The decay heat of fission products plays an important role in predictions of the heat up of nuclear fuel in reactors. The released energy is calculated as the summation of the activities of all fission products P(t) = ∑Ei λi Ni(t), where Ei is the decay energy of nuclide i (gamma and beta component), λi is the decay constant of nuclide i and Ni(t) is the number of nuclide i at cooling time t. Even though the reproduction of the measured decay heat has improved in recent years, there is still a long standing discrepancy in the t ~ 1000 s cooling time for some fuels. A possible explanation to this improper description has been found in the work of Yoshida et al. [J. Nucl. Sci. Technol. 36, 135 (1999)], where it has been shown that the incomplete knowledge of the β-decay of some Tc isotopes can be the source of the systematic discrepancy. Motivated by [Yoshida et al., J. Nucl. Sci. Technol. 36, 135 (1999)], we have recently measured the β-decay process of some Tc isotopes using a total absorption spectrometer at the IGISOL facility in Jyväskylä. The results of the measurements as well as the their consequences on summation calculations are discussed.
[Show abstract][Hide abstract] ABSTRACT: This publication presents the conclusions of the work undertaken by Subgroup 25, which focused on the assessment and improvement of the evaluated decay data sub-libraries in order to obtain more accurate estimations of decay heat. Recommendations have been prepared for total absorption gamma-ray spectroscopy (TAGS) measurements of specific fission product nuclides to be undertaken in close collaboration with experimentalists in Subgroup 25.
01/2007; Organisation for Economic Co-operation and Development., ISBN: 978-92-64-99034-0
[Show abstract][Hide abstract] ABSTRACT: In our previous paper, the theoretical overcorrection in JENDL FP Decay Data File 2000 for the decay heat summation calculation was suggested. In order to eliminate this, we redefined the criteria of applying the theoretical values to average energy release per decay, that is, Eβ and Eγ values. Furthermore, the results of the TAGS (total absorption gamma ray spectrometer) measurements up to the newest ones are adopted into the decay heat calculations. As a result, we obtained a reasonable agreement between the calculation and the sample irradiation experiments, not only for Pu but for U and Pu. The present revision of the FP decay data file will provide us with a reasonable starting point for the future revision of the decay data file by introducing the results from the TAGS effort now in progress. In addition, the effects of the so-called pandemonium problem are clearly demonstrated and this also affects the conventional decay schemes, especially for the short-lived FP nuclides having large β-decay Qβ-values.
Journal of Nuclear Science and Technology 05/2010; 47(5):492-500. DOI:10.1080/18811248.2010.9711640 · 1.12 Impact Factor
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