC) for compressive strength. Semi-dynamic leaching tests were performed using the ANS 16.1 method; the leachability indices of Cs, Co, and Sr were 11.45, 17.63, and 15.66, respectively, which also satisfy the WAC. Thus, MKPCs can provide stable matrices to immobilize radioactive concrete wastes generated by the decommissioning of nuclear power plants.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2005년도 춘계 학술대회
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• pp.205-210
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• 2005

개정예정인 중${\cdot}$저준위 방사성폐기물 처분시설 인도규정에서는 방사성폐기물 처분을 위해 폐기물 발생자가 방사성폐기물의 처분요건 적합성을 입증하도록 권고하고 있다. 이에 따르면 중${\cdot}$저준위 방사성폐기물의 처분을 위해서는 폐기물의 핵종농도, 물리화학적 특성 및 그 건전성 등이 확보 되어야하며 폐기물 발생자는 이러한 정보를 처분사업자에게 전달하도록 규정되어 있다. 또한 처분 사업자는 처분시설의 안전성 평가를 통해 부지특성을 고려한 방사성폐기물 인수기준(Site Specific Waste Acceptance Criteria, SWAC)을 규정하며, 발생자는 이 기준에 따라 중${\cdot}$저준위 방사성폐기물을 관리, 처리, 인도하도록 규정되어 있다. 상기 규정과 기준을 준수하기위해 폐기물 발생자는 처분대상이 되는 폐기물을 처분시설로 운반하기 이전에 처분적합성을 사전에 입증하여야 하며 이를 위하여 관련 제도 및 절차인 방사성폐기물인증프로그램을 개발하여야 한다. 본 연구에서는 원자력 선진국들에서 시행하고 있는 방사성폐기물인증프로그램에 대한 심층 분석을 통해 국내 원전에 적용 가능한 인증프로그램 초안을 개발하였고, 그 적용성을 검증하기 위하여 현재 울진 1, 2 발전소에서 시범 적용하고 있다. 앞으로 시범적용 결과분석을 통해 국내 여건에 부합하는 방사성폐기물인증프로그램을 개발하고자 한다.

• Nuclear Engineering and Technology
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• 제43권2호
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• pp.149-158
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• 2011

Metal waste generated from the pyroprocessing of 10 MtU of spent fuel was classified by comparing the specific activity of a relevant radionuclide with the limit value of the specific activity specified in the Korean acceptance criteria for a lowand intermediate-level waste repository. A Korean Optimized Fuel Assembly design with a 17${\times}$17 array, an initial enrichment of 4.5 weight-percent, discharge burn-up of 55 GWD/MtU, and a 10-year cooling time was considered. Initially, the mass and volume of each structural component of the assembly were calculated in detail, and a source term analysis was subsequently performed using ORIGEN-S for these components. An activation cross-section library generated by the KENO-VI/ORIGEN-S module was utilized for top-end and bottom-end pieces. As a result, an Inconel grid plate, a SUS plenum spring, a SUS guide tube subpart, SUS top-end and bottom-end pieces, and an Inconel top-end leaf spring were determined to be unacceptable for the Gyeongju low- and intermediate-level waste repository, as these waste products exceeded the acceptance criteria. In contrast, a Zircaloy grid plate and guide tube can be placed in the Gyeongju repository. Non-contaminated Zircaloy cladding occupying 76% of the metal waste was found to have a lower level of specific activity than the limit value. However, Zircaloy cladding contaminated by fission products and actinides during the decladding process of pyroprocessing was revealed to have 52 and 2 times higher specific activity levels than the limit values for alpha and $^{90}Sr$, respectively. Finally, it was found that 88.7% of the metal waste from the 17${\times}$17 Korean Optimized Fuel Assembly design should be disposed of in a deep geological repository. Therefore, it can be summarized that separation technology with a higher decontamination factor for transuranics and strontium should be developed for the efficient management of metal waste resulting from pyroprocessing.

• 시스템엔지니어링학술지
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• 제17권1호
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• pp.85-96
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• 2021

Radioactive mixed waste (RMW) means waste mixed with radioactive substances and hazardous substances. In Korea, there are definitions and disposal restrictions on RMW in the Nuclear Safety Management Act, but it is difficult to apply because the contents are insufficient, so this paper proposed applicable management standards. The main RMW generated from nuclear power plants is waste oil, waste asbestos, PCB, and waste fluorescent liquid, and their radiation characteristics are mostly at very low levels and some are estimated at low levels. In addition to nuclear power plants, RMW also occurs in research institutes, industries, and hospitals. The acceptance criteria of all disposal facilities in the world basically prohibit disposal of RMW unless the hazardous substances of RMW are removed or mitigated below the standard value. Cases in Korea, the United States, Japan and Europe were reviewed to propose the RMW management standards in Korea. With reference to the results of the above review, this paper clearly defined RMW and proposed detailed management standards for the separation, storage, treatment and disposal of hazardous substances by applying the Waste Control Act. It also mentioned legislation of management standards, regulatory methods, and acceptance criteria of disposal facility operator.