Remembering Eric Voice

Last September the RSC lost a much-valued member. Eric Voice probably had more intimate knowledge of plutonium than anyone alive in the UK today. His experience went back to the 1950s when he saw the newly-crowned Queen Elizabeth, on a visit to the UK Atomic Energy Authority (UKAEA) research establishment at Harwell, handed her a lump of plutonium in a plastic bag and invited her to feel how warm it was.

Voice was a founder member of the campaign for nuclear disarmament, and a nuclear energy enthusiast. As well as working at Harwell, he worked at the Dounreay and Winfrith UKAEA research centres, on the fast reactor, a system intended to ’breed’ plutonium from non-fissile uranium-238. After the Chernobyl explosion of a reactor designed to make both electricity and military plutonium, he made several visits to the Ukraine to study health effects.

In the 1990s a retired Voice helped plan, and took part in, ’clinical’ studies to show that much of plutonium’s alleged deadliness was pure mythology. Thestudies involved 12 or more people deliberately taking plute by injection with a citrate solution of a short-lived plutonium isotope. Later experiments involved inhaling a long-life isotope.

Just before he died - at 80, five years after these clinical studies ended, and from motor neurone disease - he told me: ’I find that I possess 15 reports of the results and deductions in professional scientific journals so far’.

Voice worked hard to debunk the plute mythology created by texts with titles like Poisoned power or The deadliest element. Radiotoxic it undoubtedly is - Glenn Seaborg, its Nobel-prize winning discoverer always recognised this - but only one-20th as toxic as radium. Voice believed ’there is no evidence that any human on Earth has ever died or suffered any health consequences whatever from plutonium radioactivity’.

A huge and mostly top-secret research effort, hundreds of millions of dollars a year, is focused on element 94, mainly in the US, Russia, the UK, France and China. The material’s properties and peculiarities in all manner of circumstances, are painstakingly studied. Weapon designers needs these details to design with confidence. Weapon storekeepers need to know how weapons may change with time. Reactor designers need the data to make safer, cheaper power systems. Custodians of plutonium’s waste products need them to plan repositories secure for thousands of years.

Plute feels warm because it is self-irradiating. Plutonium-239, the most abundant of 16 unstable isotopes, bombards itself with alpha particles. It’s pyrophoric and very heavy; the heaviest industrial metal, nearly twice as heavy as lead.

It has six allotropes - crystal structures - with significantly different properties, one is so brittle it shatters like glass. It has a perplexing tendency to switch abruptly from one to another with rising or falling temperature.

Plutonium has five valencies, giving it a large and richly coloured chemistry. Reds, greens and blues abound among its compounds.

Some of the world’s most powerful scientific tools are used to study plute’s peculiarities. US weapon scientists have recently commissioned a gas gun that fires projectiles faster than five kilometres a second and subject plutonium samples to six million times atmospheric pressure and temperatures of thousands degrees celcius.

The European Synchrotron Radiation Facility near Grenoble, France, is used to study plutonium’s phonons, crystal lattice vibrations caused as atoms are displaced by self-irradiation.

In little more than half a century, science, driven hard by the twin imperatives of military and civil needs, has learned that plutonium might claim to be the most fascinating of all the elements. To quote a Californian laboratory that works with it, ’plutonium is the most complex and perplexing element in the periodic table’.

David Fishlock