Physicist and former assistant director of Dounreay

Born: May 14, 1939;

Died: October 5, 2017

KEN Butler, who has died of cancer aged 79, was a physicist and botanist who became assistant director of the Dounreay nuclear power plant in Caithness. He spent his entire professional career at the plant, retiring after 43 years as a highly respected elder statesman of science.

After his retirement, Mr Butler also established a considerable reputation as a botanist. In 2013, he published Wild Flowers of the North Highlands of Scotland, the definitive work on the subject which included pictures by the award-winning nature photographer Ken Crossan.

Mr Butler also had lengthy service as the record-keeper for Caithness and Sutherland for the Botanical Society of Britain and Ireland.

The second son of an aircraft factory worker, Ken Butler grew up in Warrington but moved for the duration of hostilities with his family to Crewe where his father worked at the Rolls Royce factory. One early childhood memory is of an aerial dogfight over the plant between RAF fighters and Luftwaffe bombers.

His interest in botany began when he was a boy and took his three younger siblings on rambles in countryside, naming the common wild flowers to them. At the local grammar school, Ken also showed an aptitude for physics but, like many other working-class lads of his era, he needed to earn a living rather than go to college or university and got a job at the former Royal Ordnance Factory at Risley.

After his interview, the eager teenager was told that there were vacancies for trainee assistant experimental officers at far-away Dounreay, with the UK Atomic Energy Authority (UKAEA) offering a visit, prior to an six-month nuclear induction course that would be done locally in Risley.

Years later, Mr Butler recalled his first visit to the massive construction site that was to become Britain's major centre for fast reactor research and development work.

"I was taken there on a raw, cold, December day in 1956, walking around the site in a sea of mud," he said. "The shell of the Dounreay Fast Reactor dome was half-built, there were no proper surfaced site roads and the brick walls of the laboratories block where I was going to be working were up, but there was as yet no roof on the building."

However, Mr Butler was un-phased and moved north the following June when he found himself part of a team getting the newly-completed D-1200 laboratory block complex into a working state. The accommodation was spartan in the extreme: Second World War huts where up to 3,000 new recruits and construction workers lived while the massive atomic complex was being built.

Two months later, things were on the up, when the teenager was transferred to Ormlie Lodge, a mansion-house in Thurso that UKAEA had purchased and extended as a hostel for new-starts. Ormlie Lodge was his home until in 1960 when Mr Butler married Sheila (nee Sutherland), whom he had met at a regular weekend dance at Thurso Town Hall in 1958.

Later, Mr Butler was part of the team that devised and tested the measuring equipment for the fast reactor's NaK coolant circuit - challenging work for a man still in his teens, but necessary as there was no previous experience in the UK in this field.

Before the fast reactor started operating, there were reports in 1955 of problems at a smaller-scale experimental breeder reactor in America, where unplanned overheating had damaged a number of fuel rods. The question that concerned British atomic chiefs was: would Dounreay's fuel rods melt in the unlikely case of a coolant failure?

They decided to play safe and had a special armoured heavy steel plate designed, constructed and installed to ensure that its damaged core could not slump downwards in the event of a mishap, one that could have serious consequences. Mr Butler found himself assisting in preparing the necessary safety case for ensuring that the metal would sag down safely, even in a hypothetical fuel melt-down situation.

His work was noticed by Dounreay's senior managers who decided he deserved to be sent at UKAEA's expense to undertake a higher national certificate at Robert Gordon's College in Aberdeen; years later UKAEA covered the costs of his honours degree course in physics at what is now London City University.

Ken Butler was popular with his colleagues and in the mid-1960s, he was elected as an office-bearer in the local branch of the main union representing scientific staff at Dounreay, the Institute of Professional Civil Servants, IPCS. As he rose through the ranks, he was involved in more and more aspects of Dounreay's programme before becoming assistant director of the plant.

He is survived by his wife Sheila, their son Kevin, and his daughter Karen, who works at Dounreay. There are four grandchildren.

BILL MOWAT