Development of techniques for remote plasma arc cutting of a nuclear reactor vessel

Procedures for in-air water-injection plasma arc cutting and a special automated operating cycle were developed to produce the required cuts and lifting slots in the 3.1 in. (79 mm) stainless-steel-clad primary pressure vessel of the ERR. The water-injection plasma arc cutting torches, techniques, and the automated operating cycle were demonstrated to be workable for this application by cutting several vessel mockup assemblies. A plasma torch manipulator and a cutting control panel that had been designed and built at ORNL were used for remote automated underwater and in-air plasma arc cutting at the ERR. At the ERR, the primary pressure vessel was segmented and removed in 15 weeks under difficult remote working conditions. The plasma arc cutting torches, cutting control panel, and torch manipulator performed satisfactorily. The control panel and torch manipulator were subsequently used for torch manipulation during oxyacetylene cutting of the thermal shield outside the reactor vessel. Cutting of the reactor vessel and the outer thermal shield, as well as all other activities of the reactor dismantling project, were successfully completed