Formula & Calculator
Internal Radiation Dose Calculator
Internal radiation dose results from radioactive material taken into the body. The committed effective dose is calculated from the activity and the dose coefficient (effective dose per unit intake). Dose coefficients are specific to each radionuclide and chemical form. This is used in occupational exposure assessments (e.g., inhalation of uranium) and in nuclear medicine.
Internal DoseCommitted DoseRadionuclide
Internal Radiation Dose
Nuclear Engineering · Health Physics & Dosimetry
D =
A ·
d
·
D = committed dose ·
A = activity ·
d = dose coefficient
Internal radiation dose results from radioactive material taken into the body.
The committed effective dose is calculated from the activity and the dose coefficient
(effective dose per unit intake). Dose coefficients are specific to each radionuclide and chemical form.
This is used in occupational exposure assessments (e.g., inhalation of uranium) and in nuclear medicine.
Presets:
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Solve for:
Calculation Steps
Ready| Step | Operation | Value |
|---|---|---|
| Enter values and press Calculate | ||
Internal Dose Coefficients (Ingestion)
Typical values for common radionuclides
| Radionuclide | d (Sv/Bq) | Type |
|---|
D = A · d · d = dose coefficient (Sv per Bq) · Values from ICRP 72/119
D = A × (committed effective dose per unit activity)
Internal Radiation Dose Calculator
Variables
| Symbol | Quantity | Unit |
|---|---|---|
| D | Committed Effective Dose | Sv |
| A | Intake Activity | Bq |
| dose coefficient | Dose per Unit Intake | Sv/Bq |
What it means
The committed dose is the total dose expected over 50 years following intake. It depends on the clearance half‑life of the material.
Worked example
Iodine‑131 Thyroid Dose (D = A × e)
Internal DosimetryScenario: A nuclear medicine patient receives 50 MBq of I‑131 for treatment of hyperthyroidism. The committed effective dose per unit activity for oral ingestion of I‑131 is 2.2×10⁻⁸ Sv/Bq. The total effective dose is calculated to assess radiation risk and ensure it remains within acceptable limits for therapy.
| Parameter | Value |
|---|---|
| Activity Intake (A) | 50 MBq (5.0×10⁷ Bq) |
| Comm. Eff. Dose per Activity (e) | 2.2×10⁻⁸ Sv/Bq |
| Committed Effective Dose (D) | 1.10 Sv (5.0×10⁷ × 2.2×10⁻⁸) |
1Determine the activity intake (A) from the administered radiopharmaceutical or accidental intake.
2Obtain the committed effective dose per unit activity (e) from ICRP or other dose coefficients (specific to radionuclide, chemical form, and route).
3Multiply D = A × e to get the total committed effective dose.
Effective DoseD = 1.10 Sv Therapeutic doses are high but considered justified; this is ~50× the annual occupational limit.
Tritium Oxide Intake (D = A × e)
Internal DosimetryScenario: A worker at a nuclear facility accidentally inhales HTO (tritiated water) vapour. The activity intake is estimated from bioassay measurements to be 2×10⁸ Bq. The dose coefficient for tritium (HTO) ingestion is 1.8×10⁻¹¹ Sv/Bq. The committed effective dose is calculated for radiological protection assessment.
| Parameter | Value |
|---|---|
| Activity Intake (A) | 2×10⁸ Bq |
| Comm. Eff. Dose per Activity (e) | 1.8×10⁻¹¹ Sv/Bq |
| Committed Effective Dose (D) | 3.6 mSv (2×10⁸ × 1.8×10⁻¹¹) |
1Estimate the intake activity from bioassay samples (urine, breath) or from air monitoring.
2Select the appropriate dose coefficient (e) for the radionuclide and exposure route (here HTO, ingestion/inhalation).
3Compute the dose D = A × e — tritium has a low dose coefficient, so the dose is modest.
Effective DoseD = 3.6 mSv This is below the annual limit for radiation workers (20 mSv), so no immediate action needed.
Plutonium‑239 Inhalation (D = A × e)
Internal DosimetryScenario: A worker at a reprocessing plant accidentally inhales a small amount of Pu‑239 aerosol. The estimated lung retention activity is 500 Bq (Class M, 1 μm AMAD). The dose coefficient for inhalation of Pu‑239 is 5.0×10⁻⁵ Sv/Bq (for lung cancer risk). The committed effective dose is calculated to evaluate the health risk.
| Parameter | Value |
|---|---|
| Activity Intake (A) | 500 Bq |
| Comm. Eff. Dose per Activity (e) | 5.0×10⁻⁵ Sv/Bq (ICRP‑72) |
| Committed Effective Dose (D) | 25 mSv (500 × 5.0×10⁻⁵) |
1Assess the intake activity from air sampling, nasal swabs, or faecal excretion measurements.
2Use the appropriate dose coefficient (e) for Pu‑239 (inhalation, specific lung model).
3Multiply D = A × e — Pu has high radiotoxicity, so even small intakes result in significant doses.
Effective DoseD = 25 mSv This exceeds the annual limit (20 mSv); the worker would be classified as overexposed and requires follow‑up.
Common mistakes
- Using intake activity instead of committed dose coefficient: The formula is D = A × e(g) ; forgetting to multiply by the effective dose coefficient yields activity, not dose.
- Applying the wrong route of intake: Inhalation and ingestion have very different absorption fractions; using one for the other gives a large error.
- Ignoring the chemical form: The biokinetics depend on the compound (e.g., soluble vs. insoluble).
Applications
- Occupational internal dosimetry: Used to evaluate intakes from airborne contamination.
- Emergency response: Assesses the dose to the public from an accidental release.
- Nuclear medicine therapy: Calculates the dose to organs from injected radiopharmaceuticals.