Global dose rate assessment in ITER diagnostics ports based on the 3-D FEM ATTILA code

The USITER, through the Princeton Plasma Physics Lab (PPPL), is responsible for the delivery of several fully integrated upper, equatorial and lower port plugs dedicated for the diagnostics in ITER. Each port plug package consists of a generic port plug structure and a set of diagnostics and diagnostic housings. The shielding design of the integrated port plugs calls for maintaining a dose level not to exceed 100 μSv/h inside the interspace of each port; the room behind the port plug where maintenance personnel access the rear of the port. This is set as an upper target design in order to perform routine maintenance 1E6 sec (～two weeks) following shutdown. Expensive remote handling robots and tooling are required otherwise. In this paper we present results from a parametric study aimed at providing initial assessment of the attainable dose rates in the diagnostics ports and their extension areas in order to properly address the duration time and frequency for the workers to perform the scheduled maintenance. The nuclear analysis is performed using both the serial version and the distributed memory parallel (DMP) version of the ATTILA-7.1.0, 3-D FEM Discrete Ordinates code, along with the FENDL2.1/FORNAX and ANSI/ANS-6.1.1-1977 data bases.