Nuclear heating in critical components of alternative ITER first wall attachment mechanism

A nuclear analysis was performed for an alternate ITER first wall attachment scheme to estimate the nuclear heating in critical components. With a variety of components near the first wall without direct cooling, there is concern that the operating temperatures will be above engineering limits. Using DAG-MCNP5, a 1-D analysis framework was used to estimate the nuclear heating in a detailed 3-D model of the first wall and shield attachment mechanism. The parts of the stainless steel hinge at the base of system experience nuclear heating between 1.85 and 5.07 W/cm³. The copper yoke and Inconel-718 yoke pin experience a heat rate of 2.44 W/cm³. If stainless steel bolts are used, the bolt heads will experience 2.9 W/cm³, with only a small reduction from plugging the bolt access holes. If molybdenum bolts are used, the bolt head heating is increased to 3.4 W/cm³. The heating in the hinge parts and stainless steel bolts is expected to lead to temperatures higher than engineering limits. Due to a higher thermal conductivity and melting temperature, the Mo bolts are expected to operate at acceptable temperatures.