b'FAST Irradiation Test Assembly Development,Fuel Fabrication and Trials Principal Investigators: Randall Fielding and Blair Grover (INL)Team Members/ Collaborators: Korbin Tritthart, Steve Steffler and Darrell Jonak (INL); Elliott Marsden (INL Intern)T he Fission Accelerated Steadyto 50 rodlets the process must be State Test (FAST) was designedconsistent and time efficient as this to greatly increase the burnupis a very large increase in number The fuel fabricationrate of fuel, which can lead to anof samples. The test design calls for package has shown theaccelerated qualification path. Inthe sodium bonded fuel slugs to feasibility of fabricatingaddition to increased burnup rate,be 0.084 in. (2.13 mm) diameter the FAST rodlets,FAST is also designed to greatlyand 0.75 in. (19.05 mm) in length. enabling the numberincrease the number of samples thatA fuel casting method is needed to of rodlets in an integralcan be irradiated in a test position.consistently produce these fuels. Many fuel irradiation test toBoth of these attributes have beenof the test specimens will be sodium increase dramatically. accomplished by reducing the samplebonded. Again, as with casting due to size to be irradiated. Decreasing thethe number of samples and the small size of the fuel samples and increasingsize, a consistent manner of loading the total number of samples to beand eventually bonding the rodlets inserted in the reactor increasesis needed that can be used for tens fabrication difficulties and scheduleof samples in an efficient manner. risks. Work this year has focusedThe cladding walls are designed to be on fuel sample casting and rodlet0.009 in. (0.23 mm) thick and will assembly, including loading, welding,be welded to a solid endplug. Welding and sodium settling and bonding. of a thin walled tube to a solid plug Project Description: is difficult and must be demonstrated Work in this area showed thebefore test fabrication can begin. feasibility of fabrication of the FASTAs these steps are demonstrated the rodlet despite the increased difficulty.feasibility of fabricating the FAST Feasibility was shown by developingrodlets will also be demonstrated and methods for casting, rodlet loading,optimized to allow the FAST test to be closure welding, and finally sodiumfabricated and inserted on schedule. bonding. Reduced diameter claddingThe FAST tests will greatly increase was also fabricated. Mock-up testthe amount of high burnup data on hardware is shown in Figure 1. Inmetallic fuel alloys and because of the addition to simply developing aincrease in the number of samples the process, because the tests call for uptests will be used as a scoping test for advanced reactor fuels.172 2019|AFC ACCOMPLISHMENTS'