Patent Number: 
Section: claims

1. A nuclear power system, comprising:a reactor vessel defining a volume;a reactor core positioned within the volume, the reactor core including one or more nuclear fuel assemblies configured to generate a nuclear fission reaction;a containment vessel sized to enclose the reactor vessel such that an open volume is defined between the containment vessel and the reactor vessel; anda boron injection system positioned in the open volume and comprising an amount of boron in solid form sufficient to stop the nuclear fission reaction or maintain the nuclear fission reaction at a sub-critical state, wherein the boron injection system comprises a boron container sized to hold or enclose the amount of boron in solid form, wherein the boron container is configured to release the amount of boron in solid form directly into the open volume in response to at least one of a predetermined temperature and pressure within the open volume, and wherein the amount of boron in solid form is configured to go into solution upon mixing with primary coolant in the open volume such that the solution is in fluid communication with an inner surface of the containment vessel. 2. The nuclear power system of claim 1, wherein the boron container includes a latch actuatable by the at least one of the predetermined temperature and pressure to open the boron container such that the amount of boron in solid form is delivered directly into the open volume. 3. The nuclear power system of claim 1, wherein the reactor vessel further comprises at least one valve openable to fluidly couple the volume of the reactor vessel with the open volume. 4. The nuclear power system of claim 3, wherein the at least one valve comprises:a reactor vent valve configured to vent the primary coolant in vapor form from the volume of the reactor vessel to the open volume; anda reactor recirculation valve configured to circulate at least a portion of the solution to the reactor core. 5. The nuclear power system of claim 4, wherein the amount of boron in solid form is configured to go into solution with a condensed form of the primary coolant vented into to the open volume. 6. The nuclear power system of claim 4, wherein at least a portion of the boron container that holds the amount of solid boron is meltable or dissolvable, and wherein the reactor vent valve is configured to vent the primary coolant in vapor form at the predetermined temperature that is sufficient to melt or dissolve the portion of the boron container to release the amount of boron in solid form into the open volume. 7. The nuclear power system of claim 1, wherein the amount of boron in solid form is in granular form. 8. The nuclear power system of claim 1, wherein the nuclear power system does not include any control rod assemblies positionable within the reactor vessel. 9. A method for controlling a nuclear fission reaction, comprising:operating a nuclear power system to generate a nuclear fission reaction, the nuclear power system comprising:a reactor vessel defining a volume;a reactor core positioned within the volume, the reactor core comprising one or more nuclear fuel assemblies configured to generate the nuclear fission reaction,a containment vessel sized to enclose the reactor vessel such that an open volume is defined between the containment vessel and the reactor vessel, anda boron injection system positioned in the open volume and comprising an amount of boron in solid form, wherein the boron injection system comprises a boron container sized to hold or enclose the amount of boron in solid form, and wherein the boron container is configured to release the amount of boron in solid form directly into the open volume;initiating an emergency operation of the nuclear power system based on a loss of a primary coolant from the volume of the reactor vessel to the open volume;based on the emergency operation, releasing the amount of boron in solid form into the open volume of the containment vessel in response to at least one of a predetermined temperature and pressure within the open volume such that the amount of boron in solid form goes into solution upon mixing with the primary coolant in the open volume and (b) the solution is in fluid communication with an inner surface of the containment vessel;circulating the solution from the open volume of the containment vessel to the reactor core; andwith the solution, stopping the nuclear fission reaction or maintaining the nuclear fission reaction at a sub-critical state. 10. The method of claim 9, wherein releasing the amount of boron in solid form from the boron container comprises actuating a latch on the boron container by the at least one of the predetermined temperature and pressure in the open volume. 11. The method of claim 9, wherein releasing the amount of boron in solid form from the boron container comprises melting or dissolving at least a portion of the boron container based on the predetermined temperature in the open volume. 12. The method of claim 10, further comprising, based on the emergency event, opening at least one valve on the reactor vessel to fluidly couple the volume of the reactor vessel with the open volume. 13. The method of claim 12, wherein opening at least one valve on the reactor vessel comprises:opening a reactor vent valve to vent the primary coolant in vapor form from the volume of the reactor vessel to the open volume; andopening a reactor recirculation valve to circulate the solution to the reactor core. 14. The method of claim 13, wherein the amount of boron in solid form goes into solution with a condensed form of the primary coolant vented into the open volume. 15. The method of claim 13, wherein the primary coolant in vapor form is at the at least one of the predetermined pressure and temperature that is sufficient to actuate the latch to release the amount of boron in solid form from the boron container into the open volume. 16. The method of claim 9, wherein the boron in solid form is in granular form. 17. The method of claim 9, further comprising operating the nuclear power system to generate the nuclear fission reaction without any operation of control rod assemblies.