Original Date: 04/26/1999
Revision Date: 01/18/2007
Information : Nuclear Fuel Element Simulation
Marshall Space Flight Center (MSFC) is currently testing various forms of alternative propulsion methods. One such method is the Heatpipe Bimodal System (HBS), designed for nuclear thermal propulsion. The Center’s objective is to fabricate and electrically test an HBS module in order to determine its design limits and operational characteristics. Several modules will then be grouped together in a quarter core arrangement to investigate the interactions between the modules under various operational and fault modes.
The HBS uses specially designed fuel pins which essentially allow for complete system testing using electrical heaters. This approach eliminates the need for large, expensive nuclear qualified test facilities. In addition, the HBS is designed with proven fuel technologies in a modular system which reduce costs and development risks. The HBS is a near-term, low-cost, nuclear electric power and thermal propulsion system that can provide moderate levels of thrust and power for many space applications. Heat generated in the fuel is transferred by conduction to the primary module heatpipes. Propulsion is obtained by flowing hydrogen through the interstitials of the core. The system (Figure 3-4) is a 100 kWt-uranium oxide fueled concept that can deliver 250 Newtons of thrust at a specific impulse of 800 seconds. A vacuum gap surrounds the heatpipe to prevent hydrogen ingress and undesirable heat transfer.
Currently at MSFC, an electrically heated fuel element in a power-only configuration HBS has been tested to 1400° K in a vacuum. The Center is also in the process of constructing an HBS module along with a test chamber, that will be capable of electrically testing a full core HBS. Over the next two years, MSFC plans to electrically test a quarter core and possibly a full core HBS configuration to understand the details of heat transfer and fluid flow interactions within the core. The Center also expects to conduct zero power critical testing of an HBS module to determine the neutron flux distributions and criticality limits.
Figure 3-4. Heatpipe Bimodal System 5-pin Module
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