Power Transients of the HTR-10 During Reactivity Insertion ATWS Tests

Abstract

After the full power operation of the 10 MW High Temperature Gas-cooled Reactor-Test Module (HTR-10), two reactivity insertion tests were successfully conducted on this reactor by withdrawing a single control rod under 30% rated power. The reactor shutdown system was intentionally bypassed during such kind of tests, thus reflecting the anticipated transient without scram (ATWS) scenario. In the two tests, 1 and 5‰ ∆k/k positive reactivity were, respectively, introduced into the core by the control rod movement. In this study, post-test analyses are performed for the HTR-10 reactivity insertion ATWS tests using the THERMIX code. Both the analysis and the test results indicate that in the case of inadvertent control rod withdrawal the HTR-10 can be automatically shut down merely due to the negative reactivity feedback. The investigation of the reactor recriticality and the power oscillations in long term leads to a better understanding of the HTR-10 transients. For each test, the code reproduces the reactor power reasonably and accurately. Good agreement between the calculations and the tests proves the THERMIX simulation capability for the HTR-10 reactivity insertion ATWS tests.