Burn-up effect on inherent safety parameters and reactivity insertion transient analysis of Pakistan Research Reactor-1

Burn-up dependent feedback coefficients of reactivity for the reference operating core of Pakistan Research Reactor-1 (PARR-1), have been calculated employing standard computers codes WIMSD/4 and CITATION. Fast reactivity insertion transient (1.5 $/0.5 s) is simulated at each burn step using computer code RELAP5/MOD3.4 and PARET. Calculation reveals that fuel temperature coefficient of reactivity is 1.77 %Δk/k/ΔT less negative while moderator temperature and void coefficients of reactivity are 7.74 %Δk/k/ΔT and 2.04 %Δk/k/ΔT more negative at end of cycle (EOC), respectively. Fast reactivity insertion transient analysis shows that due to larger value of prompt generation time (Λ), reactor response to transient is slow at EOC. Therefore peak power, maximum fuel centreline and clad temperature decrease as the fuel is burned. This is the sign of enhanced inherent safety with the burn-up of reference operating core of PARR-1. Removal of in-pile experiment accident has also been modelled in RELAP5/MOD3.4 and results in this study are compared with PARET.

► Burn-up dependent feedback coefficients of reactivity for PARR-1 reference operating core are analyzed.
► Consequences of fast reactivity insertion at different burn-up steps are simulated.
► Comparative study by RELAP5/MOD3.4 and PARET/ANL.
► At EOC kinetic parameters ratio (βeff/Λ) is decreasing, mitigating the consequences of reactivity insertion accident.