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There was a confusion around the Q 0- and k 0-values for the reaction 130Ba(n,γ)131Ba. The problem was clarified in this work by re-determination of the k 0-values and critical evaluation of the Q 0-values. The new 131Ba k 0-values were found to be about 16% lower than the recommended ones compiled in 1989 and about 10% lower than those recommended in 2003. The Q 0-value was verified to be 24.3. These new values were successfully applied in k 0-INAA of Ba in various references samples. Possible error sources in Ba determination were investigated which might compensate the negative bias in Ba results from using the inaccurate k 0-values, consequently masking the problem of these old k 0-factors so far. In this context, a few cases were studied and presented. [ABSTRACT FROM AUTHOR]

An automated fast sample transfer system for the determination of measurements of short-lived isotopes has been constructed at the Research Reactor Munich FRM. Instrumental neutron activation analysis and analysis of fissile materials by delayed neutron counting are performed on this transfer device. A LabVIEWTM program on a PC with WindowsNT operating system controls the whole pneumatic system via a PCI-1200 interface and four signal conditioning SCXI-modules of National Instruments. Infrared sensors are used to monitor key points in the transfer system. The sample capsule can be automatically removed from the “rabbit” in a special switch prior to spectrum collection. γ-Spectra are acquired by a HPGe detector with the Loss-Free-Counting method of Westphal. The delayed neutrons are measured by five 3He-detectors and a multichannel scaler. The transfer time is about 200 ms. The system and its mode of operation for routine work will be described. [Copyright &y& Elsevier]

The delayed neutron emission of fissile isotopes after irradiation can be described by the six-groups theory. Due to the different half-lives and yields of the fission fragments, the intensity–time curve of delayed neutrons has an individual shape for different fissile isotopes. According to this characteristic, a new rapid analysis method has been developed to determine the concentration of different isotopes in a mixture, such as 235U and 239Pu, without any chemical separation. The intensity–time curve of delayed neutrons is measured by using the multichannel scanning (MCS) method with five 3He-detectors installed on a fast transfer system at the research reactor Munich (FRM). This method was validated by about 200 measurements with different isotope contents even below the microgram region. [Copyright &y& Elsevier]

This work is about k0-INAA using unstable neutron flux for sample irradiation. Due to slow transport, each irradiation in the channel DBVK consists of three phases: stable irradiation at the final position, and two additional irradiations during travelling by exposure to an increasing neutron flux in the delivery course and to a decreasing neutron flux in the fetch course. In this work, the neutron flux distribution along this channel was calibrated and the neutron flux variation with irradiation time was calculated, making it possible to evaluate activity growth during a complete irradiation period. The feasibility of the k0-method was checked by analyses of four SRM-materials and three multi-element standards at three DBVK-positions. An accuracy of better than ±10% was found for nearly all determined elements in each determination. [ABSTRACT FROM AUTHOR]

Abstract: Determination of k 0-factors for zirconium isotopes was performed by co-irradiation of Zr and Au–Al. Due to the highly thermalized irradiation position at FRM-II, interferences from epithermal neutrons were found largely decreased for 96Zr (n, γ) 97Zr–97mNb, the reaction with the highest Q 0-value in all (n, γ) reactions. Results showed that, the 95Zr k 0-values from this work were the same as the recommended ones. For 97Zr–97mNb 743.4keV gamma-line, the new k 0-value was 2.8% higher compared to the recommended value, which is not a significant difference. These results are helpful in clarifying the suspicion about the Zr k 0-factors. [Copyright &y& Elsevier]