The Fast Flux Test Facility (FFTF) was authorized by Congress in 1967. The FFTF is intended to test nuclear fuels and materials most apt to work safely and economically in future breeder reactors. The Energy Research and Development Agency believes that 37- and 19-pin tests will be adequate for closed loop test purposes; and 37-pin tests will provide valid and useful data for establishing design and operating limits. The construction project is now estimated to cost $540 million instead of the $87.5 million originally projected, and supporting costs are estimated at an additional $613 million. More than $200 million in breeder reactor program costs should also be recognized as FFTF costs. Since authorization, the project's completion date has been extended by more than 5 years to August 1978. Technical problems with major components of the heat transport system remain.