Lump corrections for radioactive waste assay

Area of Science:

• Nuclear waste assay
• Radioactive material characterization
• Non-destructive analysis

Background:

• Automated radioactive waste assay (SGS, AQ2) often underestimates fissile material.
• Underestimation is caused by missing or malfunctioning lump correction routines.
• Accurate assay is critical for safe waste management and disposal.

Purpose of the Study:

• To evaluate manual lump correction techniques for radioactive waste assay.
• To compare Monte Carlo N particle (MCNP) and spectral non-destructive assay platform (SNAP) software.
• To assess the necessity and effectiveness of lump corrections for plutonium (Pu), enriched uranium (EU), and depleted uranium (DU) waste streams.

Main Methods:

• Application of MCNP and SNAP software for lump correction calculations.
• Comparison of MCNP and SNAP results on simulated and actual waste samples.
• Analysis of waste streams containing various sizes of Pu and EU lumps.
• Examination of gamma ray peak area ratios for identifying assay anomalies.

Main Results:

• Excellent agreement was observed between MCNP and SNAP results.
• The SNAP lump correction routine demonstrated high accuracy across diverse waste scenarios.
• Lump corrections were found to be rarely necessary for typical AWE waste streams.
• Abnormal gamma ray peak area ratios often signaled the need for lump correction.

Conclusions:

• Manual techniques (MCNP, SNAP) provide reliable lump corrections for fissile material in radioactive waste.
• Most AWE waste streams do not require complex lump corrections due to light shielding.
• Gamma ray spectral analysis is a key indicator for identifying situations necessitating lump correction.