Activation analysis of coolant water in ITER blanket and divertor

Coolant water in blankets and divertor cassettes will be activated by neutrons during ITER operation. ¹⁶N and ¹⁷N are determined to be the most important activation products in the coolant water in terms of their impact on ITER design and performance. In this study, the geometry of cooling channels in blanket module 4 was described precisely in the ITER neutronics model 'Alite-4' based on the latest CAD model converted using MCAM developed by FDS Team. The ¹⁶N and ¹⁷N concentration distribution in the blanket, divertor cassette and their primary heat transport systems were calculated by MCNP with data library FENDL2.1. The activation of cooling pipes induced ¹⁷N decay neutrons was analyzed and compared with that induced by fusion neutrons, using FISPACT-2007 with data library EAF-2007. The outlet concentration of blanket and divertor cooling systems was 1.37 × 10 ¹⁰ nuclide/cm ³ and 1.05 × 10 ¹⁰ nuclide/cm ³ of ¹⁶N, 8.93 × 10 ⁶ nuclide/cm ³ and 0.33 × 10 ⁵ nuclide/cm ³ of ¹⁷N. The decay gamma-rays from ¹⁶N in activated water could be a problem for cryogenic equipments inside the cryostat. Near the cryostat, the activation of pipes from ¹⁷N decay neutrons was much lower than that from fusion neutrons.