GHARR-1 Core Conversion Project: Environmental Radiation Dose Monitoring Aspect for Irradiated fuel Transfer from Temporal to Final Storage at NRRC

Environmental Radiation Monitoring (ERM) was one of the crucial safety activity aspects which characterized the core conversion processes of the Ghana Research Reactor-1 (GHARR-1) Facility. GHARR-1 is a Chinese manufactured Miniature Neutron Source Reactor (MNSR) which belongs to the class of tank-in-pool type reactors. In response to the global trend in converting research and test reactors from the use of High Enriched Uranium (HEU) to Low Enriched Uranium (LEU), the Nuclear Reactors Research Centre (NRRC) which operates GHARR-1 undertook steps and converted the reactor's HEU fuel of 90.2% to a 13% LEU core. The processes accompanying the HEU core removal included: transferring it to an Interim Transfer Cask (ITC) for temporal storage in a National Radioactive Waste Management Centre (NRWMC), unloading from the ITC into a SKODA Cask, and finally storage in a TUK at NRRC before transferring it back to China. These processes require implementation of a Radiological Protection Programme (RPP) competent enough to provide safety to workers, the public and the environment. Key to the success of the RPP was ERM which was a chain of processes comprising: reactor hall during core removal, one meter radius distance around the ITC; strategic locations at the NRWMC; surfaces of the SKODA cask; Surfaces of the TUK and areas around the NRRC. The results of the monitoring work which was recorded using radiation hand monitors indicated that only surfaces of the ITC recorded values which ranged between 2.98-3.35 μSv/h with a mean of 3.04 μSv/h. These values were above standard background radiation of 0.133 μSv/h. However, all other monitoring locations recorded values generally related to the background. Thus, the ERM programme indicates strongly that, the core removal activities did not pose any radiological danger to the workers, the general public and the environment. (author)