InSiCal - A tool for calculating calibration factors and activity concentrations in in situ gamma spectrometry.

In situ gamma spectrometry is a widely applied analysis technique for the determination of radioactivity levels in soil. Compared to traditional laboratory analysis of soil samples, in situ techniques offer a quick and low-cost way of obtaining accurate results from on-site measurements. However, although the technique is well-known, the dependence of in situ gamma spectrometry on complex and time-consuming calibration procedures as well as in-depth knowledge of the geometric distribution of the source in the ground deters many potential users from employing it in their routine work. Aiming to alleviate this issue, a software tool named InSiCal (In Situ gamma spectrometry Calculator) has been developed to make in situ gamma spectrometry more accessible to both experts and non-experts in the field. This is done by simplifying and streamlining both calibration and activity calculation through a simple and intuitive graphical user interface. Testing in real field conditions show that InSiCal is capable of yielding results which are in very good agreement with soil sample analyses, and that the results may be obtained using different detector types (HPGe, NaI, LaBr and CZT). Overall, InSiCal, provides results which are comparable in accuracy to laboratory measurements, indicating that it fulfills its purpose successfully.

Norwegian monitoring (1990-2015) of the marine environment around the sunken nuclear submarine Komsomolets.

Norway has monitored the marine environment around the sunken Russian nuclear submarine Komsomolets since 1990. This study presents an overview of 25 years of Norwegian monitoring data (1990-2015). Komsomolets sank in 1989 at a depth of 1680 m in the Norwegian Sea while carrying two nuclear torpedoes in its armament. Subsequent Soviet and Russian expeditions to Komsomolets have shown that releases from the reactor have occurred and that the submarine has suffered considerable damage to its hulls. Norwegian monitoring detected 134Cs in surface sediments around Komsomolets in 1993 and 1994 and elevated activity concentrations of 137Cs in bottom seawater between 1991 and 1993. Since then and up to 2015, no increased activity concentrations of radionuclides above values typical for the Norwegian Sea have been observed in any environmental sample collected by Norwegian monitoring. In 2013 and 2015, Norwegian monitoring was carried out using an acoustic transponder on the sampling gear that allowed samples to be collected at precise locations, ∼20 m from the hull of Komsomolets. The observed 238Pu/239,240Pu activity ratios and 240Pu/239Pu atom ratios in surface sediments sampled close to Komsomolets in 2013 did not indicate any releases of Pu isotopes from reactor or the torpedo warheads. Rather, these values probably reflect the overprinting of global fallout ratios with fluxes of these Pu isotopes from long-range transport of authorised discharges from nuclear reprocessing facilities in Northern Europe. However, due to the depth at which Komsomolets lies, the collection of seawater and sediment samples in the immediate area around the submarine using traditional sampling techniques from surface vessels is not possible, even with the use of acoustic transponders. Further monitoring is required in order to have a clear understanding of the current status of Komsomolets as a potential source of radioactive contamination to the Norwegian marine environment. Such monitoring should involve the use of ROVs or submersibles in order to obtain samples next to and within the different compartments of the submarine.

Implications for analysis of (226)Ra in a low-level gamma spectrometry laboratory due to variations in radon background levels.

The background spectrum of HPGe detectors is found to vary significantly as function of the radon concentration in the air surrounding it, especially with regard to the count rates of (222)Rn daughter peaks. This effect is shown to potentially have a large impact on measured values of radon daughter activity concentration, as well as detection limits for low-level measurements. As these radionuclides are commonly used for estimating the activity of (226)Ra, care needs to be taken to ensure that background levels are accurately determined.

Radon tightness of different sample sealing methods for gamma spectrometric measurements of ²²6Ra.

Different methods for sealing sample containers for (222)Rn when measuring (226)Ra through its progenies (214)Pb and (214)Bi using gamma-ray spectrometry have been investigated. Results show that a method consisting of vacuum packaging of the sample container in a sealed aluminium lined bag gives excellent results for ensuring radon tightness. However, care should be taken to fill the sample container completely in order to avoid systematic errors due to radon accumulating in the void volume.

Radiological status of the marine environment in the Barents Sea.

This paper presents the results of Norwegian radiological monitoring of the Barents Sea in 2007, 2008 and 2009. Activity concentrations of the anthropogenic radionuclides (137)Cs, (90)Sr, (239,240)Pu and (241)Am in seawater were low and up to an order of magnitude lower than in previous decades. Activity concentrations of (99)Tc in seawater were low but remain elevated compared to levels prior to the increased discharge of this radionuclide from Sellafield in the 1990s. Activity concentrations of the naturally occurring radionuclide (226)Ra in seawater were comparable to expected background values. Activity concentrations of (137)Cs in surface sediments were low, with higher values observed in sediments from coastal areas along the Norwegian mainland than from locations in the open sea. Activity concentrations of (137)Cs and (99)Tc in marine biota were low and up to an order of magnitude lower than in previous decades. Committed effective dose rates to man from anthropogenic radionuclides via the consumption of seafood from the Barents Sea were low and are not a cause for concern. Weighted absorbed dose rates to biota from anthropogenic radionuclides were low and orders of magnitude below a predicted no effect screening level of 10 µGy/h. Dose rates to man from consumption of seafood and dose rates to biota in the marine environment are dominated by the contribution from naturally occurring radionuclides.