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 />
[7]. For example, Table1 shows that Tc-102, whose -feeding to the ground state is very large,<br />
proved to be free from the pandemonium problem, in other words, the current high-resolution<br />
data (ENDF/B-VII) and the UDV/TAGS give almost the same values for E and E..<br />
3.2. Important Nuclides for U-235 Decay Heat<br />
Here we propose a list of nuclides to be measured in the future TAGS program focusing our<br />
attention on the improvement of decay heat summation calculation for U-235.<br />
This study uses JENDL/FPD-2000 and the Evaluated Nuclear Structure Data File [8]<br />
(ENSDF). The library JENDL/FPD-2000 covers information on the decay data of 1229<br />
fission products. This is used to search for the nuclides that contribute much to the decay<br />
heat of U-235. Detailed data of the searched nuclides (half-life, Q-value, and released<br />
energies etc.) are obtained from ENSDF. We examine whether the pandemonium-problem<br />
influences the selected nuclides from these data library, and evaluating the priority of the<br />
future TAGS measurements.<br />
The points for selecting nuclides and deciding the priority are as follows.<br />
i) The difference between the highest known level and Q-value.<br />
When the difference is large, the nuclide has a large possibility of missing of the -feeding<br />
to the high energy regions of the daughter nuclide in the current decay schemes by influence<br />
of the pandemonium-problem.<br />
ii) The unplaced gammas.<br />
The primary cause of pandemonium-problem is that a lot of rays, though detected, failed<br />
to find their correct places in the complex decay scheme (unplaced gamma). The unplaced<br />
gammas can be confirmed by ENSDF. For example, Xe-141 has extremely many and high<br />
energy unplaced gammas. There are as many as 185 unplaced -rays besides 96 -rays which<br />
are correctly positioned in the complex decay scheme of Cs-141, its daughter nuclide.<br />
iii) Contribution to the Pu-239 decay heat.<br />
Calculation of the decay heat for Pu-239 is in a good agreement with the sample-irradiation<br />
measurements for the sake of the recent TAGS activity [5]. Therefore, when a nuclide’s<br />
contribution to the decay heat of Pu-239 is large, it is reliable and not selected for the future<br />
TAGS measurements. However, this principle is not applied for the nuclides whose<br />
contribution to the decay heat for Pu-239 in the cooling-time range 200 – 10,000s is large. In<br />
this cooling-time range the disagreement still remains between the calculation and the<br />
measurements.