▁India ▁Re actor ▁Util ity ▁Services ) ▁was ▁a ▁research ▁re actor ▁at ▁the ▁B hab ha ▁At omic ▁Research ▁Center ▁( B AR C ) ▁in ▁T rom bay ▁near ▁M umb ai , ▁India . ▁C IR US ▁was ▁supplied ▁by ▁Canada ▁in ▁ 1 9 5 4 , ▁but ▁used ▁heavy ▁water ▁( de uter ium ▁ox ide ) ▁supplied ▁by ▁the ▁United ▁States . ▁It ▁was ▁the ▁second ▁nuclear ▁re actor ▁to ▁be ▁built ▁in ▁India . ▁ ▁It ▁was ▁mode led ▁on ▁the ▁Canadian ▁Ch alk ▁River ▁National ▁Research ▁X - perimental ▁( NR X ) ▁re actor . ▁ ▁The ▁ 4 0   MW ▁re actor ▁used ▁natural ▁u ran ium ▁fuel , ▁while ▁using ▁heavy ▁water ▁as ▁a ▁moder ator . ▁It ▁is ▁a ▁tank ▁re actor ▁type ▁with ▁a ▁core ▁size ▁of ▁ 3 . 1 4   m ▁( H ) ▁× ▁ 2 . 6 7   m ▁( D ). ▁It ▁first ▁went ▁critical ▁July ▁ 1 0 , ▁ 1 9 6 0 . ▁ ▁The ▁re actor ▁was ▁not ▁under ▁I AE A ▁saf egu ards ▁( which ▁did ▁not ▁exist ▁when ▁the ▁re actor ▁was ▁sold ), ▁although ▁Canada ▁st ip ulated , ▁and ▁the ▁U . S . ▁supply ▁contract ▁for ▁the ▁heavy ▁water ▁explicitly ▁specified , ▁that ▁it ▁only ▁be ▁used ▁for ▁peace ful ▁purposes . ▁Non eth eless , ▁C IR US ▁produced ▁some ▁of ▁India ' s ▁initial ▁weapons - grade ▁plut on ium