Comparative study of 131I released during a nuclear accident

Area of Science:

• Nuclear Safety and Environmental Science
• Radiological Impact Assessment
• Nuclear Reactor Safety

Background:

• Radioiodine-131 (131I) is a major environmental contaminant from nuclear accidents.
• Thyroid exposure to 131I can cause cell destruction, hypothyroidism, and increase thyroid cancer risk, especially in children.
• Nonradioactive iodine tablets are a protective measure against radioactive iodine uptake by the thyroid.

Purpose of the Study:

• To quantify and compare atmospheric 131I emissions from nuclear incidents.
• To assess radiological impacts, including Total Effective Dose (TED) and Committed Effective Dose Equivalent (CEDE).
• To compare these impacts for the Fukushima accident and a TRIGA Mark-II research reactor.

Main Methods:

• Utilized the ORIGEN-JR code to simulate atmospheric 131I emissions.
• Employed the HOTSPOT code to estimate TED and CEDE.
• Compared simulated doses against International Atomic Energy Agency (IAEA) regulatory limits.

Main Results:

• Fukushima accident: TED ~875 mSv at 590m, thyroid CEDE ~63 mSv.
• TRIGA Mark-II reactor: TED ~379 mSv at 360m, thyroid CEDE ~19 mSv.
• Fukushima doses exceeded IAEA limits, necessitating evacuation and iodine prophylaxis; TRIGA-II doses did not require iodine tablets but containment.

Conclusions:

• The Fukushima accident posed a severe radiological threat exceeding regulatory thresholds.
• The TRIGA Mark-II research reactor presented a lower radiological risk, not warranting iodine prophylaxis.
• Dose assessment is critical for determining appropriate public health and safety measures following nuclear events.