Comparison of various hours living fission products for absolute power density determination in VVER-1000 mock up in LR-0 reactor

• Gamma Spectrometry measurements of short living fission products in VVER-1000 mock-up.
• Determination of fission density from 92Sr, 135I, 88Kr, 91Sr, and 97Zr activity.
• Application of burn card in MCNPX for activity calculation of short living fission products.
• Discrepancies between calculational and experimental fission rate.

Measuring power level of zero power reactor is a quite difficult task. Due to the absence of measurable cooling media heating, it is necessary to employ a different method. The gamma-ray spectroscopy of fission products induced within reactor operation is one of possible ways of power determination. The method is based on the proportionality between fission product buildup and released power. The 92Sr fission product was previously preferred as nuclide for LR-0 power determination for short-time irradiation experiments. This work aims to find more appropriate candidates, because the 92Sr, however suitable, has a short half-life, which limits the maximal measurable amount of fuel pins within a single irradiation batch. The comparison of various isotopes is realized for 92Sr, 97Zr, 135I, 91Sr, and 88Kr. The comparison between calculated and experimentally determined (C/E-1 values) net peak areas is assessed for these fission products. Experimental results show that studied fission products, except 88Kr, are in comparable agreement with 92Sr results. Since 91Sr has notably higher half-life than 92Sr, 91Sr seems to be more appropriate marker in experiments with a large number of measured fuel pins.