Design Space Exploration for Salt Cooled Reactor Systems

Fluoride salt-cooled Hight-temperature Reactor (FHR) is a new concept that has seen growing interest as a potential candidate to improve on the safety and economics of existing reactors. It has been suggested that FHR can benefit from advanced Gas-cooled Reactor (AGR) technologies and by that reducing the scale and time of the required R&D. This thesis contributes to the global FHR development effort by proposing and investigating an AGR-like FHR concept. It explored the thermal-hydraulic and neutronic design space of a number of AGR-like FHR assembly options covering combinations of three fuel geometries: 1) solid pin, 2) annular pin and 3) plate type fuel; three coolant options: 1) FLiBe 2) FLiNaK and 3) NaF-ZrF4, and three fuel forms: 1) Uranium Dioxide (UO2), Uranium Carbide (UC), and Fully Ceramic Microencapsulated (FCM) fuel. A package of thermal-hydraulic operating domain search and design optimisation codes was created that can identify the optimum primary and secondary loop operating condition and the corresponding maximum power and Levelised Cost of Electricity (LCOE) of the reactor. Based on preliminary thermal-hydraulic test results, which ruled out some of the design options, a series of neutronic analyses were carried out to further narrow down the design space. Neutronic simulations were first performed at Beginning of Life (BOL) conditions to identify design streams that demonstrated potential for the most favourable fuel cycle economic performance and/or other strategic advantages such as accident tolerance of FCM fuels or tritium-free NaF-ZrF4 coolant. Depletion calculations were then performed for the best performing neutronic designs at BOL. Constrained by reactivity coefficients and burnup while targeting high burnup-to-enrichment ratios (BU/e), four optimised neutronic design streams were recommended: 1) solid UC fuelled FLiBe cooled FHR, 2) solid FCM fuelled FLiBe cooled FHR, 3) annular FCM fuelled FLiBe cooled FHR and 4) solid UC fuelled NaF ZrF4 cooled FHR. Thermal-hydraulic calculations were then carried out for these design streams to produce coupled design optimisation. Final optimisation results suggest that solid FCM pin fuelled FHR with FLiBe in AGR-like assemblies is the best design option among all, delivering thermal powers from 16349 MWt to 28861 MWt (~21 times iv power uprate from AGR), LCOEs from 35.3 £/MWh to 41.7 £/MWh (less than half of the Hinkley Point C strike price of 92.5 £/MWh) and BU/e ratios from 7.2 MWd/kg to 9.5 MWd/kg, which is comparable to the current fleet of Light Water Reactors (LWRs). Other design streams offer advantages in other aspects such as being tritium-free or having more manageable on-power refuelling schemes or even lower LCOEs

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2021

Author dc:creator

• Xing, Zhiyao

Advisor dc:contributor.advisor

• Shwageraus, Eugene

• salt-cooled nuclear reactors
• neutronic design
• thermal-hydraulic design
• FHR
• high power density
• constrained optimisation

Licence

• https://www.rioxx.net/licenses/all-rights-reserved/

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.80369

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/332939