Sensitivity and uncertainty analysis for reactor stable period induced by positive reactivity using one-point adjoint kinetics equation

Abstract

In order to better predict the kinetic behavior of a nuclear fission reactor, improvement of delayed neutron parameters is essential. Since it is required to establish a path from the microscopic nuclear data to the macroscopic delayed neutron parameters for the improvement, the present paper identifies important nuclear data for reactor kinetics. Sensitivities of the reactor stable period, which describes reactor kinetic behavior, to microscopic nuclear data such as independent fission yields, decay constants and decay branching ratios are calculated efficiently by using the adjoint kinetics equation. Furthermore, nuclide-wise and nuclear data-wise uncertainties of the reactor stable period are quantified using the variance data given in the nuclear data file, and the nuclear data that require further improvement are identified. The results obtained through the present study are quite helpful, and can be a driving force for further nuclear physics studies.

235U(n, f) Independent fission product yield and isomeric ratio calculated with the statistical Hauser–Feshbach theory

“…Since these fission fragments are highly excited, they de-excite by emitting several prompt neutrons and γ rays to reach their ground or metastable states within a time-scale of compound nucleus in the fission process. The independent fission product yield Y I (Z, A), which is a distribution of nuclides after emission of the prompt particles but before beta decay, plays an important role in many applications such as estimation of decay heat [2][3][4] and delayed neutron emission 5,6 in nuclear reactors, the reactor neutrino study 7 , prediction of fission product inventory at each stage of the nuclear fuel cycle, the radio-isotope production for medical applications, development of advanced reactor and transmutation systems, fission in the galactic chemical evolution 8 , and so on. A demand for high quality data of fission product yield (FPY) in such applications is rapidly increasing.…”