An irradiation program was carried out with four submerged-arc welds and one plate of A533-B Class 1 pressure vessel steel. The welds were made by commercial vendors using current welding practice and contained relatively low copper levels. The target fluence was 2 × 10²³ neutrons (n)/m² (E > 1 MeV). The program was administered by Oak Ridge National Laboratory (ORNL) through the Heavy Section Steel Technology Program Office, and the testing was shared by ORNL and Materials Engineering Associates, Inc. (MEA). The results of the test program indicated that the welds had generally very good properties (tension, Charpy V-notch, and fracture toughness) prior to irradiation and with the exception of tearing modulus all five materials were relatively insensitive to irradiation on the upper shelf. The data further indicated that shifts of the transition region to higher temperature with irradiation is directly related to the copper and nickel content.