CIRUS (Canada India Reactor Utility Services) was a research reactor at the Bhabha Atomic Research Center (BARC) in Trombay near Mumbai, India. CIRUS was supplied by Canada in 1954, but used heavy water (deuterium oxide) supplied by the United States. It was the second nuclear reactor to be built in India. It was modeled on the Canadian Chalk River National Research X-perimental (NRX) reactor. The 40 MW reactor used natural uranium fuel, while using heavy water as a moderator. It is a tank reactor type with a core size of 3.14 m (H) × 2.67 m (D). It first went critical July 10, 1960.