The Dhruva reactor is India's largest nuclear research reactor, a 100 MW (thermal) Vertical Tank Type/Thermal Reactor, located at the Bhabha Atomic Research Centre (BARC) in Trombay, Mumbai. Indigenously designed and built by BARC, it achieved its first criticality on August 8, 1985, after construction began in the mid-seventies. The reactor was created to provide an independent, unsafeguarded source of weapons-grade plutonium for India's nuclear program, and to meet the growing national demand for high-specific-activity radioisotopes and advanced research.
The reactor operates using metallic natural uranium as fuel, with heavy water (deuterium) serving as the moderator, coolant, and reflector. It is designed to achieve a maximum thermal neutron flux of $1.8 \times 10^{14} \text{n/cm}^2/\text{s}$. Reactor power is regulated by varying the level of the heavy water moderator. For safety, it features two high-speed shutdown systems, with the primary system utilizing nine shutoff rods made of cadmium.
Dhruva is a key component of India's nuclear infrastructure, generating plutonium-bearing spent fuel for the nuclear weapons program and producing radioisotopes for medical, industrial, and agricultural applications. It is designated a National Facility for Neutron Beam Research, supporting collaborative projects with universities under the UGC-DAE Consortium for Scientific Research (UGC-DAE-CSR). The reactor's importance increased significantly after the permanent shutdown of the older CIRUS reactor in 2010. In 2016, a new Neutron Radiography and Tomography Facility (NRTF) was commissioned at Dhruva to enhance its research utilization.