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Effective specific activity

Effective specific activity of natural radionuclides

Aeff is a regulatory formula using measured activities. The EU index is a screening criterion, not a calculated annual dose.

Input

Specific activity of natural radionuclides, Bq/kg

Standard

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Enter the specific activity of Ra-226, Th-232 and K-40 (Bq/kg).

AssumptionsInputs are specific activities of Ra-226 (uranium series in equilibrium), Th-232 (thorium series) and K-40 in Bq/kg.Screening estimate. For regulatory decisions use accredited measurement and the current edition of the standard.

Effective Specific Activity of Natural Radionuclides (Aeff)

Aeff formula (NRB-99/2009)

The calculator computes the effective specific activity of natural radionuclides in building materials. Under Russian NRB-99/2009 (clause 5.3.4): Aeff = A(Ra-226) + 1.3·A(Th-232) + 0.09·A(K-40), where the inputs are the specific activities of radium-226 (uranium series in equilibrium), thorium-232 (thorium series) and potassium-40 in Bq/kg.

Building material classes

By the Aeff value, the material is assigned a class: I (≤ 370 Bq/kg) — all construction including residential and public buildings; II (≤ 740) — road construction within settlements and industrial buildings; III (≤ 1500) — road construction outside settlements; IV (≤ 4000) — case-by-case by agreement with the authorities; above 4000 Bq/kg the material is not used in construction. GOST 30108-94 uses refined coefficients 1.31 and 0.085 (difference under 1%).

European Activity Concentration Index

The calculator also computes the European Activity Concentration Index I = C(Ra-226)/300 + C(Th-232)/200 + C(K-40)/3000 (Directive 2013/59/Euratom, Annex VIII; EC RP 112): for bulk materials I ≤ 1 corresponds to a dose ≤ 1 mSv/y, I ≤ 0.5 to ≤ 0.3 mSv/y. It is a screening estimate — regulatory decisions require accredited measurement and the current edition of the standard.

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