Two heavy water upgraders have been developed and operated in the Fugen Nuclear Power Station to keep the isotopic purity of the moderator around 99.7 wt% and to recover tritium from the degraded heavy water. One of the upgraders is a combined electrolysis catalyst exchange (CECE) process that consists of 90 stages of catalytic water-hydrogen isotopic separation units. This upgrader treats 10 m3/y of degraded heavy water, produces reactor grade heavy water, and lowers the tritium and heavy water in the waste to <3700 Bq/cm3 and <0.1wt%, respectively. The other one is simple electrolysis system and terminated its operation in 1999. Heavy water recycle is completed with these two upgraders in the Fugen. A filter-separation-type tritium monitor was developed. Daughter species of Rn-Tn are separated from sampled gas with hollow fiber filters made of perfluorosulfuric-acid resin before introducing to an ionization chamber. The detection limit of the monitor is 7.4E-03 Bq/cm3-air. The upgraders and monitor contributed to control airborne and liquid tritium releases from the Fugen lower than 18 TBq/y and 11 TBq/y, respectively.