US Defence Secretary Donald Rumsfeld offers a very interesting argument as the rationale for continuing with the research on 'bunker-buster nuclear device'. According to him, the US is presently in possession of very large, very dirty, big nuclear weapons and is now interested in having something between 'no nuclear weapons' and a 'large, dirty nuclear weapon', hence the interest in nuclear bunker-busters!

The Bush administration intends to develop a nuclear weapon that could penetrate the earth and destroy underground enemy bunkers while minimizing civilian damage. The bunker-buster programme was shelved by the Congress last year, and now has received a fresh lease of life with the Senate agreeing to revive the programme. The Senate voted 53-43 to include $4 million for research into the feasibility of a bunker-buster nuclear warhead. Earlier this year, the House refused to provide the money, so a final decision will have to be worked out between the two chambers.

Supporters of the programme claim that the sanction of $4 million amount does not signal development of any new warheads. They argue that the money would be used to check whether a sufficiently hardened casing could be developed for an existing warhead for it to penetrate beneath the earth before exploding and destroy reinforced underground bunkers. The opponents of the programme are of the opinion that such a move sends the wrong signals to the rest of the world and this may eventually lead to testing and development of a new generation of nuclear weapons.

Around two years back the Bush administration had given a quiet go ahead to a controversial research for the bunker-buster project, ending a 10-year ban on research into 'low-yield' nuclear weapons. This act drew criticism because it had indirectly specified the futuristic policies of developing new generation of weapons, called 'mini nukes'. Now the Senate approval comes at a highly sensitive time diplomatically, when the US itself is focusing on countries such as Iran and North Korea to abandon their nuclear plans.

The need for bunker busters is felt because of the recent US experiences in Afghanistan and Iraq. The US forces found it extremely difficult to attack underground bunkers and are of the opinion that they require state of the art technology for successful prosecution of operations. Such bombs are designed to use shockwaves to destroy deep bunkers even if the bomb does not reach them. Currently, US scientists plan to modify two existing nuclear bombs - the B61 and B83 into a bunker-buster. The B-52 bombers or F-16 fighters could be used to deliver the load. It is estimated that the larger B83 bombs has explosive yields of one to two megatons. The present research in the arena of bunker-busters is expected to focus more on hardening the bomb casings to make them capable of penetrating layers of steel, rock and concrete.

The Pentagon estimates there could be approximately 10,000 hardened targets (above and below ground) in the territory of potential US adversaries. They further identify about 20 per cent of these targets as 'major strategic function targets' like command-and-control systems (C4I) or weapons stockpiles. Of that 20 per cent, almost half could be near or in urban areas and mostly surrounded by high population density. According to US scientists, bunker-buster nuclear bombs, if aimed accurately, would be more effective than conventional bombs in destroying such hard and deeply hidden targets.

However, many in the scientific community challenge the claims made by the US military technologists. They claim that earth-penetrating nuclear bombs would be capable of destroying military targets deep underground, but not without inflicting 'massive casualties at ground level.' Even relatively small nuclear bunker busters pose a direct or an indirect threat to human life. Such weapons are capable of killing many because such munitions emit large amounts of radioactive debris. Also, trying to reduce fallout and civilian damage by making a very small weapon is impractical because its destructive force would be insufficient to destroy military targets.

As per one report, if a warhead penetrates approximately 10 feet into the earth before detonating, much of its energy will go into the ground. This will lead to a shockwave formation that can destroy underground structures. But attacking bunkers at depths of 650 feet would require a blast of 300 kilotons, or 20 times larger than the bomb that destroyed Hiroshima. A 1,000 feet deep target would require a weapon 67 times as large. Such huge weapons would defeat the purpose of the entire programme. But in all likelihood the Bush administration will go ahead with their plan of developing bunker-busters. The failure of recent NPT Review Conference indicates that non-proliferation is not on the agenda of the current US government. Any production of bunker-busters would only be a confirmation of this policy.