NRPB-W34: Non-technical summary

Non-technical summary

Material released to atmosphere following an accident at a nuclear site is carried by the wind and part of the material is deposited in the area around the site. Following an accident, monitoring would be carried out to describe the deposition pattern around the site. This is aimed partly towards estimating doses to people near the site and identifying those areas where countermeasures are required, and partly towards building up a complete picture of the consequences of the release.

Results from the monitoring would be used to give information on the likely deposition at other locations where monitoring has not yet been carried out, and techniques have been developed to do this for accidents that occur in dry weather. The processes that deposit material on the ground in dry conditions lead to a deposition pattern that varies reasonably smoothly with distance away from the site and from the average direction in which the material was carried. Rain can also remove material from the atmosphere and deposit it on the ground, with the deposition rate varying with the rainfall rate. Rain is very effective in depositing material and so the deposition in wet weather is much greater than that in dry weather. However, rain fall rates can change considerably over short periods of time or short distances, and so the deposition pattern following an accident in wet weather could vary considerably over short distances. This study considered whether the methods of reconstructing the deposition pattern that are available for use in dry weather could also be used in wet weather, with the more rapidly varying deposition pattern.

The study concluded that the existing techniques should be appropriate for use in wet conditions, and would enable the available monitoring results to be used with appropriate models to give information on the deposition at other locations.

Last reviewed: 1 September 2009