Radiation Safety and Regulations
Radiation safety and regulations questions test dose limits, ALARA, patient release, and documentation - the rules that keep occupational and public exposures as low as reasonably achievable.
Core rules
- NRC occupational limits: 50 mSv/y total effective dose; 150 mSv/y lens; 500 mSv/y extremities and skin; declared pregnant worker 5 mSv to the fetus.
- Public dose limit is 1 mSv/y; an ALARA program sets action levels below regulatory limits.
- A written directive is required before I-131 sodium iodide above the regulatory threshold and before therapeutic radiopharmaceutical administrations.
- Patient release: evaluate exposure to others; provide written instructions when the dose to another individual could exceed 1 mSv.
- Package surveys check dose rate and removable contamination; wipe tests detect removable contamination.
Worked example
A technologist's monthly badge reads 0.6 mSv. Is this a regulatory violation? Reasoning: Annualized, 0.6 × 12 = 7.2 mSv, well below the 50 mSv/y limit. It is not a violation, but the ALARA program may set a lower action level, such as 1 mSv/month, requiring investigation. The correct response is to review workload, shielding, and technique - not to report an overexposure.
Traps
- Confusing public, occupational, and fetal dose limits.
- Releasing a therapy patient without the required instructions.
- Surveying a package for dose rate but skipping the wipe test.