Standardization of 125I and 238Pu

Area of Science:

• Nuclear Physics
• Radiochemistry
• Metrology

Background:

• Accurate standardization of radioisotopes is crucial for various scientific and medical applications.
• Existing methods for low-energy photon and alpha particle detection can have limitations in precision and versatility.

Purpose of the Study:

• To construct and evaluate a simple, distance-variable detection system for coincidence counting.
• To standardize Iodine-125 (125I) using photon-photon coincidence counting.
• To standardize Plutonium-238 (238Pu) using alpha-photon coincidence counting.

Main Methods:

• A custom-built detection table with two movable NaI(Tl) detectors for 125I standardization.
• A Si detector for alpha particles and an NaI(Tl) detector for photons were used for 238Pu standardization.
• Utilized thin aluminum windows for low-energy photon detection and specific sample films (collodion for 238Pu, polyester for 125I) to prevent leakage.

Main Results:

• The standardization of 125I using the developed system showed good agreement with established values.
• The standardization of 238Pu was successfully performed and compared favorably with liquid scintillation counting results.

Conclusions:

• The developed distance-variable detection system is effective for the coincidence counting standardization of 125I and 238Pu.
• The system offers a practical and accurate approach for radioisotope standardization, particularly for low-energy emitters.