What the calculator determines
The calculator assigns a sealed radioactive source to one of five categories of potential radiological hazard using the RF НП-067-24 method, which reproduces the IAEA RS-G-1.9 approach. The category drives the required physical protection, accounting and security of the source.
How the A/D ratio works
For a radionuclide the ratio of its activity A to the nuclide D-value — the «dangerous activity» (НП-067-24 Annex 5 Table 2, identical to IAEA EPR-D-VALUES) — is taken. Category 1 is A/D ≥ 1000, category 2 from 10 to 1000, category 3 from 1 to 10, category 4 from 0.01 to 1, category 5 below 0.01. For a multi-nuclide source the ratios are summed: A/D = Σ(Aᵢ/Dᵢ).
Activity at a date and nuclide mixtures
The category is based on the current activity, so a source can drop to a lower category over time. The calculator decays the passport activity to today by half-life and supports sources made of several radionuclides.
Frequently asked questions
How is the source category determined per НП-067-24?
By the activity-to-D-value ratio: A/D ≥ 1000 is category 1, 10–1000 category 2, 1–10 category 3, 0.01–1 category 4, below 0.01 category 5. For a set of sources or a nuclide mixture the ratios A_i/D_i are summed.
What is a D-value?
The dangerous activity — the level above which an unshielded source can cause severe deterministic effects. Values follow IAEA RS-G-1.9 and НП-067-24; for 352 nuclides they are collected in the D-value table.
Should the activity be decayed to the categorisation date?
Yes: the category is based on the actual activity. The calculator can decay the certificate activity to the date using the half-life, but for short-lived nuclides double-check that the calibration date is entered correctly.
