The coming storm.....

-06, It isn't the Control Rods that is the issue, in this kind of accident. It is the Residual Heat in the Total System that is the issue here. The Control Rods get shoved into the Core when the Reactor is Scramed. They Flood the Reactor Vessel with Boron Laced Water which is Gravity Fed. These two events are triggered by the EarthQuake, when the Operating Reactor is Scramed, and happen within minutes. This causes the Nuclear Reactions to COMPLETELY Stop. HOWEVER there is multi-MegaWatts of Residual Heat still in the system that has to be dumped, somewhere, and that is what the Cooling System Pumps do. They move that heat out of the Core, and into either the Water, or Air, or both. They MUST remove the Heat or the Core will MELT, and that then causes the BIG Problems, like Hydrogen Gas Buildup, and Zirconium Cladding on the Fuel Rods to melt, which allows the Nuclear Material to contaminate the Cooling Water, and when the Containment Vessel is breached, the atmosphere and the area around the facility. It takes a few DAYS to move all that HEAT out of the Core, and Containment, and bring the plant to a Cold Shutdown State. .... YMMV....

EMP is a Wide Bandwidth Emission, so it will go thru any Concrete and Rebar Structure, like it wasn't even there. Not even Chicken Wire, or ChainLink Fencing can stop it. The only REAL isolation comes from SOLID Conductive Materials that Have NO Seems, or Cracks.

 

BT is pretty close enough. The control rods cannot be manually operated by themselves, but the control systems for them MAY be on some of the older, smaller plants, not sure of that. Pressure and radiation fields would prevent access, even if there were a way to do it. So far as I know, all plants have fail safe rod insertion schemes that will stick the rods into the cores on loss of signal from the control systems, that is, passive safety. Residual heat from the reaction is the bugaboo. While the atom splitting stops immediately the rods are inserted, the decay of product isotopes continues for a "long" time. Typically, refueling involves moving expended fuel rods under water from the core to a holding tank until cooled enough to move to a spent fuel pool for storage until going to a reprocessing facility. (There are variations on that theme.) Initially, that is after the reactor is shut down, whether a normal rod insertion or emergency "scrammed" some means of heat removal MUST be maintained; that's where the emergency gen sets become hugely important UNLESS the particular design has a passive cooling system. Some do; Fukushima did not.

So far as EMP problems, there are no containment systems that I know of that are completely shielded against EMP, though they are against radiation. Yes, there is plenty of rebar, but the spacing is wide enough to get even the longest anticipated wavelength thru. Plus, power, control cables and pipes penetrate the radiation shielding and would allow EMP to penetrate.

Historical note: It has been said that the original Chicago pile had safety rods that were held up by a rope. The pile was hand assembled, and there was instrumentation to indicate when the pile went critical. If the power rate gain was too high, there was an ax and wood block over which the rope was passed. It is rumored that the instructions read "In emergency, Sever Control Rope And Move."