Evaluation of Particles Derived from Concrete and Glass Particulate Waste in the Gyeongju Repository Environment = 경주 처분장 환경에서 콘크리트와 유리 입자성 폐기물 기원 입자 평가

국문 초록 (Abstract)

원전 해체 등에서 발생하는 입자성 방사성 폐기물은 콜로이드에 의한 핵종 이동 우려로 인해 시멘트 고형화 처리가 필수적으로 수행되어 왔으나, 이는 폐기물 부피 증가와 처분장 용량 부족을 초래한다. 본 연구는 대표적인 입자성 폐기물인 콘크리트와 유리 폐기물에서 발생하는 콜로이드의 형성 및 안정성을 과학적으로 평가하여, 이러한 고형화 처리의 타당성을 재검토하였다.
저농도 콜로이드 분석의 한계를 극복하기 위해 Polystyrene (PS) 나노입자 표준용액을 이용하여 분석 기준을 확립하였으며, 처분장 모사 환경에서 장기(20℃, 8개월) 및 가속(60℃, 90일) 실험을 수행하였다. 입자의 형성은 동적광산란(DLS)법으로 분석하였으며, 안정성은 PHREEQC 모델링과 DLVO 이론을 적용하여 평가하였다.
연구 결과, 콘크리트 폐기물에서는 배경 농도와 구별되지 않을 정도로 입자 발생이 미미하였다. 유리 폐기물의 경우 가속 조건에서 Tobermorite 계열의 입자가 일부 형성되었으나, 이론적 분석 결과 반발력이 부족하여 열역학적으로 불안정한 것으로 확인되었다. 즉, 두 폐기물 모두에서 콜로이드는 처분장 환경 내에서 안정하게 존재하지 못하고 침전될 것으로 예측된다. 결론적으로 본 연구는 입자성 폐기물의 시멘트 고형화를 면제할 수 있는 과학적 근거를 제시하며, 이를 통해 방사성 폐기물 처분 효율성을 제고할 수 있다.

다국어 초록 (Multilingual Abstract)

Particulate radioactive waste generated during nuclear decommissioning has traditionally been solidified with cement to inhibit colloid-facilitated radionuclide migration. However, cement solidification significantly increases waste volume, straining disposal repository capacity. This study re-evaluates the necessity of solidification by scientifically assessing the formation and stability of colloids derived from representative particulate wastes, namely concrete and glass.
To address the analytical challenges associated with low-concentration colloids, specific evaluation criteria were established using Polystyrene (PS) nanoparticle standard solutions. Experiments were conducted by contacting simulated waste with synthetic porewater under long-term (20°C, 8 months) and accelerated (60°C, 90 days) conditions. Particle behavior was characterized using Dynamic Light Scattering (DLS), while thermodynamic stability was evaluated through PHREEQC modeling and DLVO theory.
The results indicated that colloid generation from concrete waste was negligible and indistinguishable from background levels. In contrast, limited particle formation was observed from glass waste under accelerated conditions, these particles were identified as Tobermorite-group (C-S-H). However, theoretical analyses demonstrated that these colloids were thermodynamically unstable due to insufficient repulsive potential. Consequently, colloids derived from both waste types are expected to aggregate and precipitate within the repository environment. These findings provide scientific evidence that cement solidification for particulate waste may be unnecessary, offering a potential pathway to optimize disposal capacity.

목차 (Table of Contents)

• Abstract i
• Chapter 1. Introduction 1
• 1.1. Generation and Disposal Status of Particulate Radioactive Waste 1
• 1.2. Impact of Colloidal Substances on Radionuclide Migration in Disposal Facilities 3
• Chapter 2. Literature Review 4
• 2.1. Current Status of Disposal for Concrete Waste from Nuclear Power Plant Decommissioning 4
• 2.2. Current Status of Glass Fiber Waste Disposal 4
• 2.3. Research Gap 5
• 2.4. Research Objective 6
• Chapter 3. Research Design 7
• 3.1. Materials 7
• 3.1.1. Polystyrene nanoparticle standard solution 7
• 3.1.2. Synthesis of Porewater 7
• 3.1.3 Simulated Concrete Waste 10
• 3.1.4. Simulated Glass Waste 12
• 3.2. Experimental Procedure and Conditions 13
• 3.3. Instrumentation 15
• 3.3.1. Zetasizer Advance Series – Pro (Blue Label) 15
• 3.3.2. Inductively Coupled Plasma - Optical Emission Spectroscopy (ICP -OES) 18
• 3.3.3. Ion Chromatography (IC): Thermo Scientific ICS-5000+ 19
• 3.3.4. pH meter – Orion VERSA STAR Pro 60 20
• 3.3.5. Field Emission Scanning Electron Microscope (FE-SEM) 21
• 3.4. Evaluation Procedure 22
• 3.4.1. Polystyrene Nanoparticle Standard Solution Experiment 24
• 3.4.2. Establishment of Colloid Evaluation Criteria 25
• 3.4.3. Evaluation 1: Formation of Particles in Synthetic Porewater Test 27
• 3.4.4. Evaluation 2: Formation of Particles in Simulated Waste Contact Test 28
• 3.4.5. Evaluation 3: Stability of Particle 30
• 3.4.6. Summary of Overall Procedure 34
• Chapter 4. Results and Discussions 35
• 4.1. Establishment of Colloid Evaluation Criteria 35
• 4.1.1. Analysis of Measurement Limit Concentration 35
• 4.1.2. Relationship Between Colloid Concentration and Scattering Count Rate 39
• 4.2. Synthetic Porewater Test 43
• 4.2.1. Long Term Synthetic Porewater Test 43
• 4.2.2. Accelerated Synthetic Porewater Test 48
• 4.3. Simulated Concrete Contact Test 53
• 4.3.1. Long Term Concrete Contact Test 53
• 4.3.2. Accelerated Concrete Contact Test 58
• 4.3.3. Concrete Contact Test SEM/EDS Surface Analysis 63
• 4.4. Simulated Glass Contact Test 67
• 4.4.1. Long Term Glass Contact Test 67
• 4.4.2. Accelerated Glass Contact Test 72
• 4.4.3. Glass Contact Test SEM/EDS Surface Analysis 77
• Chapter 5. Conclusion 83
• 5.1. Summary 83
• 5.2. Design of Evaluation Procedure 83
• 5.3. Establishment of Evaluation Criteria 84
• 5.4. Synthetic Porewater Test 84
• 5.5. Concrete Contact Test 85
• 5.6. Glass Contact Test 86
• 5.7. Limitation of Research 87
• 5.8. Impact on Nuclear Industry 88
• Bibliography 89
• Abstract in Korean 91
• 감사의 글 92