Patent Number: 
Section: claims

1. A temperature sensor array comprising:a plurality of temperature sensors including twelve passive thermocouples each spaced apart from one another by at least one foot on an axis and each having a width perpendicular to the axis of less than one inch, wherein the temperature sensors,are configured to be inserted into an instrumentation tube within a nuclear reactor so that the axis extends in the instrumentation tube and the temperature sensors are spaced in the instrumentation tube,measure temperatures of the instrumentation tube from about 100 degrees Fahrenheit to about 3000 degrees Fahrenheit, andinclude only materials with melting temperatures and cross-sections such that the temperature sensors do not fail within an operating or transient nuclear reactor environment. 2. The array of claim 1, further comprising:an axial column to which the plurality of temperature sensors are attached, wherein the axial column is configured to be inserted into the instrumentation tube. 3. The array of claim 2, wherein the axial column is a continuous and flexible metallic rod. 4. The array of claim 1, further comprising:at least one communicative connector configured to transmit data from at least one of the temperature sensors to a remote monitor. 5. The array of claim 1, wherein the plurality of temperature sensors are thermocouples configured to measure temperature without an external power source. 6. The array of claim 1, wherein the plurality of temperature sensors are bare along the axis. 7. The array of claim 1, wherein the nuclear reactor is a boiling water reactor. 8. The array of claim 1, wherein the temperature sensors are further configured to measure a temperature range including normal operating temperatures of the nuclear reactor and temperatures associated with absence of coolant in a transient scenario of the nuclear reactor. 9. A nuclear reactor comprising:a core containing nuclear fuel;an instrumentation tube extending into the core, wherein the instrumentation tube has an opening outside the reactor to permit enclosed access to the core; anda temperature sensor array extending into the instrumentation tube, wherein the temperature sensor array includes a plurality of temperature sensors including twelve passive thermocouples each aligned at different axial positions of the instrumentation tube at least one foot apart from each other and each having a width perpendicular to the instrumentation tube of less than one inch, and wherein the temperature sensors are uninsulated from the instrumentation tube in order to measure thermal temperature of the reactor. 10. The nuclear reactor of claim 9, wherein the temperature sensor array further includes,an axial column to which the plurality of temperature sensors are attached at the different axial positions, andat least one communicative connector extending outside the instrumentation tube and configured to transmit data from at least one of the temperature sensors to a remote monitor. 11. The nuclear reactor of claim 10, wherein the plurality of temperature sensors are aligned and spaced along the axial column so as to be present at a plurality of axial levels within the core. 12. The nuclear reactor of claim 9, wherein the plurality of temperature sensors are passive thermocouples configured to measure a temperature range of the instrumentation tube including normal operating temperatures of the nuclear reactor and temperatures associated with absence of coolant in a transient scenario of the nuclear reactor. 13. The nuclear reactor of claim 12, wherein the nuclear reactor is a boiling water reactor, and wherein the reactor further comprises:a plurality of instrumentation tubes extending into the core, wherein each instrumentation tube has an opening outside the reactor to permit enclosed access to the core; anda plurality of the temperature sensor arrays each extending into a respective instrumentation tube of the plurality of instrumentation tubes, wherein the temperature range is from approximately 100 degrees Fahrenheit to approximately 3000 degrees Fahrenheit. 14. A method of monitoring a nuclear reactor, the method comprising:installing a plurality of temperature sensors including twelve passive thermocouples each at different axial positions at least one foot apart from each other within an instrumentation tube of the nuclear reactor and having a width perpendicular to the instrumentation tube of less than one inch, wherein the temperature sensors measure a temperature of the instrumentation tube ranging from normal operating temperatures of the nuclear reactor to temperatures associated with absence of coolant in a transient scenario of the nuclear reactor. 15. The method of claim 14, wherein the temperature ranges from approximately 100 degrees Fahrenheit to approximately 3000 degrees Fahrenheit, the method further comprising:determining a coolant level in the nuclear reactor from temperatures measured by the plurality of temperature sensors. 16. The method of claim 15, wherein the determining includes correlating a threshold temperature to an absence of coolant condition and comparing the temperatures measured by the plurality of temperature sensors to the threshold temperature. 17. The method of claim 15, wherein the determining is performed in real-time and determines a current coolant level in the nuclear reactor. 18. The method of claim 14, wherein the installing includes inserting a temperature sensor array containing the plurality of temperature sensors aligned at different axial positions into the instrumentation tube. 19. The method of claim 14, wherein the temperature sensors are uninsulated from the instrumentation tube and measure temperature throughout the range passively with heat applied only from the reactor.