In-situ gamma spectrometry measurements of time-dependent Xenon-135 inventory in the TRIGA Mark II reactor Vienna

TL;DR

This study demonstrates that in-situ gamma spectrometry can effectively measure the time-dependent Xe-135 inventory in a reactor, even amidst high background radiation, providing valuable data for reactor monitoring and safety.

Contribution

It introduces a method for measuring Xe-135 in a reactor using gamma spectrometry with automated analysis, even under high background radiation conditions.

Findings

Successful measurement of Xe-135 inventory over one week

Automated peak detection in high background gamma spectra

Comparison of measured data with theoretical calculations

Abstract

In this work, it has been shown that the time dependent Xe-135 inventory in the TRIGA Mark II reactor in Vienna, Austria can be measured via gamma spectrometry even in the presence of strong background radiation. It is focussing on the measurement of (but not limited to) the nuclide Xe-135. The time dependent Xe-135 inventory of the TRIGA Mark II reactor Vienna has been measured using a temporary beam line between one fuel element of the core placed onto the thermal column after shutdown and a detector system located just above the water surface of the reactor tank. For the duration of one week, multiple gamma ray spectra were recorded automatically, starting each afternoon after reactor shutdown until the next morning. One measurement series has been recorded over the weekend. The Xe-135 peaks were extracted from a total of 1227 recorded spectra using an automated peak search algorithm and analyzed for their time-dependent properties. Although the background gamma radiation present in the core after shutdown was large especially in the lower energy range, the Xe-135 peak located at 249.8 keV could be extracted from the most spectra where present and could be compared to theoretical calculations.