Patent Number: 039376494
Section: summary

BACKGROUND OF THE INVENTION Tritium is a hydrogen atom containing one proton, two neutrons, and one electron. Radioactive tritium has a half-life of 12.33 years and emits beta particles during its decay. While the human skin will readily stop beta particles without any damage, tritium will easily vaporize and the inhalation of tritium is dangerous as internal body tissues are easily damaged by beta particles. In response to the increasing demands for electrical power within the United States, more atomic reactor generating plants are being built, particularly those having high temperature gas cooled reactors (HTGR). In HTGR's, there is a large production of tritium. Tritium is so pervasive, that it easily penetrates the steel tubing of the steam generator of the reactor and into the water system. Once into the water system there are several ways for tritium to escape into the atmosphere. To date, tritium has been removed from HTGR's only by unrestrained release into the atmosphere, or into the water disposal system, or otherwise into the surrounding environment. As more and larger HTGR's are built, the pollution of the environment through this indiscriminate discharge steadily increases and will soon create a significant problem unless remedied. In fact, the maximum permissible amount of release of radiation to the environment established by the Atomic Energy Commission will be exceeded by the rate of production of tritium in the large HTGR's already in the planning stage. SUMMARY OF THE INVENTION Accordingly, it is among the objects of this invention to: provide a safe process and system for the removal of radioactive tritium from high temperature gas cooled atomic reactors without polluting the environment and to provide a process and system for removal of tritium from any system containing an inert-to-oxygen circulating fluid which becomes tritiated. These and other objects of the invention are achieved by a process and system in which part of the reactor coolant which becomes permeated with tritium is continually removed and processed to remove the tritium. The process involves combining the removed reactor coolant under conditions of elevated temperature and pressure with gaseous oxygen, so as to result in a tritiated water vapor formation reaction from the tritium in the reactor coolant and the gaseous oxygen. The tritiated water vapor and the remaining gaseous oxygen are then successively removed by fractional liquefaction steps. The liquefied tritiated water vapor is then removed from the processing system and safely disposed of; the liquefied gaseous oxygen is used as cooling means in the water vapor liquefaction step and then used as the gaseous oxygen combined to form the water vapor; and the now untritiated reactor coolant is returned to the reactor for re-circulation. The processing system is designed against accidents through the inclusion of radiation monitors at points immediately after removal of the reactor coolant from circulation and immediately prior to its return to recirculation, and through pressure and temperature sensors connected through electronic controls to fast-acting pneumatic valves which immediately shut the processing system down in case of any malfunction. An additional provision is the heating of the reactor coolant prior to its return to be re-circulated by means of a heat exchange with ordinary circulating water, thus resulting in a supply of chilled water for use elsewhere in the reactor system and supporting environment.