Confidential government files from 1983, details of which were released on Friday, confirm the secret dumping of radioactive waste took place in Derry in the early 1980s.
A memo, dated 5 December 1982, revealed that solid radioactive waste had been buried at two local authority disposal sites during the period 1977-1982.
These were at Culmore Point outside Derry and at Duncrue Street in north Belfast.
At Culmore Point, two consignments of hospital waste had been disposed of by controlled burial; the total activity amounted to 170 microcuries.
At Duncrue Street, the memo noted “a number of controlled burials of hospital/university waste of short half-life, together with small amounts of industrial waste were arranged.”
The total activity disposed of was approximately 180 millicuries, of which the bulk comprised radioactive iodine with a half-life of less than two months.
The file noted that a number of hospitals, fertiliser plants and both of Northern Ireland universities had been authorised to dispose of radioactive waste by controlled burials at these sites.