I should note that the ability to overcome the xenon transient is dependent on the geometry and neutron moderator configuration of the reactor. There probably are some reactors out there that would not be able to start up immediately. A link further down the page indicates that this is the case for heavy water-moderated CANDU reactors, which use natural unenriched uranium. The 20-hour startup I mentioned above occurred at a boiling water reactor.
U.S. power reactors generally do not have any problems starting up after a shutdown due to a buildup of poisons (neutron absorbers) in the reactor. Yes, xenon-135, a strong absorber, increases after shutdown, peaking about 10-15 hours after the scram. It decays to zero in about 72 hours. No, the xenon transient is not the reason why the plant owners don't start the reactors back up immediately. They evaluate the cause of the shutdown and the response of plant systems and make any necessary repairs before entering the startup mode. This typically takes somewhere between 12 and 72 hours. Then you go into your startup procedures. The best response I've seen got the reactor back online within 20 hours (near the peak of the xenon-135 transient) and at full power about 24 hours after that.
Slashdot Mirror
I should note that the ability to overcome the xenon transient is dependent on the geometry and neutron moderator configuration of the reactor. There probably are some reactors out there that would not be able to start up immediately. A link further down the page indicates that this is the case for heavy water-moderated CANDU reactors, which use natural unenriched uranium. The 20-hour startup I mentioned above occurred at a boiling water reactor.
U.S. power reactors generally do not have any problems starting up after a shutdown due to a buildup of poisons (neutron absorbers) in the reactor. Yes, xenon-135, a strong absorber, increases after shutdown, peaking about 10-15 hours after the scram. It decays to zero in about 72 hours. No, the xenon transient is not the reason why the plant owners don't start the reactors back up immediately. They evaluate the cause of the shutdown and the response of plant systems and make any necessary repairs before entering the startup mode. This typically takes somewhere between 12 and 72 hours. Then you go into your startup procedures. The best response I've seen got the reactor back online within 20 hours (near the peak of the xenon-135 transient) and at full power about 24 hours after that.