B - PLUTO
Lawrence Livermore National Laboratory is the leading proponent of the PLUTO Derivative, PLUTO/NERVA Derivative Reactor, and UB2 Reactor concepts, which have been evaluated for SDI power applications.(1) These reactor concepts draw on the experience LLNL accumulated in the PLUTO nuclear ramjet program in the 1960s. Along with Idaho National Engineering Lab, Livermore has also investigated Fission Fragment Rockets of the type advocated by Sandia.(2)
B - 710 REACTOR PROGRAM
The General Electirc 710 reactor program was initiated in 1962, to capitalize on the ceramic fuel elements developed under the Aircraft Nuclear Propulsion program.(3)
The initial goal of the program was the development of fuel elements for both open and closed cycle fast spectrum reactor systems. Primary characteristics included:
Cycle Open Closed
Operating Temperature 2750o K 2420o K
Operating Time 10 hours
Coolant hydrogen inert gas
Restart Cycles 100 100
The selected fuel element was a tungsten matrix impregnated with UC2, with a tantalum cladding to provide structural support, protect the fuel from hydrogen erosion, and retain fission products. Subsequent development focused on a sintered tungsten fuel particle with a diameter of 1-2 microns.
However, before testing could begin on these configurations, program objectives were reoriented toward development of a closed cycle neon-cooled 10 MW reactor with an outlet temperature of 2420 K.
Program objectives were again reoriented in July 1965, when the goal was established of developing a reactor with a 200 kWe output over a 10,000 hour lifetime. Use of a Brayton conversion cycle mandated a core operating temperature of 2000 to 2250 K. Uranium Nitride was substituted for Uranium Oxide as the fuel.
This program was cancelled in 1967, after having conducted some testing of fuel particle elements.
1. Marshall, A.C., "A Review of Gas-Cooled Reactor Concepts for SDI Applications," SAND87-0558, (Sandia National Laboratory, Albuquerque, NM, August, 1989).
2. Chapline, George, et al, "Fission Fragment Rockets -- A New Frontier," 50 Years With Nuclear Fission, National Academy of Sciences and National Institute of Standards & Technology conference, 25-28 April 1989, (American Nuclear Society, La Grange Park, IL, 1990), pages 601-605.
3. Horman, F.J., et al, "Particle Fuels Technology for Nuclear Thermal Propulsion," AIAA/NASA/OAI Conference on Advanced SEI Technologies, Cleveland, Ohio, 4-6 September 1991, Paper AIAA 91-3457.