No abstract available

[en] The half-life of ¹³⁴Cs was determined from the change of the ¹³⁴Cs to ¹³⁷Cs activity ratio. Gamma-spectrometric analyses of used RA reactor fuel were performed twice over a long time interval. The value obtained is 2.04 +- 0.03 years. The declared error of the mean value of the ¹³⁴Cs decay constant is calculated as a probable error due to: the statistics of the mean value, 8.8x10^-6 days^-1, the error of the ¹³⁷Cs decay constant, 1.0x10^-6 days^-1, the errors of O₁ and Q₂ resulting from the approximation of a Compton distribution under the photo-peaks, 6.3x10^-6 days^-1, each, the error of the interval t, 0.006x10^-6 days^-1. The result is an agreement with most of the literature data. (T.G.)

[en] The errors made in the activity ratio determination (method described in [1]) are estimated. They are given for ¹⁰⁶Ru, ¹/H3/H4Cs and ¹⁴⁴Ce. Different calculation procedures are considered. The obtained results show that the error depends on the used procedure and on the corresponding gamma activity ratios. It amounts from a few promilles to some ten per cent. For the most favourable procedure, the error in the activity ratios of the considered isotopes, is only few promilles

[en] The reactor RA is a heavy-water channel-type research reactor. Regarding the accountability of nuclear material, the specific features of reactor RA are: The segmental form of fuel elements; numerous fuel elements in the reactor core and numerous elements to be reloaded annually; and the flexibility and complexity of the in-core fuel management. Consequently, there are many fuel elements in the spent fuel storage with an incoherent and rather complex irradiation history. To account for the nuclear material in the irradiated fuel elements, under the given circumstances, some ''fast'' procedure for the fuel burnup evaluation should be used. In this respect, the fuel work integration procedure, based on the power distribution evaluation, has been investigated. The radial power distribution is measurable by the channel coolant flow-rate and the inlet/outlet temperature difference. The axial distribution is calculated by the two-group homogeneous diffusion approach. The gamma spectrometry method is used to verify the ''power distribution procedure''. The intercomparison is made on 17 fuel elements from two fuel channels with different in-core history. The differences between obtained results were within the experimental error associated with both methods. This indicates that the ''power distribution method'' is a useful tool for routine application on the irradiated fuel of the RA reactor. However, to correlate it successfully further measurements by gamma spectrometry should be done. (author)

[en] This report contains calculation basis and obtained results of activities for three groups of isotopes in the RA reactor 80% enriched fuel element. The following isotopes are included: 1) ^85mKr, ⁸⁷Kr, ⁸⁸Kr, ¹³¹J, ¹³²J, ¹³³J, ¹³⁴J, ¹³⁵J, ¹³³Xe, ¹³⁸Xe i ¹³⁸Cs, 2) ⁸⁹Sr, ⁹⁰Sr, ⁹¹Sr, ⁹²Sr, ⁹⁵Zr, ⁹⁷Zr, ¹⁰³Ru, ¹⁰⁵Ru, ¹⁰⁶Ru, ^129mTe, ¹³⁴Cs, ¹³⁷Cs, ¹⁴⁰Ba, ¹⁴⁴Ce, kao i 3) ²³⁸Pu, ²³⁹Pu i ²⁴⁰Pu. It was estimated that the fuel is exposed to mean neutron flux. The periodicity of reactor operation is taken into account. Calculation results are given dependent on the time of exposure. These results are to be used as source data for Ra reactor safety analyses

[en] Possibility of determination of the neutron flux in the fuel of a heavy water reactor has been examined. In determination of the flux an iterative procedure was used to compare calculated and measured contents of several fission products. The former contents were determined by calculation of the burning process balance and the latter by non-destructive gamma-spectrometric analysis of fuel. The obtained results prove the possibility of such determination of not only the average value of the flux but also of the change of its intensity during utilization of fuel (author)

No abstract available

[en] The correlation of isotope composition of uranium and plutonium with the fuel burn-up in a natural uranium based fuel of the first Czechoslovak atomic power station A1 has been investigated experimentally. The isotope composition of both elements, after their separation from the samples, was estimated mass-spectrometrically; the burn-up was determined by cesium (from ¹³⁷Cs radioactivity) and neodymium (from ¹⁴⁸Nd amount) methods. The dependences of isotope composition of U and Pu on burn-up are illustrated graphically. (author)

No abstract available

[en] The procedure for determining the plutonium isotopic composition and content in irradiated uranium fuel of a heavy water nuclear reactor by measuring ¹³⁷Cs, ¹³⁴Cs and ¹⁰⁶Ru activities has been experimentally tested. Irradiated fuel from the First Czechoslovak Nuclear Power Plant A1 was used for the tests. Accuracy was determined by comparing the results with those obtained from mass spectrometric measurements. The differences vary between 1 and 9%. The causes of deviations were analyzed, and the influence of the error of the gamma spectrometry measurements on the accuracy of the investigated procedure has been estimated. (author)