Publications
Advanced Nuclear Power Program
Thermal Hydraulics and Shutdown Cooling of Supercritical CO2 GT-GCFRs
Y. Okano, P. Hejzlar, N.E. Todreas, and M.J. Driscoll
MIT-ANP-TR-088 (August 2002)
Abstract
Parametric studies on the thermal hydraulic performance of supercritical CO2-cooled fast reactor cores under both steady-state and post-LOCA conditions have been carried out as a first step in their iterative optimization. Balancing specific power of the reactor core under steady-state operation with maximum use of natural convection for passive system heat removal after a postulated LOCA were principal objectives.
It was found that even for core specific powers at the lower bound of fuel cycle economic practicality, approximately 25 kW/kgHM, fully passive post-LOCA natural convection cooling is practical only if CO2 coolant pressure exceeds approximately 4 atm. Cooling capacity increases roughly proportionally to pressure in the open loop model used in the present analysis.
Two core design options were considered: matrix and pin. For both the clad temperature constraint was found to be limiting. Matrix (i.e. coolant holes in a metallic block) cores have a larger post-LOCA grace period before effective cooling must be established, while conventional pin-type cores can achieve higher steady state power density.
Cooling effectiveness of supercritical CO2 (at 19 MPa) is nearly equal to He (at 7 MPa) under full power forced convection conditions. However, CO2 is 6 – 17 times more effective than He under 1 ~ 4 atm after a LOCA.
Optimizations of geometry (e.g. reducing core height) and of core thermal conditions using a complete loop transient analysis are identified as priority topics for the next round of studies.
