NASA will test simple nuclear power system which will be in the 1 to 10 kilowatt power range

NASA's technology development branch has been funding a project called Kilopower for three years and testing is due to start in September, 2017 and end in January 2018.

NASA Game Changing Development program backed Kilopower, with the goal of building and testing a small fission reactor by Sept. 30, 2017, the end of the current fiscal year. The project is costing about $15 million.

The test reactor, which is about 6.5 feet tall (1.9 meters), is designed to produce up to 1 kilowatt of electric power, but to keep costs down, the test unit does not include a full array of Stirling engines to convert energy generated by the fission process into heat. Thermal simulators will be used for the balance of the engines to verify the reactor's power output

NASA recently completed a feasibility study for small fission power systems (FPS). As NASA is seeking game changing technologies to transform the nation's space mission capabilities, small FPS could reduce NASA's dependence on plutonium. A small kilowatt-class FPS could enable future flagship science missions and exploration precursor missions that may not otherwise be possible.

The objective of the proposed Nuclear Systems Kilopower Project is to advance the subsystem level readiness of small, 1-10 kWe fission power for space applications from TRL 2/3 to 5. Full success will consist primarily of demonstrating production of 150 We (90 We minimum) from 800 Wt heat supplied by a nuclear reactor through heat pipes to a Stirling engine pair, all in a relevant (thermal vacuum) environment.

Previous space reactor development programs (e.g. SP-100, Prometheus) have failed to complete the all-important system- level demonstration. The Nuclear Systems Project will demonstrate fission power subsystem technology readiness in a relevant environment for two classes of NASA's mission requirements: 10-100's kWe for exploration outposts and nuclear electric propulsion via the Technology Demonstration Unit (TDU), and 1-10 kWe for robotic science and small exploration systems (Kilopower).

The Nuclear Systems Kilopower Project consists of three elements. The primary element is the Kilopower Prototype Test. This element consists of the development and testing of a 1/4 electrical power output and full thermal power ground technology demonstration of a small fission power system based on an 800 We reference space science power requirement. The second element, the Mars Kilopower System Concept, consists of the analysis and design of a scaled-up version of the 800 We reference concept to 3-10 kWe for Mars surface power requirements. The third element is the design and development of a Kilopower high temperature water heat pipe radiator experiment prototype in preparation for a FY19 or later flight experiment development and test opportunity on the International Space Station.

The core of the Nuclear Systems Kilopower Project is the development and testing of a 1/4 power electric, full thermal power ground technology demonstration of a small fission power system based on an 800 We space science power requirement. An 800 We Kilopower system will use four pairs of Stirling engines, with each pair generating 200 We. All technology objectives can be achieved with only one pair of full-scale Stirling engines. The components of the demonstration include the reactor core, heat pipes to transfer the heat from the core to the power conversion system, the power conversion system, and the radiators to reject power conversion waste heat. Los Alamos National Laboratory will lead the design of the reactor, and the Y-12 National Security Complex will fabricate it. NASA Glenn Research Center (GRC) will design, build, and demonstrate the balance of plant heat transfer, power conversion, and heat rejection portions of the Kilopower Prototype. NASA MSFC will develop an electrical reactor simulator for non-nuclear testing, and the shielding for nuclear testing. A non-nuclear electrically heated demonstration of sodium heat pipe heat transfer, Stirling engine power conversion, and heat rejection will be assembled and tested at NASA GRC. Once the balance of plant has been tested and the reactor core has been fabricated, the balance of plant system will be reconfigured for a nuclear ground test, and the prototype will be assembled and tested at the Device Assembly Facility at the Nevada Nuclear Test Site.

Kilopower Fuel Design Goals and Requirements

The Kilopower space reactor fuel is to produce the right level of power while keeping the core small and light.

" Work neutronically
" Maintain geometry
" Transfer heat to the heat pipes

The fuel will not need to hold in fission products. No cladding is needed. It will not be used until it is in deep space.

Los Alamos published an analysis of the materials.

Fuel Burn Up, Swelling and Radiation Damage

The fuel will have almost no burnup over a 15 year life. Less htan 0.1% will be used.