Study on anti-disturbance capacity of LBE cooled double loop natural circulation system under asymmetric conditions

Abstract

Heat exchangers in natural circulation LBE-cooled fast reactors are used in harsh conditions such as extreme temperatures, significant pressure differences, high density, and corrosive environments. Therefore, heat transfer tube rupture and flow blockage accidents are common and result in an asymmetric heat load or asymmetric resistance thereby significantly impacting the safe and stable operation of the reactor.In this study, SNCLFR-10 has been used as the reference reactor and FLUENT simulation is used to establish the LBE-cooled dual-loop natural circulation system. Consequently, a theoretical solution of the natural circulation flow of a dual-loop system (TSNCD) is deduced using dimensionless analysis.The TSNCD theoretical solution is verified by using a dual-loop natural circulation system established via FLUENT simulation. Subsequently disturbance characteristics of the natural circulation system under different heat load differences or resistance differences are analyzed. The characteristic parameters representing the anti-disturbance capacity of natural circulation are determined using fitting approximation, and the best anti-disturbance interval is obtained.The results show that the TSNCD theoretical calculation formula of dual-loop natural circulation flow is extremely reliable, and the error between the calculations and the FLUENT simulation result is less than 5 %.When an asymmetric heat load disturbance and asymmetric resistance disturbance are incorporated into the system together or alone, the loop flow changes insignificantly in a certain interval; the anti-disturbance capacity of the system is strong in this interval. The resistance of the system to heat load disturbance is 0.2<k1<0.8, and the resistance disturbance is 0.6<B<4.8. When an asymmetric heat load and asymmetric resistance disturbance are simultaneously introduced into the system, an optimal resistance disturbance is achieved (k1∈[0.40,0.60] and B∈[0.7,2.9]).