I suspect there are radiators of some sort to absorb heat inside and radiate to the container. I wonder if they would have pumps at all since those typically need maintenance. Might be passive cooling piping that lets water flow, perhaps using natural movement as water heats. There isn't air inside, so no moisture issues. I would suspect that they hope it remains uncovered and water flows across it, just using convection for heat dispersal.
And I'm wrong. Reading closer, there is piping for move water through the interior and they are concerned about fouling. Still a chore/job that likely will be needed.
though, perhaps AI robots can do this.