Evacuated containment vessel for a nuclear reactor

A power module assembly comprising:

• a containment vessel;
• a reactor vessel housed in the containment vessel, wherein the reactor vessel is configured to release coolant into a containment region, and wherein the containment vessel is configured to prohibit a release of the coolant out of the containment vessel;
• and
• a thermal insulation of the reactor vessel including the containment region located between the reactor vessel and the containment vessel, wherein the containment region comprises a partial vacuum that substantially surrounds the reactor vessel and is maintained at a below atmospheric pressure, and wherein the below atmospheric pressure prohibits substantially all convective heat transfer between the reactor vessel and the containment vessel.

A power module assembly, comprising:

• a thermal insulation including a containment region, wherein the containment region comprises a partial vacuum;
• means for releasing coolant into the containment region, wherein a reactor core is housed in the means for releasing;
• and
• containment means for maintaining the partial vacuum at less than 300 mmHG absolute, wherein the containment region is located between the means for releasing and the containment means, wherein the partial vacuum substantially surrounds the means for releasing, and wherein the containment means is configured to completely retain the released coolant within the containment means.