PURPOSE: To keep leak percent below 0.1% by reducing fluctuations of background, by using heavy water steam or ordinary steam as sample gas in an active carbon filter provided in the emergency gas processing system in a nuclear power plant.
CONSTITUTION: Sample air is introduced into a chamber 2 through an opening 3, and, after removal of fine particles contained in a high performance filter 4, is dehumidified in a heater 5. By the gas pressure in N2 cylinder 17, heavy water steam in a heavy water steam generator 16 is injected out of a sample gas lead-in port 18 to be mixed with sample air, which then passes through baffle plate 6 and straightening grating 7 to reach a radioactive iodine removal filter 8. In this process, part of the mixture gas enters gas chromatographs 14, 15 through sampling holes 12, 13, and the leak percentage is calculated by measuring the concentration. The mixed gas after passing through the filter 8 is further sent into straightening grating 9, orifice 10, and exhaust blower 11 to be released into the atmosphere through the exhaust tower which is not shown in the illustration.
ISHIKAWA SADAHISA
MIHARADA HACHIMIZU
TOKYO SHIBAURA ELECTRIC CO