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Originally published in Tuttoscienze of LA STAMPA, 6 July 2005

On the evening of 6 August 1945, the BBC announced to the world that an atomic bomb had just been launched on a “Japanese army base." That “base” was actually a city: Hiroshima. Three days later, another city was hit by an atomic bomb: Nagasaki. Roughly 300,000 civilians were killed in those two bombings and those bombings changed history forever as, for the first time in our civilization, man acquired the capability to destroy the entire human species in a single blow, through a catastrophic nuclear war. Sixty years after Hiroshima and Nagasaki, the first nuclear power in history, the United States, is “rethinking” nuclear weapons. We spoke about this topic with eminent physicist Frank von Hippel, professor at Princeton University (USA).

Professor Hippel, could you briefly illustrate the debate currently going on in the U.S. concerning a new generation of nuclear weapons? Basically, it is about two kinds of weapons: bunker busters and mini nukes - the former being anti-bunker weapons. In fact, over the last few years, we have often heard that bunkers could be of concern, being extremely strong underground structures where the leaders of the so-called “rogue states” could construct or stockpile weapons of mass destruction. According to some, we should reassemble some of our existent nuclear weapons - or, if the packaging would not survive, construct something completely new - so that we might have these so-called bunker busters to penetrate the rocks in a few minutes, with the shock of the impact and the nuclear explosion able to destroy the bunker and possibly the weapons stockpiled in it.

How powerful are bunker busters?

They are in the range of 1-megaton, that is, they release an energy equivalent to 1 million tons of TNT.

How can one imagine using a 1-megaton weapon? I mean, the Hiroshima bomb was just 12,5 kilotons - that is, 12,500 tons of TNT, and it killed 200,000 people.

In fact, the debate is about the bunker buster usability: a 1-megaton weapon could contaminate 200 square kilometers with its lethal radioactivity. But the bunker buster supporters argue that, since those weapons explode underground, “collateral damage” such as deaths and radioactive contamination will be significantly reduced.

Is this true?

It is just self-deception. Physicists who have taken the trouble to make some calculations have demonstrated that, although bunker busters can penetrate the rocks, they can’t actually penetrate deep enough so that the nuclear explosion will be totally confined to the ground.

And what about mini nukes?

Those are weapons with less than a 5-kiloton yield.

Why make them?

It is a mind game. During the entire Cold War there was a psychological game of trying to convince the Soviets and even ourselves that our nuclear weapons were usable and therefore were a credible threat to our enemy. But actually, we also had our own doubts, as using them in a war would have been the end of our civilization. Now, we are back to that psychological game; the advocates of these new arms are convinced that no one would take the responsibility of using such destructive weapons as those currently stockpiled in our nuclear arsenals, and so we must make smaller and more usable nuclear weapons to make our threat credible.

Do you think they will make them?

For now, it seems they will not; a key committee, chaired by a Republican, cut the funding for the scientific research on these weapons. But what will happen remains to be seen. And if they decide to make those weapons, it will most certainly be necessary to test them, and so the States will resume nuclear testing, which we stopped more than 10 years ago. This in turn will make other countries resume nuclear testing, with all the consequences of the proliferation of nuclear weapons.


People opposing these “usable weapons” sustain that the most serious risk is that they can clear the use of nuclear weapons, which for sixty years have been considered “last resource” weapons.

The public opinion thinks that nuclear weapons are “last resource weapons," which is indeed a reassuring idea. But in the late fifties, I had the possibility of speaking to the man who commanded the nuclear artillery in Germany and he told me frankly that if he saw Soviet tanks coming over, he had the authority to use nuclear weapons. And so nuclear weapons were seen as usable, at least in that period.

Nevertheless, it is true that after Nagasaki they have not been used in combat and there has been a nuclear taboo.

Well, I think it is much more appropriate to speak about a continuous struggle between those people who see these things as usable and those who work to keep the implications of using them in people's minds. I think there are a lot of people even in this government who realise that nuclear weapons are not usable, but there are also people like Cheney who, when he was Secretary of Defence during Bush Sr.'s Administration, had a plan for using them in Iraq in the first Gulf War. So far, we have been lucky; people who consider nuclear weapons usable haven’t prevailed, but the struggle goes on. And I am concerned that the anti-nuclear movement has not being active now for more than 20 years; worldwide public opinion has become detached from reality.

What does the physics community think about these “new weapons”?

Personally, I don’t know any independent physicist in favour of them. Whereas, the leadership of the weapons labs of Los Alamos, Livermore, and Sandia is influenced by politics and encouraged to think about those weapons.

What kind of people are the physicists who work in those labs?

They don’t have an ideological approach and they are not politically sophisticated. Basically, they conceive of democracy as an “elective dictatorship,” as they reason: “We have elected a president, and so we should do what the president says. And if he says we should work on these weapons, we should do it, as making decisions is not up to us - we are just technicians”.

Meanwhile, if the “hawks” have not prevailed so far, it is thanks to those physicists who have not confined themselves to the role of simple technicians, but have taken the responsibility of working for arms control. You have worked on it for 30 years and you have been an insider as well...

Yes, in 1993 I took a two year leave from Princeton and I was an “insider” - that is, a science advisor at the White House during the Clinton Administration.

And what was your experience there?

Well, the fact that I left after 16 months, rather than two years, is an indication...

And so even those who have the technical skills, the desire to change things and the opportunity to arrive at the “engine room” can’t actually impose their ideas..

Well, it depends. In some areas, working inside the system was actually fruitful, but I got very modest results in trying to change the direction of nuclear policy. And, as far as some areas are concerned, such as the comprehensive test ban treaty, I had even more impact as an outsider - working as an expert analyst together with activists - rather than as an insider, working as a White House advisor.

What kind of opposition did you encounter exactly?

Basically, decisions in matters of nuclear policy are in the hands of the National Security Council. But, having always worked for arms control, I was recognized by the Council as having an agenda - an agenda which they didn’t particularly like. And so they tried to keep me out as much as possible.

Actually, that agenda is in your own DNA, as you're the grandson of James Franck, who authored the famous “Franck Report”. In that report, a group of physicists who had worked on the making of the first atomic bomb asked President Truman, among other things, not to use that bomb on the civilian populations of Japan. They suggested that Truman use the atomic bomb only in a demonstrative way - for example, on a desert island - so that the Japanese would have surrendered without that terrible slaughter. What is, in your opinion, the legacy of Hiroshima and Nagasaki?

Personally, I think that using those bombs on civilians was a war crime. But I also think that the fact that we did not use nuclear weapons during the Cold War is also thanks to the fact that we saw the implications of their use in Hiroshima. And so, Hiroshima was a war crime, but it was also a lesson. Of course, we certainly didn't need a second lesson: Nagasaki.