A matrix effect correction method for fissile nuclear material mass measurement by delayed neutrons

Area of Science:

• Nuclear Engineering
• Nuclear Safeguards
• Applied Physics

Background:

• Active neutron interrogation (ANI) is crucial for nuclear safeguards but is hindered by matrix effects impacting fissile mass measurement precision.
• Matrix materials interact with neutrons, weakening the accuracy of assays performed by ANI systems.

Purpose of the Study:

• To develop and validate a matrix correction method for ANI systems to enhance assay performance.
• To ensure fissile mass evaluation remains unaffected by matrix materials.

Main Methods:

• A matrix correction method based on the neutron flux monitor group (NFMG) response was proposed.
• Geant4 toolkit was used to model a Shuffler system and various matrix compositions.
• An improved simulated annealing (SA) algorithm was employed for matrix identification and mass correction.

Main Results:

• The improved SA algorithm achieved a 90.4% matrix identification rate at a threshold of α ≥ 0.90.
• The average relative deviation for corrected 235U mass was within 7% for known matrices.
• For unknown matrices, the average relative deviation of corrected 235U mass was less than 28%.

Conclusions:

• The NFMG response method effectively quantifies matrix effects, enabling identification and compensation for both known and unknown matrices.
• The proposed method significantly improves the accuracy of fissile mass measurements in ANI systems.
• The improved SA algorithm demonstrates stability and accuracy in assessing fissile materials within complex matrix environments.