Thermal Hydraulic and Safety Assessment of First Wall Helium Cooling System of a Generalized Test Blanket System in ITER Using RELAP/SCDAPSIM/MOD4.0 Code

The key objective of the test blanket module (TBM) program is to develop the design technology for DEMO and future power-producing fusion reactors. The proposed first wall of the test blanket system (TBS) is a generalized concept for testing in ITER, an experimental fusion reactor under construction in France presently. The first wall of TBM (TBM FW) directly faces the plasma and is cooled by the first wall helium cooling system (FWHCS), which is considered as a critical component from an ITER safety point of view. The scope of this work comprises thermal hydraulic analysis of the FWHCS of a generalized TBS and the assessment of postulated initiating events (PIEs) on the ITER safety with the help of thermal-hydraulic code RELAP/SCDAPSIM/MOD4.0. The three reference accidents: in-vacuum vessel (VV) loss of coolant accident (in-vessel LOCA), ex-vessel LOCA, and loss of flow accident (LOFA) in FWHCS are selected for the safety assessment. This safety assessment addresses safety concerns resulting from FWHCS component failure, such as VV pressurization, TBM FW temperature profile, pressurization of port cell (PC) and Tokomak cooling water system vault annex (TCWS-VA), and passive decay heat removal capability. The analysis shows that the critical parameters are under the design limit and have large safety margins, in the investigated accident scenarios. A comparative analysis is also carried out with the previous results to validate the results.