Control rod interaction in a conceptual research reactor

TARYO, Taswanda, Promotor Prof.Dr.Ir. Prayoto, MSc

2003 | Disertasi | S3 MIPA

Investigation on control rod interaction in RSG-GAS reactor as well as in a conceptual MTR-type reactor (material testing reactor) has been attempted. The investigation deals with estimating the reactivity worths of the reactor control rods as well as the simulated behavior of the neutron fluxes caused by the control rod interaction. This study was attempted to improve the safety assurance and to enhance the safety scope of the reactors. Up to the present, there is no tool yet available to investigate the transient neutron flux behavior as affected by control rod interaction in the reactors. To begin with, a model has been developed as a basis of simulation where the RSG-GAS core was represented as mesh points along X, Y and Z direction and then used as a model of an MTR-type reactor. Two models were developed, namely. a conceptual MTR-type reactor with 2 absorber blades and with 2 pairs of absorber blades. The models were then utilized to estimate the reactivity worths of single and collective rods and hence the interaction among the rods can be analyzed. To simulate all conditions relevant to the above matter, the verified WIMS-D4 and CITATION codes were utilized as the main tools. While WIMS-D4 had been applied to generate group diffusion parameters, CITATION was activated to estimate effective multiplication factor (ken), reactivity worth of the reactor core, power peaking factor and others in more detail. To investigate the neutron flux behavior at different locations in RSG-GAS reactor core, 5 similar channel-power detectors were simulated in different positions in the pool reactor and for various control rod insertion depth and the model analysis was developed for steady state condition. The results showed that for the same condition and similar channel power detector, the characteristics of the neutron flux depends on the location of each detector in a reactor core. For 2 and 7 rod interactions in RSG-GAS reactor using high density sillicide fuels, the results showed that anti-shadowing effect dominantly takes place in both cases. The models were then applied to estimate the reactivity worths of a conceptual MTR reactor by applying some scenarios of typical blade separations. The results showed that, for all rods down, either shadowing or anti-shadowing effect always occurs in the reactor. In the case of control rod interaction in a conceptual MTR-type reactor equipped with 2 absorber blades and 2 pairs of absorber blades, the results indicated that the shadowing effects in the MTR-type reactor vary depending on the extent of absorber blades insertion into the reactor core and the effect is certainly more dominant for the case of 2 pairs of absorber blades rather than 2 absorber blades. Finally, to simulate control rod interaction in RSG-GAS and in the conceptual MTR-type reactors, the neutron flux behavior caused by the rod interaction in those 2 reactors was investigated using a LabView-based model combined with Microsoft Excel!. The developed software is capable to perform the neutron flux behavior due to control rod interaction in detail. The new software developed can be utilized to analyze the phenomena of control rod interaction in any nuclear reactor through performing a 3-D representation of neutron flux behavior in more detail. This represents an important contribution that would support simulation of a nuclear reactor design in detail in the future. Since not all of the original objectives have been achieved, there is still a need to develop softwares capable of generating a complete 3-D transient behavior of neutron flux distribution under conditions of multiple control rods interaction in a nuclear reactor.

Kata Kunci : Control rod interaction, RSG-GAS reactor, MTR-type reactor, Material testing reactor