The NIST Primary Radon-222 Measurement System

Area of Science:

• Metrology
• Environmental Science
• Radiological Health

Background:

• The U.S. national standard for radon measurements relies on a primary measurement system.
• This system has been operational for over 50 years, ensuring accurate radon (²²²Rn) quantification against radium (²²⁶Ra) standards.
• All National Institute of Standards and Technology (NIST) radon measurements and calibrations are traceable to this national standard.

Purpose of the Study:

• To describe the primary radon measurement system at NIST.
• To highlight the system's role in national radon standards and calibrations.
• To introduce the ongoing upgrade and expansion of this critical measurement infrastructure.

Main Methods:

• Utilizes a primary radon measurement system.
• Employs pulse ionization chambers.
• Incorporates ancillary gas handling and purification equipment.

Main Results:

• The system has maintained the national standard for radon measurements for over five decades.
• It underpins NIST's radon transfer calibration standards and services.
• The system is currently being upgraded and expanded.

Conclusions:

• The primary radon measurement system is fundamental to U.S. radon metrology.
• NIST's radon measurement capabilities are directly linked to this established standard.
• The ongoing modernization will ensure continued accuracy and reliability in national radon measurements.