Dry deposition of 88Rb and 138Cs from a boiling water reactor plume.

Double tracer experiments were made in May 1981 at the Ringhals nuclear power plant in Sweden to investigate atmospheric-dispersion and dose models. Sulphurhexafluoride (SF6) and radioactive noble gases were released simultaneously from a 110-m stack and detected downwind at distances of 3-4 km. The experiments were made under near-neutral conditions. One-hour measurements at ground level yielded cross-wind profiles of SF6 concentrations and gamma radiation from the plume. In-situ gamma spectrometric measurements demonstrated a significant surplus of gamma rays from the noble gas daughters (88Rb and 138Cs) compared with those from the noble gases. This surplus was interpreted as due to dry deposition from the plume, and deposition velocities were estimated at 0.02-0.10 m s-1. These values are very high when compared with values recommended for calculating consequences of nuclear accidents. The high values are believed to be due to the very small size of the daughter particles.

Physical and chemical processes of sulphur dioxide in the plume from an oil-fired power station.

The Danish contribution to the EUROCOP COST 61a project is described. Work concerned the physical and chemical reactions of sulphur dioxide released from a power station. The investigation was based on the application of two tracers. Inactive, inert SF6 is used to monitor the dispersion of and deposition from the plume; it was intended to use radioactive 35SO2 to determine the degree of oxidation of sulphur released from the stack; so far, however, public reaction has prevented the use of a release of activity in field experiments. The report describes the construction and testing of airborne instruments for continuous registration of sulphur dioxide, nitrogen oxides, ozone and the tracer SF6, as well as for measurements of temperature and humidity. Sulphur samples were collected on filter paper in a specially constructed low volume air sampler, and the subsequentchemical analysis in the laboratory is described. Finally, the problem of navigation is treated. It is shown that nitrogen oxides may be used as an internal tracer in plume experiments. Preliminary experiments based on inactive analysis only indicated an overall half-life for SO2 in the plume of about half an hour.