| Abstrak/Abstract |
The GAMA aqueous homogeneous reactor (GAMA-AHR) is an AHR design developed by the Nuclear Reactor
Research Team at the Department of Nuclear Engineering and Engineering Physics, Universitas Gadjah Mada.
This nonpower reactor produces valuable radioisotopes, mostly molybdenum-99, that are intended for medical
purposes. The standard GAMA-AHR design utilizes 3.0 % mole of uranyl nitrate as seed (fissile) fuel and 4 %
mole of thorium nitrate as blanket (fertile) fuel, and both are dissolved in light water as solutions. Compared with
other AHR designs, the GAMA-AHR utilizes light water as the reflector instead of graphite. This design allows the
use of a completely passive post-shutdown cooling system. Criticality calculation and neutronic parameter
analysis were performed utilizing SCALE6.2 and OpenMC computer codes with the ENDF/B-VII.1 neutron cross
section library, respectively. The analyzed parameters comprised power distribution, excess reactivity, shutdown
margin, shutdown capability using a fuel drain tank, control-rod worth, temperature reactivity coefficient, and
void reactivity coefficient (αθ). From the calculation results, the GAMA-AHR exhibited an excess reactivity of
0.07843 Δk/k at zero burn-up in 3.0 % mole of uranyl nitrate solution. The excess reactivity at zero burn-up
increased with the increase in the mole fraction of uranyl nitrate until the maximum value of 0.215 Δk/k at
15 % mole of uranyl nitrate. The GAMA-AHR exhibited the control-rod shutdown margin of − 0.03072 Δk/k at a
normal operation temperature (80 ◦C) and − 0.01958 Δk/k at 40 ◦C. Draining of the seed-fuel solution shut down
the reactor with a shutdown reactivity of − 1.40385 Δk/k. The GAMA-AHR showed a negative feedback for
temperature and αθ, with values of − 0.000155 Δk/(k.◦C) and − 0.00353 Δk/(k.%), respectively. These results
prove the inherent safety characteristic of the GAMA-AHR. The GAMA-AHR with the thermal power of 200 kWth
capable to produce 2500 six day Ci per week of Mo-99. |
