NDTsi 2001 Session: Structural Integrity and NDE I-II
Fabrication Flaw Rate Estimates for Base Metal of Pressure Vessels and Initial Validation Results
S. Crawford, G. Schuster, S. Doctor, PNNL, USA
ABSTRACT
The U.S. Nuclear Regulatory Commission (NRC) has been funding a multi-year program at the Pacific Northwest National Laboratory (PNNL) entitled "Assessment of the Reliability of UT and Improved Programs for Inservice Inspection (ISI)." As a part of this program, ultrasonic research on reactor pressure vessel material is being conducted to develop empirical estimates of fabrication flaw rates in reactor pressure vessels (RPVs). The estimates of fabrication flaws are intended for use in fracture mechanics structural integrity assessments. Structural integrity assessments, such as those relating to pressurized thermal shock (PTS) events, are performed by computer codes that require, as input, accurate estimates of flaw rates. Bent plate material from the Pressure Vessel Research User Facility (PVRUF) vessel, the Shoreham nuclear power station vessel, the River Bend Unit 2, and Hope Creek Unit 2 vessels, and forging material from the Midland vessel was ultrasonically inspected with a previously characterized SAFT system. The inner (clad side) portion of the RPV material has been the focus of this study because this area is of great concern in the PTS analysis. Estimates of flaw rates were made for small flaws, < 4mm in through-wall depth, and for large flaws. Several indications were removed from the material contained within one-inch thick plates or cubes. These plates/cubes were further analyzed with higher resolution techniques to validate the flaw presence and to fully document its characteristics. Work supported by the U.S. Nuclear Regulatory commission under Contract DE-AC06-76RLO1830; NRC JCN W6275; Ms. Deborah Jackson, Program Manager.
Publication Source: 3nd International Conference on NDE in Relation to Structural Integrity for Nuclear and Pressurized Components, November 14-16, 2001, Seville Spain. Publisher: Tecnatom s.a. - [Homepage]
