Helle Karina Aage

The Solubility of struvite

The solubility of magnesium-ammonium-phosphate (struvite) has been studied employing radioisotope32P as tracer. The amount of sample in solution is determined by measuring the Cherenkov radiation due to the fast β-particles emitted from this radionuclide. The themodynamic solubility product is determined at various temperatures and compared with former results.

Search for lost or orphan radioactive sources based on NaI gamma spectrometry

Within recent decades many radioactive sources have been lost, stolen, or abandoned, and some have caused contamination or irradiation of people. Therefore reliable methods for source recovery are needed. The use of car borne NaI(Tl) detectors is discussed. Standard processing of spectra in general can disclose strong and medium level signals from manmade nuclides. But methods for detecting low level signals from weak, distant or shielded sources can be improved. New methods for source detection and identification based on noise adjusted singular value decomposition and on area specific stripping of spectra are presented.

A new technique for processing airborne gamma ray spectrometry data for mapping low level contaminations

A new technique for processing airborne gamma ray spectrometry data has been developed. It is based on the noise adjusted singular value decomposition method introduced by Hovgaard in 1997. The new technique opens for mapping of very low contamination levels. It is tested with data from Latvia where the remaining contamination from the 1986 Chernobyl accident together with fallout from the atmospheric nuclear weapon tests includes 137Cs at levels often well below 1 kBq/m2 equivalent surface contamination. The limiting factors for obtaining reliable results are radon in the air, spectrum stability and accurate altitude measurements.

Atmospheric dispersion of argon-41 from a nuclear research reactor: measurement and modelling of plume geometry and gamma radiation field

An atmospheric dispersion experiment was conducted using a visible tracer along with the routine releases of 41Ar from the BR1 research reactor in Mol, Belgium. Simultaneous measurements of plume geometry and radiation field from 41Ar decay were performed as well as measurements of the 41Ar source term and the meteorological parameters. Good overall agreement is found between measurement data and model results using the mesoscale atmospheric dispersion and dose rate model RIMPUFF.