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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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- PU-MET-FAST-001 (Jezebel): a bare sphere of plutonium-239 metal.<br />

- U233-MET-FAST-001 (Jezebel-233): a bare sphere of uranium-233 metal.<br />

- HEU-MET-FAST-028 (Flattop-U): a highly enriched uranium sphere reflected by normal<br />

uranium.<br />

- PU-MET-FAST-006 (Flattop-Pu): a plutonium sphere reflected by normal uranium.<br />

- U233-MET-FAST-006 (Flattop-233): a uranium-233 sphere reflected by normal uranium.<br />

- HEU-MET-FAST-003-011: a highly enriched uranium sphere reflected by tungsten-carbide.<br />

- HEU-MET-FAST-021: a highly enriched uranium sphere reflected by iron.<br />

- PU-MET-FAST-040: a plutonium sphere reflected by copper.<br />

- HEU-MET-FAST-027: a highly enriched uranium sphere reflected by lead.<br />

70-group sensitivity coefficients are derived with forward and adjoint neutron fluxes<br />

calculated by using an in-house discrete ordinates neutron transport code. In the discrete<br />

ordinates neutron transport calculations, Legendre coefficients of scattering matrices are<br />

accounted for up to the fifth order, and the 32-point double Gaussian angular quadrature set is<br />

used. Effective cross sections used for the neutron transport calculations are obtained by using<br />

the SLAROM-UF code [2] and UFLIB-J4.0 based on JENDL-4.0. Figure 1 shows a sensitivity of<br />

the HEU-MET-FAST-028 criticality to Legendre coefficients of elastic scattering cross sections of<br />

uranium-238.<br />

Library effects are calculated according to Eq.(1) with the sensitivity coefficients and the<br />

infinite dilution cross sections stored in UFLIB. JENDL-4.0 is treated as a base library, and<br />

differences of the other libraries to JENDL-4.0 are evaluated.<br />

4. Result of sensitivity analysis<br />

Table 1 shows differences in criticalities due to differences in each order of Legendre coefficient<br />

of elastic scattering matrices. Large effects over 0.001 are written in a bold style.<br />

While library effects due to differences in higher order Legendre coefficients are generally<br />

small, non-negligible effects are observed in PU-MET-FAST-006 with JENDL-3.3 and<br />

ENDF/B-VII.0, and HEU-MET-FAST-021 with all the libraries. The former is due to the<br />

difference in the uranium-238 data and the latter is due to the difference in the iron-56 data.<br />

Please remember that the above library effect calculations are carried out by using infinite<br />

dilution cross sections. Since medium-heavy nuclides such as iron-56 have resonance cross<br />

sections in the energy range above 0.1MeV, which is a dominant range in the present benchmark<br />

systems, the resonance self-shielding effect should be considered for accurate evaluation of<br />

library effects. Thus, a library effect calculation is again carried out for HEU-MET-FAST-021<br />

with shielded cross sections. In the resonance self-shielding factor calculation, background cross<br />

sections for iron isotopes are set at 50, 0.5, 150 and 1,000 barns for iron-54, -56, -57 and -58,<br />

respectively. These values are evaluated for the reflector medium of HEU-MET-FAST-021. In<br />

this case, a library effect is calculated with the following equation:<br />

<br />

<br />

k , LIB1<br />

k S<br />

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n l 1 g g'<br />

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k , LIB1<br />

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LIB 2 LIB1<br />

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f<br />

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LIB2<br />

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LIB 2<br />

l,<br />

g<br />

g '<br />

l,<br />

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LIB 2<br />

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<strong>JAEA</strong>-<strong>Conf</strong> <strong>2011</strong>-<strong>002</strong><br />

f<br />

<br />

LIB1<br />

g<br />

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LIB 2<br />

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LIB1<br />

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LIB1<br />

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LIB1<br />

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