Reactivity Management in APR-1400 during Transient Operation

  • Hasan Alnuaimi

    Student thesis: Master's Thesis


    APR-1400 Nuclear Power Plants (NPPs) are planned to operate in the Baseload Operation (BO) mode. Baseload power generating plants means that it will operate at the designed full power for the whole period of cycle length without much consideration to demand changes. On the other hand, Load Following Operation (LFO) is meant to operate at a varying power scheme in which power level is changed once or twice daily to a lower power level (up to 50% or less from the rated power) than designed full power to meet the changes in power demand. The reactor will remain at that power level for a short period where demand is low, and then return to the designed full power with a ramp rate of up to 5%/min. This can be done by reducing the power through control rods movement and then control boron concentration to compensate for Xenon changes in the reactor core. Having an automated power control system to support daily LFO is significant to minimize intervention by NPP personnel working to control power during the evolution. Utilizing Part Strength Control Element Assemblies (PSCEAs) with auto adjustment of Boron concentration is needed to maintain daily load following Axial Offset (AO) within permitted band that accounts for Xenon concentration changes with power maneuvering. Many researches on power control systems utilized the two-point reactor model in a way to support automation of power maneuvering during LFO. However, in this research paper the different control methods were investigated and Casmo-4/Simulate-3 code was utilized to run different simulations. Simulations confirmed that PSCEAs will maintain AO within band following a (1-6-1-16) maneuvering strategy where power reduction and increase is done within an hour to stabilize first at a lower power target for 6 hours then go back to 100% power level for 16 hours of operation. On the other hand, the (2-6-2-14) maneuvering strategy simulations showed more deviations in AO from the initial value. Simulations of different scenarios were initiated to analyze reactor core behavior, where reactivity control strategies have been established.
    Date of AwardMay 2020
    Original languageAmerican English


    • LFO
    • PSCEAs
    • AO
    • Reactivity
    • and Boron Concentration.

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