• Title/Summary/Keyword: nuclear waste disposal

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Evaluation of dose received by workers while repairing a failed spent resin mixture treatment device

  • Choi, Woo Nyun;Byun, Jaehoon;Kim, Hee Reyoung
    • Nuclear Engineering and Technology
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    • v.54 no.2
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    • pp.442-448
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    • 2022
  • Intermediate-level radioactive waste (ILW) is not subject to legal approval for cave disposal in Korea. To solve this problem, a spent resin treatment device that separates 14C-containing resin from zeolite/activated carbon and desorbs 14C through a microwave device has been developed. In this study, we evaluated the radiological safety of the operators performing repair work in the event of a failure in such a device treating 1 ton of spent resin mixture per day. Based on the safety evaluation results, it is possible to formulate a design plan that can ensure the safety of workers while developing a commercialized device. When each component of the resin treatment device can be repaired from the outside, the maximum and minimum allowable repair times are calculated as 263.2 h and 27.7 h for the 14C-detached resin storage tank and zeolite/activated carbon storage tank, respectively. For at least 6 h per quarter, the worker's annual dose limit remains within 50 mSv/year; further, over 5 years, it remained within 100 mSv. At least 6 h of repair time per quarter is considered, under conservative conditions, to verify the radiological safety of the worker during repair work within that time.

A study on pressurizer cutting scenario for radiation dose reduction for workers using VISIPLAN

  • Lee, Hak Yun;Kim, Sun Il;Song, Jong Soon
    • Nuclear Engineering and Technology
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    • v.54 no.7
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    • pp.2736-2747
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    • 2022
  • The operations in the design lifecycle of a nuclear power plant targeted to be decommissioned lead to neutron activation. Operations in the decommissioning process include cutting, decontamination, disposal, and processing. Among these, cutting is done close to the target material, and thus workers are exposed to radiation. As there are only a few studies on pressurizers, there arises the need for further research to assess the radiation exposure dose. This study obtained the specifications of the AP1000 pressurizer of Westinghouse and the distribution of radionuclide inventory of a pressurizer in a pressurised water reactor for evaluation based on literature studies. A cutting scenario was created to develop an optimal method so that the cut pieces fill a radioactive solid waste drum with dimensions 0.571 m × 0.834 m. The estimated exposure dose, estimated using the tool VISIPLAN SW, in terms of the decontamination factor (DF) ranged from DF-0 to DF-100, indicating that DF-90 and DF-100 meet the ICRP recommendation on exposure dose 0.0057 mSv/h. At the end of the study, although flame cutting was considered the most efficient method in terms of cutting speed, laser cutting was the most reasonable one in terms of the financial aspects and secondary waste.

Feasibility Study on the Vitrification of Concentrated Boric Acid Waste (붕산농축폐액 유리화 타당성 연구)

  • Cho, Hyun-Je;Kim, Deuk-Man;Park, Jong-Kil
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.8 no.2
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    • pp.143-150
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    • 2010
  • Vitrification technology has been gradually recognized as one of effective solidification methods for concentrated boric acid wastes generated in PWR. Vitrification for low- and intermediate-level radioactive wastes has a large volume reduction and good durability for the final products. A feasibility study for the vitrification of concentrated boric acid wastes has been performed with developing the pre-treatment methods of powdered wastes, glass compositions using glass formulation and demonstration test. The pre-treatment method is pelletizing the powder type for stable feeding within cold crucible melter. The glass compositions should be developed considering molten glass are related with wastes reduction. High contents of sodium and boron within borate wastes give influence to waste loading. A variety of factors obtained from the demonstration test are reviewed, which is wastes feeding rate, off-gas characteristics on stack and glass characteristics of final products such as durability for implementing the wastes disposal requirement. The aim of this paper is to present the feasibility of vitrification and review the solidification method for concentrated boric acid wastes and obtain the physicochemical characteristics of solidified glass.

Characterization of Domestic Earthquake Events for the Safety Assessment of the Geological Disposal System (심지층 처분시스템의 안전성평가를 위한 국내 지진 발생 특성 평가)

  • Kim, Jung-Woo;Cho, Dong-Keun;Ko, Nak-Youl;Jeong, Jongtae
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.13 no.2
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    • pp.87-98
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    • 2015
  • Safety assessments of geological radioactive waste disposal systems, need to consider the abnormal scenario in which a system is impacted by external events in addition to a reference scenario. In this study, the characterization and prediction of an earthquake as an external event which will impact disposal systems were conducted probabilistically and statistically for the safety assessment. The domestic earthquake data were analyzed, and the prediction methodologies of the earthquake were suggested with a computational example. From the results, the earthquake occurrence rates in Korea ranged from 0.4 /yr to 36.2 /yr depending on the data set and the completeness magnitude. From a conservative point of view, the earthquake occurrence rate in the disposal system was suggested as 5.4×10-4 /yr considering the area of the disposal system. At that time, the completeness magnitude of an earthquake was 2.3. This study will be followed by an appraisal of impacts associated with external events on the geological disposal system, and it will contribute to improvements in reliability of the safety assessment.

Evaluation of X-ray System for Nondestructive Testing on Radioactive Waste Drums (방사성폐기물 드럼 비파괴 검사를 위한 X-ray 장비 평가)

  • Park, Jong-Kil;Maeng, Seong-Jun;Lee, Yeon-Ee;Hwang, Tae-Won
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.6 no.3
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    • pp.189-203
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    • 2008
  • The physical and chemical properties of radioactive waste drums, which have been temporarily stored on site, should be characterized before their shipment to a disposal facility in order to prove that the properties meet the acceptance guideline. The investigation of NDT(Nondestructive Test) method was figured out that the contents in drum, the quantitative analysis of free standing water and void fraction can be examined with X-ray NDT techniques. This paper describes the characteristics of X-ray NDT such as its principles, the considerations for selection of X-ray system, etc. And then, the waste drum characteristics such as drum type and dimension, contents in drum, etc. were examined, which are necessary to estimate the optimal X-ray energy for NDT of a drum. The estimation results were that: $(R)\acute{A}$ the proper X-ray energy is under 3 MeV to test the drums of 320 ${\beta}\S$ and less; $(R)\ddot{E}$ both X-ray systems of 450 keV and/or 3 MeV might be needed considering the economical efficiency and the realization. The number of drums that can be tested with 450 keV and 3 MeV X-ray system was figured out as 42,327 and 18,105 drums (based on storage of 2006. 12), respectively. Four testing scenarios were derived considering equipment procurement method, outsourcing or not, etc. The economical and feasibility assessment for the scenarios was resulted in that an optimal scenario is dependent on the acceptance guide line, the waste generator's policy on the waste treatment and the delivery to a disposal facility, etc. For example, it might be desirable that a waste generator purchases two 450 keV mobile system to examine the drums containing low density waste, and that outsourcing examination for the high density drums, if all NDT items such as quantitative analysis for 'free standing water' and 'void fraction', and confirmation of contents in drum have to be characterized. However, one 450 keV mobile system seems to be required to test only the contents in 13,000 drums per year.

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SFR DEPLOYMENT STRATEGY FOR THE RE-USE OF SPENT FUEL IN KOREA

  • Kim, Young-In;Hong, Ser-Ghi;Hahn, Do-Hee
    • Nuclear Engineering and Technology
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    • v.40 no.6
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    • pp.517-526
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    • 2008
  • The widespread concern regarding the management of spent fuel that mainly contributes to nuclear waste has led to the development of the sodium-cooled fast reactor (SFR) as one of the most promising future types of reactors at both national and international levels. Various reactor deployment scenarios with SFR introductions with different conversion ratios in the existing PWR-dominant nuclear fleet have been assessed to optimize the SFR deployment strategy to replace PWRs with the view toward a reduction in the level of spent fuel as well as efficient uranium utilization through its reuse in a closed fuel cycle. An efficient reactor deployment strategy with the SFR introduction starting in 2040 has been drawn based on an SFR deployment strategy in which burners are deployed prior to breakeven reactors to reduce the amount of PWR spent fuel substantially at the early deployment stage. The PWR spent fuel disposal is reduced in this way by 98% and the cumulative uranium demand for PWRs to 2100 is projected to be 445 ktU, implying a uranium savings of 115 ktU. The SFR mix ratio in the nuclear fleet near the year 2100 is estimated to be approximately 35-40%. PWRs will remain as a main power reactor type until 2100 and SFRs will support waste minimization and fuel utilization.

Uncertainty Cases in Economic Evaluation of Back-End Nuclear Fuel Cycle (후행 핵연료주기 경제성 평가의 불확실성 사례)

  • Kim, Hyung-Joon;Cho, Chun-Hyung;Lee, Kyung-Ku
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.6 no.2
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    • pp.141-145
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    • 2008
  • Due to the uncertainties resulting from cost projection, evaluation over long term period, and adequacy of applied discount rate, the economic assessment for back-end fuel cycle is different from each organizations or individuals. In this paper, the features and limitations of some noticeable economic evaluations were investigated and analysed to contribute for the public participation and back-end fuel cycle policy related researches. As a result of analysis, we found that the reprocess and recycling is more economical than direct disposal option, but the result includes high uncertainty that depends on the input parameters.

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Analysis of Functional Criteria for Buffer Material in a High-level Radioactive Waste Repository

  • W. J. Cho;Lee, J. O.;K. S. Chun;Park, Hyun-Soo
    • Nuclear Engineering and Technology
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    • v.31 no.1
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    • pp.116-132
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    • 1999
  • This study is intended to analyze the requirements of a buffer material that is one of the major components of the engineered barriers in a high-level radioactive waste repository. The characteristics of potential materials for the buffer in the repository were analyzed and a candidate material was selected. And, based on the current knowledge and the information from various sources, the requirements of a buffer material were evaluated. Finally its quantitative functional criteria on the generic viewpoint has been recommended to be supplied as a guideline for the development of the reference disposal concept and the related buffer material in Korea. The criteria are composed of seven major items, such as hydraulic conductivity, retardation capacity, swelling potential and swelling pressure, thermal conductivity, longevity, organic matter content, and mechanical properties.

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Three-Dimensional Modelling and Sensitivity Analysis for the Stability Assessment of Deep Underground Repository

  • Kwon, S.;Park, J.H.;Park, J.W.;Kang, C.H.
    • Nuclear Engineering and Technology
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    • v.33 no.6
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    • pp.605-618
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    • 2001
  • For the mechanical stability assessment of a deep underground high-level waste repository. computer simulations using FLAC3D were carried out and important parameters including stress ratio, depth, tunnel size, joint spacing, and joint properties were chosen from sensitivity analysis. The main effect as well as the interaction effect between the important parameters could be investigated effectively using fractional factorial design . In order to analyze the stability of the disposal tunnel and deposition hole in a discontinuous rock mass, different modelings were performed under different conditions using 3DEC and the influence of joint distribution and properties, rock properties and stress ratio could be determined. From the three dimensional modelings, it was concluded that the conceptual repository design was mechanically stable even in a discontinuous rock mass.

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Optimization of Artificial Neural Network Model in Scaling Factor Determination Method

  • Lee, Sang-Chul;Hwang, Ki-Ha;Kang, Sang-Hee;Lee, Kun-Jai
    • Proceedings of the Korean Radioactive Waste Society Conference
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    • 2004.06a
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    • pp.254-254
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    • 2004
  • Final disposal of radioactive waste generated from Nuclear Power Plant (NPP) requires the detailed information about the characteristics and the quantities of radionuclides in waste package. Most radionuclides are difficult to measure and expensive to assay. Thus it is suggested to the indirect method by which the concentration of the Difficult-to-Measure (DTM) nuclide is estimated using the correlations of concentration-it is called the scaling factor-between Easy-to-Measure (Key) nuclides and DTM nuclides with the measured concentration of the Key nuclide.(omitted)

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