Neutron to start the chain reaction

Thread starter sstone
Start date Feb 8, 2007
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Chain Neutron Reaction

AI Thread Summary

The discussion centers on the source of neutrons needed to initiate a chain reaction in nuclear reactors. It highlights that while uranium can spontaneously fission and release neutrons, reactors typically require a startup neutron source for monitoring and control, especially when sub-critical. Commonly used sources include Sb-124-Be, which generates neutrons through photoneutron reactions. The conversation also notes that after several operational cycles, reactors may achieve a 'sourceless' startup due to accumulated transuranics. Ultimately, the presence of neutrons is essential for achieving and maintaining criticality in nuclear systems.

Mar 8, 2007

curie

Just adding an operational-based aside here, that will be obvious to most, but may not be for readers that are novices to reactors. Another important reason for having a source is to help determine the neutron detectors are functioning correctly. If they are reading reading zero all the time, there is more chance there could be a problem with the signal than if they are displaying a positvie signal, which would be expected to show fluctuation & which can be tested by moving the source too in some reactors.