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> But, I think "single rod-drop" will not shut down a reactor

Why do you think that? When rods are used to control the reaction rate I thought it was by raising and lowering them small amounts usually.

Being able to have a single fully inserted rod stop things would certainly make it more likely dropping rods into the core would stop an even than if you needed (say) all 3 to be fully inserted.

3x the chance of successfully stopping a serious problem, 1/3rd the chance of a blockage prevent the emergency shutdown.

by joebig1 hours ago|

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I'm already getting downvoted to oblivion for my gp comment, but whatever: what I was trying to convey based on my limited exposure is that a single rod will have a zone restricted shadow or local effect and multiple uniformly distributed rod banks are therefore needed for a an effective control or emergency shutoff. Additionally, on the flip side, I feel a single rod capable of shutoff will insert excessive positive reactivity in case of an ejection (could be a local steam overpressure, idk, don't hunt me down with hounds).

by s1artibartfast1 hours ago|

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Why don't you just look it up instead of actively arguing an assumption?

This reactor type has 73 assemblies of 5 rods each.

Nuclear safety regulations require that the control rod system must be powerful enough to bring the reactor completely subcritical with all Control Element Assemblies (CEAs) inserted minus one assembly stuck in the fully withdrawn position.

One assembly (or 3) inserted would not bring the reactor subcritical.

by CoryOndrejka1 hours ago|

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Yup, this is me focusing on US Navy reactors, which is my experience. For them, a rod would already take you sub critical.