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Record 1,  Textual support,  English

Record number: 1, Textual support number: 1 CONT

Nuclear reactors can be controlled by a mechanical control rod system for a very subtle reason. In a chain reaction there are only fractions of seconds between one fission event and the next one(s), initiated by the former. However, since a small fraction of the neutrons needed to keep the chain going are generated with a delay in the range of ten seconds the necessary response time of the control system is in the range of 0.1 seconds, thus making mechanical control possible in the first place. For plutonium the delayed neutron fraction is almost a factor of three smaller than for uranium, increasing demands on the control system.  2, record 1, English, - mechanical%20control%20rod

Record 1,  Textual support,  French

Record number: 1, Textual support number: 1 CONT

Cœur du réacteur. [...] Les dispositifs de réglage de la réactivité montés verticalement comprennent [...] les barres de commande mécaniques qui se trouvent normalement à l'extérieur du cœur. Elles sont insérées pour compléter la réactivité négative des barres de commande à eau ordinaire ou on les fait chuter pour effectuer une réduction rapide de la puissance.  1, record 1, French, - barre%20de%20commande%20m%C3%A9canique

Record 1,  Textual support,  Spanish