Radioprotection No. 60-1 | Page 93

N. T. Le: Radioprotection 2025, 60( 1), 84 – 90 87

Table 1. Physical( f), operational dosimetric( _ H ð10Þ), and radiation( E, h *) quantities of different neutron reference fields available in Vietnam for calibrations of neutron meters.

Source Quantity Source-to-detector distance( cm) 100 150 200 250

2.5 Assessment of combined standard uncertainty of technical parameter

Based on the uncertainty propagation principle, one can figure out that the combined standard uncertainties of all quantities( i. e., physical, operational dosimetric, and radiation quantitites � calculation models in equations( 2)–( 7)) have the same uncertainty propagation rule. In other words, the combined standard uncertainty of an individual quantity( u Q) is equal to square root of summed squares of its all uncertainty budgets( u b). In general, the value of u Q can be calculated using equation( 8). vffiffiffiffiffiffiffiffiffiffiffi u u u Q ¼ t

X all

b¼1 u 2 b ð8Þ

3 Result

3.1 Technical parameter of neutron calibration field

Table 1 shows the technical parameters( including of physical � f, operational dosimetric � _ H ð10Þ, and radiation � E, h *, quantities) at different distances from the sources’ centers for different neutron reference fields.

3.2 Combined standard uncertainty of technical parameter

Table 2 shows the combined standard uncertainties of conventional true values of technical parameters of different neutron reference fields in conjunction with the uncertainty budgets.