SLAROM-UF; Ultra Fine Group Cell Calculation Code for Fast Reactor
Hazama, Taira ; Chiba, Go; Sato, Wakaei*; Numata, Kazuyuki*
A cell calculation code SLAROM-UF was developed to improve calculation accuracy of effective cross sections for various fast reactor types. SLAROM-UF has a capability to calculate effective cross sections in ultra fine groups of about 100,000 below 50keV and in fine groups above the energy (maximum 900 groups), Resonance interaction among the fuel, the coolant, and the structure materials can be treated accurately even in a heterogeneous cell structure. Temperature can be set up freely in a cell by the ultra fine group calculation. Improvement in nuclear characteristics was observed in the analysis of JUPITER critical experiment, as O.1% for criticality, 4% for sodium void reactivity, several % for radial reaction rate distribution, when SLAROM-UF was used insead of the typical cell calculation code. The effect of the ultra fine group calculation is remarkable in the non-leakage term of sodium void reactivity, and that of the fine group calculation is in the case that neutron spectrum in a core can not be represented by the cell calculation. When it is compared with a calculation by continuous energy Monte Carlo code MVP in a homogeneous lattice system, agreement lies within 1% for criticality, a few % for sodium void reactivity, and several % for radial reaction rate distribution of ZPPR-13A whose non-homogeneity is significant. The differences are reduced by about half, from those with the typical cell calculation code. SLRAOM-UF is easily available in the JOINT system currently being used in JNC, including all the functions available in the existent cell calculation code.