Long-Term Integrity of Waste Package Final Closure for HLW Geological Disposal, (III) Applicability of Electron Beam Welding to Overpack Final Closure

Asano, Hitoshi; Maeda, Koki; Aritomi, Masanori

doi:10.3327/jnst.43.206

Cited by 7 publications

(9 citation statements)

References 23 publications

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“…MAG and EBW cannot be compared because the efficiency of EBW is higher for thick plate welding, at 10 min for 100 mm and 26 min for 190 mm in the full penetration/ circumferential welding of a full-scale overpack lid structure, 7) which corresponds to working efficiencies that are approximately 9.0 and 5.5 times higher than that of MAG.…”

Section: Comparison With Tig and Ebw Test Results (1) Welding Efficiencymentioning

confidence: 99%

“…7) Although heat input conditions were identified as a potential solution to manage these weld flaws, this has not been examined yet. 7) In the case of MAG, slag inclusion generation is seen and these inclusions are randomly scattered, even if slag removal is conducted. There are two sides to the issue of weld flaw presence, as stated in our first report.…”

Section: Comparison With Tig and Ebw Test Results (1) Welding Efficiencymentioning

confidence: 99%

“…[3][4][5][6][7][8][9][10] In these studies, the basic specifications for overpack were those from the JNC H12 Report, in which the carbon steel overpack was thought to have a wall thickness of 190 mm. 1) In evaluating welding methods, gas tungsten arc welding (GTAW; hereinafter referred to as tungsten inert gas (TIG) welding) as a typical arc welding method and electron beam welding (EBW) as a high-energy beam welding method were tested for applicability to the lid closure of carbon steel overpack with a maximum wall thickness of 190 mm, considered to be the full-scale lid structure.…”

Section: Introductionmentioning

confidence: 99%

“…The welding parameters were measured, and the metallurgical structure, mechanical properties and residual stress distribution of the weld joint were also observed and calculated. 3,6,7,9) Gas metal arc welding (GMAW; hereinafter referred to as metal active gas (MAG) welding) is another typical arc welding method, in which metals are joined together by heating them with an electric arc established between a consumable electrode and a workpiece. The technical advantage of MAG welding is a higher welding speed with a higher deposition rate than other gas-shielded metal arc welding methods.…”

Section: Introductionmentioning

confidence: 99%

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Long-Term Integrity of Waste Package Final Closure for HLW Geological Disposal, (V) Applicability of MAG Welding Method to Overpack Final Closure

Asano¹,

Ito

2008

J. Nucl. Sci. Technol.

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Overpack, a high-level radioactive waste package for Japan's geological disposal program, is required for preventing the sealed vitrified waste from contact with groundwater for 1,000 years. In this study, metal active gas (MAG) welding, a typical arc welding method, was evaluated for its applicability in sealing a carbon steel overpack lid with a thickness of 190 mm. Welding conditions and parameters were examined with multilayer welding for three different groove depths. Welded joint tests including the observation of macro-and microstructures were conducted, and mechanical properties were within tentatively applied criteria. Measurements and numerical calculations for residual stress were also conducted, and residual stress distribution tendencies were discussed. These test results were compared with those previously reported for tungsten inert gas welding (TIG) and electron beam welding (EBW). MAG welding possesses the potential to complete overpack lid closure with a maximum groove depth of 190 mm, but the applicability of MAG welding to overpack final closure should be discussed from the viewpoint of the presence of slag inclusions possibly induced in the weld metal.

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Section: Comparison With Tig and Ebw Test Results (1) Welding Efficiencymentioning

confidence: 99%

Section: Comparison With Tig and Ebw Test Results (1) Welding Efficiencymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Long-Term Integrity of Waste Package Final Closure for HLW Geological Disposal, (V) Applicability of MAG Welding Method to Overpack Final Closure

Asano¹,

Ito

2008

J. Nucl. Sci. Technol.

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“…In this series of studies, a structural integrity evaluation model of the lid closure based on the fracture mechanics assessment was proposed. [2][3][4][5][6][7] This evaluation method refers to the fitness for service (FFS) assessment of nuclear power plant components, an assessment method specified for the overpack, which takes into consideration the technical limitations caused by emplacement of the overpack in a deep underground geological formation. It is intended to assure the structural integrity of the weld joint for 1000 years without any inspection or repair of the overpack after it is emplaced in a repository.…”

Section: Introductionmentioning

confidence: 99%

Long term integrity of overpack closure weld for HLW geological disposal Part 1 - prediction and evaluation method for structural integrity of weld joint

Asano¹,

nakamura²,

Kobayashi³

2011

Corrosion Engineering, Science and Technology

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The weld joint of the carbon steel overpack is required to isolate the sealed vitrified waste from coming into contact with groundwater for a duration equal to the base metal, which is 1000 years. The authors have proposed a structural integrity evaluation model of the lid closure, which is based on fracture mechanics assessment. Corrosion phenomena at the weld joint and sizing capability of non-destructive examination for weld flaws are key issues in this evaluation model. In this paper, reviewing the most recent test results on the susceptibility of stress corrosion cracking at the weld joint and the estimation of the probability of detection for ultrasonic testing methods, consistency of the evaluation model was discussed.

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Long-Term Integrity of Waste Package Final Closure for HLW Geological Disposal, (VI) Consistency of the Structural Integrity Evaluation Model for the Weld Joint

Asano¹,

Aritomi

2010

Journal of Nuclear Science and Technology

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Overpack, a container of high-level radioactive waste for Japan's geological disposal program, is required to prevent the sealed vitrified waste from coming into contact with groundwater for 1,000 years. This means that the same duration and function are required for the weld joint between the body and lid of the overpack. The authors have initiated studies on a methodology evaluating the long-term integrity of the lid closure, including welding tests and non-destructive examination tests, and proposed a structural integrity evaluation model for the lid closure as a basis for fracture mechanics assessment. The model makes two main assumptions consistent with six prerequisites. This article examines the consistency of the mechanical strength of the lid closure (one of the two assumptions) with its prerequisites, through a review of the test results of corrosion behavior and numerical calculations of neutron irradiation embrittlement for weld joints. Furthermore, a comparison of the critical crack lengths at different penetration depths was conducted, and an estimation of the maximum tolerable flaw size, which serves as a form of an acceptance criterion after adding a safety factor for the size of the weld flaw, was made. Based on these results, the consistency of the proposed evaluation model was discussed and identified.

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Long-Term Integrity of Waste Package Final Closure for HLW Geological Disposal, (III) Applicability of Electron Beam Welding to Overpack Final Closure

Cited by 7 publications

References 23 publications

Long-Term Integrity of Waste Package Final Closure for HLW Geological Disposal, (V) Applicability of MAG Welding Method to Overpack Final Closure

Long-Term Integrity of Waste Package Final Closure for HLW Geological Disposal, (V) Applicability of MAG Welding Method to Overpack Final Closure

Long term integrity of overpack closure weld for HLW geological disposal Part 1 - prediction and evaluation method for structural integrity of weld joint

Long-Term Integrity of Waste Package Final Closure for HLW Geological Disposal, (VI) Consistency of the Structural Integrity Evaluation Model for the Weld Joint

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