Browsing by Author "Essel, P.A.A."
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Item Estimation of Decay Heat in Ghana Research Reactor-1 Auxiliary Components Using ORIGEN-S: A Case Study(Nuclear Technology, 2019-04) Abrefah, R.G.; Essel, P.A.A.The high-enriched-uranium core of the Ghana Research Reactor-1 has been removed and replaced by low-enriched-uranium fuel. Some components of the reactor that were not transported to China as part of the Chinese take-back program will be managed and stored in Ghana. The amount of decay heat and activity in these components were estimated using the ORIGEN-S code in order to select the best waste management option and to protect the personnel that will handle these components. The results obtained showed relatively low decay heat and activity in the reactor components that were considered in this study.Item Estimation of the Dose Rate of Nuclear Fuel of Ghana Research Reactor-1 (Gharr-1)(University of Ghana, 2016-07) Essel, P.A.A.; Abrefah, R.G.; Odoi, H.C.; University of Ghana, College of Basic and Applied Sciences, Department of Nuclear EngineeringGhana is in the process of converting its fuel from Highly Enriched Uranium (HEU) to Lowly Enriched Uranium (LEU) even though the HEU fuel is not fully spent, thus the handling of the irradiated fuel is in the offing. Irradiated fuel consists of radioactive fission and activation products generated in the nuclear fuel which are hazardous to personnel, environment and the public. As a result, the knowledge of the dose rate will aid in safe guarding the process of core conversion. Two computer codes used to carry out this research work were ORIGEN-S; for computing changes in the isotopic concentrations during neutron irradiation and radioactive decay as well as to determine the source term and MCNP6; which used the source term estimated by the ORIGEN-S code to calculate the dose rate in mrem using point detectors and also to determine the criticality of the core at different heights above the bottom of the core in order to mimic the process of unloading the core. Most of the radionuclides present after the core depletion contributed to the source term of 1.767X1013photons/sec which was observed after thirty days of the cooling period. The dose rates ranged between 3.51x10-25mGy/hr and 4.27x104mGy/hr with the detectors placed at positions above the reactor core, the control room (wall, door and window) and the rabbit room. The criticality (keff) also decreased from 0.99442 to 0.01238 which indicates that the nuclear fuel will remain sub critical. The results proved that the core unloading will be done safely.Item Estimation of the dose rate of nuclear fuel of Ghana Research Reactor-1 (GHARR-1) using ORIGEN-S and MCNP 6(Elsevier Ltd, 2018-05) Abrefah, R.G.; Essel, P.A.A.; Odoi, H.C.Ghana is in the process of converting its fuel from Highly Enriched Uranium (HEU) to Lowly Enriched Uranium (LEU). Radioactive fission and activation products generated in the irradiated nuclear fuel are hazardous to personnel, environment and the public. Investigation into the levels of radiation dose will help in a safe and efficient core conversion process. Two computer codes used were ORIGEN-S; for computing changes in the isotopic concentrations during neutron irradiation and radioactive decay as well as to determine the source term and MCNP6; which used the source term estimated by ORIGEN-S code to calculate the dose rate. The criticality of the core at different heights above the bottom of the core was also obtained. Most of the radionuclides present after the core depletion contributed to the source term of 1.767 × 1013 ± 0.0008 photons/sec which was observed after thirty days of the cooling period. The dose rates ranged between 3.51 × 10−25 ± 0.0003 mGy/h and 4.27 × 104 ± 0.0006 mGy/h at different positions above the reactor core, the control room (wall, door and window) and the rabbit room. The criticality (keff) also decreased from 0.99442 ± 0.00006 to 0.01238 ± 0.00002 as the core moved from the bottom of the reactor vessel to the top. © 2018 Elsevier Ltd