Conditioning the gamma spectrometer for activity measurement at very high background

TL;DR

This study evaluates the performance of a high purity germanium gamma spectrometer under high background conditions, demonstrating its potential for accurate fuel burnup measurement in future reactors.

Contribution

The paper develops a procedure for conditioning an HPGe detector to operate effectively at very high background rates for reactor fuel burnup analysis.

Findings

Energy resolution remains acceptable at high irradiation rates.

Background subtraction method effectively reduces background influence.

Counting precision for Cs137 is below 2.8% at relevant rates.

Abstract

The application of a high purity germanium (HPGe) gamma spectrometer in determining the fuel element burnup in a future reactor is studied. The HPGe detector is exposed by a Co60 source with varying irradiation rate from 10 kcps to 150 kcps to simulate the input counting rate in real reactor environment. A Cs137 and a Eu152 source are positioned at given distances to generate certain event rate in the detector with the former being proposed as a labeling nuclide to measure the burnup of fuel element. It is shown that both the energy resolution slightly increasing with the irradiation rate and the passthrough rate at high irradiation level match the requirement of the real application. The influence of the background is studied in different parameter sets used in the particularly developed procedure of the background subtraction. It is demonstrated that with the typical input irradiation rate and Cs137 intensity relevant to deep burnup situation, the precision of the Cs137 counting rate in the current experiment is consistently below 2.8%, indicating a promising feasibility of utilizing an HPGe detector in the burnup measurement in future bed-like reactor.