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

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

Correlation between ¹⁴C activity and the mass of graphite samples.

<p>The parameters of linear approximation (y = a + bx) are: a = -34 ± 45, b = 0.8 ± 0.2; R = 0.62. Sample mass was determined by the elemental analyzer.</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

Correlation between LSC and semiconductor detector data.

<p>The horizontal axis represents LSC measurement data of ¹⁴C activity and the vertical axis represents semiconductor β detector pulse counts obtained per 100 s. The parameters of linear approximation (y = a + bx) are a = 8.83, b = 0.63, R = 0.94.</p

CO₂ gas flow in the TCD and the β counter chamber during the first cycle of combustion of sample No. 6.

<p>CO₂ gas flow in the TCD and the β counter chamber during the first cycle of combustion of sample No. 6.</p

The correlation of the graphite sample mass as determined by two independent methods: Weighing and combustion in the elemental analyzer.

<p>Graphite sample mass in the same sample was determined by weighing with balances (horizontal axis) and by combustion in the elemental analyzer, measured from the resulting CO₂ (vertical axis). The parameters of linear approximation (y = a + bx) are: a = 3 ± 10, b = 0.96 ± 0.06, R = 0.97.</p

Experimentally determined activity of ¹³⁷Cs, ⁶⁰Co and ¹⁴C in the graphite sample.

<p>The mass of the same sample was determined by two methods: weighing with balances, and later by combustion in an elemental analyzer.</p

β particle registration system in CO₂ gas flow with semiconductor detectors.

<p>β particle registration system in CO₂ gas flow with semiconductor detectors.</p

MCNP model of a detection chamber with zoomed fragments of the Si detector and inactive layer on the top of the detector.

<p>MCNP model of a detection chamber with zoomed fragments of the Si detector and inactive layer on the top of the detector.</p