DescriptionAEC-71-9023 In a Hanford plutonium production reactor, uranium fuel is "charged" into the horizontal process tubes that penetrate front to rear through the graphite moderator. Treated water from the Columbia River is pumped through these tubes to remove the heat released during the fission process. This coolant leaves the reactor through a similar piping complex and, after an interval in retention basins, is returned to the river. Manipulation of horizontal rods that contain neutron absorbing material controls the fission process. Other "poison" rods on top of the reactor are dropped into vertical channels in the reactor block, as an additional control feature. Credit: Battelle-Northwest
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