CANFLEX : A new CANDU fuel bundle with expanded operating capabilities

CANFLEX1 is a 43-element CANDUR bundle, which is being developed jointly by AECL and KAERI, to facilitate the use of various advanced fuel cycles in CANDU reactors through the provision of enhanced operating margins in the bundle design. This 43-element bundle design uses two diameters of elements (13.5 and 11.5 mm) to reduce element ratings by 20%, yet maintain the same bundle power, and a uranium content very close to that of a standard 37-element bundle. The CANFLEX design also includes the use of critical-heat-flux (CHF) enhancing appendages, to increase the minimum CHF ratio, or dryout margin of the bundle. The combination of these two features also makes the CANFLEX bundle of interest for use in older CANDU reactors, where it can compensate for any operating margin lost because of steam-generator fouling or pressure tube creep. The program to develop and demonstrate the CANFLEX bundle is currently at the stage of separate, bundle demonstration tests, including demonstration irradiation in the NRU reactor, flow testing in the KAERI hydraulics laboratory, reactor physics characterization tests in the ZED-2 reactor, fuelling machine compatibility tests at the Sheridan Park Engineering Laboratory, and CHF tests in a thermal hydraulics Laboratory at Chalk River. A dialogue is underway with utilities, focussed on the demonstration irradiation in power reactors, and to support this, a Fuel Design Manual and other safety analysis reports are being prepared