Exam category: Safety → Radiation Protection
Why it matters: Each dosimeter you wear produces a report that is kept on record, showing your dose for the period, the year, and your lifetime. The registry tests the NCRP dose limits and what each type of dosimeter measures.
Occupational dosimeters measure how much radiation a worker actually received, and NCRP recommendations set the ceiling on how much they're allowed to receive in the first place. Survey instruments measure the radiation present in a room, not the dose a person received.
| Population | Effective dose limit | Notes |
|---|---|---|
| Occupational | 50 mSv/yr | Cumulative lifetime limit: 10 mSv × age in years |
| Occupational — lens of eye | 150 mSv/yr | Equivalent dose, specific organ |
| Occupational — thyroid, skin, hands, feet | 500 mSv/yr | Equivalent dose, specific organs |
| Public — frequent/continuous exposure | 1 mSv/yr | Ongoing/repeated exposure scenario |
| Public — infrequent exposure | 5 mSv/yr | Occasional/one-off exposure scenario |
| Education & training (students under 18) | 1 mSv/yr | Scoped by age, not by being enrolled — a student aged 18 or older is occupationally exposed at 50 mSv |
| Minors (under 18, occupationally exposed) | 10% of the adult limits | NRC regulatory limit (10 CFR 20), not an NCRP tier |
| Embryo/fetus (declared pregnancy) | 5 mSv total (NRC 10 CFR 20.1208) | 0.5 mSv/month recommended — triggered once the pregnancy is declared in writing |
| Negligible individual dose | 0.01 mSv/yr | Below this, protective action generally isn't warranted |
None of these limits count natural background radiation or a worker's own medical imaging — every ceiling above is occupational or public dose alone. These figures are the NCRP recommendations. The NRC's regulatory limits in 10 CFR Part 20 are the ones an employer is legally held to, and they carry the same core numbers:
The regulation also adds the minors 10% rule. The exam treats the shared numbers interchangeably; you only need to know which framework a fact belongs to when it exists in one and not the other.
Memory cue — anchor on 50, then multiply: occupational whole-body is 50, the lens of the eye is 3× that (150), and everything-else-organs is 10× the whole-body limit (500). Fix 50 first and the other two hang off it.
Answer this to keep going. 11 more sections unlock below.
A radiographer is 30 years old. What is their cumulative lifetime effective dose limit?
Section 1 of 12. Answer the check to keep going.