Reflecting the ``excellent synergy'' between the Department of Atomic Energy (DAE) and the Defence Research and Development Organisation (DRDO), the five nuclear tests conducted on May 11 and 13 at Pokhran and nicknamed `Shakti 1998' have ``conferred the country with a capability to vacate nuclear threats'', DAE chairman R Chidambaram, told a press conference which he jointly addressed alongwith A P J Kalam, Scientific Advisor to the Defence Minister.

Giving some critical details about the thermonuclear, fission and low yield devices tested, Chidambaram said the five tests have generated critical data to validate India's ``capability in designing nuclear weapons of different yields for different applications anddifferent delivery systems''.

The press conference, the first since the Indian nuclear tests shook the world, was a reflection of the exploding global interest that India's nuclear tests have provoked. Despite unprecedented security checks to keep out curious onlookers, the PIB conference hall was jampacked beyond capacity. And as the prepared statement was distributed there was a near stampede as journalists stepped over each other to grab a copy of the long-awaited statement from the Indian scientific establishment.

The detailed question and answer session that followed the prepared statements by Chidambaram and Kalam, scotched much of the speculation in the Western media whether Indian scientists were capable of exploding an indigenously produced hydrogen bomb, especially in the face of the stringent export controls regime aimed at crippling the Indian nuclear programme.

Kalam, too stressed the dovetailed operations of the different arms of the DAE, DRDO, the Indian army and the Air Force, once thenew government took the political decision to go ahead with the tests. According to Kalam, ``when nuclear technology and defence technology meet, they get transformed into nuclear weapons technology. This is what the nation witnessed on May 11''.

He, however, declined to reveal the nature of the fissile fuel used in this and four other blasts. Replying to questions whether India is going to induct nuclear weapons, Kalam said ``India is a nuclear weapon state under clause nine of the nuclear Non-Proliferation Treaty (NPT).''

Another significant announcement by Kalam was that the ``Agni'' missile could be mass produced by India while work is on to develop an advanced version of the intermediate range ballistic missile.

``If needed Agni can be made in numbers. The Government has given approval for the next version of Agni and this is in an advanced stage of development'', he said, adding that the new version of the missile would have an ``even higher strike range and will be modular in construction''.

Both Agni and India's surface-to-surface ``Prithvi'' missiles were designed to carry a complete range of both conventional and nuclear warheads, he said. Asked if the tests were adequate for a shift to computer simulated tests, Chidambaram said the tests have ``significantly enhanced India's capability in computer simulation of new designs'' taking scientists to the stage of subcritical experiments in the future, if considered neccessary.

Reassuring that the tests were fully contained, he said there had been no release of radioactivity into the atmosphere.

Though there were a number of issues on which the top scientists preferred to remain silent, the interaction with the media shed light on a number of grey areas which had led to speculation in the Western media on whether or not Indian scientists were capable of exploding a hydrogen bomb.

Ever since the series of tests, including the thermonuclear, a fission device and three low-yield devices, Western newspapers, quoting U S nuclear experts andseismologists, have been rife with speculation that the explosive yield could have been caused by one or more smaller devices and not necessarily by a hydrogen bomb.

Chidamabaram clarified that the confusion may have been created by the low seismic signals picked up by international stations since the tests were conducted simultaneously.

Indian scientists were constrained by the presence of Ketolai village a mere five kilometres away from the test site and had to contain the yields to the lowest optimum level.

Doubting the ability of Indian scientists to put together a sophisticated H-bomb, the general agreement among the US-based experts was that the Indian thermonuclear device was not a hydrogen bomb, but a ``boosted fission device''.

Asked about the logic of conducting simultaneous tests, Chidambaram said another reason why the seismic data was confusing was because the two shafts where the tests were conducted were just one kilometre apart and there was the danger that the shock from one testwould damage the second shaft. To circumvent this, it was decided to conduct the three tests simultaneously, he said.

Chidambaram also pointed out that the thermonuclear device or the hydrogen bomb used an advanced fission device to trigger the thermonuclear core.The fission trigger produced about 12 kilotonnes to activate the thermonuclear core to ultimately yield 45 kilotonnes.

Maintaining that the yield of the hydrogen bomb could have been designed to be much higher, Chidamabaram said it was deliberately kept low to avoid damages to the structures at the nearest village of Khetolai.

The thermonuclear (45 kt), fission (15 kt) and low-yield (0.2 kt) devices were detonated simultaneously and two more subkiloton devices (0.5 and 0.3 kt) were also simultaneously triggered on May 13.