Search

Nuclear isomers are investigated to perform precise epithermal neutron dosimetry. One key physical property for reactor dosimetry is the precise knowledge of the isomer half-life. In the list of potential candidates, the half-life values available in the literature or in the recommended database for reactor dosimetry for 117mSn, 125mTe, 135mBa and 195mPt show some discrepancy. New half-life measurements are presented in this work. Those isomers were produced by neutron activation at the JSI TRIGA Reactor from tin, tellurium, barium (all three of them enriched in their parent of interest) and natural platinum dosimeters. Precise half-lives measurements were performed at the MADERE platform using gamma and X-ray spectrometry. Special care has been taken on the uncertainty determinations. • New elements for fast neutron dosimetry are currently under investigation. • Metastable states of Tellurium, Tin, Barium, and Platinum are promising candidates. • Half-lives are key elements in reactor dosimetry. • For nuclear data assessment, uncertainties must be determined with high accuracy. • Good agreement of the measurement with the litterature. [ABSTRACT FROM AUTHOR]

Abstract: The calculation of axial neutron flux distributions with the MCNP code at the JSI TRIGA Mark II reactor has been validated with experimental measurements of the 197Au(n,γ)198Au reaction rate. The calculated absolute reaction rate values, scaled according to the reactor power and corrected for the flux redistribution effect, are in good agreement with the experimental results. The effect of different cross-section libraries on the calculations has been investigated and shown to be minor. [Copyright &y& Elsevier]

CEA developed fission chambers and ionization chambers were utilized at the JSI TRIGA reactor to measure neutron and gamma fields. The measured axial fission rate distributions in the reactor core are generally in good agreement with the calculated values using the Monte Carlo model of the reactor thus verifying both the computational model and the fission chambers. In future, multiple absolutely calibrated fission chambers could be used for more accurate online reactor thermal power monitoring. [ABSTRACT FROM AUTHOR]

Neutron activation analysis is the reference method used for offline determination of the neutron flux density in defined positions. It can be used in the nuclear energy industry-as well as in medical- or space applications. For accurate neutron flux evaluation, well-known and reliable cross sections are needed. In the thermal and fast energy region, many reliable monitoring reactions exists, however, in case of the epithermal and intermediate energy region, there are practically no dosimetry nuclear reactions sensitive specifically in this energy range. Due to this fact, both new data are being measured and methodologies are under development to describe and test this energy region. It was found that various neutron filters can be used to cut parts of neutron spectra and thus methodology based on spectrum filtering could potentially be employed to survey cross sections of interest. It this paper, the use of 3 different filters – B 4 C, Cd, and In is studied, on the case of the 55Mn(n,γ) reaction. Measured values of that cross section in the given filtered reference spectra are reported. • Measurement of reaction rates in various neutron filters in reference neutron field. • Calculation of reaction rates in various neutron filters in reference neutron field. • Discrepancies between calculation and experiment. • Testing of 55Mn(n,γ) cross section in various energy regions. [ABSTRACT FROM AUTHOR]