How quickly an SSN can increase reactor power

How long does an SSN reactor take to move from silent crawling to peak output?

A running submarine reactor can increase power quickly because it is never fully shut down, although exact timings are not available in open sources.

An operating naval reactor remains active at reduced power instead of shutting down completely. That persistent operation contributes some noise, which is one reason a nuclear submarine cannot reproduce the battery-only silence of a diesel-electric boat. It also allows an SSN to demand much more power on short notice. Open sources do not provide a reliable exact ramp time, so only a qualitative judgment is possible. For comparison, a panellist tentatively recalls operators taking one to two weeks to restore an 800 MW civilian reactor after a trip. That starting condition follows a fault and the insertion of control rods to suppress the reaction, with operators then proceeding cautiously. It does not establish the time an already operating submarine reactor needs to increase output.