A century ago, radioactivity seemed harmless and intriguing. Henri Becquerel had discovered it in 1896, as a property of uranium salts. People just loved their uranium samples, which produced energy apparently from nowhere and apparently endlessly. Two years after Becquerel, Marie and Pierre Curie discovered another element, radium, so powerfully radioactive that it glowed in the dark, and by 1901 they were in the process of producing pure radium samples.

Radioactivity was fascinating science. No one saw on the horizon the dark images that the word conjures up today. True, Henri Becquerel had a habit of carrying in his waistcoat pocket a little vial of the uranium salts that made him world-famous, and after a few months he developed an ulcer on his chest close to the vial. But it was many years before the full dangers of handling radioactive material were understood, and by then it was too late for the early workers. Marie Curie had lesions on her fingers that would not heal, and she developed and at last died from anemia that almost certainly arose from radiation poisoning.

Carelessness in handling radioactive materials in those early days was no more than the result of ignorance, and it needed no explaining. Half a century later, the overriding urgencies of the Second World War and the race to produce an atomic bomb led to a similar lack of attention to nuclear waste disposal.

The late 1940s and the 1950s are another matter. By that time we knew, very well, the dangers. Many nuclear waste materials remain radioactive for thousands and even millions of years. With such a long-term legacy, this country should have given the highest priority, on the one hand to controlling the production of such materials, and on the other hand to storing them with great care. We needed to know exactly where those nuclear dumps were located.

What happened in practice is frightening. Hidden under the cloak of national security, careful monitoring was low on the list of priorities. Sometimes information was lost completely, as in 1977 when a fire destroyed records at the Oak Ridge National Laboratory in Tennessee. Even in the best of cases, radioactive wastes were dumped over large areas, with little attempt at accurate inventory. In the worst cases, nuclear wastes were able to seep through into subterranean aquifers below national test sites, and spread far beyond their presumed limiting boundaries. Looking at our record of performance, or lack of it, through the 1960s, about the best that can be said is that the Soviet Union was even worse.

Today, we have a national cleanup program for radioactive wastes, but the size of the task is monstrous. An area bigger than Vermont is involved, scattered across many states: Idaho, New Mexico, Tennessee, Washington, Nevada, and Georgia, to name just some of the most affected. I was at a review meeting in which one representative of the Department of Energy estimated the cost at $20 trillion. The man sitting next to me, more practical than cynical, muttered, "If that's a good number it guarantees one thing: a full cleanup won't be done."

That's the present situation, and everything I have said so far sounds pessimistic. However, I want to point out a scientific possibility - and it is today no more than a possibility - which might transform the problem.

Radioactivity occurs when the nucleus of an atom is unstable. In energy terms, it is not in its "ground state." The unstable nucleus will, after a shorter or longer period over which we have no control, emit either a particle or radiation, and proceed to a state of lower energy. This new state may be the state of lowest energy, or it may be some new transitional state, in which case there will again, after a shorter or longer period, be another emission of a particle or of radiation, moving the nucleus to still another lower energy level. This can happen many times, but at last the nucleus must achieve its lowest energy state. It will then no longer be radioactive.

>From our point of view, there are two big problems with this process. First, although we know on average how long it takes a radioactive nucleus to go from one state to another, we have no way to predict when any given nucleus will undergo a decay. The "half-life" for a radioactive material merely measures the time it will take for half the nuclei in a large sample to make the change. Second, we have no control of the process. We can't speed up a radioactive change.

Now for the key question: Is there any way to make these nuclear changes take place just when we want them to, rather than waiting for unpredictable nature?

There is, at least in principle. Outside the nucleus we have a device that achieves exactly such an objective. It is called a laser, standing for Light Amplification by Stimulated Emission of Radiation, and although we may think of it mainly as something used in CD players or eye surgery, it does for the whole atom exactly what we would like to do for the nucleus of an atom. When a laser operates, the electrons of the atom, which have been sitting in an unstable state higher in energy than their ground state, all descend at once to occupy that stable ground state.

What we need, but do not yet have, is a device to produce stimulated emission within the nucleus. We need a nuclear laser. With such an instrument, the application of radiation at very short wavelengths will trigger a change of the particles in the nucleus to a lower energy state. Since several changes usually are involved, we will need to apply the nuclear laser multiple times. However, we should be able to accomplish in minutes or seconds what in nature may take thousands or millions of years. The process will call for careful control, because all the energy provided by nuclear transitions will be given off in a short time. However, there is a strong positive side to this. Although our nuclear waste sites contain large amounts of stored energy, we have no way to tap it when we want it. If we can stimulate the nuclear changes that we need, not only will we solve the problem of radioactive waste, we will also have a supply of useful energy.

In my perfect future, our despised dumps of radioactive wastes will be as sought after and commercially valuable as today's oil fields.

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