Analysis of Reactivity Insertion Accident of Kartini Research Reactor using RELAP5 Sutanto (a*), Handika Dito Aulia Baihaqi (a), Anhar Riza Antariksawan (a)
(a) Polytecnic Institute of Nuclear Technology, National Research and Innovation Agency, Indonesia
(*) Corresponding author: suta012[at]brin.go.id
Abstract
Kartini research nuclear reactor is operated by National Research and Innovation Agency of Indonesia (BRIN) with the main purpose for education and training. A lot of students from departments of physics or nuclear engineering/science frequently uses the reactor for hands on activity related to reactor physics course. Therefore, reliability of the reactor operation in safety view is important to make sure the satisfaction of the safety standard in normal and abnormal conditions. Excess reactivity insertion is a possible accident to occur due to uncontrolled withdrawal of the control rods. It might lead to a very high temperature of the fuel and the fuel cladding which could affect the integrity of the fuel rod. This research has a purpose to analize the accident of reactivity insertion of the Kartini research reactor. A RELAP 5 code is used for the analysis. A calculation model is developed based on the Kartini reactor structure and applied in the RELAP5 code. Stepwise increases of the reactivity by 0.5 dollars (-) and 1.0 dollars (-) are simulated for the accident with two scenarios of the safety system responses, which are with and without SCRAM (rapid drop of control rods) actuation. The effects of the accident on the fuel and cladding temperatures are calculated. Calculation results show that higher reactivity insertion accident with SCRAM actuation leads to a tolerable fuel and cladding temperature increase, which is much lower than the safety citerion of 700 oC. When the SCRAM actuation is assumed to fail, the accidents effect higher fuel and cladding temperatures due to the absence of the negative reactivity feedback from the control rods. However, the temperature increases still satisfy the safety criterion. Kartini research reactor has a low thermal power of 100 kW with large volume of light water as the coolant. The accidents will be inherently mitigated by large negative reactivity of coolant density and Doppler, even in the failure of SCRAM actuation.
