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[en] The flux oscillations due to the Xenon distribution in homogeneous thermal reactors are studied treating the space dependence through the modal expansion technique. The effect of the feedbacks due to Xenon and a power feedback coefficient on the linear stability of the reactor is investigated employing various number of terms in the modal expansion. Stability calculations are perform varying the reactor size in order to establish the size of the reactor which is unstable against spatial oscillations at the flux levels of the currently operating power reactors. (author)
[en] The aim of this study is to compare radioxenon beta–gamma analysis algorithms using simulated spectra with experimentally measured background, where the ground truth of the signal is known. We believe that this is among the largest efforts to date in terms of the number of synthetic spectra generated and number of algorithms compared using identical spectra. We generate an estimate for the minimum detectable counts for each isotope using each algorithm. The paper also points out a conceptual model to put the various algorithms into a continuum. Finally, our results show that existing algorithms can be improved and some newer algorithms can be better than the ones currently used.
[en] To our best knowledge, the effect of the omission of Xe-135m has never been evaluated before. Recently, we found that the cross section data of Xe-135m are available from the TENDL-2011 library based on the theoretical evaluations. According to the TENDL data, the neutron absorption cross section of Xe-135m turns out to be much larger than that of Xe-135 in the thermal neutron region, as shown in Fig. 1. In this paper, we evaluated the impacts of Xe-135m on the total steady-state and transient Xe reactivity. By taking into account Xe-135m in the I-135 decay, we have found the followings. First, the steady state total xenon reactivity is slightly increased by ∼0.94% as compared with the conventional model. Second, the impact of Xe-135m on the transient Xe reactivity is rather significant. In particular, the reactivity change during the early transient period can be noticeably enhanced by accounting for Xe-135. And this indicates that Xe-135m may play an important role in measuring the PCR for which the transient Xenon reactivity should be accurately estimated. Currently, the impacts of Xe-135 on the PCR measurement are under investigation
[en] Highlights: • Dendified isostatic graphite was obtained from isostatic graphite by impregnating with phenolic resin. • The obtained graphite exhibited better integrated properties including barrier property than pristine graphite. • The obtained graphite could effectively inhibit molten fluoride salt and Xe135 from infiltration.
[en] The ratio of the probabilities of population of the isomeric and ground states, so called the isomeric ratio is closely connected to the angular momentum of the initial fission fragments that is dissipated at the later stages of gamma ray cascade. This ratio also provides important information on the nuclear level structure as well as the nuclear reaction mechanism involved. In this work, the isomeric ratio in fission fragment 135Xe from photofission of 233U induced by 23.5 MeV bremsstrahlung has been determined by the method that uses inert gaseous flow. The results have been discussed and compared with that of other authors. (author)
[en] A numerical diagram is suggested of minimizing a period of xenon transient process in the reactor without any limitation of xenon-135 concentration. The problem is solved with a computer in a point model. Pontryagin's maximum principle is used so as to check optimization of the transient process
[en] There was an experimental evaluation of the PCR of a CANDU6 reactor in Korea in 2012. In the assessment, the PCR was evaluated by a methodology which requires the estimation of the reactivity variation due to Xe, liquid zone controller (LZC), etc. Unlike the conventional Xe analysis, Xe-135m was also considered in this work to estimate the total Xe worth during transient. The impact of Xe-135m on the experimental evaluation of CANDU6 PCR was evaluated based on the Xe-135m cross section data of TENDL-2014. As a result, the evaluated PCR was reduced by about 0.2 pcm/%P due to the consideration of Xe-135m. (author)