The ecological half-life of ¹³7Cs in undisturbed silt soil.

The time necessary to safely cultivate agricultural areas after they have been contaminated by radioactivity (e.g. after the Chernobyl accident) is not determined by the physical half-life of the radioactive isotopes in question but by their (usually much shorter) ecological half-life (Brisbin et al., 2002). This half-life not only depends on the type of soil but also on whether the soil was fertilized or not. Therefore it is not possible to determine an ecological half-life that is universally valid. However, the value for undisturbed, unfertilized soil should provide a general indication for the duration of ecological half-life. In a silt soil in Vienna, Austria, the ecological half-life of (137)Cs was determined to be 0.8 years, which is much shorter than the physical half-life of 30 years.

Detection of explosive remnants of war by neutron thermalisation.

The HYDAD-D landmine detector (Brooks and Drosg, 2005) has been modified and field-tested for 17 months in a variety of soil conditions. Test objects containing about the same mass of hydrogen (20g) as small explosive remnants of war, such as antipersonnel landmines, were detected with efficiency 100% when buried at cover depths up to 10cm. The false alarm rate under the same conditions was 9%. Plots of detection efficiency versus false alarm rate are presented.

The HYDAD-D antipersonnel landmine detector.

HYDAD (HYdrogen Density Anomaly Detection) systems have been developed to detect small (>200 g) antipersonnel landmines (APM) of plastic construction. The HYDAD-D detector is based on the earlier HYDAD designs HYDAD-H and HYDAD-VM. It consists of a neutron source and two identical slow neutron detectors. The difference between the responses of the two detectors is monitored as a function of position in the minefield and APM detection is based on an analysis of this difference. Laboratory tests and Monte Carlo simulations demonstrate that HYDAD-D is capable of detecting the IAEA standard dummy landmine DLM2 at burial depths up to 23 cm in dry sand and at burial depths up to 7 cm in damp sand containing 12% (by mass) water.

Increasing the capability of MNBRP for the detection of anti-personnel landmines.

Monte Carlo simulations were used to show that even very small explosives (<100g) can be detected by monoenergetic neutron backscattering with resonance penetration (MNBRP) at a depth well beyond 30 cm when time slicing is used for background suppression. At the present state of technology no other nuclear method appears to have a comparable sensitivity or penetration capability. This method has been successfully tested experimentally at a depth of 16.5 cm. A substantial simplification of the detection procedure could be achieved either by taking advantage of the time shadow rather than the geometric shadow or by applying neutron threshold detectors. Using a threshold detector could simplify the application, too.

Detection of anti-personnel landmines by neutron scattering and attenuation.

Four methods for employing neutrons to detect abandoned small anti-personnel landmines are presented and discussed. The techniques used are based on measurements of effects due to the scattering of neutrons on the hydrogen content of the landmine.