초록 ▼

1. 연구개발 목표 및 내용
○ SF 폐 피복관/구조재 핵종 및 재료 특성분석 및 평가
○ 폐 피복관 기초실험 및 모델링을 통한 폐 피복관 처리 핵심기술개발 및 기술선정
○ 폐 피복관 처리장치 설계/제작/성능평가
2. 연구 결과
○ 연소도에 따른 폐 피복관, 구조재폐기물 특성 분석을 통해 폐기물의 준위를 결정함.
○ 전해정련 및 염소화를 이용한 폐 피복관 처리 기초실험 및 모델링을 통해 최적공정조건을 도출하여 회수 Zr 순도 99 %이상, 회수율 약 98 % 달성함.
○ 폐 피복관 처리기술에 평

1. 연구개발 목표 및 내용
○ SF 폐 피복관/구조재 핵종 및 재료 특성분석 및 평가
○ 폐 피복관 기초실험 및 모델링을 통한 폐 피복관 처리 핵심기술개발 및 기술선정
○ 폐 피복관 처리장치 설계/제작/성능평가
2. 연구 결과
○ 연소도에 따른 폐 피복관, 구조재폐기물 특성 분석을 통해 폐기물의 준위를 결정함.
○ 전해정련 및 염소화를 이용한 폐 피복관 처리 기초실험 및 모델링을 통해 최적공정조건을 도출하여 회수 Zr 순도 99 %이상, 회수율 약 98 % 달성함.
○ 폐 피복관 처리기술에 평가를 통해 최적기술을 선정함.
○ 폐 피복관 처리장치를 설계/제작하여 성능을 평가하고 1 kg규모 설계자료를 생산함.
3. 기대효과 및 활용방안
○ 본 연구를 통해 생산된 금속폐기물의 특성 및 처리기술 개발은 사용후핵연료의 전처리 폐기물의 운반/저장 등 관리 분야에서 필요한 기반기술 자료로서 기술적 파급효과가 기대됨.
○ 본 연구를 통해 생산된 기초자료는 파이로 폐기물 관리정책에 기초자료로 활용될 것으로 판단됨.

(출처 : 보고서 요약서 5p)

Abstract ▼

IV. Results of the Project
1. Characterization of radionuclides in SNF cladding hull/hardware wastes
○ Material characterization of SNF cladding hull wastes
- Based on 10 tons of SNF, hull wastes are generated in the weight of 2,500 kg and in the volume of 2.504 m³, which corresp

IV. Results of the Project
1. Characterization of radionuclides in SNF cladding hull/hardware wastes
○ Material characterization of SNF cladding hull wastes
- Based on 10 tons of SNF, hull wastes are generated in the weight of 2,500 kg and in the volume of 2.504 m³, which corresponds to 25 % in weight and 100 % in volume of total SNF.
- About 5 % of oxide layer on the basis of hull waste and 0.02 % of actinides including TRU and fission products on the basis of SNF are included on the surface of cladding hull waste by the pellet-cladding interaction (PCI), thereby being categorized as an intermediate-level waste.
- Zr recovery is effective to reduce the weight/volume of cladding hull wastes because about 90 % of metallic Zr is contained in the hull wastes.
○ Irradiation characterization of cladding hull wastes in accordance with burn-up
- For Zircaloy-4 hull wastes, the level of activity and decay heat of radionuclides generated by irradiation is confirmed to meet the acceptance criteria for Gyeongju nuclear waste disposal facility.
- For Zirlo hull wastes, while the level of decay heat meets the criteria, ⁹⁴Nb among the radionuclides generated by irradiation is found to be 5.459 x 10⁵ ~ 6.577 x 10⁵, which exceeds the acceptance criteria for Gyeongju nuclear waste disposal facility.
- For HANA hull wastes, the concentration of ⁹⁴Nb reaches over 140 % compared to the Zirlo case due to a higher chemical composition of Nb.
- Consequently, Zirlo and HANA hull wastes are categorized as intermediate-level wastes even without fission products generated by PCI phenomena.
○ Chemical analysis for SNF cladding hull wastes in accordance with burn-up
- For low burn-up samples, most of radionuclides are remained in the cladding hull tube, while a 1/100 of the radionuclides is dissolved in the wash liquid. However, for high burn-up samples, most of radionuclides are found to be in the wash liquid, which is due to a more significant PCI effect in high burn-up samples.
- The calculated decladding ratio based on the chemical analysis showed more than 99.9 % for low burn-up samples and less than 99.9 % for high burn-up samples in most cases.
- Therefore, to meet the decladding ratio of 99.98 %, which was assumed in the head-end process, it is recommended to perform a mechanical decladding process followed by an oxidative decladding process.
○ Material characterization of hardware wastes
- Based on 10 tons of SNF, hardware wastes are generated in the weight of 1,000 kg and in the volume of 4.5 m³, which corresponds to 10 % in weight and 100 % in volume of total SNF. Therefore, weight/volume reduction of hardware is required.
○ Irradiation characterization of hardware wastes in accordance with burn-up
- For the top/bottom nozzles, which is relatively at far distance from nuclear fuel, radioactive Ni-59 is found to exceed the acceptance criteria of waste disposal.
- For the grid and guide tubes, the radioactivity of Co-60 can be reduced below the acceptance criteria for disposal of intermediate/low-level wastes after 70-year cooling, a long-term storage for about 1,000 years to million years will be required to meet the criteria in the cases of Ni-59, Ni-64, and Nb-94.
○ Simulated cladding hull production
- For the production of simulated cladding hull tubes, Zr oxide layer with surrogates was grown on the hull surface using wet and dry processes. The dry process using a room-temperature powder implantation equipment was revealed to be effective in the control of composition and thickness.
- The simulated cladding hulls were produced with Zr oxide layer with surrogates in various thicknesses using the powder implantation equipment.

2. Fundamental studies and modeling for the treatment of cladding hull wastes
○ Fundamental studies for the treatment of cladding hull wastes using electrorefining and chlorination processes
- Chlorination experiments for 10 g- and 50 g-scale cladding hull tubes were performed using a quartz tube reactor and Zr was recovered from oxidized Zircaloy-4 tubes in a recovery yield of 97.5 wt.% with a purity of 99.8 wt.%. In addition, an oxidation effect of cladding hull tubes on the chlorination reaction rate was examined by fundamental studies of chlorination kinetics.
- By electrorefining of Zircaloy-4 cladding tubes in LiCl-KCl based molten salts using an 10 g-scale Zr electrorefiner, Zr was recovered in the purity of 99.74 wt.%. In addition, the recovery yield of Zr was achieved up to 84 wt.% through the studies on the effect of fluoride in chloride based molten salts.
○ Fundamental studies for the treatment of cladding hull wastes with surrogates
- The chemical behavior of residual SNF during chlorination process was simulated using HSC chemistry code and Zr was confirmed to be selectively recovered from SNF residue by the chlorination process.
- The reaction behavior of Cs I, one of major radionuclides of interest, was examined using TGA for chlorination and a reaction kinetic equation of chlorine gas and CsI was established.
- Representative surrogate materials including the oxides of RE elements such as La, Ce, Nd, Y and alkali metal such as Cs are found not to be influential on the electrorefining of Zr, and Nb, which is an alloy element of Zirlo, is not expected to be dissolved from cladding tubes due to its high reduction potential.
○ Modeling and optimization for the treatment process of cladding hull wastes
- An highly efficient TGA system for chlorination was designed and built through an improvement work. In addition, reaction kinetic equations for Zircaloy-4 and chlorine gas was established in accordance with the partial pressure of chlorine and reaction temperature using the TGA system.
- A mathematical model for Zr electrorefining in LiCl-KCl molten salts was established and representative electrochemical parameters such as exchange current and diffusion coefficient of Zr ions based on the electrochemical measurement. In addition, effect of U was found not to be influential on Zr electrorefining by simulating the concentration profile and properties of boundary layer thickness of U and Zr.

3. Design/manufacture/performance evaluation of treatment equipments for cladding hull wastes
○ Design/manufacture of g-scale/kg-scale treatment equipments for cladding hull wastes
- A proper reactor material (Inconnel) was selected by literature investigation and preliminary experiments and a chlorinator equipment for 100 g-scale cladding hull wastes was manufactured, thereby being able to proceed chlorination and purification simultaneously.
- A 100 g-scale cylindrical electrorefiner, a rectangular-type electrorefiner for basic experiments for large-scale treatment, and transparent furnace system for a direct observation of Zr deposition behavior in molten salts were designed and manufactured.
○ Performance evaluation of treatment equipments for cladding hull wastes - Zr recovery yeild of 81 wt.% with a purity of 98.7 wt.% was achieved by chlorination for 3 hrs using 100 g Zirlo cladding tubes. In addition, the relationship between the reaction rate and internal temperature transient of reactor was confirmed.
- The oxygen and moisture level of the glove box including the 100 g-scale electrorefiner were confirmed to be normal by long-term operation test and temperature change in the crucible was recorded according to the furnace temperature.
○ Upgrade of treatment equipments for cladding hull wastes and design data production
- The Viton was selected as a gasket material of the chlorinater for cladding hull wastes and the Zr recovery yield was enhanced up to 99 wt.% by the modification of recovery system.
- Based on the 100 g-scale chlorination experiments, design data for 1 kg-scale chlorinator was produced for the treatment of cladding hull wastes.

(출처 : SUMMARY 14p)

목차 Contents

• 표지 ... 1
• 제 출 문 ... 3
• 보고서 요약서 ... 5
• 요약문 ... 7
• SUMMARY ... 13
• CONTENTS ... 21
• 목차 ... 25
• 표목차 ... 27
• 그림목차 ... 29
• 제 1 장 연구개발 과제의 개요 ... 39
• 제 1 절 연구개발 목적 및 필요성 ... 39
• 제 2 절 연구개발 목표 및 내용 ... 39
• 1. 단계 목표 ... 39
• 2. 주요 연구 수행내용 ... 40
• 제 2 장 국내외 기술개발 현황 ... 41
• 제 1 절 SF 폐 피복관/ 구조재 핵종 및 재료 특성분석 ... 41
• 1. 국외 연구 동향 ... 41
• 2. 국내 연구 동향 ... 42
• 제 2 절 폐 피복관 처리 기초실험 ... 44
• 1. 국외 연구 동향 ... 44
• 2. 국내 연구 동향 ... 45
• 제 3 절 폐 피복관 처리장치 개발 ... 46
• 1. 국외 연구 동향 ... 46
• 2. 국내 연구 동향 ... 47
• 제 3 장 연구개발 수행 내용 및 결과 ... 49
• 제 1 절 SF 폐 피복관/ 구조재 핵종 및 재료 특성분석 ... 49
• 1. 폐 피복관 특성 분석 ... 49
• 2. 구조재폐기물 특성 분석 ... 87
• 3. 모의 폐피복관 제조 ... 96
• 제 2 절 폐 피복관 처리 기초실험 및 모델링 ... 115
• 1. 전해정련 및 염소화 방법을 이용한 폐 피복관 처리 실험 ... 115
• 2. Surrogate가 포함된 폐 피복관 처리실험 ... 164
• 3. 폐 피복관 처리공정 기초모델 수립 및 모델링을 이용한 최적공정조건 도출 ... 178
• 제 3 절 폐 피복관 처리장치 설계/제작/성능평가 ... 210
• 1. 폐 피복관 처리장치 설계 및 제작 ... 210
• 2. 폐 피복관 처리장치 성능평가 ... 222
• 3. 폐 피복관 처리장치 개선 및 설계자료 생산 ... 224
• 제 4 절 폐 피복관 처리기술 선정 ... 228
• 1. 처리기술 현황 ... 229
• 2. 폐 피복관 처리기술의 장단점 분석 ... 232
• 3. Zr 회수 기술 선정 ... 245
• 제 4 장 목표 달성도 및 관련 분야에의 기여도 ... 247
• 제 1 절 연구개발 목표 달성도 ... 247
• 1. 연구개발 목표 ... 247
• 2. 주요 연구결과 ... 247
• 제 2 절 관련 분야에의 기여도 ... 253
• 제 5 장 연구개발 결과의 활용 계획 ... 255
• 제 1 절 연구개발 결과의 활용체계 구축 ... 255
• 제 2 절 연구개발 결과 활용실적 및 계획 ... 256
• 1. 연구개발 결과의 활용성 ... 256
• 2. 연구개발 항목별 타과제 연계 활용 종합 ... 256
• 제 6 장 연구개발 과정에서 수집한 해외 과학기술정보 ... 259
• 제 7 장 연구시설⋅장비 현황 ... 261
• 제 8 장 참 고 문 헌 ... 263
• 끝페이지 ... 266