EngineerHub.orgCombine major NORM worker exposure pathways
Estimate annual external gamma dose, dust-inhalation dose, radon-progeny dose and optional inadvertent-ingestion dose. All internal coefficients remain visible and editable.
Worker scenario
Dust inhalation
Radon and optional ingestion
Annual dose by pathway
Background
Open a section to understand the model, equations and limitations.
Eext = H*(10) × k × t
Measured dose rate is preferred. The default conversion factor of 0.6 is a screening assumption used in some NORM workplace guidance and can be edited.
Intake = dust × activity × breathing rate × time ÷ RPF
Dust concentration in mg/m³ is converted to g/m³ before multiplying by Bq/g. Committed effective dose is intake multiplied by the selected Sv/Bq coefficient.
ERn = C × F × t × 9 nSv/(Bq·h/m³)
This is the conventional UNSCEAR equilibrium-factor method. Underground and unusual aerosol conditions may require different assumptions.
ICRP coefficients vary with radionuclide, chemical form, absorption type and aerosol size. The calculator therefore keeps coefficients user-entered and emphasizes verification against the applicable regulatory dataset.
Source characterization, representative work groups, measured dose rates and dust, occupancy, PPE performance, decay-chain equilibrium, radon/thoron, contamination control, uncertainty and regulatory comparison all require professional assessment.
NORM means naturally occurring radioactive material. Uranium-238, thorium-232 and their decay products, together with potassium-40, occur naturally in rocks, soils and mineral feedstocks. Industrial activities can concentrate these radionuclides or bring them into workplaces where exposure would otherwise be low.
Examples include oil-and-gas scale and sludge, phosphate processing, mineral sands, rare-earth production, coal ash, geothermal scale, water-treatment residues and bauxite residue. NORM does not mean harmless: the relevant question is whether the activity, form, quantity and work practice create significant external, inhalation, ingestion or radon exposure.
For regulated occupational exposure in planned situations, international recommendations commonly use an effective-dose limit of 20 mSv/year averaged over five years, with national rules controlling annual maxima and investigation levels.
Many NORM assessments use 1 mSv/year above background as an initial public or regulatory-screening context, but it is not a universal NORM worker action level. Classification, exemption, clearance, dose constraints and remedial reference levels depend on national legislation and the exposure situation.
Frequently Asked Questions
Practical questions about interpretation and use.
Inhalation and ingestion coefficients depend on radionuclide, chemical form, absorption type, particle size and the applicable regulatory dataset. A generic preset could be dangerously misleading.
Not necessarily. Ingestion is often a minor occupational pathway under controlled hygiene conditions, but it may require assessment for dusty work, hand-to-mouth transfer or contaminated food areas.
The default is a screening conversion from ambient dose equivalent rate H*(10) to effective dose used in some NORM assessment guidance. Site-specific dosimetry should be used when available.
Yes, it uses concentration, equilibrium factor, exposure time and the conventional UNSCEAR 9 nSv/(Bq·h/m³) coefficient.