Analysis of experimental measurements of PWR fresh and spent fuel assemblies using Self-Interrogation Neutron Resonance Densitometry

Abstract

Self-Interrogation Neutron Resonance Densitometry (SINRD) is a new NDA technique that was developed at Los Alamos National Laboratory (LANL) to improve existing nuclear safeguards measurements for LWR fuel assemblies. The SINRD detector consists of four fission chambers (FCs) wrapped with different absorber filters to isolate different parts of the neutron energy spectrum and one ion chamber (IC) to measure the gross gamma rate. As a result, two different techniques can be utilized using the same SINRD detector unit and hardware. These techniques are the Passive Neutron Multiplication Counter (PNMC) method and the SINRD method. The focus of the work described in this paper is the analysis of experimental measurements of fresh and spent PWR fuel assemblies that were performed at LANL and the Korea Atomic Energy Research Institute (KAERI), respectively, using the SINRD detector. The purpose of these experiments was to assess the following capabilities of the SINRD detector: 1) reproducibility of measurements to quantify systematic errors, 2) sensitivity to water gap between detector and fuel assembly, 3) sensitivity and penetrability to the removal of fuel rods from the assembly, and 4) use of PNMC/SINRD ratios to quantify neutron multiplication and/or fissile content. The results from these simulations and measurements provides valuable experimental data that directly supports safeguards research and development (R&D) efforts on the viability of passive neutron NDA techniques and detector designs for partial defect verification of spent fuel assemblies.

Experiments at the GELINA facility for the validation of the self-indication neutron resonance densitometry technique

“…The application of SINRD to spent fuel measurements was proposed in [2][3][4][5] by measuring a fuel assembly under water and by placing a set of 235 U fission chambers on one side of the assembly.…”

Neutron absorbers and detector types for spent fuel verification using the self-interrogation neutron resonance densitometry

“…At Los Alamos National Laboratory the SINRD technique was investigated for the measurement of spent fuel under water by placing a set of fission chambers on one side of the fuel assembly to measure the spontaneous neutron emission [5][6][7][8][9]. However, this configuration relied on the accurate positioning of the detectors [10] and was more sensitive to the first outer fuel pin rows [5].…”