Stephen M. Parker, PE

Cracking in boiling water reactor (BWR) core shroud welds has been identified in operating nuclear plants worldwide. The nuclear industry has taken extensive efforts to disposition and evaluate core shroud cracking, most notably within the BWR Vessel and Internals Project (BWRVIP) where many industry guidance documents have been published regarding core shroud integrity [1, 2, 3, 4]. This guidance is predominately focused on evaluating crack stability. Calculating through-wall leakage was… Show more

Cracking in boiling water reactor (BWR) core shroud welds has been identified in operating nuclear plants worldwide. The nuclear industry has taken extensive efforts to disposition and evaluate core shroud cracking, most notably within the BWR Vessel and Internals Project (BWRVIP) where many industry guidance documents have been published regarding core shroud integrity [1, 2, 3, 4]. This guidance is predominately focused on evaluating crack stability. Calculating through-wall leakage was not previously a focus of the existing BWRVIP inspection and evaluation (I&E) guidelines for the core shroud; however, there is some guidance in the current documentation. In recent years there has been some evidence of through-wall indications in the core shroud where the through-wall indications were aligned in an array of co-linear, short, flaws.
The purpose of the study documented in this paper is to characterize the COA for axial co-linear crack distributions compared to the COA of an individual crack. Cracks that are aligned in series with an uncracked ligament between them are considered to be co-linear. To better understand how these crack distributions behave, an evaluation is conducted to analyze axial co-linear flaw configurations in core shrouds using traditional linear-elastic fracture mechanics (LEFM) and finite element analysis (FEA) techniques. Through FEA, the COAs and displacements of various co-linear flaw configurations are calculated and compared to the COAs for single flaw configurations. These flaw geometries are useful for the purpose of determining the potential core leakage associated with through-wall co-linear cracks.
Results show that crack openings of co-linear flaw configurations compared to a single flaw can vary substantially depending the crack size and ligament length. Trends of these crack openings are summarized within this report.
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Plants in the United States (U.S.) and many plants outside of the U.S. are required to meet the regulations of the Pressurized Thermal Shock (PTS) Rule, 10 CFR 50.61. The Alternate Pressurized Thermal Shock (PTS) Rule (10 CFR 50.61a) was approved by the U.S. Nuclear Regulatory Commission (NRC) and included in the Federal Register, with an effective date of February 3, 2010. This Alternate Rule provides a new metric and screening criteria for PTS. This metric, RTMAX-X, and the corresponding… Show more

Plants in the United States (U.S.) and many plants outside of the U.S. are required to meet the regulations of the Pressurized Thermal Shock (PTS) Rule, 10 CFR 50.61. The Alternate Pressurized Thermal Shock (PTS) Rule (10 CFR 50.61a) was approved by the U.S. Nuclear Regulatory Commission (NRC) and included in the Federal Register, with an effective date of February 3, 2010. This Alternate Rule provides a new metric and screening criteria for PTS. This metric, RTMAX-X, and the corresponding screening criteria are far less restrictive than the RTPTS metrics and screening criteria in the original PTS Rule (10 CFR 50.61).

The Alternate PTS Rule was developed through probabilistic fracture mechanics (PFM) evaluations performed for selected U.S. pilot plants. A Generalization Study was also performed which determined that the plants used for these evaluations were representative of and applicable to the U.S. Pressurized Water Reactor (PWR) nuclear power plant fleet.

Plants outside of the U.S. may be interested in implementing the Alternate PTS Rule. However, direct implementation of the Alternate PTS Rule may not be possible due to differences in plant design, embrittlement prediction techniques, inservice inspection requirements, etc. The objective of this paper is to explore the use the Alternate PTS Rule by PWR plants outside of the U.S. by proposing methods to account for the potential differences mentioned above.
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Section XI of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code specifies a 10-year interval between reactor vessel (RV) nozzle weld inspections. The industry has expended significant cost and man-rem exposure performing inspections that have found no service-induced flaws in ASME Section XI Category B-F or B-J RV nozzle welds that do not contain Alloy 82/182. Furthermore, many plants have implemented a 20-year inspection interval for the RV shell-to-shell and… Show more

Section XI of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code specifies a 10-year interval between reactor vessel (RV) nozzle weld inspections. The industry has expended significant cost and man-rem exposure performing inspections that have found no service-induced flaws in ASME Section XI Category B-F or B-J RV nozzle welds that do not contain Alloy 82/182. Furthermore, many plants have implemented a 20-year inspection interval for the RV shell-to-shell and shell-to-nozzle welds in accordance with WCAP-16168-NP-A, Revision 2. For many of these plants, continuing to inspect the RV nozzle welds on a 10-year interval presents a significant hardship without a corresponding increase in safety from performing the inspections. This paper will provide a summary of the technical basis and methodology developed by Westinghouse for extending the Section XI inspection interval from the current 10 years to 20 years for Category B-F and B-J RV nozzle-to-safe-end and safe-end-to-pipe welds that are not fabricated with Alloy 82/182 materials. Bounding change-in-failure-frequency values have been calculated for use in plant-specific implementation of the extended inspection interval. Plant-specific pilot studies have been performed and the results show that the change in risk associated with extending the interval from 10 to 20 years after the initial 10-year inservice inspection (ISI) satisfies the guidelines specified in Regulatory Guide 1.174 for an acceptably low change in risk for core damage frequency (CDF) and large early release frequency (LERF). Further, the pilot-plant results show that the effect of the extended inspection interval on the plant's risk-informed inservice inspection (RI-ISI) program for piping, if any, would also be acceptable. Show less

Many products have been released into the market that claim to be designed for sustainability. However there is little data available to validate their performance, especially those that are incorporated within building designs. This thesis presents the design of a facility that can be used to conduct research on sustainable products and designs. The facility is a flexible, live-in test bed designed to be built as a modular home. The proposed house is divided into two sections where one is… Show more

Many products have been released into the market that claim to be designed for sustainability. However there is little data available to validate their performance, especially those that are incorporated within building designs. This thesis presents the design of a facility that can be used to conduct research on sustainable products and designs. The facility is a flexible, live-in test bed designed to be built as a modular home. The proposed house is divided into two sections where one is a permanent area for students to live in and the other is a flexible research laboratory for students and faculty to test and monitor different technologies. To enhance sustainability, the house is designed based on the LEED for Homes certification plan. The preliminary design criteria for this plan are detailed with suggested measures that can be taken to attain LEED point credits. Finally, the energy efficiency of the house was verified by creating models within the building energy simulation software eQUEST. Once built, this facility would be an invaluable resource for Bucknell University, the modular home industry, and the local community. Show less