[en] The governing equations for crack propagation and arrest in a cylinder under thermal and/or pressure stresses are derived and preliminary numerical tests of a computer algorithm that will eventually simulate the ORNL thermal shock experiments are presented. The basic computational procedure is found to be acceptable but a particular need for accurate propagating-crack fracture toughness (K/sub m/) input data is identified. To this end the test procedure has been successfully modified by the adoption of transverse wedge loading which substantially eliminates the errors due to extraneous load-point displacement. This test procedure is to be applied to a series of data-base materials, including A508-2 and A533B steel, as well as a submerged arc weldment. Composition, heat treatment, yield strength, and K/sub Ic/ values for these materials have been collected and are reported. The planning for irradiation has been completed