Simulation of reactivity transients in a miniature neutron source reactor core

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“…For both cases, it was indicated that large surface heat fluxes would be generated and saturation temperature would be reached, and also subcooled nucleate boiling was expected to occur within the flow channels of the reactor for these reactivity insertions. They also predicted a peak power of 100.8 kW for inserting ramp reactivity of the cold clean core excess reactivity of 4 mk, which compared favorably with the experimental value of 100.2 kW (Akaho and Maaku, 2002). It was also indicated that subcooled nucleate boiling was expected within the flow channels of the reactor for this predicted peak power of 100.8 kW.Ampomah-Amoako et al, 2009 performed thermal-hydraulic analysis on GHARR-1 using Program for the Analysis of Reactor Transients/Argonne National Laboratory (PARET/ANL) code.…”

“…Coolant exit velocity was obtained by combining the conservation of one dimensional mass and energy equations (Akaho and Maaku, 2002;Guo et al, 2008;Ampomah-Amoako et al, 2009) (Equation 8). …”

“…The frictional pressure drop was estimated by integrating the frictional pressure drop component of Equation (2), which gives Equation (15) The single-phase friction factor is given by the relation (Akaho and Maaku, 2002) (Equation 16). …”

“…The heat generated by fission in the multichannel is transferred in an upward direction and the hot water, which moves to the upper section of the reactor tank, is transferred to the water in the pool. For safety assessment of the reactor GHARR-1 and in order to update the Safety Analysis Report, Akaho et al developed a computer code to simulate the peak powers that could be associated with large reactivity insertions of 6.71 mk and 9 mk during the time of abnormal reactor operations such as installation of a new core (fresh fuel replacement) and addition of incorrect thickness of top Be plates in the Al tray located at the top of the reactor core respectively (Akaho and Maaku, 2002). Peak powers of 187.23 kW and 254.30 kW for reactivity insertions of 6.71 mk and 9 mk respectively were predicted.…”

“…The GHARR-1, which under normal reactor operating conditions has its flow through the channels as single phase experiences two phase flow regime due to reactor power excursion because of large reactivity insertions associated with abnormal operations of the low power reactor (Akaho and Maaku, 2002). These large reactivity insertions that associate with abnormal operating conditions with high reactor powers could be experienced during the time of abnormal operations such as installation of a new core, addition of incorrect thickness of top Be plates in the Al tray located at the top of the core and insertion of ramp reactivity of the cold clean core.…”