New difficulty for radioactive disposal

Press, 10 August 1985, Page 1

New difficulty for radioactive disposal

Radioactive waste, collected by the National Radiation Laboratory, may have to be disposed of in New Zealand now that the new South Pacific NuclearFree Zone Treaty has been endorsed by the Government.

This possibility was confirmed yesterday by the laboratory’s director, Dr Andrew McEwan, who said it would present new difficulties.

Until now, the laboratory has disposed of radioactive waste, collected from hospitals and industries throughout the country, by dumping it in sealed concrete containers at sea.

Treaty signatories have agreed not to dump radioactive waste in the South Pacific between Australia’s west coast, the Latin American nuclear-free zone and between the equator and the Antarctic demilitarised zone.

If the radioactive waste had to be disposed of in New Zealand, it would mean finding an area of land that could be protected and not developed for many years, Dr McEwan said. “The land would have to be segregated and supervised in some way,” he

said. “The radium that we dispose of has a long halflife, taking 1600 years to lose half its radioactivity. “Deep disposal of the waste down an old mine might be one possible site for disposal, or using a military base. So far there have been no possible sites put forward that are suitable for disposal of the waste.” The laboratory did not have to find a suitable land site in the immediate future, he said. “We could store the waste in lead containers at the laboratory until the next century. By then, a shortage of space and lead containers in the laboratory, and the continuing collection of the waste would mean we would have to find somewhere to dispose of it,” Dr McEwan said.

“As well as radium, we dispose of caesium 137, with a half-life of about 30 years, and small quantities of

cobalt and strontium 90. If a hospital was to replace its radium stock in one year we would have a larger amount of radium to dispose of in that year. “So, the figures for the quantities of waste fluctuate from year to year.” The last disposal at sea of the collected radioactive waste was in 1976, and another 10 years of waste collected since then had to be dealt with at some stage, Dr McEwan said. “The treaty doesn’t appear to cover the release into the sea of radioactive waste via water outlets such as sewerage systems,” he said. “This applies to some radioactive materials used in unsealed form, particularly in nuclear medicine where the material is injected into the patients. “There are agreed levels of discharge of such waste into sewerage systems, and ultimately some of the material reaches the sea.

This radioactive waste has a short half-life and in general is non-radioactive by the time it reaches the sea,” Dr McEwan said.

He said he thought the treaty would also not affect studies done with radioactive material in some water systems. “These studies trace the movements of radioactive material in a water system such as a harbour to find out how that system could cope with a sewage outlet into it,” Dr McEwan said. “The researchers check whether any of the water would return to the land, and radioactive material with a half-life of about eight days is used for this. “The environmental impact of releasing the radioactive material is always assessed before the study is carried out. The material is not considered radioactive waste and is chosen for its short half-life,” he said. Once it was placed into the water system, it quickly became diluted and distributed over a wide area. “These studies have already been carried out at a number of sites throughout New Zealand and also on land to trace geothermal flows,” Dr McEwan said.