COMPARATIVE STUDY ON PERFORMANCE OF VARIOUS ENVIRONMENTAL RADIATION MONITORS

Area of Science:

• Nuclear Safety and Environmental Monitoring
• Radiation Detection and Measurement

Background:

• Inaccurate radiation dose evaluations for first responders occurred post-Fukushima Daiichi Nuclear Power Plant accident due to insufficient monitoring data.
• Effective radiation dose assessment for workers during nuclear emergencies is a critical safety requirement.

Purpose of the Study:

• To develop a novel device capable of assessing both external and internal radiation exposure doses.
• To evaluate and compare the performance of various environmental radiation monitors, including commercial options, for emergency situations.

Main Methods:

• Development of a new device for simultaneous external and internal radiation exposure assessment.
• Performance testing of environmental radiation monitors, measuring background counts and ambient dose equivalent rates in Fukushima Prefecture.
• Evaluation of detection limits for beta particles using ISO11929 standards and assessment of gamma-ray sensitivity for dust and external exposure monitors.

Main Results:

• The developed internal exposure monitor and dust monitors (using ZnS(Ag) and plastic scintillators) demonstrated suitability for emergency monitoring.
• Detection limits for beta particles ranged from 190-280 Bq m-3 at 100 μSv h-1, exceeding Japan's National Regulation Authority minimum requirement of 100 Bq m-3.
• Lead shielding is necessary to meet the minimum detection limit requirements for certain monitors.

Conclusions:

• The developed internal exposure monitor and specific dust monitors are recommended for emergency radiation monitoring.
• Further research will focus on counting efficiency, uncertainty, alpha particle detection, and portability for optimal monitor selection.