Final Report - Assessment of Testing Options for the NTR at the INL

Abstract

Executive SummaryOne of the main technologies that can be developed to dramatically enhance the human exploration of space is the nuclear thermal rocket (NTR). Several studies over the past thirty years have shown that the NTR can reduce the cost of a lunar outpost, reduce the risk of a human mission to Mars, enable fast transits for most missions throughout the solar system, and reduce the cost and time for robotic probes to deep space. Three separate committees of the National Research Council of the National Academy of Sciences have recommended that NASA develop the NTR. One of the primary issues in development of the NTR is the ability to verify a flight ready unit.Three main methods can be used to validate safe operation of a NTR, after which a fully complete engine could be launched into orbit for the first full power test. The NTR testing options include 1) Full power, full duration test in an above ground facility that scrubs the rocket exhaust clean of any fission products;2) Full power , full duration test using the Subsurface Active Filtering of Exhaust (SAFE) technique to capture the exhaust in subsurface strata;3) Test of the reactor fuel at temperature and power density in a driver reactor with subsequent first test of the fully integrated NTR in space.The first method, the above ground facility, has been studied in the past [Rocketdyne, INL, MSFC]. The second method, SAFE, has been examined for application at the Nevada Test Site.The third method relies on the fact that the Nuclear Furnace series of tests in 1971 showed that the radioactive exhaust coming from graphite based fuel for the NTR could be completely scrubbed of fission products and the clean hydrogen flared into the atmosphere.Under funding from the MSFC, the Center for Space Nuclear Research (CSNR) at the Idaho National laboratory (INL) has completed a reexamination of Methods 2 and 3 for implementation at the INL site. In short, the effort performed the following:Assess the geology of the INL site and determine a location suitable SAFE testing; Perform calculations of gas transport throughout the geology; Produce a cost estimate of a non-nuclear , sub-scale test using gas injection to validate the computational models;Produce a preliminary cost estimate to build a nuclear furnace equivalent facility to test NTR fuel on a green field location on the INL site.Reexamination of Method 3, involving test of the reactor fuel in a driver reactor indicated that a new Category I facility would be required, which would cost in excess of $250M. Reexamination of Method 2, showed that the INL geology is substantially better suited to the SAFE testing method than the NTS site. The existence of impermeable interbeds just above the sub-surface aquifer ensure that no material from the test, radioactive or not, can enter the water table. Similar beds located just below the surface will prevent any gaseous products from reaching the surface for dispersion. The extremely high permeability of the basalt strata between the interbeds should allow rapid di...