Reducing concentration of gases in nuclear reactor

The time taken to reduce concentration of radioactive gas in the coolant of a nuclear reactor to permissible levels during refueling or the like is reduced by injecting into the reactor coolant a quantity large compared to the quantity of fission gas, of stable gas of the same atomic number as each radioactive gas. The fission gas includes both stable and radioactive isotopes, the quantity of stable isotopes being large compared to the quantity of radioactive isotopes. The stable gas added and the fission gas of each atomic number are dissolved as one gas in the reactor fluid and are purges together, the added stable gas accelerating the dissolution of the radioactive gas. 3 claims, 2 drawing figures