| 11. | A map of slow neutrons shows there is a broad deposit of water around the Martian south pole.
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| 12. | This is because U-234 is not fissile, and tends to absorb slow neutrons in a nuclear reactor-becoming U-235.
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| 13. | In a GFR reactor design, the unit operates on fast neutrons, no moderator is needed to slow neutrons down.
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| 14. | For example, hydrogen-rich materials are often used to shield against neutrons, since ordinary hydrogen both scatters and slows neutrons.
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| 15. | Gas, oil, water and sand all have different concentrations of hydrogen atoms which reflect different amounts of slow neutrons.
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| 16. | This is because U-234 is not fissile, and tends to absorb slow neutrons in a nuclear reactor becoming U-235.
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| 17. | In Ottawa, the delegation also met a Canadian, George Laurence, who had secretly built his own slow neutron experiment.
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| 18. | Control rods used to be tipped with graphite, a material that slows neutrons and thus speeds up the chain reaction.
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| 19. | Thus, when Mars Odyssey passes over a region containing hydrogen, it sees more slow neutrons and fewer of the faster ones.
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| 20. | Therefore, if the primary coolant is removed, there are not enough slow neutrons to sustain the reaction and the core cools.
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