When Bellona Web last summer for the first time reported about the planned subcritical tests at Novaya Zemlya, officials from the Ministry of Nuclear Energy denied that any radioactive substances would be involved in what the Ministry call ‘hydrodynamic experiments’. But now, Deputy Minister Ryabev says to Interfax that both weapon-grade plutonium and highly enriched uranium was used in the tests conducted at the northern test range near Matotchin Shar at Novaya Zemlya. The international Comprehensive Test Ban Treaty (CTBT) does not prohibit subcritical nuclear bomb tests, because the amount of radioactive plutonium or uranium used is considered insufficient to create a nuclear explosion.

"There was no discharge of radioactivity from any of the five tests," said Ryabev in the interview with Interfax. The last two subcritical tests were carried out in less than a week, between December 9 and 13. The tests are used both for improving old nuclear warheads and for developing new nuclear devices. Various physical-modelling experiments follow the subcritical tests.

Russian officials last autumn announced plans for more ‘hydrodynamic experiments’ in 1999, but according to Ryabev the five tests this autumn were the last.