Refaat Hassan Ismail
The present studyinvestigates the differences between two recommendations (NCRP49& NCRP147) and their applications to calculate the shielding requirement for primary and secondary radiation barrier of an x-ray facility in four hospitals in Sudan. The studied facilities have different layout and dimension where the rooms have divergence from standard radiographic room dimension. The investigations were performed at the following hospitals: 1) Khartoum hospital (Sudatel), 2) Khartoum hospital, 3) Khartoum Bahry hospital and 4) Al Qwaity specialist hospital. Measurement of unshielded scatter and leakage radiation at selected point around the examination table and the scatter dose were carried out. The product of dose per unit of workload– x-ray workload – scatter fraction and field size as corrected for inverse square law were calculated. A comparison of scattered dose and workload distribution show that when workload distribution concept is utilized to determine the dose due to scatter radiation, the unshielded scatter doses is lower than that generated by the NCRP 49 when the workload is performed at a single kvp. The research show that NCRP 147 reduce the thickness of primary barriers e to 1) Khartoum hospital (Sudatel) 55% , 2) Khartoum hospital 56% , 3) Khartoum Bahry hospital 46% and 4) AlQwaity specialist hospital 48% than traditional method based on report NCRP 49 when the workload is performed at a single kvp. Also leakage radiation was calculate and the ratio of the calculated to measured dose level inside the xray room show that the exposure inside the rooms was highly variable and the difference between the calculated and measurement scatter were attributed due to measurement uncertainties - the scatter from the surrounding material in x-ray room - x-ray absorption by objects inside x-ray rooms. Primary and secondary thicknesses according to report 49 were estimated in order to determine lead thickness required to shield the barrier. It is found that the new method (NCRP147) better determines the thickness of the barrier required
