Abstract
SNCLFR-100 is a small modular natural circulation lead-cooled fast reactor, developed by University of Science and Technology of China, aiming at taking full advantage of the good economics and inherent safety of lead-cooled fast reactors to develop miniaturized, lightweight and multi-purpose special nuclear reactor technology. SNCLFR-100 is still in the conceptual design stage, in order to fully evaluate the safety features of the reactor and provide reference for the optimization design of the next stage, three typical transients are selected based on the analysis of the SNCLFR-100 initiating events by using the code Analysis of Thermal-hydraulics of Leaks and Transients (ATHLET), which are unprotected transient overpower (UTOP), unprotected loss of heat sink (ULOHS) and unprotected partial blockage in the hottest fuel assembly. For UTOP, the unexpected positive reactivity insertion of 0.7$ in 15s led to two large power peaks in the core quickly, and then the core power began to decrease and gradually stabilized under the action of various of negative feedbacks of the reactor, the peak temperatures of fuel and cladding rose rapidly with the increase of core power and eventually stabilized at a higher temperature. For ULOHS, as the reactor were driven by natural circulation, the coolant mass flow rate continued to decline after the transient, both core and cladding temperatures rose quickly and the temperature rise were smaller than that of UTOP transient, the reactor shutdown by itself and the peak temperatures of fuel and cladding were smaller than the safety limit. For unprotected partial blockage in the hottest fuel assembly, with the increase of the blockage rate of the hottest fuel assembly inlet, the coolant flow rate, the peak temperatures of coolant, fuel and cladding increased significantly, when the blockage rate increased to 0.9, the coolant flow rate of the hottest fuel assembly dropped to about 12.6% of the normal value, and the cladding peak temperature would exceed the cladding melting point, measures should be taken to avoid the happening of severe accident.
Highlights
The Lead-cooled Fast Reactor (LFR) is one of the innovative systems envisaged by the Generation IV International Forum (GIF) in order to provide sustainable, safe and proliferation resistant nuclear energy production (Lorusso et al, 2018; Zhang et al, 2019)
For SNCLFR-100, a total of six transients were selected as representative of all identified design extension condition (DEC) transients reflecting a wide range of potential transient initiators using the main logic diagram method (MLD) (Kangli, 2017), these transients include several unprotected transients such as unprotected transient overpower (UTOP), unprotected loss of heat sink (ULOHS) etc
Unlike the driving cycle lead-cooled fast reactor, the ULOHS accident of the natural circulation leadcooled fast reactor will indirectly cause the loss of flow of primary loop and lead to core temperature rise
Summary
The Lead-cooled Fast Reactor (LFR) is one of the innovative systems envisaged by the Generation IV International Forum (GIF) in order to provide sustainable, safe and proliferation resistant nuclear energy production (Lorusso et al, 2018; Zhang et al, 2019). In China, a 10 MWth lead-based research reactor named China Lead-based Reactor (CLEAR-I), proposed by the Institute of Nuclear Energy Safety Technology, was selected as the reference reactor for ADS development, as well as the technology development of the Generation IV lead-cooled fast reactor (Smith et al, 2008). For natural circulation LFRs, the outstanding inherent safety performance can greatly reduce the construction and operation difficulty of LFR, and provide a good technical route for the engineering and commercialization of LFR as soon as possible. Part of LFR design and operation, it can be seen from the open literature that the current transient analysis of leadcooled fast reactors (LFRs) is mainly aimed at forced circulation LFRs, while the research on the transient thermalhydraulic safety performance of natural-cycle lead-cooled fast
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