초록 ▼

○ 금속이온 용출완화 표면 및 합금 개량기술
∙ 표면 미세변형층 전해연마 제거기술 개발 및 용출저항성 2.4배 향상 달성
∙ 표면조도 요건을 0.1 ㎛로 개선함에 따라 용출억제 효과 2.8배 향상 달성
∙ 표면 압축응력 형성기술 개발 및 용출저항성 1.5배 향상 달성
∙ Alloy 690 개량 후보합금 제조 및 용출억제 효과 2배 향상 확인
∙ 고품질 증기발생기 전열관 제조 및 설계기술로 활용

○ 금속이온 용출완화 수화학 기술
∙ 1차계통 냉각수 용존수소 농도 측정용 Pd-25%Ag 센서

○ 금속이온 용출완화 표면 및 합금 개량기술
∙ 표면 미세변형층 전해연마 제거기술 개발 및 용출저항성 2.4배 향상 달성
∙ 표면조도 요건을 0.1 ㎛로 개선함에 따라 용출억제 효과 2.8배 향상 달성
∙ 표면 압축응력 형성기술 개발 및 용출저항성 1.5배 향상 달성
∙ Alloy 690 개량 후보합금 제조 및 용출억제 효과 2배 향상 확인
∙ 고품질 증기발생기 전열관 제조 및 설계기술로 활용

○ 금속이온 용출완화 수화학 기술
∙ 1차계통 냉각수 용존수소 농도 측정용 Pd-25%Ag 센서 제작 및 신뢰도 검증 완료
∙ 50 cc/kg 이상의 고농도 용존수소 수화학 지침 개선 근거자료 확보

○ 피복관 부식생성물 부착완화 기술
∙ 원전 피복관 부착 부식생성물인 다면체 니켈페라이트 및 침상 니켈산화물 재현 성공
∙ 1차계통 운전온도/압력 조건에서 pH를 7.4로 상향 조절한 수화학 기술 제시 및 3배 이상의 혁신적 부식생성물 부착완화 효과 입증
∙ 용존수소 농도에 따른 부식생성물 부착량 및 형상변화 관계 규명

○ 증기발생기 전열관 덴팅 원천방지 신기술
∙ 세계 최초 덴팅 원천방지 신기술 개발, 국내특허등록 및 해외 4개국 등록 심사중
∙ 튜브시트 2차측 표면에 Alloy 690 클래딩 기술 적용으로 30~680배의 획기적 부식 방지 효과 실증 및 원전 적용성 입증
∙ 고품질 증기발생기 제작기술로 기술이전 추진

(출처 : 보고서 요약서 3p)

Abstract ▼

Ⅳ. Results of the project

1. Surface modification for metal ion release mitigation

(1) Effect of surface microstrain on corrosion release
Technologies for removal of microstrained layer on inner surface, improvement of surface roughness and 2-step descale process for quantification

Ⅳ. Results of the project

1. Surface modification for metal ion release mitigation

(1) Effect of surface microstrain on corrosion release
Technologies for removal of microstrained layer on inner surface, improvement of surface roughness and 2-step descale process for quantification of corrosion and release rates of Alloy 690 SG tubes exposed to a primary water were developed using electropolishing method. The steam generator tubes electropolished under optimized condition showed a factor of 2.4 in corrosion and release resistance under simulated primary condition compared with untreated tube.

(2) Effect of compressive stress on corrosion release
Compressive residual stress is induced by shot peening treatment of Alloy 690 and the corrosion resistance was increased to 1.5 times by a shot peening process with high intensity. But the high shot peening intensity caused an increasement of surface roughness. For that reason, the surface was electropolised after weak shot peening process and it shows a more than quadruple resistance in corrosion release property on Alloy 690 surface.

(3) Effect of surface roughness on corrosion release
The corrosion and release rates of the Alloy 690TT specimens having the surface roughness less than or around 500 nm considering a material requirement were investigated in simulated primary water. As a result, corrosion and release rates decreased by about 70% as their surface roughness decreased. In addition, the corrosion and release rates presented similar value at the roughness less than 150 nm and the main factors on the corrosion and release rates should be a surface micro-hardness and work functions due to roughness change.

2. Alloy modification for mitigation of metal ion release

(1) Design and fabrication of improved Alloy 690-X materials for reducing corrosion release
To investigate the control of corrosion release of steam generator tubing material in the primary coolant of nuclear power plant, some Alloy 690-X materials including small amount of specific element were designed. Zinc and cerium were selected as alloying elements, and Alloy 690-Zn, Alloy 690-Ce were fabricated by vacuum induction melting. Hot forging, cold rolling, and heat treatment for casting ingots of these alloys were processed consecutively, and specimens for microstructure evaluation and corrosion test were finally fabricated.

(2) Optimization of technical specification of the candidate Alloy 690-X materials
Chemical composition analysis on the cast Alloy 690-Zn, Alloy 690-Ce were performed by ICP and XRF. The fitness of some designed variables for hot/cold working process and thermal treatment in this study were evaluated referring the related conditions in the manufacturing process of commercial Alloy 690 tube. Optimization of microstructure requirement was also established through the characterization of recrystallization, grain size, carbide distribution for the candidate Alloy 690-X materials.

(3) Performance evaluation on the corrosion release of Alloy 690-X materials
Corrosion tests to evaluate the performance of corrosion release of the candidate Alloy 690-X materials were carried out under the condition of simulated primary coolant chemistry. It was shown that corrosion rate of Alloy 690-Zn was reduced to 45% of Alloy 690-ref. material at the early stage of corrosion test. Further study is needed to investigate the effect of Ce addition to Alloy 690 material.

3. Water chemistry technology for metal ion release mitigation

(1) Technology development for measurement of dissolved hydrogen at high temperature and pressure
A Pd-Ag sensor was fabricated in-situ measurement of hydrogen partial pressures in simulated NPP environment at high temperature and pressure. The hydrogen partial pressures were measured in pure water and 2 ppm Li/1200 ppm B solution at 290∼330℃ and at 2000∼2900 psig. The hydrogen partial pressure decreased with increasing temperature and increased with increasing pressure. The difference in hydrogen partial pressure in water and solution was insignificant.

(2) Technology development for measurement of corrosion rate of Alloy 690 in high and low concentration hydrogen solutions
Metal ion release tests of Alloy 690 specimens were conducted in high(35, 50, 65, 100 cc(STP)/kg) and low(0, 5, 10cc(STP)/kg) hydrogen solutions at 330℃ during 500 h. The metal ion release rates decreased as hydrogen contents increased. The surface of specimens was covered with needle like oxides in low content hydrogen solutions, whereas with crystals varying in size in high content hydrogen solutions. The crystal size decreased and part of the crystals changed into amorphous with increasing hydrogen contents. Depth profiles of oxide layers showed that Cr and Fe contents increased and Ni content decreased as hydrogen contents increased. This is because Ni/NiO phase transition occurred in 35 cc(STP)/kg hydrogen solution.

4. Crud deposition mitigation on fuel clad

(1) Simulation technology for shapes and types of AOA cruds
Crud deposition was accelerated under sub-cooled nucleate boiling (SNB) condition using a primary loop simulating thermal hydraulic condition of fuel cladding. Cruds, which have similar shape and chemical composition with cruds obtained from nuclear power plant, were simulated using Ni- and Fe-EDTAs in this work.

(2) Effect of Li/B concentration on crud deposition rate
The concentrations of Li and B in a primary water of domestic nuclear power plants were controlled in the pH range from 6.9 to 7.4 to ensure the integrity of primary-side materials and target power. Therefore, crud deposition rates have been investigated under SNB condition at the pH_T range from 6.9 to 7.4. As a result, crud deposition rates decreased as the pH_T of coolant increased and it decreased by a factor of four at pH_T of 7.4 compared to that at pH_T=6.9.

(3) Effect of dissolved hydrogen on crud deposition rate
Crud deposition rate on the fuel clad was evaluated at the dissolved hydrogen range from 5 to 70 cc/kg·H₂O under SNB condition, considering the water chemistry in domestic and international practical condition. Needle-shaped NiO was formed at the DH concentration lower than 25 cc/kg·H₂O due to Ni/NiO thermodynamic stability, while nickel ferrite particles were only observed at the DH concentration higher than 35 cc/kg·H₂O. However, the deposition rate was not affected by the variation of the DH concentration.

5. Denting prevention technology

(1) Advanced technology development for denting prevention and simulation test
Advanced technology for denting prevention was successfully developed first in the world, which clads Alloy 690 on the secondary surface of a steam generator tubesheet. The superior corrosion prevention performance of the Alloy 690 clad was verified from the simulation tests conducted in a acidic and caustic faulted environment.

(2) Applicability evaluation of denting prevention technology
It was verified that the developed technology is applicable to the tubesheet manufacturing process without a technical limitation. Denting prevention performance was also verified through the simulation corrosion tests using a tubesheet specimens equipped with an expanded tube in a simulated secondary environment.

(3) Optimization of denting prevention technology
Denting prevention technology was optimized as follows: For denting prevention at the top of tubesheet, the secondary surface of tubesheet is covered by Alloy 52/152 weld overlay cadding to a thickness of 8~9 mm using SAW(sub-merged arc welding) method.

(출처 : SUMMARY 11p)

목차 Contents

• 표지 ... 1
• 제 출 문 ... 2
• 보고서 요약서 ... 3
• 요 약 문 ... 4
• SUMMARY ... 10
• CONTENTS ... 17
• 목차 ... 19
• 표목차 ... 21
• 그림목차 ... 22
• 제 1 장 연구개발과제의 개요 ... 28
• 제 2 장 국내외 기술개발 현황 ... 29
• 제 1 절 금속이온 용출완화 표면개량 ... 29
• 제 2 절 금속이온 용출완화 합금개량 ... 32
• 제 3 절 금속이온 용출완화 수화학 ... 34
• 제 4 절 부식생성물 부착완화 ... 36
• 제 5 절 덴팅 원천방지 기술 ... 39
• 제 3 장 연구개발수행 내용 및 결과 ... 43
• 제 1 절 금속이온 용출완화 표면개량 ... 43
• 1. 표면 미세변형층 효과 실험 ... 43
• 2. 표면 압축응력 효과 실험 ... 54
• 3. 표면 조도 용출 영향 평가 ... 66
• 제 2 절 금속이온 용출완화 합금개량 기술 ... 77
• 1. 용출완화 후보합금 설계 및 제조 ... 77
• 2. 후보합금 규격기준 최적화 ... 82
• 3. 개량후보합금 용출완화 성능평가 ... 90
• 제 3 절 금속이온 용출완화 수화학 기술 ... 98
• 1. 고온고압 용존수소 측정 신기술개발 ... 98
• 2. 고/저농도 용존수소 범위 용출속도 측정 ... 106
• 제 4 절 부식생성물 부착완화 ... 116
• 1. 부식생성물 부착 형상, 종류 재현 실증시험 ... 116
• 2. Li/B 조건별 방사성 부식생성물 부착속도 측정 ... 126
• 3. 수소농도별 방사성 부식생성물 부착속도 측정 ... 131
• 제 5 절 덴팅 원천방지 기술 ... 138
• 1. 덴팅 원천방지 신기술 개발 및 실증평가 ... 138
• 2. 덴팅 원천방지 신기술 적용성 평가 ... 144
• 3. 덴팅 원천방지 신기술 최적화 ... 148
• 제 4 장 목표달성도 및 관련분야에의 기여도 ... 151
• 제 1 절 연구개발 목표의 달성도 ... 151
• 제 2 절 관련분야에의 기여도 ... 156
• 제 5 장 연구개발결과의 활용계획 ... 159
• 제 6 장 연구개발과정에서 수집한 해외과학기술정보 ... 161
• 제 7 장 참고문헌 ... 163
• 끝페이지 ... 168