Patent Number: 
Section: claims

1. A reactor for containing a nuclear reaction, the reactor comprising:a sealable containment envelope having an inner surface, the containment envelope having a pressure limit of a gas contained within the containment envelope;a vessel including core material and located within the containment envelope, the vessel designed to enclose the core material at temperatures below a breach temperature;the inner surface having a containment temperature below the breach temperature; andan apparatus comprising a first material disposed in a location within the containment envelope such that upon a breach of the vessel by the core material, the breached core material contacts the first material; the first material having:a melting point below the breach temperature;a boiling point above the containment temperature; anda difference between the melting point and boiling point that is greater than 100 degrees Celsius. 2. The reactor of claim 1, wherein the first material has a boiling point above 100 degrees Celsius at a pressure of 1 atmosphere. 3. The reactor of claim 1, wherein the breach temperature is above 500 degrees Celsius and the boiling point is below the breach temperature. 4. The reactor of claim 1, wherein the first material has a melting point between 50 and 800 degrees Celsius. 5. The reactor of claim 1, wherein the first material has a boiling point at 1 atmosphere between 150 and 3000 degrees Celsius. 6. The reactor of claim 1, wherein the first material has a melting point between 200 and 700 degrees Celsius, and a boiling point between 800 and 2650 degrees Celsius. 7. The reactor of claim 1, wherein the melting point is greater than the containment temperature. 8. The reactor of claim 1, wherein the first material comprises a composition that is not expected to exothermically react with any component comprising more than 1% of the breached core material at the breach temperature and the pressure limit. 9. The reactor of claim 1, wherein the boiling point of the first material is above a third temperature between the breach and containment temperatures, and the third temperature is within 400 degrees Celsius of the containment temperature. 10. The reactor of claim 9, wherein the melting point of the first material is below the third temperature. 11. The reactor of claim 1, wherein the difference between the melting point and the boiling point is greater than 100 degrees Celsius and less than 2700 degrees Celsius. 12. The reactor of claim 1, wherein a liquid phase of the first material has a density greater than a density of at least 10% of core material. 13. The reactor of claim 1, further comprising a system to contain the breached core material and a liquid phase associated with the first material, wherein the system includes a depth sufficient to float the breached core material above a bottom surface of the containment envelope, and the first material has at least the volume necessary to float the breached core material above the bottom surface. 14. The reactor of claim 1, further comprising a system to contain the breached core material and a liquid phase associated with the first material, wherein upon contact between the breached core material and the first material, the first material forms a liquid puddle having a depth and a width, and the depth is less than 20% of the width. 15. The reactor of claim 1, wherein the first material comprises any of Pb, Zn, Sn, S, and Bi. 16. The reactor of claim 1, wherein the first material comprises Al. 17. The reactor of claim 1, further comprising an apparatus associated with the inner surface configured to increase the condensation rate. 18. The reactor of claim 1, wherein the inner surface is in fluid communication with the first material. 19. The reactor of claim 1, wherein the first material has a melting point below 700 degrees Celsius. 20. A method of transferring heat from a core material inside a containment envelope to a region outside the containment envelope, the method comprising providing a reactor having:a sealable containment envelope having an inner surface, the containment envelope having a pressure limit of a gas contained within the containment envelope, the containment envelope in thermal communication with the region outside the containment envelope;a vessel including the core material and located within the containment envelope, the vessel designed to enclose the core material at temperatures below a breach temperature;the inner surface having a containment temperature below the breach temperature; andan apparatus comprising a first material disposed in a location within the containment envelope such that upon a breach of the vessel by the core material, the breached core material contacts the first material; the first material having:a melting point below the breach temperature;a boiling point above the containment temperature; anda difference between the melting point and boiling point that is greater than 100 degrees Celsius at a pressure of 1 atmosphere;operating the reactor; andallowing core material at a temperature above the breach temperature to contact the first material.