In 1963, Len Owen, once #2 under pioneer Christopher Hinton, but now seven years into his latest role of the production/engineering arm of the United Kingdom Atomic Energy Authority, addressed the Institution of Civil Engineers in Great George Street, Westminster, not far from Parliament Square. He called his speech “Nuclear engineering in the United Kingdom in the first ten years,” and he restricted himself to the first decade, i.e. 1946 to 1956.
One incident he described to his audience would reverberate five years later:
On the operational side an event which gave cause for some alarm occurred in September 1952, almost two years after the start-up of Pile 1. An unexpected temperature rise was recorded during a period of shutdown following a short period of operation at low power. I remember being telephoned in the middle of the night and told that the pile temperature was rising although the shut-down blowers were full on and all the shut off rods had been inserted into the pile. Fortunately the temperature on that occasion levelled off and subsequently fell without any damage being done. It did not take long to show that this temperature rise could be explained as a manifestation of the Wigner effect. Wigner, an American physicist, had predicted that neutrons would displace atoms from the graphite crystal lattice, but it had not been appreciated that the energy stored in the graphite could be released under certain temperature conditions. Once the phenomenon was understood routine procedures were developed for annealing at regular intervals so that excessive releases of energy could not occur.
Owen, Leonard. 1963. “Nuclear engineering in the United Kingdom in the first ten years.” Journal of the British Nuclear Energy Society, Jan., p. 12.
An astute observer might note two things. One, Eugene Wigner had in fact predicted exactly the phenomenon observed in 1952. It was called the Wigner effect. The Americans did not share this information fully with the British but it surprises me that well-connected British scientists such as John Cockcroft never cottoned on before construction. Two, this Wigner effect was probably the main underlying cause of the 1957 Windscale reactor fire, one of the four “big” nuclear accidents, but Owen strategically fails to mention that fact.
