STUDI PERHITUNGAN REAKTOR HTR PEBBLE-BED DENGAN BERBAGAI OPSI DESAIN MATRIKS BAHAN BAKAR

ABSTRAK
STUDI PERHITUNGAN REAKTOR HTR PEBBLE-BED DENGAN BERBAGAI OPSI DESAIN
MATRIKS BAHAN BAKAR. Teras HTR pebble-bed dapat mengakomodasi berbagai bahan bakar secara
luas tanpa modifikasi desain teras yang signifikan. Dalam makalah ini dilakukan studi perhitungan reaktor
HTR pebble-bed dengan tiga opsi desain matriks bahan bakar UO2 (pengkayaan U235 8,2%), PuO2
(pengkayaan Pu239 53,85%) dan ThO2/UO2 (pengkayaan U233 7,47%). Perhitungan reaktor meliputi
perhitungan sel menggunakan model array infinit bahan bakar pebble dengan kondisi batas reflektif dan
perhitungan teras penuh memanfaatkan model silindris (2-D R-Z) dengan diameter 300 cm dan tinggi 943
cm. Seluruh perhitungan dilakukan dengan program transport Monte Carlo MCNP5 pada temperatur 293,6
K dan 1.000 K. Secara keseluruhan perhitungan MCNP5 menunjukkan konsistensi dengan nilai kinf dan keff
teras UO2 yang hampir selalu lebih tinggi dibandingkan teras PuO2 dan ThO2/UO2. Komparasi dengan
simulasi Monte Carlo lainnya memperlihatkan bahwa MCNP5 memproduksi nilai kinf sesuai dengan yang
dihasilkan MCNP-4B dibandingkan MONK9 dengan bias perhitungan kurang dari 1,3%. Perhitungan keff
MCNP5 merefleksikan kecenderungan dekat dengan MCNP-4B, KENO-V.a maupun MONK9 namun bias
perhitungannya relatif lebih besar dibandingkan TRIPOLI4, khususnya di teras PuO2. Dapat disimpulkan
bahwa estimasi MCNP5 berada di dalam rentang prediksi seluruh program perhitungan Monte Carlo dan
diekspektasi paling presisi bila data eksperimen didapatkan nanti.
Kata kunci: HTR pebble-bed, bahan bakar, MCNP5, ENDF/B-VI
ABSTRACT
STUDY ON PEBBLE-BED HTR REACTOR CALCULATION WITH SEVERAL OPTIONS OF
FUEL MATRIX DESIGNS. Pebble-bed HTR core is able to accomodate various types of fuel without
significant core modification. This paper presents study of calculation of pebble-bed HTR core with three
options of fuel matrix designs: UO2 (8.2% U235 enrichment), PuO2 (53.85% Pu239 enrichment) and ThO2/UO2
(7.47% U233 enrichment). Core calculation includes cell calculation using infinite array model of pebble-bed
fuel with reflective boundary and full core calculation uses cylindrical model (2-D R-Z) with 300 cm in
diameter and 943 cm in height. All computations are carried out using Monte Carlo transport code MCNP5
at temperature of 293.6 K and 1000 K. In general, MCNP5 calculations indicate consistency with kinf and keff
values of UO2 core which always almost higher than those of PuO2 and ThO2/UO2 cores. Compared to the
other Monte Carlo simulation show that MCNP5 produces the value of kinf which is closer to that obtained by
MCNP-4B than that obtained by MONK9 with the computation bias less than 1.3%. The MCNP5's keff
calculation reflect a close tendency to that achieved by MCNP-4B, KENO-V.a, and MONK9, however, its
computation bias is relatively high compared to the TRIPOLI4, especially for reactor core with PuO2. It can
be concluded that MCNP5 estimations excist in the range of all Monte Carlo calculation codes and are
expected to be the most precision if the experimental data found later.
Keywords: HTR pebble-bed, fuel, MCNP5, ENDF/B-VI