Patent Number: 
Section: claims

1. A simplified nuclear reactor system for commercially generating electricity, the system comprising:a nuclear reactor;a primary coolant loop connecting to the nuclear reactor;a containment surrounding the nuclear reactor; anda depressurization system including,a coolant tank and a filter pool vertically above the nuclear reactor outside the containment and including no flow path opening into the containment outside the nuclear reactor,an injection line crossing the containment and connecting the coolant tank and the nuclear reactor, wherein the injection line includes a closable and openable valve,a relief line crossing the containment and connecting the filter pool and the nuclear reactor, anda rupture disk connecting the relief line to the nuclear reactor, wherein the rupture disk is integral in a wall of the nuclear reactor so as to have material continuity with the wall, and wherein the rupture disk is configured to open the reactor at a pressure setpoint below failure of the reactor. 2. The system of claim 1, whereinthe relief line is configured to carry coolant away from the reactor following opening of the rupture disk. 3. The system of claim 2, further comprising:wherein the relief line extends into and opens below a surface of the filter pool so as to exhaust the coolant into the filter pool for condensation and/or scrubbing. 4. The system of claim 3, wherein the filter pool includes a particulate filter configured to filter particulate matter out of gas exiting the filter pool to the atmosphere. 5. The system of claim 4, wherein the containment and the reactor are below ground, wherein the filter pool is above ground outside the containment, and wherein the relief line extends through the containment from the reactor to the filter pool. 6. The system of claim 1, wherein the depressurization system includes a plurality of the rupture disks in series, and wherein the pressure setpoint is about 120% of the operating pressure of the nuclear reactor. 7. The system of claim 1, wherein the rupture disk is configured to open the reactor by failure due to stress at the pressure setpoint. 8. The system of claim 1,wherein the depressurization system further includes a valve on the injection line and integral with the nuclear reactor, wherein the valve permits only injection of coolant from the coolant tank into the nuclear reactor. 9. A simplified nuclear reactor system for commercially generating electricity, the system comprising:a nuclear reactor;a primary coolant loop connecting to the nuclear reactor;a containment surrounding the nuclear reactor; anda gravity-driven injection system including,a coolant tank and a filter pool vertically above the nuclear reactor outside the containment and including no flow path opening into the containment outside the nuclear reactor,an injection line crossing the containment and connecting the coolant tank and the nuclear reactor, wherein the injection line includes a closable and openable valve, and wherein the valve and a wall of the nuclear reactor are integral so as to have material continuity, anda relief line crossing the containment and connecting the filter pool and the nuclear reactor, wherein the relief line is connected to the nuclear reactor by a rupture disk. 10. The system of claim 9, wherein the valve permits only injection of coolant from the coolant tank into the nuclear reactor. 11. The system of claim 10, wherein the valve is configured to passively open at detection of a low liquid level in the nuclear reactor. 12. The system of claim 9, wherein the nuclear reactor is completely underground and the coolant tank is above ground. 13. The system of claim 9,wherein the rupture disk is configured to open the reactor at a pressure setpoint below failure of the reactor. 14. The system of claim 13, wherein therelief line is configured to carry coolant away from the reactor following opening of the rupture disk. 15. The system of claim 14, wherein the injection line flows into the nuclear reactor at the valve at a first vertical position of a downcomer annulus in the nuclear reactor, and wherein the relief line flows out of the nuclear reactor at the rupture disk at a second vertical position of the reactor above a core of the nuclear reactor and above the first vertical position. 16. The system of claim 14, wherein the relief line extends into the filter pool so as to exhaust the coolant into the filter pool for condensation and/or scrubbing. 17. The system of claim 16, wherein the containment and the reactor are below ground, and wherein the filter pool and coolant tank are outside containment and above ground. 18. The system of claim 13, wherein the injection system is configured to lower a pressure of the nuclear reactor to a level where coolant will be injected from the coolant tank due to gravity. 19. A simplified nuclear reactor system for commercially generating electricity, the system comprising:a nuclear reactor;a primary coolant loop connecting to the nuclear reactor;a containment surrounding the nuclear reactor; anda gravity-driven injection system including,a coolant tank and a filter pool vertically above the nuclear reactor outside the containment and including no flow path opening into the containment outside the nuclear reactor,an injection line crossing the containment and connecting the coolant tank and the nuclear reactor, wherein the injection line includes a closable and openable valve, anda relief line crossing the containment and connecting the filter pool and the nuclear reactor, wherein the relief line is connected to the nuclear reactor by a rupture disk.