What about drilling a hole through the shield blocks and filling the refuel cavity with demin water? The amount of water over the top of the drywell dome might be limited, but there will be A LOT all around it. You would think that amount of water acting as shielding would surly lower the dose rates over the spent fuel pool and the ISFSI cask wash down area. Once full, fly the ISFSI cask out of the top of the Reactor Building via badass crane. That way you don't have to worry about the dose rates coming from containment while craning it down to the Reactor Building truck bay.