Take a look at this 2010 DIA document.
If you want a primer on implosion, here’s a handy one from LANL:
This article is set during the 1944 and 1945 final push to complete Project Y—the Manhattan Project at Los Alamos—and focuses primarily on overcoming the challenge of creating and demonstrating a successful convergent explosive implosion to turn a subcritical quantity of plutonium into a critical mass. The critical mass would then efficiently yield kilotons of trinitrotoluene (TNT)-equivalent energy in about a microsecond, demonstrating the implosion atomic bomb concept. This work culminated in the Trinity atomic test near Alamogordo on July 16, 1945.
Here’s what DAE told the Lok Sabha this past March:
Uranium fuel requirement for the reactors which are not covered under the International Atomic Energy Agency (IAEA) safeguards is adequately met by Uranium Corporation of India Limited (UCIL), aPublic Sector Enterprise under the Department of Atomic Energy (DAE). Time to time, projects which include capacity expansion of some of existing units as well as for establishing new projects in various parts of the country, are planned for maintaining sustained supply.
Regarding fuel supply for Pressurized Heavy Water Reactors (PHWRs) which are under IAEA safeguards, a strategic reserve of imported natural uranium is maintained for enabling uninterrupted supply of fuel. Fuel for Boiling Water Reactors (BWRs) and water-water energetic reactor (VVERs) is met from the imports from Russia