Autonomous self-powered system for removing thermal energy from pools of liquid heated by radioactive materials, and method of the same

Abstract

An autonomous self-powered system for cooling radioactive materials comprising: a pool of liquid; a closed-loop fluid circuit comprising a working fluid having a boiling temperature that is less than a boiling temperature of the liquid of the pool, the closed-loop fluid circuit comprising, in operable fluid coupling, an evaporative heat exchanger at least partially immersed in the liquid of the pool, a turbogenerator, and a condenser; one or more forced flow units operably coupled to the closed-loop fluid circuit to induce flow of the working fluid through the closed-loop fluid circuit; and the closed-loop fluid circuit converting thermal energy extracted from the liquid of the pool into electrical energy in accordance with the Rankine Cycle, the electrical energy powering the one or more forced flow units.

What is claimed is: 
     
         1 . An autonomous self-powered system for cooling radioactive materials, the system comprising:
 a pool of liquid heated by the radioactive materials immersed therein;   a closed-loop flow circuit comprising a hydraulic pump circulating a working fluid through the closed-loop flow circuit, the working fluid having a boiling temperature less than a boiling temperature of the liquid of the pool;   the closed-loop fluid circuit comprising, in operable fluidly coupled relationship:
 an evaporative heat exchanger immersed in the liquid of the pool, the heat exchanger comprising a top header, a bottom header, and a bundle of heat exchange tubes extending therebetween, the heat exchange tubes having exposed outer surfaces in directly wetted fluid contact with the liquid of the pool to convert a liquid working fluid received by the tubes into vaporous working fluid; 
 a turbogenerator receiving the vaporous working fluid for the heat exchanger; 
 a condenser receiving the vaporous working fluid and condensing it back into the liquid working fluid; and 
 the hydraulic pump receiving the liquid working fluid from the condenser and the pumping the liquid working fluid back to the heat exchanger; 
   the turbogenerator being operable to convert thermal energy extracted from the vaporous working fluid into electrical energy, the electrical energy powering the pump.   
     
     
         2 . The system according to  claim 1 , wherein the evaporative heat exchanger is located at a top of the pool of liquid proximate to a top surface of the liquid thereby exposing the heat exchange tubes to hottest liquid in the pool for optimum heat transfer. 
     
     
         3 . The system according to  claim 2 , wherein the bottom header is located in an upper half of the pool of liquid. 
     
     
         4 . The system according to  claim 1 , wherein the condenser is an air-cooled condenser comprises a blower operable to draw or blow ambient cooling air over a tube bundle comprising plurality of heat exchange tubes in the air-cooled condenser, the working fluid being a tube-side fluid flowing through the heat exchange tubes of the air-cooled condenser. 
     
     
         5 . The system according to  claim 4 , wherein the blower is also electrically powered by the turbogenerator. 
     
     
         6 . The system according to  claim 4 , wherein the heat exchange tubes of the air-cooled condenser are arranged in a substantially vertical orientation, and wherein the vaporous working fluid enters the heat exchange tubes of the air-cooled condenser via a top fluid inlet header and the condensed liquid working fluid exits the heat exchange tubes via a bottom fluid outlet header. 
     
     
         7 . The autonomous self-powered system of  claim 4  wherein the air cooled condenser further comprises a shroud forming a cavity, the heat exchange tubes of the air-cooled condenser located within the cavity of the shroud, the shroud having an air inlet for introducing cool air into the cavity and an air outlet for allowing heated air to exit the cavity, the heat exchange tubes located at an elevation between an elevation of the air inlet and an elevation of the air outlet so that thermal energy transferred from the working fluid flowing to the air through the heat exchange tubes causes a natural convective air flow within the shroud. 
     
     
         8 . The system according to  claim 1 , further comprising a reservoir which receives the liquid working fluid from the condenser, the hydraulic pump downstream of and taking suction from the reservoir. 
     
     
         9 . The system according to  claim 1 , wherein the pool of the liquid is at a first pressure and the working fluid within the evaporative heat exchanger is at a second pressure that is greater than the first pressure, the boiling temperature of the working fluid at the second pressure being less than the boiling temperature of the liquid of the pool at the first pressure. 
     
     
         10 . The system according to  claim 8 , wherein the first pressure is atmospheric and the second pressure is in a range of 250 psia to 400 psia. 
     
     
         11 . The system according to  claim 1 , wherein the liquid of the pool is water and the working fluid is selected from a group consisting of a refrigerant and a hydrocarbon. 
     
     
         12 . The system according to  claim 1 , wherein the heat exchange tubes of the heat exchanger are vertically oriented. 
     
     
         13 . The system according to  claim 12 , wherein the top and bottom headers of the heat exchanger are dome shaped. 
     
     
         14 . The system according to  claim 12 , further comprising a central core tube circumferentially surrounded by the bundle of heat exchange tubes, the core tube forming a downcomer passageway between the top header and the bottom header for bypassing the top header and introducing the liquid working fluid from the hydraulic pump directly into the bottom header of the heat exchanger. 
     
     
         15 . The system according to  claim 14 , wherein the downcomer tube comprises a thermal insulating layer. 
     
     
         16 . The system according to  claim 2 , wherein the heat exchanger is mounted to a vertical sidewall of the pool of liquid. 
     
     
         17 . An autonomous self-powered system for cooling radioactive materials, the system comprising:
 a pool of liquid heated by the radioactive materials immersed therein;   a closed-loop flow circuit comprising a hydraulic pump circulating a working fluid through the closed-loop flow circuit, the working fluid having a boiling temperature less than a boiling temperature of the liquid of the pool;   the closed-loop fluid circuit comprising, in operable fluidly coupled relationship:
 an evaporative heat exchanger immersed in the liquid of the pool, the heat exchanger comprising a top header, a bottom header, and a first bundle of heat exchange tubes extending therebetween, the heat exchange tubes having exposed outer surfaces in directly wetted fluid contact with the liquid of the pool to convert a liquid working fluid received by the tubes into vaporous working fluid; 
 a turbogenerator receiving the vaporous working fluid for the heat exchanger; 
 an air-cooled condenser receiving the vaporous working fluid and condensing it back into the liquid working fluid, the air-cooled condenser comprising a fluid inlet head, a fluid outlet header, and a second bundle of heat exchange tubes extending therebetween; and 
 the hydraulic pump receiving the liquid working fluid from the condenser and the pumping the liquid working fluid back to the heat exchanger; 
   the turbogenerator being operable to convert thermal energy extracted from the vaporous working fluid into electrical energy, the electrical energy powering the pump.   
     
     
         18 . The system according to  claim 17 , wherein the evaporative heat exchanger is located in an upper half of the pool of liquid proximate to a top surface level of the liquid thereby exposing the heat exchange tubes to hottest liquid in the pool for optimum heat transfer. 
     
     
         19 . The system according to  claim 17 , wherein the air-cooled condenser comprises a blower operable to draw or blow ambient cooling air over the second tube bundle of heat exchange tubes, the working fluid being a tube-side fluid flowing through the heat exchange tubes of the air-cooled condenser. 
     
     
         20 . The system according to  claim 17 , wherein the heat exchanger further comprises a central core tube extending between the top and bottom headers of the heat exchanger, core tube having a first effective coefficient of thermal conductivity and the heat exchange tubes having a second effective coefficient of thermal conductivity greater than the first effective coefficient of thermal conductivity to promote thermosiphon flow of the liquid working fluid within the heat exchange tubes of the heat exchanger.