There is considerable controversy over the yield and reliability of India's nuclear devices. When India tested its first fission device in May 1974, Indian scientists claimed the device had a yield of about 12 kilotons (kt); however, some Indian officials later stated that the figure was closer to 8 to 10 kt, while other independent analysts estimate that the yield was as low as between 4 and 6 kt.[9]
Similar disputes surround India's May 1998 tests. After the first of round of tests on 11 May India's Department of Atomic Energy (DAE) announced that it had simultaneously tested three nuclear devices: a thermonuclear device with a yield of 43 kt; a fission device with a yield of 12 kt; and a sub-kiloton device with a yield of 0.2 kt.[10] However, analysts and scientists outside of India – citing evidence from geologic and seismic data – concluded that the cumulative yield of the Indian tests was much lower, implying that the second stage of the thermonuclear test had not detonated successfully.[11] In subsequent years, the controversy was reignited following announcements in 2000 by P.K. Iyengar, former chief of the Department of Atomic Energy, and in 2009 by K. Santhanam, field director of the 1998 tests, that the tests did not achieve the desired results.[12] These scientists argue that India should therefore refrain from signing the Comprehensive Nuclear Test Ban Treaty (CTBT) and conduct further tests.[13] However, Anil Kakodkar and R. Chidambaram, present and former leaders of the Atomic Energy Commission (AEC), have consistently disputed these claims, maintaining that their original estimates were correct and that further testing is unnecessary.[14]
*ttp://www.nti.org/country-profiles/india/nuclear/