Liquid hydrogen reservoir of the power unit

The liquid hydrogen is contained within a closed system feeding the power unit, its extreme volatility a constant hazard in the cramped chamber. A metallic reservoir of modest size stands integrated into the core systems, connected by thick conduits to the fusion matrix. Its temperature renders nearby surfaces frost-coated and condensation drips steadily along the pipework, demanding constant monitoring. The Doctor and Romana direct heated glances at its gauges during their debate, their dispute over priorities hinging on the stability it must maintain.