JAEA-Conf 2011-002 - 日本原子力研究開発機構
JAEA-Conf 2011-002 - 日本原子力研究開発機構
JAEA-Conf 2011-002 - 日本原子力研究開発機構
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<strong>JAEA</strong>-<strong>Conf</strong> <strong>2011</strong>-<strong>002</strong><br />
Table 1. Characteristics of samples<br />
Sample<br />
Chemical<br />
Form<br />
Isotopic<br />
Compsition [%]<br />
weight of<br />
sample [g]<br />
Diameter of<br />
sample [mm]<br />
Outer diameter of<br />
container [mm]<br />
93<br />
Zr ZrO2 18.9 3.31 20.0 30.0<br />
99 Tc Tc 100 0.078 6.3 9.0<br />
107 Pd Pd 15.3 0.137 4.5 9.0<br />
10 B B 19.9 0.083 10.0 ---<br />
35 Cl NaCl 75.8 0.500 10.0 ---<br />
of the spectrometer and in a neutron beam duct. The neutron beam was collimated to a<br />
diameter of 3 or 7 mm at the sample position using a rotary collimator system [11].<br />
The signals from the Ge crystals were stored using a data acquisition (DAQ) system<br />
[12,13] with event-by-event mode as three-dimensional data of -ray pulse height, TOF, and<br />
time-interval between coincidence signals. Random timing pulses were also fed into every<br />
pre-amplifier from a random generator for making a dead-time correction [14].<br />
The measurement times for 93Zr, 99Tc and 107Pd samples were about 52, 25 and 31 hours,<br />
respectively. In order to estimate the background, a measurement with an empty aluminum<br />
container was also done.<br />
3. Data Processing and Analysis<br />
The neutron flux at the sample position was deduced from the TOF spectrum<br />
corresponding to the 478-keV ray emitted via the 10B(n,) 7Li reaction. The neutron capture<br />
cross section data were taken from JENDL-3.3 [15].<br />
For TOF spectrum of 99Tc, the background subtraction was performed using the capture<br />
-ray yields from an empty aluminum container. The normalization of the background TOF<br />
spectrum was performed on the basis of the prompt -ray emitted from the neutron capture<br />
reaction of 27Al. For 93Zr and 107Pd which contain a large amount of impurities, the events<br />
related to an objective nuclide were extracted with a ground-state transition method [16,17].<br />
In the case of 93Zr, five ground-state transitions from the 919-, 1671-, 2846-, 2908-keV states<br />
and the capture state were clearly observed in the -ray pulse-height spectrum. Especially, the<br />
very strong ground-state transition at 919 keV is remarkable and the intensity amounts to<br />
about 83 % of the total intensity of five ground-state transitions. We have gated on those -ray<br />
peaks corresponding to the ground-state transitions and derived the net TOF spectrum for<br />
93Zr. The background component was estimated from the TOF spectra for the continuous<br />
region around the -ray peaks of ground-state transitions. The absolute neutron capture<br />
yields were derived with the full-energy peak efficiency curve for the 4 Ge spectrometer. In<br />
the case of 107Pd, it is summarized how to reject the contribution due to impurities. The<br />
details of analysis have been described in Ref.[18]. The components due to 105Pd mainly<br />
contained in the sample were extracted by gating on the ground-state transition ray peak at<br />
512 keV.<br />
The neutron capture cross sections of 93Zr, 99Tc and 107Pd were derived from the neutron<br />
flux and the net TOF spectra. The corrections were made for the self-shielding and<br />
multiple-scattering of neutron in the sample, dead time, and so on.