Radiological assessment of ionizing radiation impact on the terrestrial non-human biota in Lithuania

The quantitative assessment of radionuclides transfer to non-human biota using their activity concentration ratios is required for models of predictive doses of ionizing radiation. Based on long-term data regarding activity concentration of radionuclides in the top soil layer of the entire territory of Lithuania, and with the help of ERICA Assessment Tool – a software application that calculates dose rates to selected biota, we estimated the radiological impact on the terrestrial non-human biota with special emphasis on the protected areas located in the vicinity of Ignalina Nuclear Power Plant (INPP). Estimated total dose rates of artificial radionuclides – after-Chernobyl 137Cs and 90Sr as well as discharged by INPP – and natural radionuclides, such as 238U and 232Th, were found to be less than ERICA screening value of 10 μGy h–1. First published online: 25 Oct 201

Admixtures in spent plutonium sources and gamma-radiation

The isotopic composition of several spent smoke detectors containing plutonium has been investigated. The article also presents the calculated results of 241Am and 241Pu activities in smoke detectors. The received values vary from (0.934±0.028) MBq to (91.2±4.6) MBq. The eguivalent dose rate of the established gamma radiation vary from 220 nSv/h to 500 nSv/h. A dose caused by artificial radionuclides in spent smoke detectors was evaluated and compared in the article. It has been found out that due to smoke detectors, an annual dose varies from 0.06 mSv to 0.31 mSv.Lietuviška santrauka. Šiame darbe nagrinėjama naudotų plutonio šaltinių izotopinė sudėtis ir galimų priemaišinių radionuklidų įtaka žmonių saugai. Pateikti radionuklidų americio 241Am ir plutonio 241Pu aktyvumo dūmų jutikliuose skaičiavimo rezultatai. Gautos vertės kinta nuo 0,934±0,028 MBq iki 91,2±4,6 MBq. Išmatuota gama spinduliuotės sukelta lygiavertės dozės galia. Nustatytos lygiavertės dozės galios vertės kinta nuo 220 nSv/h iki 500 nSv/h. Vidutinė dozės galia patalpoje yra apie 140 nSv/h. Įvertinta išorinė apšvita, sukelta dirbtinės kilmės americio 241Am radionuklidų, esančių naudotuose dūmų jutikliuose. Nustatyta, kad metinė išorinė apšvita žmogui, dirbančiam patalpoje, kurioje įmontuotas dūmų jutiklis, kinta nuo 0,06 mSv iki 0,31 mSv

Rapid analysis method for the determination of 14C specific activity in irradiated graphite.

14C is one of the limiting radionuclides used in the categorization of radioactive graphite waste; this categorization is crucial in selecting the appropriate graphite treatment/disposal method. We propose a rapid analysis method for 14C specific activity determination in small graphite samples in the 1-100 μg range. The method applies an oxidation procedure to the sample, which extracts 14C from the different carbonaceous matrices in a controlled manner. Because this method enables fast online measurement and 14C specific activity evaluation, it can be especially useful for characterizing 14C in irradiated graphite when dismantling graphite moderator and reflector parts, or when sorting radioactive graphite waste from decommissioned nuclear power plants. The proposed rapid method is based on graphite combustion and the subsequent measurement of both CO2 and 14C, using a commercial elemental analyser and the semiconductor detector, respectively. The method was verified using the liquid scintillation counting (LSC) technique. The uncertainty of this rapid method is within the acceptable range for radioactive waste characterization purposes. The 14C specific activity determination procedure proposed in this study takes approximately ten minutes, comparing favorably to the more complicated and time consuming LSC method. This method can be potentially used to radiologically characterize radioactive waste or used in biomedical applications when dealing with the specific activity determination of 14C in the sample

CO₂ flow intensity signal measured by TCD (black line) and cps spectra of samples No. 3 (green), No. 6 (blue) and background (red) as determined with the semiconductor detector.

<p>In total, three combustion cycles (400 s each) were used to completely combust the non-ground graphite sample.</p

Rapid system for ¹⁴C specific activity determination in the sample.

<p>System contains elemental analyzer (autosampler, oxidation and reduction columns, water trap, gas chromatography column, thermal conductivity detector (TCD)) and β particle detection system. In the present study, gas catchers (3 M NaOH) and LSC were used to evaluate the accuracy of the measurements of samples with low ¹⁴C activity.</p

An example spectrum of ¹⁴C measured using semiconductor detectors.

<p>The green color denotes the spectrum of sample No. 3 and the black color denotes a typical background spectrum. Both spectra were collected over 100 s time intervals.</p

Radiocarbon spectra of a graphite sample.

<p>(<b>a</b>) from the first catcher, (<b>b</b>) from the second catcher.</p