This study was carried out to verify the adequacy of the shielding mechanisms in place at the Gamma Irradiation Facility (now Radiation Technology Centre) of the Ghana Atomic Energy Commission to ensure that workers of the facility are not over-exposed to radiation in routine work as prescribed by the local authority and international regulations. A category IV Wet Storage Gamma Irradiation Facility, Ghana Atomic Energy Commission, Accra Ghana. The duration of the study was six months. Use of Rad-Eye G-10 Thermo Scientific Gamma Survey Meter to measure dose rate around the biological shield of a Co-60 source (activity of 27.4kCi, was in the irradiation position) at controlled areas of the facility, which included control room, electrical power room, deionizer room, the roof of irradiation chamber (specifically roof plugs) and two entrances to the irradiation chamber (the personnel door and the goods door). Background reading was 0.08 ± 0.01μSv/h. Radiation dose rates at the Personnel door and the goods door were 0.090μSv/h and 0.109μSv/h, respectively. Practical measurements at the roof plugs produced average values of 0.135μSv/h. A particular point on Plug-3 produced a relatively higher reading of 8.151μSv/h. Measurements in the control room, electrical room, and deionizer room gave average readings of 0.116μSv/h, 0.089μSv/h, and 0.614μSv/h, respectively. All average values were below the limits of 7.5μSv/h and 50mSv/yr. Total radiation at the entrances of the mazes is due mainly to scattered radiation. The shielding by lead doors (0.009m) and concrete walls (1.6 m-1.9m) of the installed 1.85 PBq (50kCi) rectangular plaque Co-60 source irradiation chamber are sufficient to shield occupationally exposed workers at the facility when the source is in the storage position and operation. The dose limit of 7.5μSv/h (i.e., 50mSv per year) is not exceeded. The presence of an entrance maze (8.1m and 9.1m) is also adequate and contributes to multiple scattering. The visual and audio warning mechanisms and interlock systems are satisfactory and adequate, provided the facility is operated safely to prevent over-exposure. Shielding calculations (in particular for the deionizer room) would need to be carried out before such an upgrade to a 500kCi source.

1. P. Dethier, “Industrial gamma and x-ray: “Same but different”,” Louvain-la-Neuve, Belgium: Ion Beam Applications (IBA), White paper, 2016. [Online]. Available: https://bit.ly/3BJlSpL
2. IAEA-1454 , Radiation Safety of Gamma, Electron and X-Ray Irradiation Facilities. Vienna, Austria: International Atomic Energy Agency, 2010.
3. Thomas. (2015) Materials used in radiation shielding. [Online]. Available: https://bit.ly/2WP8fpC
4. A. S. Medeiros, M. R. Gual, C. Pereira, and L. O. Faria, “Thermal analysis for study of the gamma radiation effects in poly (vinylidene fluoride),” Radiation Physics and Chemistry, vol. 116, pp. 345–348, 2015. doi: https://doi.org/10.1016/j.radphyschem.2015.05.006
5. H. Silva and M. FS, “Beryl colorless, quartz, and brazilianita study using x-ray diffraction, spectroscopy in the infrared region and gamma irradiation in,” in Proceedings of the Semana de Engenharia Nuclear e Ciências das Radiaçoes (Sencir), Portuguese, 2014.
6. A. Adu-Gyamfi, “Safety analysis report.” Radiation Technology Centre, Accra, Ghana, Tech. Rep., 2011.
7. Stanford University, Radiation Safety Manual. Stanford, CA: Stanford University, 2015.
8. C. Cousins, D. Miller, G. Bernardi, M. Rehani, P. Schofield, E. Vañó, A. Einstein, B. Geiger, P. Heintz, R. Padovani et al., “International commission on radiological protection,” ICRP Publication, vol. 120, pp. 1–125, 2011.
9. G. Emi-Reynolds, G. Banini, and E. H. Akaho, “Practical evaluation of the biological shielding effectiveness of the gamma irradiation facility at Kwabenya, Ghana,” Ghana Atomic Energy Commission, Accra, Ghana, Tech. Rep., 1997.
10. G. Emi-Reynolds and E. H. Akaho, “A theoretical evaluation of the effectiveness of the biological shields for the 0.5 MCi irradiation facility,” Journal of the Kumasi University of Science and Technology, vol. 14, no. 2, pp. 79–89, 1994.
11. J. Fletcher, G. Emi-Reynolds, and E. Glover, “Shielding calculations for changing from circular to a rectangular source configuration for a pilot scale irradiator,” Journal of Applied Science and Technology, vol. 5, no. 1, pp. 39–44, 2000.
12. T. E. Mavuso, “Experimental evaluation of the biological shielding effects of the upgraded gamma irradiation facility,” University of Ghana, Legon-Accra, Ghana, Master thesis, 2013.
13. I. Publ, “2007 recommendations of the international commission on radiological protection,” Annals of the ICRP, vol. 37, pp. 2–4, 2008.

T. A. Sackey, G. K. Banini, G. Emi-Reynolds, and E. Gyasi, “Dose rate assessment at a gamma processing facility in Ghana” International Journal of Applied and Physical Sciences, vol. 6, pp. 9-15, 2020. doi: https://dx.doi.org/10.20469/ijaps.6.50002