Abstract
The Nigeria Research Reactor-1 (NIRR-1) is one of the Commercial Miniature Neutron Source Reactors (MNSRs) sited outside China and scheduled for conversion under the auspices of Reduced Enrichment for Research and Test Reactors (RERTR) program. Since 2006, the reduction in the fuel enrichment of MSNR facilities from greater than 90% HEU cores to less than 20% LEU cores has been embarked upon. Consequently in this work, the physics parameters of three dispersion LEU fuels, which include U3Si, U3Si2, and U9Mo enriched to 19.75% were determined by the MCNP code to investigate their suitability for the conversion of NIRR-1 to LEU. The following reactor core physics parameters were computed for the LEU fuel options: clean cold core excess reactivity (ρex), control rod (CR) worth, shut down margin (SDM), neutron flux distributions in the irradiation channels and kinetics data (i.e. effective delayed neutron fraction, βeff and prompt neutron lifetime, lf). Results are compared with experimental and calculated data of the current HEU core and indicate that it would be feasible to use any of the LEU options for the conversion of commercial MNSR in general and NIRR-1 in particular from HEU to LEU.
Highlights
In this work, the physics parameters of three dispersion LEU fuels, which include U3Si, U3Si2, and U9Mo enriched to 19.75% were determined by the MCNP code to investigate their suitability for the conversion of Nigeria Research Reactor-1 (NIRR-1) to LEU
In order to obtain the licensed value of 3 - 4 mk for Miniature Neutron Source Reactors (MNSRs), a Cd absorber with reactivity worth of −1.2 mk was inserted into an unconnected inner irradiation channel
The physics parameters of three dispersion LEU fuels, which include U3Si, U3Si2, and U9Mo enriched to 19.75% have been determined by the MCNP code in order to investigate their suitability for the conversion of NIRR-1 to LEU
Summary
Under the aegis of the International Atomic Energy Agency’s (IAEA) Coordinated Research Project (CRP) from 2006 to 2012, a neutronics feasibility study for LEU conversion of the reactor was performed [5]. Matos et al, 2005 [8] investigated the use of some qualified LEU fuels that can be used for the conversion of commercial MNSR. The results they obtained were found to be outside the recommended data for the cold core excess reactivity. Three of the dispersion fuels, which include U3Si, U3Si2, and U9-Mo enriched to 19.75% were re-investigated in this work vis-à-vis their core physics parameters
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