Prior to that, Ratan Kumar Sinha had served as Director of Bhabha Atomic Research Centre (BARC), Mumbai from May 2010 to June 2012.

As chairman, AEC and Secretary, DAE, Ratan Kumar Sinha had put special thrust on several key deliverables for sustainable development and deployment of nuclear energy.

[8][9] Major thrust areas, in continuation to his research at BARC, include advanced nuclear energy systems for thorium utilisation[10][11][12] and accelerator technology.

[13] He had given high priority to application of radiation technology in the areas of healthcare management, agriculture, food preservation and water purification.

[16][17][18] Under his leadership, DAE displayed its first ever tableau in the 66th Republic Day Parade 2015 and had launched its social media page on Facebook as a part of public outreach initiatives.

Ratan Kumar Sinha has made significant contributions to the design, experimental development and implementation of next generation Indian reactors.

[10] These programmes include the Advanced Heavy Water Reactor (AHWR), which produces most of its power from thorium and has several innovative passive safety systems.

[31][32] Ratan Kumar Sinha has enabled development of self-reliance, and achievement of international excellence in several domains of nuclear technology.

Ratan Kumar Sinha has strengthened outreach activities of DAE for spreading awareness about nuclear energy among the general public.