Neutronic Modeling for Modular High Temperature Pebble Bed Reactor during Reactivity Accident

Abstract

Neutronic modeling for the modular high temperature pebble bed reactor during reactivity accident was investigated for safety analysis purposes. Three existing dynamic models, i.e. the point reactor, adiabatic and improved quasistatic models were compared with each other, and their accuracy was discussed, A one-dimensional numerical experiment was performed for simulating the severest reactivity accident involving withdrawal of all absorber rods in the reflector region. The results showed that the adiabatic model gave the highest estimation of the power excursion since it over-estimated the input reactivity worth. Although the point reactor model required the minimum computation time, it under-estimated the input reactivity worth and gave less accuracy in predicting the power excursion. The improved quasistatic model gave the highest accuracy and its computation time was comparable to the adiabatic model.

KEYWORDS:

• neutronic modeling
• modular high temperature pebble bed reactor
• reactivity accident
• reactivity worth
• safety analysis
• point reactor model
• adiabatic model
• improved quasistatic model
• numerical experiment
• computation time
• accuracy