The half-life of 129I.

The radionuclide 129I is a long-lived fission product that decays to 129Xe by beta-particle emission. It is an important tracer in geological and biological processes and is considered one of the most important radionuclides to be assessed in studies of global circulation. It is also one of the major contributors to radiation dose from nuclear waste in a deep geological repository. Its half-life has been obtained by a combination of activity and mass concentration measurements in the frame of a cooperation of 6 European metrology institutes. The value obtained for the half-life of 129I is 16.14 (12) × 106 a, in good agreement with recommended data but with a significant improvement in the uncertainty.

Standardisation of the (129)I, (151)Sm and (166m)Ho activity concentration using the CIEMAT/NIST efficiency tracing method.

The (129)I, (151)Sm and (166m)Ho standardisations using the CIEMAT/NIST efficiency tracing method, that have been carried out in the frame of the European Metrology Research Program project "Metrology for Radioactive Waste Management" are described. The radionuclide beta counting efficiencies were calculated using two computer codes CN2005 and MICELLE2. The sensitivity analysis of the code input parameters (ionization quenching factor, beta shape factor) on the calculated efficiencies was performed, and the results are discussed. The combined relative standard uncertainty of the standardisations of the (129)I, (151)Sm and (166m)Ho solutions were 0.4%, 0.5% and 0.4%, respectively. The stated precision obtained using the CIEMAT/NIST method is better than that previously reported in the literature obtained by the TDCR ((129)I), the 4πγ-NaI ((166m)Ho) counting or the CIEMAT/NIST method ((151)Sm).

Results of a European interlaboratory comparison on gross alpha/beta activity determination in drinking water.

An interlaboratory comparison was organised by JRC-IRMM among environmental radioactivity monitoring laboratories for the determination of gross alpha/beta activity concentration in drinking water. Independent standard methods were used for the reference value determination. The performance of participating laboratories was evaluated with respect to the reference values using relative deviations. Sample preparation and measurement methods used by the participating laboratories are detailed, in particular in the view of method-dependency of the results. Many of the participants' results deviate by more than two orders of magnitude from the reference values regardless of the techniques used. This suggests that gross methods need revision.

Distribution of artificial gamma-ray emitting radionuclide activity concentration in the top soil in the vicinity of the Ignalina Nuclear Power Plant and other regions in Lithuania.

The impact of the operating Ignalina Nuclear Power Plant (INPP) on the contamination of top soil layer with artificial radionuclides has been studied. Results of the investigation of artificial gamma-ray emitting radionuclide distribution in soil in the vicinity of the INPP and distant regions in Lithuania in 1996-2008 (INPP operational period) show that nowadays (137)Cs remains the most important artificial gamma-ray emitting radionuclide in the upper soil layer. Mean (137)Cs activity concentrations in the top soil layer in the vicinity of the INPP were found to be significantly lower compared to those in remote regions of Varena and Plunge (~300 km from INPP). In 1996 and 1998 mean (137)Cs activity concentrations were in the range of 28-45 Bq/kg in the nearest vicinity to the INPP, 103 Bq/kg in Varena and 340 Bq/kg in Plunge region. (137)Cs activity concentrations were 5-20 times lower in meadow soil (4-14 Bq/kg) compared to swamp and forest soil. (60)Co, the INPP origin radionuclide, was detected in samples only in 1996 and 2000, and the activity concentration of (60)Co was found to be in the range from 0.4 to 7.0 Bq/kg at the sampling ground nearest to the INPP. Average annual activity concentrations of the INPP origin (137)Cs and (60)Co in the air and depositions in the INPP region were modeled using Pasquill-Gifford equations. The modeling results of (137)Cs and (60)Co depositional load in the INPP vicinity agree with the experimentally obtained values. Our results provide the evidence that the operation of INPP did not cause any significant contamination in soil surface.

The solubility of the aerosol, 137Cs and 60Co carrier, in the Ignalina Nuclear Power Plant region.

The dissolution of aerosol particles, carrier of (137)Cs and (60)Co, sampled on filters is studied by means of a leaching test with distilled water. Samples were collected from the ventilation stack of the operating Ignalina Nuclear Power Plant (NPP) reactor, the shut down reactor and in the ground-level air. The insolubility in water of radionuclides attached to aerosol particles sampled on filters, collected in the operating Unit 2 reactor effluents, is clearly lower than the insolubility in water of radionuclides attached to aerosol particles sampled on filters, collected in the ground-level air. The mean rate of the change in the insolubility in water of (60)Co and (137)Cs attached to aerosol particles, released from the Ignalina NPP and registered at a 3.5km distance from the NPP, is estimated. The radionuclide activity concentration distribution in the ground-level air is calculated in respect of the insolubility in water of (60)Co attached to aerosol particles and compared with experimental data.