Hilda B. Klasky

Analysis of Ductile Crack Growth in Pipe Test in STYLE Project

The Oak Ridge National Laboratory (ORNL) is conducting structural analyses, both deterministic and probabilistic, to simulate a large scale mock-up experiment planned within the European Network for Structural Integrity for Lifetime Management – non-RPV Components (STYLE).The paper summarizes current ORNL analyses of STYLE’s Mock-Up3 experiment to simulate/evaluate ductile crack growth in a cladded ferritic pipe. Deterministic analyses of the large-scale bending test of a ferritic surge pipe, with an internal circumferential crack, are being simulated with a number of local micromechanical approaches, such as Gurson-Tvergaard-Needleman (GTN) model. Both FEACrack [1] and ABAQUS [2] general purpose finite element programs are being used to predict the failure load and the failure mode, i.e. ductile tearing or net-section collapse, as part of the pre-test phase of the project.Companion probabilistic analyses of the experiment are utilizing the ORNL developed open-source Structural Integrity Assessment Modular - Probabilistic Fracture Mechanics (SIAM-PFM) framework. SIAM-PFM contains engineering assessment methodologies such as the tearing instability (J-T analysis) module developed for inner surface cracks under bending load. The driving force J-integral estimations are based on the SC.ENG1 or SC.ENG2 models. The J-A2 methodology is used to transfer (constraint-adjust) J-R curve material data from standard test specimens to the Mock-Up3 experiment configuration. The probabilistic results of the Mock-Up3 experiment obtained from SIAM-PFM will be compared to those generated using the deterministic finite element modeling approach. The objective of the probabilistic analysis is to provide uncertainty bounds that will assist in assessing the more detailed 3D finite-element solutions and to also assess the level of confidence that can be placed in the best-estimate finite-element solutions.Copyright

A Dislocation-Based Cleavage Initiation Model for Pressure Vessel Steels

Efforts are under way to develop a theoretical, multi-scale model for the prediction of fracture toughness of ferritic steels in the ductile-to-brittle transition temperature (DBTT) region that accounts for temperature, irradiation, strain rate, and material condition (chemistry and heat treatment) effects. This new model is intended to address difficulties associated with existing empirically-derived models of the DBTT region that cannot be extrapolated to conditions for which data are unavailable. Dislocation distribution equations, derived from the theories of Yokobori et al., are incorporated to account for the local stress state prior to and following initiation of a microcrack from a second-phase particle. The new model is the basis for the DISlocation-based FRACture (DISFRAC) computer code being developed at the Oak Ridge National Laboratory (ORNL). The purpose of this code is to permit fracture safety assessments of ferritic structures with only tensile properties required as input. The primary motivation for the code is to assist in the prediction of radiation effects on nuclear reactor pressure vessels, in parallel with the EURATOM PERFORM 60 project.

Probabilistic Fracture Mechanics of Reactor Pressure Vessels with Populations of Flaws

This report documents recent progress in developing a tool that uses the Grizzly and RAVEN codes to perform probabilistic fracture mechanics analyses of reactor pressure vessels in light water reactor nuclear power plants. The Grizzly code is being developed with the goal of creating a general tool that can be applied to study a variety of degradation mechanisms in nuclear power plant components. Because of the central role of the reactor pressure vessel (RPV) in a nuclear power plant, particular emphasis is being placed on developing capabilities to model fracture in embrittled RPVs to aid in the process surrounding decision making relating to life extension of existing plants. A typical RPV contains a large population of pre-existing flaws introduced during the manufacturing process. The use of probabilistic techniques is necessary to assess the likelihood of crack initiation at one or more of these flaws during a transient event. This report documents development and initial testing of a capability to perform probabilistic fracture mechanics of large populations of flaws in RPVs using reduced order models to compute fracture parameters. The work documented here builds on prior efforts to perform probabilistic analyses of a single flaw with uncertain parameters, as well as earlier work to develop deterministic capabilities to model the thermo-mechanical response of the RPV under transient events, and compute fracture mechanics parameters at locations of pre-defined flaws. The capabilities developed as part of this work provide a foundation for future work, which will develop a platform that provides the flexibility needed to consider scenarios that cannot be addressed with the tools used in current practice.

UML and SOA Overview with Example Applications to the xLPR V.2 Project

This document presents an overview of the Unified Modeling Language and the Service Oriented Architecture with real examples from the xLPR V2.0 project.

A Role-Based Access Control (RBAC) Schema for REAP Web App

This document describes a Role-Based Access Control (RBAC) Schema for Reactor Embrittlement Archive Project Web App.

GRIZZLY/FAVOR Interface Project Report

As part of the Light Water Reactor Sustainability (LWRS) Program, the objective of the GRIZZLY/FAVOR Interface project is to create the capability to apply GRIZZLY 3-D finite element (thermal and stress) analysis results as input to FAVOR probabilistic fracture mechanics (PFM) analyses. The one benefit of FAVOR to Grizzly is the PROBABILISTIC capability. This document describes the implementation of the GRIZZLY/FAVOR Interface, the preliminary verification and tests results and a user guide that provides detailed step-by-step instructions to run the program.

White Paper on the Use of Team Calendars with the JIRA Issue Tracking System and Confluence Collaboration Tools for the xLPR Project

ORNL was tasked by xLPR project management to propose a team calendar for use within the xLPR consortium. Among various options that were considered, the approach judged by ORNL to best fit the needs of the xLPR project is presented in this document. The Atlassian Team Calendars plug-in used with the Confluence collaboration tool was recommended for several reasons, including the advantage that it provides for a tight integration between Confluence (found at https://xlpr.ornl.gov/wiki ) and xLPR s JIRA issue tracking system (found at https://xlpr.ornl.gov/jira ). This document is divided into two parts. The first part (Sections 1-6) consists of the white paper, which highlights some of the ways that Team Calendars can improve com mun ication between xLPR project managers, group leads, and team members when JIRA is applied for both issue tracking and change-management activities. Specific points emphasized herein are as follows: The Team Calendar application greatly enhances the added value that the JIRA and Confluence tools bring to the xLPR Project. The Team Calendar can improve com mun ication between xLPR project managers, group leads, and team members when JIRA is applied for both issue tracking and change-management activities. The Team Calendar works across different email tools such as Outlook 2011, Outlook 2010, Outlook 2007, Google Calendars and Mac s iCalendar to name a few. xLPR users can now access the wiki Confluence (with embedded Team Calendars) directly from JIRA without having to re-validate their login. The second part consists of an Annex (Section 7), which describes how users can subscribe to Team Calendars from different calendar applications. Specific instructions are given in the Annex that describe how to Import xLPR Team Calendar to Outlook Version Office 2010 Import xLPR Team Calendar to Outlook Version Office 2007 Subscribe to Team Calendar from Google Calendar The reader is directed to Section 4 for instructions on adding events to the Team Calendar or accessing ORNL staff for assistance with such additions. To seek help with your questions and problems regarding the content of this document, please contact Hilda Klasky at klaskyhb@ornl.gov

White Paper on Data Repository Reorganization Proposal for the xLPR Project

As the xLPR project moves along, it is important to properly manage the knowledge generated by the different groups. We focus specifically on the knowledge and communications written in files, including general documents, source code and executable files. Data generated through the project are different in nature and, for this reason, need to be treated differently. To that end, ORNL put in place a series of tools that facilitate proper storage and management of project data, document and code changes, group collaboration, knowledge transfer, transparency, accountability and auditability. This paper describes the approaches/tools that we recommend for moving the project forward on knowledge management.

ORNL Pre-Test Analyses of a Large-Scale Experiment in STYLE

Oak Ridge National Laboratory (ORNL) is conducting a series of numerical analyses to simulate a large scale mock-up experiment planned within the European Network for S tructural Int egrity for L ifetime Manage ment – non-RPV Components (STYLE). STYLE is a European cooperative effort to assess the structural integrity of (non-reactor pressure vessel) reactor coolant pressure boundary components relevant to ageing and life-time management and to integrate the knowledge created in the project into mainstream nuclear industry assessment codes. ORNL contributes “work-in-kind” support to STYLE Work Package 2 (Numerical Analysis/Advanced Tools) and Work Package 3 (Engineering Assessment Methods/LBB Analyses). This paper summarizes the current status of ORNL analyses of the STYLE Mock-Up3 large-scale experiment to simulate and evaluate crack growth in a cladded ferritic pipe. The analyses are being performed in two parts. In the first part, advanced fracture mechanics models are being developed and performed to evaluate several experiment designs taking into account the capabilities of the test facility while satisfying the test objectives. Then these advanced fracture mechanics models will be utilized to simulate the crack growth in the large scale mock-up test. For the second part, the recently developed ORNL SIAM-PFM open-source, cross-platform, probabilistic computational tool will be used to generate an alternative assessment for comparison with the advanced fracture mechanics model results. The SIAM-PFM probabilistic analysis of the Mock-Up3 experiment will utilize fracture modules that are installed into a general probabilistic framework. The probabilistic results of the Mock-Up3 experiment obtained from SIAM-PFM will be compared to those results generated using the deterministic 3D nonlinear finite-element modeling approach. The objective of the probabilistic analysis is to provide uncertainty bounds that will assist in assessing the more detailed 3D finite-element solutions and to also assess the level of confidence that can be placed in the best-estimate finite-element solutions.Copyright