[en] In crack-arrest studies sponsored by the Heavy-Section Steel Technology (HSST) Program, a primary objective has been to produce fracture toughness data for reactor pressure vessel materials at temperatures approaching the Charpy upper-shelf regime. Wide-plate tests being conducted at the National Bureau of Standards for the HSST Program are providing an opportunity to obtain significant numbers of data points at affordable costs. In these tests, a single-edge crack in a wide-plate which is subjected to tensile loading initiates at low temperature and arrests in a region of increased fracture toughness. The gradient in toughness is achieved by applying a linear transverse temperature profile across the plate. The second test in this series for A 533 grade B class 1 steel involves crack initiation in cleavage followed by arrest at a temperature corresponding to Charpy upper-shelf behavior. The plate geometry, the material properties, and the instrumentation are discussed along with conditions and results for this test. Pretest static and elastodynamic analyses are described, and posttest analyses based on actual boundary conditions are shown to compare favorably with the observed run-arrest events