Claims that the Dounreay nuclear plant in Caithness was being run with a "reckless" disregard for public health have been dismissed by its operators.
Radioactive particles have been found close to Dounreay
Herbie Lyall, a former safety officer, has said that high level waste was washed down drains and a radioactive particle discovery was covered up.
Dounreay is facing prosecution for releasing particles into the open.
Site operators, the United Kingdom Atomic Energy Authority said there was no record of the particle find.
But it did concede that practices in previous decades were not as stringent as they are now.
Speaking to The Sunday Times, Mr Lyall a health physics surveyor at the north coast plant for 30 years, branded his former employees "nuclear cowboys".
In the last two decades more than 50 radioactive particles have been recovered from Sandside beach, two miles west of the plant.
Lat month the Scottish Environment Protection Agency (Sepa) lodged a report with the procurator fiscal into the release of fragments of spent nuclear fuel from the reprocessing plant into the environment in the 1960s and 1970s.
Mr Lyall accused Dounreay bosses of covering up the discovery of a radioactive particle on Sandside beach, near the facility, in 1984.
He claimed high-level nuclear waste was washed down drains intended for low-level waste and that radioactive materials were handled without appropriate protection.
Mr Lyall, who was at Dounreay from 1960 to 1989, also alleged that effluent samples were collected for analysis using a Wellington boot on a piece of string because sampling machinery was "a heap of rust".
The UKAEA insisted that the discovery of a particle on Sandside was made public in 1984 and they could find no record to substantiate claims about a second find that year.
Monitoring of radioactive particles has been stepped up
However, Mr Lyall said he was a member of a survey team which found a particle on Sandside which was not reported.
Mr Lyall had intended that his account should come to light after his death, but said continuing concerns about the health risks to the public had persuaded him to speak now.
"There have been so many lies said to con the public about Dounreay that I fell I must put the record straight," he told the paper.
"This contamination is a legacy being left for my children's children. It is an absolute disaster.
"They are talking about prosecuting these people. They deserve execution, not prosecution.
"This was people's lives they were playing with. They were acting like nuclear cowboys."
A UKAEA spokesman said the company had already spoken to Mr Lyall about his concerns.
He said: "It is absolutely true to say that, as with any industry, not all of the processes which were in place in the 1950s, 1960s and 1970s would be acceptable by today's much more stringent standards.
"The question in our minds is why Mr Lyall took 20 years after retiring to complain."
He added: "However, as regards the particle find in 1984, one was discovered that year, it was reported to the Scottish Office and the regulators and made public.
"We spoke to former employees involved in surveying beaches at the time but found no information or record to substantiate claims of a further find that year."