Detection, demarcation and assessment of surface contaminations

Radioactive surface contaminations can arise because of the following reasons:

• Shipment of excavated material from former mining facilities
• Residues from production processes (slags from power stations, former watchmaking industry)
• Accidents in nuclear plants
• Former nuclear weapons testing

In the past, excavated material from mining plants was used for backfill works in public areas and likewise for foundations of roads. In this way, today's legal limit values have been possibly exceeded and remediation works will be required.

Mining dumps of minerals must be shipped or sealed in order to prevent radioactive materials from spreading by wind and water. Such remediation works are expensive; enormous quantities of material must be moved and disposed. Therefore an exact demarcation and quantitative assessment is of great importance.

Residues from production processes are locally limited in most cases, but even here, the cost issues must be solved because mostly private persons or enterprises have to bear the costs for the required remediation works.

After accidents in nuclear plants or in military testing areas, a remediation won't be possible at all. Usually, the demarcation of restricted areas is the only solution here.

Measuring instruments for those applications must be able to continuously detect emitted gamma radiation and, assisted by GPS, their position. The spatial resolution will be determined by the velocity when walking or driving within the areas under suspicion and by the integration interval used. On behalf of a precise and speedy measurement the integration interval should be minimized. But in order to get a statistically reliable result for short integration intervals, the counting efficiency should be as high as possible.

Large-volume scintillation detectors are especially suited her. This can be two- or three-inch NaI crystals. For facilitating the field operations, the instrument should have low weight and should be able easy to carry at equal distance from the surface. The instrument should work spectroscopically in order to distinguish contaminations from the usual background radiation by means of their reference nuclides.

The SARAD instrument Nuc Scout with its temperature-compensated two-inch NaI detector (three-inch one available as an option) offers a high counting efficiency, is low in weight and is available at a moderate purchase price.

The integrated spectroscopy will verify up to 28 emission lines. While used in a measurement campaign the instrument requires no control. A large display, legible even in direct sunlight, as well as the 16-hour battery lifetime facilitate the operation in the field.

For the presentation of the measured data, a mapping component has been integrated into the PC software coming with the instrument. The data can also be exported as KML file for further processing with all current GIS programs.