Thomas Nelson Marsham, 10 November 1923 - 12 October 1989

Abstract

Thomas Nelson Marsham was one of that band of distinguished men of strong intellect and strong personality who laid the foundations of a programme of nuclear power generation in this country on a sound technical basis. He joined the new atomic energy enterprise when it was still the responsibility of the Ministry of Supply, transferring to the United Kingdom Atomic Energy Authority on its formation, and eventually retired from the UKAEA as a main board member in 1988. After war-time service in the Merchant Navy, he was trained as a physicist and did his doctoral research in nuclear physics. This training enabled him to master rapidly the basic neutron physics underlying the operation of nuclear reactors but, as his career advanced in the UKAEA, he showed also an excellent grasp of engineering principles. Significantly he was elected to the Fellowship of Engineering in the same year as he was elected to the Royal Society. He attained managerial rank and responsibilities in the expanding AEA at a relatively early age, so his career inevitably mirrors the changing tasks and responsibilities of the Authority itself. However, he will be remembered mainly for two outstanding contributions. The first is to the development of gas-cooled reactors in this country. He played a major role in the successful commissioning of the first generation of gas-cooled reactors at Calder Hall and Chapelcross, and later in the introduction of the more efficient advanced gas-cooled reactors, for which he was a persuasive advocate. His second main interest was the development of the fast-neutron fission reactor, a technology in which he became a national and international authority. He saw the introduction of fast reactors as an essential step towards achieving the long-term gains to the national economy from nuclear power that he believed to be both possible and essential.