Everything is natural convection or gravity-fed in a blackout station scenario, so there's no way to pump the steam back down into the ground. Also, the ground

Everything is natural convection or gravity-fed in a blackout station scenario, so there's no way to pump the steam back down into the ground. Also, the ground wouldn't dissipate the heat from the steam fast enough, and would quickly reach a hot equilibrium temperature. It's basically a low capacity heat sink quickly saturated.