Heavy-Section Steel Technology Program

The Heavy-Section Steel Technology (HSST) Program studies concern all areas of the technology of materials fabricated into thick-section, primary-coolant containment systems of light-water-cooled nuclear power reactors. The focus is on the behavior and structural integrity of steel reactor pressure vessels (RPVs) containing cracklike flaws. During this period, analytical efforts included examining the influence of high crack-arrest toughness on RPV integrity and an increased emphasis on evaluating large international structural experiments. Two areas of NRC topical support were continued: (1) the evaluation of mechanisms for enhanced low-temperature, low-flux irradiation embrittlement that may affect the integrity of RPV supports; and (2) an overall assessment of low upper-shelf (LUS) welds in RPVs with special emphasis on reevaluating ductile tearing criteria. The first four stub-panel crack-arrest tests were performed. Posttest material characterization was performed for clad-plate and wide-plate Series 2 test materials. Statistical analyses were performed on the data from the Fifth HSST Irradiation Series on the study of KIc shifts. Analysis of the irradiated fracture-toughness testing was completed for the Seventh HSST Irradiation Series on cladding. Detailed planning was begun for the next pressurized-thermal-shock experiment, PTSE-4, to examine the extent of ductile tearing and its interaction with cleavage fracture in an LUS weld metal. 99 refs., 12 figs., 5 tabs