Calculations of maximum temperature in centerline of nuclear fuel ROD and fissile fuel enrichment in hybrid reactor

الملخص EN

Behavior of nuclear fuel material and temperature distribution in fuel rods are observed over 4 years for a discrete time interval of Δt = 15 days, different coolants, and volumetric ratio ε (ε = Vm/Vf ) by a plant factor (PF) of 75% under various first wall loads (Pw = 2, 5, 7, 8, 9, and 10 MWm–2).

The fissile fuel zone in a hybrid reactor fueled with UO2 is considered to be cooled with four different coolants, gas (He, CO2), flibe (Li2BeF4), natural lithium (Li), and eutectic lithium (Li17Pb83).

Plasma chamber dimension, DR, with a line fusion neutron source is 300 cm in hybrid system.

All neutronic calculations have been done with four different coolants mentioned above and three different coolant-to-fuel volumetric ratio ε simultaneously.

ε = 1:1 (45.515% coolant, 45.52% fuel, 8.97% clad), ε = 1:2 (29.46% coolant, 58.92% fuel, 11.61% clad) and ε = 2:1 (62.56% coolant, 31.28% fuel, 6.17% clad).

As a result of the calculations, the best CFFE (11.15%) is obtained in gas coolant blanket for ε = 1:2 under 10 MWm–2 first wall load, followed by flibe with CFFE = 11.08% for ε = 2:1 under 7 MWm–2 first wall, and eutectic lithium with CFFE = 10.81% for ε = 1:2 under 7 MWm–2 first wall load, and natural lithium with CFFE = 10.03% for ε = 1:2 under 8 MWm–2 first wall load, without reaching the melting point of the fuel material during the operation period.

Melting point of the fuel materials has been exceeded in a short operating period in the blankets cooled with flibe and eutectic lithium for all ε, Tc > 500°C, and Pw > 7 MWm–2, since the temperature at the centerline of the fuel rods has been reached the higher temperature values, whereas it has been exceeded in gas and natural lithium coolant blankets for Pw > 10 MWm–2 and ε = 1:2 after 48 months, and Pw > 9 MWm–2 and ε = 2:1 after 44 months respectively.

In all investigated cases, TBR values are higher than unity.

Therefore, investigated hybrid blankets are self-sufficient for all coolant and volume fraction for Pw > 5 MWm–2.

The best neutron economy has been shown by flibe.

The isotopic percentage of 240Pu is higher than 5% in all blankets for Pw = 7 and Pw > 7 MWm–2, so that the plutonium component in all blankets can never reach nuclear weapons grade quality during the operation period.