Delayed gamma determination at the JSI TRIGA reactor by synchronous measurements with fission and ionization chambers

In this paper we propose a new technique to accurately determine the magnitude of the delayed gamma component and its time evolution, based on synchronous acquisition of fission and ionization chamber signals. The measurements were performed at the JSI TRIGA reactor, using fission and ionization chambers placed in several in-core measurement positions. Their signal was acquired synchronously and at the highest possible acquisition rate in order to distinguish between measurement noise and reactor transients. Using the novel delayed gamma extraction technique we were able to estimate the magnitude of the delayed gamma contribution to be: 18.9 % ± 2.0 % at the reactor core periphery, linearly increasing towards the reactor core center to 31.4 % ± 2.8 % of the total measured gamma flux signal after 10 min of reactor operation.