Patent Number: 055419690
Section: claims

1. In a pressurized water nuclear power plant, a water level monitor responsive to the water level in a reactor vessel that is fluidly connected to a steam generator, comprising: a main pipe for delivering heated water from said reactor vessel to said steam generator during normal plant operation, said main pipe including a horizontal portion having a top region at a top elevation and a bottom region at a bottom elevation;  a tank forming a chamber, the chamber having an upper region at an upper elevation and a lower region at a lower elevation, wherein said top region of the pipe is at the same elevation as said upper region of the chamber, and said bottom region of the pipe is at the same elevation as said lower region of the chamber;  a secondary upper pipe in fluid connection with the top region of the main pipe;  a secondary lower pipe in fluid connection with the bottom region of the main pipe;  an upper connecting pipe, fluidly connecting the secondary upper pipe to the upper region of the chamber;  a lower connecting pipe, fluidly connecting the secondary lower pipe to the lower region of the chamber, whereby water in the horizontal portion of the main pipe can communicate freely with said chamber;  means in the chamber for generating a signal indicative of a water level in the chamber; and  means for transmitting the signal to a remote location.  a control room;  a nuclear reactor vessel situated remotely from the control room;  a steam generator having a lower head;  a hot leg water pipe having a horizontal run which defines top and bottom elevations, said pipe fluidly connecting the reactor vessel to the steam generator lower head for supplying a flow of hot water from the vessel to the steam generator during normal operation;  a water level monitor chamber having an upper region at the same elevation as the top elevation of the pipe and a lower region at the same elevation as the bottom elevation of the pipe;  means for fluidly connecting the pipe at the top elevation to the upper region of the chamber;  means for fluidly connecting the pipe at the bottom elevation to the lower region of the chamber;  means for generating a signal indicative of a water level in the chamber; and  means for transmitting the signal from the chamber to the control room. 2. The nuclear power plant of claim 1, wherein the upper connecting and the lower connecting pipes have valves for selectively isolating the chamber from the main pipe. 3. The nuclear power plant of claim 1, wherein the means for generating a signal is a plurality of heated junction thermocouples. 4. The nuclear power plant of claim 1, wherein the chamber is sealed from atmosphere. 5. The nuclear power plant of claim 1, wherein the remote location is a control room in the nuclear power plant. 6. The nuclear power plant of claim 1, wherein the secondary upper pipe is a surge line. 7. The nuclear power plant of claim 1, wherein the secondary lower pipe is a shut down cooling line. 8. The nuclear power plant of claim 7, wherein the secondary upper pipe is a surge line. 9. The nuclear power plant of claim 8, wherein the upper connecting and the lower connecting pipes have valves for isolating the chamber from the main pipe. 10. A nuclear power plant comprising; 11. The power plant of claim 10, wherein the means for generating a signal is a plurality of heated junction thermocouples. 12. The power plant of claim 10, wherein the control room has means for displaying the signal on a computer monitor.