Thermal-hydraulic simulation of ITER tungsten divertor monoblock for loss of flow transient

•Thermal-hydraulic simulation is conducted on ITER tungsten divertor monoblock under loss of flow transient.•This transient is initiated by a trip of the main pump during plasma burn at an incident heat flux of 10 MW/m2.•The pump coast-down is represented by an exponential reduction in the coolant velocity with time constant, a = 5, 10, 15, 20 and 25 s.•The loss of flow leads the divertor coolant temperature to increase until FPSS shutdown the plasma at a coolant temperature of 170 °C.•The simulation is performed for a divertor of bare cooling tube and a divertor of cooling tube with swirl-tape inserts. The divertor is a fundamental component of a fusion tokamak reactor, being primarily responsible for power exhaust and impurity removal via guided plasma exhaust. In ITER reactor, it receives a very high heat load arising from the plasma (up to 20 MW/m2) and needs sufficient cooling by its cooling system to maintain divertor integrity during normal operation and accidental conditions. Therefore; attention should be paid to the thermal–hydraulic design of the divertor cooling system. In this work, thermal–hydraulic simulation and safety analysis have been carried out on ITER tungsten divertor monoblock in order to predict the thermal response of its structural materials under loss of flow transient using a model developed in a previous work. This transient is initiated by a trip of the main pump during plasma burn at an incident heat flux of 10 MW/m2 at the divertor surface and a coolant velocity of 16 m/s. The pump coast-down is represented by an exponential reduction in the coolant velocity with time constants of 5, 10, 15, 20 and 25 s that cover almost all possible pump coast-down flow. The loss of flow leads the coolant temperature to increase because of continue plasma operation at full power until the Fast Plasma Shutdown System (FPSS) shutdown the plasma at a coolant temperature trip limit set point (170 °C). The plasma shutdown leads to an intense plasma disruption of 20 MW/m2 incident surface heat flux within time assumed to be 1 s. The simulation is performed for a divertor of bare cooling tube and a divertor of cooling tube with swirl-tape inserts. The results show that, the divertor structure materials will be melted in case of bare cooling tube for all the proposed coast-down flow while the divertor with swirl-tape tube can overcome this transient safely. The results of this study are important to designers and analysts in order to design and ev