scholarly journals Life extension analysis of the High Flux Isotope Reactor vessel by applying fracture mechanics

1995 ◽  
Author(s):  
S.J. Chang
Keyword(s):  
Fracture Mechanics ◽  
Reactor Vessel ◽  
Life Extension ◽  
High Flux ◽  
Extension Analysis

Probability of Fracture and Life Extension Estimate of the High-Flux Isotope Reactor Vessel

1998 ◽  
Vol 120 (3) ◽  
pp. 290-296 ◽  
Author(s):  
S.-J. Chang
Keyword(s):  
Transition Temperature ◽  
Hydrostatic Pressure ◽  
Fracture Probability ◽  
Reactor Vessel ◽  
Numerical Results ◽  
Life Extension ◽  
Time Interval ◽  
High Flux ◽  
Vessel Steel ◽  
Pressure Test

The state of the vessel steel embrittlement as a result of neutron irradiation can be measured by its increase in ductile-brittle transition temperature (DBTT) for fracture, often denoted by RTNDT for carbon steel. This transition temperature can be calibrated by the drop-weight test and, sometimes, by the Charpy impact test. The life extension for the high-flux isotope reactor (HFIR) vessel is calculated by using the method of fracture mechanics that is incorporated with the effect of the DBTT change. The failure probability of the HFIR vessel is limited as the life of the vessel by the reactor core melt probability of 10−4. The operating safety of the reactor is ensured by periodic hydrostatic pressure test (hydrotest). The hydrotest is performed in order to determine a safe vessel static pressure. The fracture probability as a result of the hydrostatic pressure test is calculated and is used to determine the life of the vessel. Failure to perform hydrotest imposes the limit on the life of the vessel. The conventional method of fracture probability calculations such as that used by the NRC-sponsored PRAISE CODE and the FAVOR CODE developed in this Laboratory are based on the Monte Carlo simulation. Heavy computations are required. An alternative method of fracture probability calculation by direct probability integration is developed in this paper. The present approach offers simple and expedient ways to obtain numerical results without losing any generality. This approach provides a clear analytical expression on the physical random variables to be integrated, yet requires much less computation time. In this paper, numerical results on 1) the probability of vessel fracture, 2) the hydrotest time interval, and 3) the hydrotest pressure as a result of the DBTT increase are obtained. Limiting the probabilities of the vessel fracture as a result of hydrotest to 10−4 implies that the reactor vessel life can be extended up to 50 EFPY (100 MW) with the minimum vessel operating temperature equal to 85°F.

An Update on the Investigation of Fracture Toughness Properties of the High Flux Reactor Vessel From Surveillance Test Campaign in 2017

2019 ◽  
Author(s):  
M. Kolluri ◽  
F. H. E. de Haan – de Wilde ◽  
H. S. Nolles ◽  
A. J. M. de Jong
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Fracture Surface ◽  
Neutron Fluence ◽  
Reactor Vessel ◽  
Surveillance Program ◽  
High Flux ◽  
High Flux Reactor ◽  
Flux Reactor ◽  
Vessel Material

Abstract The reactor vessel of the High Flux Reactor (HFR) in Petten has been fabricated from Al 5154-O alloy grade with a maximum Mg content of 3.5 wt. %. The vessel experiences large amount of neutron fluences (notably at hot spot), of the order of 1027 n/m2, during its operational life. Substantial damage to the material’s microstructure and mechanical properties can occur at these high fluence conditions. To this end, a dedicated surveillance program: SURP (SURveillance Program) is executed to understand, predict and measure the influence of neutron radiation damage on the mechanical properties of the vessel material. In the SURP program, test specimens fabricated from representative HFR vessel material are continuously irradiated in two specially designed experimental rigs. A number of surveillance specimens are periodically extracted and tested to evaluate the changes in fracture toughness properties of the vessel as function neutron fluence. The surveillance testing results of test campaigns performed until 2015 were published previously in [1, 2]. The current paper presents fracture toughness and SEM results from the recent surveillance campaign performed in 2017. The fracture toughness specimen tested in this campaign received a thermal neutron fluence of 13.56 x1026 n/m2, which is ∼8.9 × 1025 n/m2 more than the thermal fluence received by the specimen tested in SURP 2015 campaign. These results from this campaign have shown no change in the fracture toughness from the values measured in the previous SURP campaign. The SEM observations are performed to study the fracture surface, to measure (by WDS) the transmutation Si formed near crack tip and to investigate various inclusions in the microstructure. SEM fracture surface investigation revealed a tortuous (bumpy) fracture surface constituting micro-scale dimples over majority of the fracture area. Islands of cleavage facets and secondary cracks have been observed as well. EDS analysis of various inclusions in the microstructure revealed presence of Fe rich inclusions and Mg-Si rich precipitates. Additionally, inclusions rich in Al-Mg-Cr-Ti were identified. Finally, changes in mechanical properties of Al 5154-O alloy with an increase in neutron fluence (or transmutation Si) are discussed in correlation with SEM microstructure and fracture morphology observed in SEM. TEM investigation of precipitate microstructure is ongoing and those results will be published in future.

Use of ultrasonic models in the design and validation of new NDE techniques

1986 ◽  
Vol 320 (1554) ◽  
pp. 329-340 ◽  
Keyword(s):  
Fracture Mechanics ◽  
Elastic Wave ◽  
Structural Integrity ◽  
Life Extension ◽  
Experimental Demonstration ◽  
Structural Components ◽  
Model Calculations ◽  
Model Predictions ◽  
The Cost ◽  
Theoretical Scattering

In implementing fracture mechanics based techniques for the design and life extension of structural components, it is necessary to establish the reliability with which various flaw sizes and types can be detected and characterized. Traditionally, this has been accomplished through extensive experimental demonstration programmes. This paper discusses present efforts to use model predictions to reduce the required amount of experimentation, and hence the cost, of such programmes. Formalisms whereby the extensive elastic-wave theoretical scattering effort of the last decade can be applied to practical problems are first reviewed. This is followed by several specific examples which have occurred in the nuclear and aerospace industries. The paper concludes with the identification of some important remaining theoretical problems and a discussion of possible strategies for future implementation of model calculations as tools in structural integrity programmes.

Advances in Offshore Structural Analysis Using Response-Based Time-Domain Approach

2021 ◽  
Author(s):  
Johyun Kyoung ◽  
Sagar Samaria ◽  
Jeffrey O’Donnell ◽  
Sudhakar Tallavajhula
Keyword(s):  
Structural Analysis ◽  
Fracture Mechanics ◽  
Time Domain ◽  
Structural Strength ◽  
Structural Response ◽  
Life Extension ◽  
Environmental Loads ◽  
Analysis Methodology ◽  
Non Linear ◽  
The Time Domain

Abstract Demand for life extension assessments of floating offshore platforms continues to grow worldwide. Conventional structural analysis methods have limited ability to accurately capture non-linear environmental loading, non-linear loading by the mooring and riser systems, and resulting higher order hull responses. The uncertainties are typically managed by the factors of safety applied in the structural analysis. Time domain structural analyses have long promised to improve analysis accuracy and reduce these uncertainties. This paper describes a comprehensive and practical time domain structural analysis methodology applied to a deep-water semi-submersible-type floating platform including results for structural strength and fatigue. In addition, the time domain structural analysis was extended for use in fracture mechanics and the assessment of notional weld flaws to facilitate specification of impactful non-destructive examination (NDE). Present time domain structural analysis methodology employs a response-based finite element analysis (FEA) conducted in the time domain. All external environmental loads and inertial forces are converted to a response-based stress-time history. Previously, conventional time domain structural analysis involves massive computation resources to resolve solutions at every time interval. Present methodology significantly improves computational efficiency to be practical in real-world problems. The improvement is achieved by decomposing the structural response into a set of multiple load components selected on the bases of function for hull motion response and environmental loadings. Structural response in time domain is directly obtained by synthesizing the load components. An actual time domain structural response is captured effectively and efficiently to simulate the strength and fatigue criterion for the structure with consistent environmental loads and hull responses. Utilizing the level of detail provided by the time domain structural analysis methodology, a fracture mechanics evaluation of notional initial flaws (engineering criticality assessments – ECAs) can be conducted providing meaningful technical basis for in-service NDE and life extension assessments. The procedures for fatigue crack growth and fracture documented in BS 7910 were employed to derive the smallest initial flaws (critical initial flaws) that may result in structural failure during a facility's lifetime. A comparison indicates that conventional structural analysis methods provide conservative results for both structural strength and fatigue damage calculations resulting from the linear assumption of environmental loads and hull responses. Present time domain structural analysis methodology provides an innovative, cutting-edge approach providing accuracy and fewer uncertainties, which can be pragmatically used during a typical project.

Engineering Criticality Assessments of Floating Offshore Platforms Based on Time Domain Structural Response Analysis

2021 ◽  
Author(s):  
Jeffrey O’Donnell ◽  
Johyun Kyoung ◽  
Sagar Samaria ◽  
Anil Sablok
Keyword(s):  
Fracture Mechanics ◽  
Time Domain ◽  
Structural Integrity ◽  
Structural Response ◽  
Life Extension ◽  
Response Analysis ◽  
Offshore Platforms ◽  
Industry Standards ◽  
Offshore Industry ◽  
Integrity Assessments

Abstract This paper presents a time-domain S-N fatigue analysis and an approach to reliable and robust engineering criticality assessments to supplement or provide an alternative to S-N fatigue assessments of offshore platform structures based on time domain structural response analysis. It also provides recommendations for industry standards to improve guidance for structural integrity assessments of offshore platforms using fracture mechanics. Demand continues to grow in the offshore industry to attain value from captured operational data for a number of purposes, including the reduction of uncertainties in structural integrity assessments during design and over the operational lifetime of floating offshore platforms. Recent advances in time domain structural analysis technology demonstrate substantially more accurate assessments of non-linear platform loadings and responses with enhanced computational efficiency. The current S-N approach for fatigue design and integrity assessments calculates a fatigue damage factor that does not address how loading occurs over time (ABS, DNVGL-RP-C203). For the present study, engineering criticality assessments (ECAs) based on fracture mechanics theory (BS 7910) are applied utilizing time-domain loading information theory. The ECA returns the smallest initial flaws that can grow to a critical size during a design lifetime, which can serve as an indicator of acceptability during design, a technical basis for in-service inspection intervals and facilitates asset integrity and life extension assessments. Critical initial flaws are calculated using the Paris Law (BS 7910) and cumulative fatigue crack growth in two ways: with and without an integrated and consistent check for fracture instability. The results are compared with those from S-N fatigue analyses and recommendations are provided.

TRACS JIP – TTR Life Extension Process

2021 ◽  
Author(s):  
Dhyanjyoti Deka ◽  
Mike Campbell ◽  
Vinayak Patil ◽  
Michael Long Ge ◽  
Steve Wong ◽  
...  
Keyword(s):  
Initial Data ◽  
Data Gathering ◽  
Real Life ◽  
Threat Assessment ◽  
Life Extension ◽  
Design Life ◽  
Extended Life ◽  
Accessibility Issues ◽  
Extension Analysis ◽  
Extension Process

Abstract The Tensioned Riser Assessment for Continued Service (TRACS) JIP develops a structured life extension process for TTR systems including single casing, dual casing, buoyancy can supported and tensioner supported TTRs. The JIP bridges regulatory and API frameworks and achieves industry consensus on analysis, inspections, and documentation. The life extension process developed in this JIP consists of detailed roadmaps that guide the operator through the different assessment steps starting from initial data gathering through to the development of the forward-looking IMP. The JIP life extension process is based on a threat assessment philosophy which ensures identification and assessment of all possible threats to the integrity of the TTR in its extended life. The JIP process is validated against three real life TTR systems that are nearing the end of their design lives. Potential threats to the integrity of these TTRs during the projected continued service beyond the design life are identified and specific inspection and analysis recommendations to safely manage or mitigate these threats are made. The JIP also provides TTR life extension analysis guidance while considering the opportunities to reduce conservatism compared to new designs. Inspection of TTRs is challenging due to accessibility issues and the pipe in pipe construction. Several subsea NDE inspection tools are surveyed in this JIP and their applicability to TTRs is discussed.

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