ATLANTA — If disaster strikes a US nuclear power plant, the utility industry wants to be able to fly in heavy-duty equipment that could avert a meltdown.

That capability is part of a larger plan being developed to meet new rules that emerged after a 2011 tsunami struck the Fukushima Daiichi nuclear plant in ­Japan, flooding its emergency equipment and causing nuclear meltdowns that leaked radiation into the environment. The tsunami exceeded the worst-case scenario the plant was designed to withstand, and it showed how an extreme, widespread disaster can complicate emergency plans.