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Testing Options for Nuclear Thermal Propulsion Systems

NERVA Program. Four reactor test series to demonstrate Basic nuclear technologyKIWIPhoebus Pewee-1 Nuclear Furnace-1 KIWI, Phoebus, and Pewee-1; open cycle systems and exhausted their effluent into the atmosphere Nuclear Furnace-1 used an effluent treatment systemBetween 1959 and 19

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Testing Options for Nuclear Thermal Propulsion Systems

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    1. Testing Options for Nuclear Thermal Propulsion Systems

    2. NERVA Program Four reactor test series to demonstrate Basic nuclear technology KIWI Phoebus Pewee-1 Nuclear Furnace-1 KIWI, Phoebus, and Pewee-1; open cycle systems and exhausted their effluent into the atmosphere Nuclear Furnace-1 used an effluent treatment system Between 1959 and 1972, the Space Nuclear Propulsion Office oversaw 23 reactor tests

    3. Why Build a Nuclear Rocket? Three times the ISP of chemical engines its have been shown to be: Faster Reduced Transit times for long stay missions Reduced round trip times for short stay missions for the same initial mass to low earth orbit (IMLEO) Cheaper Reduced IMLEO requirements for the same mission duration Greater mission flexibility for VSE Mars (cargo and especially piloted) missions with respect to departure windows Fewer launches required Fewer supplies, equipment, power needed Better One propulsion system capable providing a step change capability in meeting many exploration mission needs Technology within developmental timeframe Reduced exposure for manned missions

    4. Basic Options Ground test with the US Ground test remotely (i.e. in an ocean) No ground test

    5. Elements of a Ground Test Facility Facilities Containment Building Control Building Test Cell Exhaust Treatment System Hydrogen Supply System Cold Engine Assembly Building Hot Engine Disassembly Building other support systems and buildings Dependent on size (thrust), thermal power level and duration NTR engine physical size modestly affects size of containment building

    6. Test Facility Concepts Above Ground Effluent Treatment System (ETS) Subsurface Active Filtration of Exhaust (SAFE) Test Facility Other?

    7. Effluent Treatment Systems Needs Cooling the hydrogen effluent Removing particles from the gas flow stream Further reduction of the temperature Removing the water and dissolved fission products Removing the noble gases Flaring the exiting hydrogen stream (containing no detectable fission products)

    8. SNTP Effluent Treatment System for 550 MWt

    9. Parametric Estimation of ETS Costs

    10. Subsurface Active Filtration of Exhaust (SAFE) Test Facility Filtration of the engine exhaust using the NTS alluvium soil / rock as the holdup and active filtration medium relies upon the alluvial soil characteristics to filter the effluents from the NTR exhaust Nozzle exit is sealed at the surface Exhaust pressure will drive exhaust and water vapor into the porous soil or rock at a rate equal to the NTR mass flow Could be operated for long periods over a wide range of engine thrust levels

    11. SAFE Facility Description Uses a borehole 8 feet in diameter by 1200 feet deep Upper 100 feet would be steel encased Cooling water would be sprayed into the borehole to limit the exhaust temperature Maximum back pressure buildup in the borehole would be 36 psi Independent study by the Desert Research Institute (DRI): Some radionuclides would reach the surface within several years after injection but, at acceptably allowable levels for the NTS

    12. Comparison between ETS and SAFE ETS Pros: No large quantity of contaminated liquid effluent will be generated. Altitude simulation may be possible with this system. A center for ground testing with dedicated test facilities could be established for NTP systems up to the design rating. Performance of the system will be well characterized after initial testing. Cons: Large quantities of liquid hydrogen will be required for each test. Large, complex effluent filtration systems have not yet been demonstrated. Public acceptance of once through exhaust treatment with discharge to the atmosphere may be challenging. Containment isolation system during abnormal events may be complex.

    13. Comparison between ETS and SAFE SAFE Pros: No active effluent treatment system required. Existing boreholes are available. Less hydrogen will be required per test. Potential for significant costs savings Cons: Further studies could show the need for waste coolant water removal and a filtration system. Boreholes may have limited reuse capability and require relocation of certain GTF assets, (e.g., portable containment structure). Monitoring of borehole alluvial soil performance during and after testing will be required.

    14. Next Steps Fuel Development - driving force for the design of the effluent treatment system will be the integrity of the fuel under normal operating and abnormal operating conditions. Limited information available as to how much of the halogen or noble gases can be retained in the fuel (needed for both ETS and SAFE) Demonstration of Subsurface Filtration System - a subscale proof of concept test is needed Gas would be spiked with Krypton-85 to permit monitoring of the gas permeation in the alluvial soils ambient and elevated temperature tests could be performed

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