Activation analysis of coolant in a water-cooled loop of China fusion engineering test reactor

摘要

In the design scheme of China Fusion Engineering Test Reactor (CFETR), water will be adopted as the coolant in some cooling loops. The water itself and the impurities in it will be activated by neutrons, and the activation products16N,17N,3H and14C are important to the occupational radiation exposure (ORE) during operation and maintenance. In this paper, two analysis models (homogeneous model and two-node model) are developed to calculate the radioactivity of activation products in the water-cooled loop. Then, the impact of water chemistry parameters (pH and7Li abundance) on tritium production is analyzed. At last, the dose rate of one typical blanket water-cooled loop is calculated using the point kernel code ARShield. The results show that: (1) the radioactivity of short-lived nuclides16N and17N is obviously affected by coolant flow and the results from the two-node model considering coolant flow are more conservative; (2) the radioactivity of long-lived nuclides3H and14C is obviously affected by purification; (3)16N and17N are the main contributors to radioactivity, whose radioactivity are several orders of magnitude higher than that of3H and14C; (4) tritium is susceptible to water chemistry environment, and at pH of 7.1 tritium radioactivity is about two orders of magnitude higher than that at pH of 5.7; (5) at pH of 7.1, the contribution of lithium to tritium production increases linearly with increase of7Li abundance in LiOH in the water.